AS 2593—2004 2593—2004 (Incorporating Amendment No. 1) A S 2 5 9 3 — 2 0 0 4
Australian Standard
®
Boilers—Safety management and supervision systems ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
T his A us ust tralian S tan and d ard® w as prep prep ar ared ed b y C om m ittee M E -00 1, P ressur essure e Equ E qu ipm ent ent. . It w as ap p rove oved d on b eh ehal alf o f the C ou ncilof S tan and d ar ard d s A ust ustr ralia o n 26 M ay 2 00 4. Thi Th is S tand ar ard d w as p ub lished on 28 June 20 04 .
Th e follow ing ar are e rep rep resen ted on C om m ittee M E -00 1: • • • • • • • • • • • • • • • • •
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
• • • • •
A .C .T. W or orkC kC over A u st str ralas asi ian In st sti itu te o f E n g in e e r S u rve veyo yor rs A us ust tralian A lum iniu m C o u nc il A ust ustr ralian B uild ing C o d es B o ar ard d A ustralian C ham b er of C om m er erce ce an d Ind ust ustr ry A u st str ralian Ind u stry G ro up A u stralian In stitu te o f E n e rg y A u stralia n In stitu te o f P e tro le u m A us ust tralian L iq ue fied P et etr ro leu m G as A sso ciat ati io n B u rea eau u o f S tee eel lM an uf ufac act tu rers of o f A us ust tralia D ep artm en t fo r A d m in ist str rat ati ive an d Inf nfo o rm at ati io n S ervice ces, s, S .A . D ep ar art tm en ent t of C on sum er & E m p lo ym en ent t P ro tect ecti ion , W or orkS kS afe D ivisio n, W .A . D ep ar art tm en ent t o f Inf nfr rast astr ruc uct tur ure, e, E ne ner rg y and a nd R eso ur urce ces, s, T as. E ne ner rg y S up p ly A sso ciat ati io n o f A us ust tralia E n g in ee rs A u st str ralia In stitu te o f M ate rials E n g in ee rin g A u stralasia In su sur ra n ce C o u n cilo f A u st str ra lia L td N atio n a lA ss sso o c iatio n o f T estin g A u th o rities, A u stra lia P ressu essur re E q uip m en ent t A ssoc ssoci iat ati ion V ict cto o rian W o rkC o ver A ut utho ho rity W eld in g T e ch n o lo g y In st sti itu te o f A u st str ra lia W or orkC kC overN ew So uth W ales
Th is S tand ar ard d w as issue ssued d in d raft for orm m fo r co m m en ent t as D R 02 32 8. S tan d a rd s A u st str ra lia w ish she e s to ac ackn kn o w led g e th th e p articip atio n o fth e exp e xp ert in d ivid u a ls th a t co n trib ut uted ed to th e d eve lo p m en ent t o f th is S tan d ard throu throug g h the ir rep res esen en tat ati io n o n the C om m ittee an d thr hrou ou gh pu b lic co m m ent pe riod .
K eep ing S tand ar ard d s up up--to -dat -d ate at e date A us ust tralian S tan d ards® are living d o cu m en ts tha tha t reflec ect t p ro g res ess s in sc sci ien ce ce, , tec ech h n o lo g y an d system syst em s. T o m ain tain th eir cu rren cy, allS tan d ards are p er eri io d ica cal lly review ed , an d n ew ed itio n s are ar e pub p ub lishe shed d . B et etw w een ed ition s, am en end d m en ent ts m ay be b e issue ssued d. S tan and d ar ard d s m ay al a lso b e w ithd raw n. It is im p o rtan ant t tha hat t rea ead d er ers s assu a ssur re the them m selves the hey y are using a cur cu rren ent t S tan and d ar ard d , w hich shou sh ou ld inc ncl lud e any an y am en end d m en ent ts tha hat t m ay have b een p ub lishe shed d sinc nce e the the S tan and d ar ard d w as p ub lish shed ed . D et etai ailed inf nfo o rm at ati io n ab o ut A us ust tralian S tan and d ar ard d s, d rafts, am en d m en ent ts and a nd ne new w p ro jec ect ts can ca n b e fou fou nd b y visiting w w w .st stan an d ar ards.o ards. rd s.or org. o rg.au g .au stand andda ard S tan and d ar ard d s A ust ustr ralia w elco com m es su gg est esti ion s for im p rove ovem m en ent ts, an and d en enco cour urag ages es read read er ers s to to no tify us u s im m ed iat atel ely o f an y ap a p p arent in ac accu cu rac aci ies o r am b ig u ities es. . C o ntact us via em ailat m ail@ st stan an d ar ard d s. o rg .au , or w rite to to S tand ar ards ds A ustralia, G P O B ox 47 6, S ydn ydney, ey, N S W 20 01 . s.org. org.au
T his A us ust tralian S tan and d ard® w as prep prep ar ared ed b y C om m ittee M E -00 1, P ressur essure e Equ E qu ipm ent ent. . It w as ap p rove oved d on b eh ehal alf o f the C ou ncilof S tan and d ar ard d s A ust ustr ralia o n 26 M ay 2 00 4. Thi Th is S tand ar ard d w as p ub lished on 28 June 20 04 .
Th e follow ing ar are e rep rep resen ted on C om m ittee M E -00 1: • • • • • • • • • • • • • • • • •
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
• • • • •
A .C .T. W or orkC kC over A u st str ralas asi ian In st sti itu te o f E n g in e e r S u rve veyo yor rs A us ust tralian A lum iniu m C o u nc il A ust ustr ralian B uild ing C o d es B o ar ard d A ustralian C ham b er of C om m er erce ce an d Ind ust ustr ry A u st str ralian Ind u stry G ro up A u stralian In stitu te o f E n e rg y A u stralia n In stitu te o f P e tro le u m A us ust tralian L iq ue fied P et etr ro leu m G as A sso ciat ati io n B u rea eau u o f S tee eel lM an uf ufac act tu rers of o f A us ust tralia D ep artm en t fo r A d m in ist str rat ati ive an d Inf nfo o rm at ati io n S ervice ces, s, S .A . D ep ar art tm en ent t of C on sum er & E m p lo ym en ent t P ro tect ecti ion , W or orkS kS afe D ivisio n, W .A . D ep ar art tm en ent t o f Inf nfr rast astr ruc uct tur ure, e, E ne ner rg y and a nd R eso ur urce ces, s, T as. E ne ner rg y S up p ly A sso ciat ati io n o f A us ust tralia E n g in ee rs A u st str ralia In stitu te o f M ate rials E n g in ee rin g A u stralasia In su sur ra n ce C o u n cilo f A u st str ra lia L td N atio n a lA ss sso o c iatio n o f T estin g A u th o rities, A u stra lia P ressu essur re E q uip m en ent t A ssoc ssoci iat ati ion V ict cto o rian W o rkC o ver A ut utho ho rity W eld in g T e ch n o lo g y In st sti itu te o f A u st str ra lia W or orkC kC overN ew So uth W ales
Th is S tand ar ard d w as issue ssued d in d raft for orm m fo r co m m en ent t as D R 02 32 8. S tan d a rd s A u st str ra lia w ish she e s to ac ackn kn o w led g e th th e p articip atio n o fth e exp e xp ert in d ivid u a ls th a t co n trib ut uted ed to th e d eve lo p m en ent t o f th is S tan d ard throu throug g h the ir rep res esen en tat ati io n o n the C om m ittee an d thr hrou ou gh pu b lic co m m ent pe riod .
K eep ing S tand ar ard d s up up--to -dat -d ate at e date A us ust tralian S tan d ards® are living d o cu m en ts tha tha t reflec ect t p ro g res ess s in sc sci ien ce ce, , tec ech h n o lo g y an d system syst em s. T o m ain tain th eir cu rren cy, allS tan d ards are p er eri io d ica cal lly review ed , an d n ew ed itio n s are ar e pub p ub lishe shed d . B et etw w een ed ition s, am en end d m en ent ts m ay be b e issue ssued d. S tan and d ar ard d s m ay al a lso b e w ithd raw n. It is im p o rtan ant t tha hat t rea ead d er ers s assu a ssur re the them m selves the hey y are using a cur cu rren ent t S tan and d ar ard d , w hich shou sh ou ld inc ncl lud e any an y am en end d m en ent ts tha hat t m ay have b een p ub lishe shed d sinc nce e the the S tan and d ar ard d w as p ub lish shed ed . D et etai ailed inf nfo o rm at ati io n ab o ut A us ust tralian S tan and d ar ard d s, d rafts, am en d m en ent ts and a nd ne new w p ro jec ect ts can ca n b e fou fou nd b y visiting w w w .st stan an d ar ards.o ards. rd s.or org. o rg.au g .au stand andda ard S tan and d ar ard d s A ust ustr ralia w elco com m es su gg est esti ion s for im p rove ovem m en ent ts, an and d en enco cour urag ages es read read er ers s to to no tify us u s im m ed iat atel ely o f an y ap a p p arent in ac accu cu rac aci ies o r am b ig u ities es. . C o ntact us via em ailat m ail@ st stan an d ar ard d s. o rg .au , or w rite to to S tand ar ards ds A ustralia, G P O B ox 47 6, S ydn ydney, ey, N S W 20 01 . s.org. org.au
AS 2593— 2593—2004 (Incorporating Amendment No. 1)
Australian Standard
®
Boilers—Safety management and Boilers— supervision systems ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
First published as AS 2593—1983 and part of AS 3653—1993. Previous edition AS 2593—2001. AS 2593—2001 and part of AS 3653—1993 3653—1993 revised, amalgamated amalgamated and redesignated as AS 2593—2004. Reissued incorporating Amendment Amendment No. 1 (February 2007).
COPYRIGHT
© Standards Australia All rig hts are res erv ed. No par t o f t his wor k m ay be rep rod uced or cop ied in any for m o r b y any means, electronic or mechanical, including photocopying, without the written permission of the publisher. Published by Standards Australia, GPO Box 476, Sydney, NSW 2001, Australia ISBN 0 7337 6111 9
AS 2593 —200 4
2
PREFACE
This Standard was prepared by the Australian members of Standards Australia/Standards New Zeal Zealand and Com Commit mittee tee M E-0 E-001, 01, Press ure Equ Equipm ipment ent to sup superse ersede de AS 259 2593—20 3—2001, 01, Boilers Boi lers Unattended Unattended and limited attendance. Parts of AS 3653—1993, Boilers—Safety, management, combustion and other ancillary equipment, have been integrated into this Standard. AS 3653 will be withdrawn after publication of this Standard. This Standard incorporates Amendment No. 1 (February 2007). The changes required by the Amendment are indicated in the text by a marginal bar and amendment number against the clause, note, table, figure or part thereof affected. After consultation with stakeholders in both countries, Standards Australia and Standards New Zeal Zealand and deci decided ded to dev develop elop this Stan Standard dard as an Aust Australi ralian, an, rath rather er than as an Australian/New Zealand Standard. The objective of this Standard is to provide operators of all boilers with requirements for their safe operation. This edition introduces requirements for attended boilers. Users of this Standard are reminded that it has no legal authority in its own right, but may acquire legal standing in one or more of the following circumstances: ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
(a)
Adoption by a government authority.
(b)
Adoption by a purchaser purchaser as as a required standard standard of construction when placing placing a contract.
(c)
Adoption where a manufacturer manufacturer states that a vessel is in accordance accordance with this Standard.
Statements expressed in mandatory terms in footnotes to tables are deemed to be requirements of this Standard. The terms ‘normative’ and ‘informative’ have been used in this Standard to define the application of the appendices to which they apply. A ‘normative’ appendix is an integral part of a Standard, whereas an ‘informative’ appendix is for information and guidance only.
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AS 2593 — 2 004
CONTENTS
Page SECTION 1 SCOPE AND GENERAL 1.1 SCOPE ........................................................................................................................ 6 1.2 REFERENCED DOCUMENTS .................................................................................. 7 1.3 DEFINITIONS ............................................................................................................ 7 1.4 NEW DESIGNS, MATERIALS AND CONSTRUCTION METHODS ...................... 9 SECTION 2 2.1 2.2 2.3 2.4 2.5 2.6
DESIGN AND CONSTRUCTION FOR UNATTENDED AND LIMITED ATTENDANCE BOILERS GENERAL REQUIREMENTS ................................................................................. 11 STEAM BOILERS (OTHER THAN ELECTRIC BOILERS) ................................... 11 HOT WATER BOILERS........................................................................................... 12 WASTE HEAT BOILERS......................................................................................... 12 ELECTRIC BOILERS............................................................................................... 13 SUPERHEATERS ..................................................................................................... 13
SECTION 3
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16
BOILER MANAGEMENT SYSTEM FOR UNATTENDED AND LIMITED ATTENDANCE BOILERS GENERAL ................................................................................................................ 14 FAIL-SAFE TECHNIQUES...................................................................................... 14 TEMPERATURE SUITABILITY OF COMPONENTS............................................ 14 COMBUSTION MANAGEMENT............................................................................ 14 WATER MANAGEMENT SYSTEMS ..................................................................... 15 ELECTRICAL POWER ISOLATION ....................................................................... 20 POWER FAILURE PROTECTION........................................................................... 20 CONTROL EQUIPMENT......................................................................................... 21 ALARMS .................................................................................................................. 21 VISUAL DISPLAY FOR BOILERS UP TO AND INCLUDING A POWER OUTPUT OF 500 kW................................................................................................ 21 VISUAL DISPLAY FOR BOILERS EXCEEDING A POWER OUTPUT OF 500 kW ................................................................................................................ 22 COMBUSTION EQUIPMENT FOR FUEL-FIRED BOILERS................................. 23 MULTIPLE-BURNER INSTALLATIONS ................................................................ 25 AIR SUPPLY AND CONTROL SYSTEM ................................................................ 25 IGNITION SYSTEM................................................................................................. 26 MAIN FUEL FIRING RATE ..................................................................................... 26
SECTION 4
4.1 4.2
4.3
4.4 4.5 4.6
ADDITIONAL REQUIREMENTS FOR OIL-FIRED, GAS-FIRED AND SOLID-FUEL-IN-SUSPENSION-FIRED UNATTENDED AND LIMITED ATTENDANCE BOILERS APPLICATION ......................................................................................................... 28 OPERATIONAL REQUIREMENTS FOR OIL, GAS AND SOLID-FUEL-INSUSPENSION MANAGEMENT SYSTEMS FOR BOILERS WITH A POWER OUTPUT ABOVE 500 kW........................................................................................ 28 OPERATIONAL REQUIREMENTS FOR OIL, GAS AND SOLID-FUEL-INSUSPENSION MANAGEMENT SYSTEMS FOR BOILERS UP TO AND INCLUDING A POWER OUTPUT OF 500 kW....................................................... 31 SPECIFIC REQUIREMENTS FOR OIL-FIRED BOILERS ..................................... 34 SPECIFIC REQUIREMENTS FOR GAS-FIRED BOILERS .................................... 34 SPECIFIC REQUIREMENTS FOR SOLID-FUEL-IN-SUSPENSION-FIRED BOILERS .................................................................................................................. 35
AS 2593 — 2 004
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Page
SECTION 5 5.1 5.2 5.3
ADDITIONAL REQUIREMENTS FOR SOLID-FUEL-FIRED (BED OR GRATE) UNATTENDED OR LIMITED ATTENDANCE BOILERS APPLICATION ......................................................................................................... 36 OPERATIONAL REQUIREMENTS FOR SOLID FUEL (BED OR GRATE) MANAGEMENT SYSTEMS .................................................................................... 36 SPECIFIC REQUIREMENTS FOR SOLID-FUEL-FIRED (BED OR GRATE) BOILERS .................................................................................................................. 37
SECTION 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
CHECKING, TESTING AND MAINTENANCE FOR UNATTENDED AND LIMITED ATTENDANCE BOILERS GENERAL ................................................................................................................ 39 ORGANIZATION AND PERSONNEL .................................................................... 39 RESPONSIBILITIES CHECKING, TESTING AND MAINTENANCE................... 39 CHECKING AND TESTING.................................................................................... 39 MAINTENANCE ...................................................................................................... 42 RETENTION OF RECORDS.................................................................................... 42 MAINTENANCE CONTRACT ................................................................................ 42
SECTION 7 ATTENDED BOILERS 7.1 GENERAL ................................................................................................................ 44 7.2 MANAGEMENT SYSTEM ...................................................................................... 44 7.3 MANUAL OPERATION........................................................................................... 44 7.4 AUTOMATIC OPERATION .................................................................................... 44 7.5 LOW-WATER CUT-OUT AND ALARM ................................................................ 45 7.6 WATERFEED CONTROL........................................................................................ 45 7.7 OPERATIONAL SUPERVISION ............................................................................. 45 7.8 TESTING AND CHECKING PROGRAMS............................................................. 45 7.9 PROGRAMMABLE LOGIC CONTROLLER (PLC) MANAGEMENT SYSTEMS................................................................................................................. 46 7.10 NOTICES .................................................................................................................. 46 SECTION 8 8.1 8.2 8.3
WATER LEVEL MANAGEMENT AND SECURITY FOR ALL TYPES OF BOILERS WATER LEVEL DEVICES AND INTERLOCKS.................................................... 47 WATER LEVEL INDICATORS ............................................................................... 47 FEED SYSTEMS ...................................................................................................... 51
SECTION 9 INSTALLATION REQUIREMENTS OF ALL TYPES OF BOILERS 9.1 STATUTORY REQUIREMENTS............................................................................. 53 9.2 HOUSING, ACCESS AND SECURITY ................................................................... 53 9.3 FEEDWATER SUPPLY............................................................................................ 53 9.4 WATER TREATMENT ............................................................................................ 53 9.5 BLOWDOWN ........................................................................................................... 53 9.6 FLUES AND CHIMNEYS ........................................................................................ 53 9.7 ELECTRICAL EQUIPMENT.................................................................................... 53 SECTION 10 MARKING AND INSTRUCTIONS FOR ALL TYPES OF BOILERS 10.1 MARKING ................................................................................................................ 55 10.2 ELECTRICAL DATA ............................................................................................... 55 10.3 INSTRUCTIONS ...................................................................................................... 55 10.4 LANGUAGE AND UNITS ....................................................................................... 55 10.5 CERTIFICATES........................................................................................................ 55
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AS 2593 — 2 004
Page SECTION 11 ENERGY INPUT SYSTEMS FOR ALL TYPES OF BOILERS 11.1 COMBUSTION SYSTEMS ...................................................................................... 56 11.2 WASTE HEAT ENERGY RECOVERY SYSTEM................................................... 57 11.3 ELECTRIC ENERGY INPUT SYSTEMS ................................................................ 57 SECTION 12 VALVES FOR ALL TYPES OF BOILERS 12.1 GENERAL ................................................................................................................ 59 12.2 SIZE, NUMBER AND LOCATION OF SAFETY VALVES FOR BOILERS .......... 59 12.3 BLOWDOWN VALVES........................................................................................... 62 12.4 MAIN STEAM ISOLATING VALVE ...................................................................... 62 12.5 MAIN FEEDWATER ISOLATION VALVE ............................................................ 62 SECTION 13 INTEGRAL AND BOILER PRESSURE PIPING FOR ALL TYPES OF BOILERS 13.1 GENERAL ................................................................................................................ 63 13.2 WATER-HEATING BOILER SYSTEM DESIGN.................................................... 63
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
APPENDICES A LIST OF REFERENCED DOCUMENTS ................................................................. 65 B ACCEPTABLE CRITERIA FOR ORGANIZATIONS AND PERSONNEL UNDERTAKING BOILER CONTROL DESIGN, TESTING AND SERVICING FOR UNATTENDED AND LIMITED ATTENDANCE BOILERS ONLY.............. 67 C TYPE TEST FOR A BOILER SUBJECT TO POWER FAILURE............................ 70 D TYPICAL OIL OR GAS BURNER FIRING SEQUENCES...................................... 71 E TYPICAL OIL SUPPLY AND CONTROL SYSTEMS ............................................ 72 F EXAMPLE OF INTEGRAL BOILER PIPING COVERED BY AS 1228 AND THIS STANDARD.................................................................................................... 74
AS 2593 — 2 004
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STANDARDS AUSTRALIA
Australian Standard Boilers—Safety management and supervision systems
S E C T I O N
1
S C O P E
A N D
G E N E R A L
1.1 SCOPE
This Standard specifies the requirements for the operation of boilers, including unattended, limited attendance and fully attended. It includes the special features within the control, management and supervision systems, associated valves and fittings, housing and installation for those boilers operating in the unattended or limited attendance modes. It also details the checking, testing and maintenance requirements for each category of attendance. The details and limits on the type, design criteria, and usage of unattended, limited attendance and attended boilers to which this Standard is intended to apply are as follows:
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
©
(a)
Boilers for fixed land installations.
(b)
Boilers having a design pressure as shown in Table 1.
(c)
Boilers having a power output within the capacity specified in Table 1 for the boiler type and category. (See Note 1.)
(d)
Boilers complying with the supervision and maintenance requirements specified in Table 1 for the boiler type and category.
(e)
Boilers for the generation of steam, or other vapour, for which duty the types of boilers permitted are — (i)
water-tube type electric type or small boiler types (see Table 1) for unattended operation;
(ii)
any type of boiler for limited attendance operation (see Table 1); and
(iii)
any type of boiler for attended operation (see Table 1).
(f)
Boilers for the heating of water or other liquids at a pressure above that of the atmosphere and to a temperature not less than the normal atmospheric boiling temperature of the liquid, for which duty any type of boiler complying with AS 1228 is permitted for unattended operation, provided that for other than water-tube and electric type boilers, steam or vapour is not generated in the boiler and the boiler drum or shell is fully flooded.
(g)
Boilers having any of the following sources of energy input: (i)
Gas fuel (mains or other gases).
(ii)
Oil fuel with a closed flashpoint greater than 23 ° C.
(iii)
Solid fuels, including solid-fuel-in-suspension.
(iv)
Waste heat fluids.
(v)
Electric power.
(vi)
Solar energy.
Standards Australia
www.standards.org.au
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AS 2593 — 2 004
NOTE S: 1
This Standard may also be applied to boilers outside the limits specified in Items (a) to (g) where equivalent safety and reliability are required by the owner.
2
Except for definitions in Clause 1.3, other clauses in the Standard refer to steam and water only. The Standard may be applied to other fluids with attention by the owner to the owner s duty of care to the operational personnel and the general public. ’
1.2 REFERENCED DOCUMENTS
A list with titles of the documents referred to in this Standard is given in Appendix A. 1.3 DEFINITIONS
For the purpose of this Standard, the definitions below apply. See AS 4942 for definitions other than those listed below. 1.3.1 Acceptable, acceptance, accepted
The equipment or procedure conforms to the Australian Standard applicable to the equipment or procedure, or it can be shown to fulfil the performance requirements of this Standard if no such Standard exists. 1.3.2 Certificated boiler attendant
A person who is the holder of an appropriate certificate of competency to operate a boiler issued by the relevant regulatory authority. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
1.3.3 Boilers 1.3.3.1 Boiler
An arrangement of vessels and interconnecting parts, wherein steam or other vapour is generated, or water or other liquid is heated at a pressure above that of the atmosphere by the application of fire or the products of combustion or process, or by electrical or solar means. It also includes valves, gauges, fittings and controls directly associated with the boiler and, where consistent with the requirements of this Standard, includes the boiler setting and associated equipment. It does not include fully flooded systems or pressurized systems where the water or other liquid is heated to a temperature lower than the normal atmospheric boiling temperature of the liquid. 1.3.3.2 Attended boiler
A boiler which requires supervision by a certificated boiler attendant and not classified as unattended or limited attendance. The boiler attendant has effective control of the boiler at all times while it is in use and is in a position to hear the alarms and to respond to them immediately. 1.3.3.3 Combined water-tube, fire-tube steam boilers
A boiler having a combination of design features as follows: (a)
The fire-tube section only receives hot gases that have first passed through the watertube section of the combination unit. The design of the water-tube section to be such that the temperature of these gases entering the fire-tube section does not exceed 800°C.
(b)
The fire-tube section output does not exceed 60% of the total energy output of the combined unit.
(c)
The fire-tube section has no furnace or any combustion taking place within its tubes.
ww w.s tan dard s.o rg. au
© Standards
Australia
AS 2593 — 2 004
8
(d)
The shell or tube plate of the fire-tube section is not subjected to any direct combustion or radiation.
(e)
The maximum temperature of the plate of a multi-pass fire-tube section is measured just belo w the low-water line, at entry of the second fire-tube pass of the flue gases. The design of this multi-pass fire-tube section to be such that the maximum temperature of the plate does not exceed the steam saturation temperature by more than 50°C.
1.3.4 Boiler management system
A system that controls the entire boiler function including the energy input management system, the water level management system, the pressure controls, instruments and circuitry. 1.3.5 Chimney
A vertical duct or stack which finally conveys products of combustion from the boiler flue or flues or from the boiler direct to the atmosphere. 1.3.6 Complete shutdown and lockout—unattended and limited attended boilers
A condition in which the boiler is immediately and effectively isolated from energy sources to the combustion management and the controls can only be reset by hand manually. The safety controls and sequence indicator system (mimic or visual indicator panel) and feed water supply can not be isolated. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
The second feed water pump where fitted, is energized to run, when the boiler water level activates the extra low water level device. Both feed water pumps remain running until normal water level is retained. 1.3.7 Energy input management system
A system for the management of the combustion or energy input equipment, including the operating controls, limit switches, safety interlocks, and flame supervision devices. 1.3.8 Fail-safe
A feature which ensures that the absence or malfunction of any critical control or safety component, system, signal or function will not result in an unsafe condition. 1.3.9 Flue
A horizontal, inclined or vertical duct conveying the products of combustion from the boiler to the induced fan or fans, flue gas cleaning installation and the boiler chimney. 1.3.10 Maintenance contractor
A person or organization covered by a maintenance contract to perform testing and maintenance on the boiler and its operating and safety systems. 1.3.11 Owner
A body corporate, firm or person who has right of title to, or management of, or control over the pressure equipment and includes a person exercising such management or control as an agent of the owner. 1.3.12 Power output
The maximum continuous rated output of the boiler as specified by the manufacturer. 1.3.13 Proved
The relevant conditions have been sensed and registered as being correct.
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AS 2593 — 2 004
1.3.14 Purging
The use of air or inert gas to remove and r eplace a potentially dangerous atmosphere. 1.3.15 Self-checking system
A sub-system within the boiler management system, designed and arranged to automatically and regularly test the integrity of the flame failure devices by dynamic testing of each and every component on which safe and correct operation is dependent, usually by creating a change of state. 1.3.16 Shutdown and lockout – unattended and limited attendance boilers
A condition in which the boiler is immediately and effectively isolated from energy sources to the combustion management (or for a solid fuel boiler, from all sources of combustion air) and the controls can only be reset by hand manually. The safety control and sequence indicator system (mimic or visual indicator panel) and feed water supply shall not be isolated. This will enable the feed pump/s to run after the boiler has shutdown with —
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
(a)
low water level alarm condition/s;
(b)
fault in low-level water device;
(c)
failure of the system to go to a self-checking sequence;
(d)
failure of the system during the self-checking function; and
(e)
failure to return to a normal operating position.
NOTE : Fo r at tended boil ers ref er to S ection 7.
1.3.17 Trained person
A person who has received adequate instruction and training provided by the owner in the operation of unattended boiler(s). 1.4 NEW DESIGNS, MATERIALS AND CONSTRUCTION METHODS
This Standard does not intend to prohibit the use of materials, methods of design or construction, which comply with AS/NZS 1200 and other relevant Standards referred to therein.
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AS 2 593— 2004
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S E C T I O N F O R
AS 2593 —200 4
2 D E S I G N A N D C O N S T R U C T I O N U N A T T E N D E D A N D L I M I T E D A T T E N D A NC E B O I L E R S
2.1 GENERAL REQUIREMENTS 2.1.1 Basic design
Each boiler or superheater shall comply with the relevant boiler Standard, i.e. AS 1228, and in addition shall be designed to— (a)
incorporate a highly reliable management and control system with fail-safe features;
(b)
incorporate such construction features as are necessary to minimize the effect of any failure in the safety systems from creating a hazardous condition (see Note); and
(c)
comply with the relevant requirements specified in Clauses 2.2 to 2.6.
NOTE : In order to min imi ze the opera tin g wat er cont ent and pote nti al over heat ing eff ect s in the event of a loss of water, unattended and limited attendance steam boilers are limited in Table 1 to the construction types noted.
2.1.2 Tube diameter
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The maximum outside diameter of any water tube exposed to combustion flame or furnace radiation shall be 80 mm. NOTE : This restricti on on the maximu m tub e d iamete r i s to limit the harm ful dis charge of energy from the furnace if a tube ruptures.
2.1.3 Water gauges
Water gauges and protective guards shall comply with AS 1271 and, if of the tubular type, shall be fitted with safety balls, to prevent the escape of both steam and water from a ruptured glass. NOTE : The fit tin g of tubular gau ge gla sse s wit h safet y bal ls does not appl y to ele ctri c boilers with a power output of 100 kW and below and in the steam mount of small boilers with a power output of 200 kW and below.
2.2 STEAM BOILERS (OTHER THAN ELECTRIC BOILERS) 2.2.1 General
Each steam boiler except electric boilers (see Clause 2.5) shall comply with Clause 2.2.2 or Clause 2.2.3, as applicable. 2.2.2 Water-tube steam boilers
Water-tube steam boilers of the natural circulation type or the forced circulation type shall comply with Clause 2.1 and AS 1228. The heat transfer surface shall be wholly composed of water tubes. Pressure vessels sections, such as drums or headers, shall be protected from direct flame radiation. 2.2.3 Steam boilers other than water-tube or electric boilers
Each steam boiler other than a water-tube or electric type shall comply with Clause 2.1. The shell, tube plate and tube ends of a fire-tube boiler shall be protected from direct flame radiation, e.g. ensuring that combustion is complete with the combustion chamber. Where a fire-tube boiler is converted to gas-firing, a reappraisal of the metal temperature and permissible heat input shall be made to ascertain that the converted boiler complies with the design temperature requirements of AS 1228. ww w.s tan dard s.o rg. au
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2.3 HOT WATER BOILERS 2.3.1 General
Each hot water boiler except electric boilers not built to AS 1228 (see Clause 2.5) shall comply with Clause 2.1 and with the following: (a)
Except as specified in Item (c), the boiler shall be part of a closed circulation hot water system.
(b)
For boilers other than water-tube and electric types not built to AS 1228, the boiler shall be designed to remain in a fully flooded condition at all times.
(c)
Water-tube and electric type boilers not built to AS 1228 which are operated with steam space for expansion purposes shall be fitted with the controls required for steam boilers, refer to Clause 2.2.
(d)
For fire-tube boilers, the water inlet and outlet shall be located at the top of the boiler and arranged so as to promote circulation in order to minimize both thermal shock and loss of water in the event of external pipe breakage.
2.3.2 Hot water systems
Each hot water system shall —
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
(a)
be a circulation system with no steam or water consumed during operation;
(b)
be designed and constructed so that loss of system water or loss of flow (circulation) cannot create a hazard in the boiler or system;
(c)
be equipped with the provision to expand, to accommodate the volume fluctuations in the system, with such an expansion vessel maintaining a positive system pressure at all times that the boiler is in operation, using inert gas, steam, or liquid head for pressurization; and
(d)
have a temperature difference between the outflow temperature and the return flow temperature of the hot water at the boiler connections not exceeding the following: (i)
For fire-tube boilers..................................................................... 25°C.
(ii)
For natural circulation water-tube boilers ..................................... 50 C.
(iii)
For forced circulation water-tube boilers ...................................... 80 C.
° °
Where the temperature difference between the outflow temperature and the temperature of the water returning to the boiler exceeds the temperature difference specified in Items (i), (ii) or (iii), as applicable, an external mixing device shall be fitted to raise the return flow temperature to a value that would comply with the specified maximum temperature difference at the boiler connections. 2.4 WASTE HEAT BOILERS
Waste heat boilers shall comply with Clause 2.2 or Clause 2.3, as applicable, and with one of the following:
©
(a)
Maximum temperature design The design strengths of all parts of the waste heat boiler shall be based on the strengths of the various materials at the maximum temperature attainable under any condition, including complete loss of water. As well, the heating medium shall not be capable of exceeding the maximum design temperature of the boiler. No provision shall be necessary for input energy control or safety controls, or water level safety devices.
(b)
Controlled input design The waste heat boiler shall have an input energy control system that regulates the flow of waste fluid automatically according to the output requirements, and shall be interlocked with a water level management system in accordance with Clauses 3.5.3, 3.5.4, 3.5.5 and 7.2, as applicable.
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AS 2593 — 2 004
2.5 ELECTRIC BOILERS
Electrode boilers and element boilers can be used as steam or hot water boilers. If used in this way they shall comply with AS 1228 . 2.6
SUPERHEATERS
Where a superheater is fitted to the unattended or limited attendance boiler, the superheater shall be suitable for safe automatic start-up and operation, i.e. without manual supervision or operator control. Two devices shall be provided to protect against overheating of any tube circuit due to loss of flow or scale build-up. The action of any overheating protection device shall cause complete shutdown and require independent manual reset of that device. The superheater design shall be such as to allow for the safe automatic start and operation of the boiler and superheater.
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
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S E C T I O N 3 B O I L E R M A N A G E ME N T S Y S T E M F O R U N A T T E N D E D A N D L I M I T E D A T T E N D A NC E B O I L E R S 3.1 GENERAL
In addition to compl ying with the requirements of AS 3920.1 and AS 4343, the boiler management system shall be suitable for fully automatic operation and adequate safety control of all the functions of the boiler, combustion or energy input, water level security and electric systems without the intervention of operating personnel, except for initial startup or for restarting after complete shutdown or any lockout. Time clocks may be used for start-up and shutdown of unattended boilers provided that the checking and testing requirements of Section 6 are carried out. Under no circumstances shall the time clock initiate an automatic start following lockout or complete shutdown. The boiler management system shall not have any provisions for the bypassing of safety features or controls except those to permit competent maintenance by competent maintenance personnel, for which acceptable security arrangements shall be incorporated. NOTE S:
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1
Maintenance personnel are defined in Appendix B. See also Clause 6.2.
2
Where bypassing of electrical circuits is required for testing, it is recommended that suitable facilities and test equipment should be supplied. Such test equipment is to be retained by the competent maintenance personnel.
3.2 FAIL-SAFE TECHNIQUES
The boiler management system should incorporate fail-safe components, circuits and techniques so that the loss or removal of a control signal will result in a shutdown and lockout or a r esulting situation which is safe. 3.3 TEMPERATURE SUITABILITY OF COMPONENTS
Each component of the boiler management system shall operate reliably and safely within the temperature and humidity limits specified by the manufacturer. The lower temperature limit shall be not higher than 0 C and the higher temperature limit shall be not lower than 50 C. °
°
3.4 COMBUSTION MANAGEMENT 3.4.1 General
The boiler management system of each oil-fired, gas-fired or solid-fuel-in-suspension-fired boiler shall include a combustion and flame failure protection system which shall provide the following f acilities: (a)
An automatically controlled starting and operating combustion sequence as required by Section 4.
(b)
Supervision of the start flame and main flame during ignition and main flame operation by means of a flame detector.
Boilers not exceeding 500 kW power output require one flame detector in accordance with Clause 3.4.3. Boilers exceeding 500 kW power output shall have two flame detector in accordance with Clause 3.4.3 operating so that, if flame failure is detected by either unit, lockout shall occur. One flame detector at least shall sense the start flame and both detectors shall sense the main flame.
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AS 2593 — 2 004
3.4.2 Power-operated valves 3.4.2.1 Fail-safe design
Any power-operated valve shall be of a type which will move to a safe condition when deenergized, or on failure of the actuating medium, or on power failure, i.e. main fuel valves shall fail shut and vent valves in a double block and vent gas sy stem shall fail open. 3.4.2.2 Closing time
One main fuel safety shut-off valve at least in a gas-fired system or an oil-fired system and the main diverter valve in a solid-fuel-in-suspension-fired system shall close in not more than 1 s after it has been de-energized. The combined time for the flame supervision system and its associated valves to shut off the fuel supply in the event of a flame failure at the point of supervision shall not exceed 3 s. 3.4.3 Flame detectors
Where flame detectors are required by Clause 3.4.1, each detector shall be of an ultravioletsensing type or other acceptable type. Where two flame detectors are required, a flame failure detected by either unit shall cause lockout. The flame d etectors shall be as follows:
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(a)
For a single flame detector installation, the flame detector shall be of a type which provides a circuitry pre-check prior to any ignition attempt.
(b)
For a dual flame detector installation, one flame detector shall be of a type capable of self-checking at intervals n ot exceeding 5 s and shall not extend the flame failure period to more than 2 s, the second flame detector shall be of a type described in Item (a).
NOTE : Fo r locat ion and mounti ng of fla me detectors, s ee Clause 3.15.4.
3.5 WATER MANAGEMENT SYSTEMS 3.5.1 Blowdown
Each boiler shall be provided with blowdown facilities in accordance with AS 3892. In addition, each steam boiler which consumes water containing over 5 mg/L total solids and intended for operation for a period in excess of 8 h without human supervision, shall be provided with at least one automatic device to control the level of the total dissolved solids during that period. 3.5.2 Feedwater supply
All boilers exceeding 500 kW power output shall be provided with the means to cause complete shutdown and lockout in the event of inadequate feedwater supply to the boiler feed pump suction inlet. Compliance with this requirement s hall be achieved by a low water safety device fitted in the feed tank. There is no requirement to fit a low water safety device in the feed tank of boilers not exceeding 500 kW power output. The position of the feed tank shall be at a sufficient height above the boiler feed pump suction to give an adequate margin on the net positive suction head (NPSH) for the pump. The calculation of NPSH should allow for the water temperature to be at 100 °C and the level to be at the point where the low-water device is activated. 3.5.3 Steam boilers, other than coil-type forced circulation boilers and electric boilers 3.5.3.1 General
The water management systems for steam boilers, other than coil-type forced circulation boilers and electric boilers, shall comply with this Standard, as applicable, and in addition shall be fitted with the equipment specified in Clauses 3.5.2 and 3.5.3.2 to 3.5.3.4.
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3.5.3.2 Water level controls and safety devices 3.5.3.2.1 Low level water safety devices
For boilers not exceeding 500 kW power output, one low level water safety device shall be fitted in the boiler drum. For boilers exceeding 500 kW power output, not less than two low level water safety devices, independent of each other, shall be fitted. The settings for the two devices shall be low and extra low. One of the devices shall be incorporated into an acceptable self-checking low level water system and one shall be fitted directly into the steam drum. The extra low water level set point shall be no less than 50 mm above the level where the top most heating surface would be exposed. This point shall be at the lowest visible water level in the gauge glass when viewed from the operator level. The low water level set point shall be above the extra low level set point. The operation of low water safety devices shall be in accordance with the fault shutdown requirements of Clause 4.2.3 or Clause 5.2.4, as appropriate. One low level water safety device or, alternatively, two high integrity conductive probes shall be used as part of a self-checking system. The details shall be as follows: (a)
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(b)
©
Low level water safety device Where used as part of a self-checking system, the low level water safety device shall comply with the following requirements: (i)
Shall operate on a time cycle so that the self-checking operation is performed at least once every 10 min. The duration of the self-checking bypass operation shall be no greater than 50% of the time taken for the water level to drop from normal operating level to a level that would expose any uncooled heating surface to the products of combustion, with the boiler operating at its rated power output and the feedwater isolated, or 1.5 min, whichever is greater.
(ii)
Shall operate as a normal low level water device at all times except for the period of the self-checking bypass operation.
(iii)
Shall have fail-safe circuitry and operating sequences.
(iv)
Shall be actuated to a complete shutdown by any of the following: (A)
Lowering of the water surface below a preset level.
(B)
Malfunctioning of the level device.
(C)
Failure to go into self-checking mode after the prescribed interval.
(D)
Failure of the switch mechanism to operate during the changeover (selfcheck to operating).
(E)
Failure of the low level water device or switch mechanism to return to the normal position after the self-checking operation.
High integrity conductive probes As an alternative to the system mentioned in item (a) above, two self-testing, high integrity conductive probes can be u sed and shall comply with the following requirements: (i)
Shall be of fail-safe design so that a single fault in any related part shall not lead to a loss of t he safety function.
(ii)
Shall have screened cable directly connected from the controller to the probe such that a complete or partial short-circuit of the screen to earth or to the electrode, or a break in any of the wires in the cable is detected.
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AS 2593 — 2 004
(iii)
Shall be of a two-tip design, one tip to sense the water level, the second tip (comparator tip) used to ensure that correct water levels are sensed under all normal and abnormal operating conditions.
(iv)
Shall perform a self-test within a 60-second interval that proves status of the probe, the probe cable and the operation of the controller.
(v)
Shall continually monitor the water level.
(vi)
Each conductive probe shall be located in separate locations on the boiler.
3.5.3.2.2 Automatic water level controller
An automatic water level controller shall be fitted, incorporating one of the low level water safety devices required by Clause 3.5.3.2.1. For boilers exceeding 3 MW power output, the water level controller shall be of the continuous flow or modulating type. 3.5.3.2.3 Externally fitted water level device other than gauge glasses
Where an externally fitted water level device is fitted, there shall be no isolating valves between the chamber and the boiler, with the sole exception of a sequencing blowdown valve. The sequencing blowdown valve shall be of a type that ensures that the following operations shall be carried out in the specified sequence and in a gradual manner:
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(a)
Close the water connection to the chamber and simultaneously open the water connection direct to the drain.
(b)
Maintain closed the water connection to the chamber and the drain while simultaneously opening the chamber direct to the drain.
(c)
Open the water connection to the chamber and simultaneously close the drain (normal operating position).
3.5.3.3 Feedwater pumps
Each boiler exceeding 500 kW power output shall be fitted with two automatically controlled feedwater pumps, each capable of supplying not less than 120 percent of the mass of steam generated at the power output of the boiler calculated on the basis of feedwater at 100 C and at design pressure. °
The feedwater pump system shall be controlled so that after each automatic pump stop, the operating pump shuts down and the alternative pump is started. Where the pump operation is continuous, a pump changeover shall occur at a maximum period not exceeding one week. Boilers not exceeding 500 kW power output may be fitted with one feedwater pump in accordance with this Standard, as applicable. 3.5.3.4 Assisted circulation
Each boiler fitted with a pump to assist natural circulation shall be interlocked to prevent operation of the combustion equipment unless water flow is established and maintained. 3.5.4 Water management systems for coil-type forced circulation boilers 3.5.4.1 General
Each coil-type forced circulation boiler shall comply with the requirements of AS 1228 for such boilers, and shall be fitted with equipment specified in Clauses 3.5.4.2 to 3.5.4.4. 3.5.4.2 Overheating interlock
Two devices shall be provided to protect against the overheating of any tube circuit due to loss of flow or scale build-up. The actuation of any overheating protection device shall cause complete shutdown and require independent manual reset of that dev ice. ww w.s tan dard s.o rg. au
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3.5.4.3 Water circulation pump
Each boiler shall be fitted with a controlled circulating pump which shall be interlocked to prevent the operation of the combustion equipment unless water flow is established and maintained. NOTE : In some boilers, t he c irculat ing pump m ay be the feedwa ter pump.
3.5.4.4 Feedwater pumps
Feedwater pumps shall comply with the requirements of Clause 3.5.3.3, except that only one pump need be fitted for coil-type forced circulation boilers complying with the limitations applicable to boilers for which modified design and construction requirements are permitted in accordance with AS 1228. 3.5.5 Water management systems for hot water boilers 3.5.5.1 General
In addition to complying with AS 1228 as appropriate, each boiler shall be fitted with the equipment specified in Clauses 3.5.5.2 to 3.5.5.4. 3.5.5.2 Low water safety devices
Low water safety devices s hall be provided in accordance with the following schedule:
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(a)
Power output not exceeding 500 kW .............................................one device.
(b)
Power output exceeding 500 kW ................................................. two devices.
The lowering of the actual water level to a level such as will cause any low water safety device to be actuated shall cause complete shutdown. 3.5.5.3 Water circulation pump
Each boiler shall be fitted with a controlled circulating pump which shall be interlocked to prevent operation of the combustion equipment unless water flow is established and maintained. A water flow safety device shall be fitted to indicate water flowing. 3.5.5.4 Safety thermostat or pressure switch
Each boiler shall be fitted with a separate high limit thermostat or pressure switch, and the operation of that thermostat or switch shall cause complete shutdown of the boiler. The device (thermostat or switch) shall be of a type that requires independent manual reset. Any high limit thermostat shall operate not higher than 6 C less than the boiling point temperature corresponding to the design pressure. °
3.5.6 Water management systems for waste heat boilers
The water management system for a waste heat boiler shall comply with this Standard as applicable. In addition, each controlled input design type boiler (see Clause 2.4(b)) shall comply with Clause 3.5.3, 3.5.4 or 3.5.5, as applicable. 3.5.7 Water management systems for electric boilers 3.5.7.1 General
For electrode boilers, no provision is necessary for input energy controls or safety controls or low water level safety devices. A high level safety device shall be fitted to each electrode boiler to protect the boiler insulators. The device may be of either the float or probe type and need not be self-checking. The rise of the actual water level to a level such as will cause the high water safety dev ice to be actuated shall cause complete shutdown. For element boilers, the water management system shall comply with the following:
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(a)
Steam boilers — with Clause 3.5.7.2.
(b)
Hot water boilers — with Clause 3.5.5 or Clause 3.5.7.2, as applicable.
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3.5.7.2 Water level controls and safety devices for electric element boilers
The following water level devices shall be fitted except where otherwise permitted in Clause 3.5.7.1: (a)
An effective and reliable automatic water level controller of the float or probe type shall be fitted. For boilers exceeding 3 MW power output, the water level controller shall be of the continuous or modulating type. The water level controller shall operate within the visible range of the water gauge glass. NOTE : This control ler may inc orporate one of the low wat er saf ety devi ces required in Item (b).
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(b)
Boilers with a power output not exceeding 500 kW shall have at least one low water safety device. For a boiler with a power output exceeding 500 kW two independent low water safety devices, one of which shall incorporate approved self-checking features. The lowering of the actual boiler water level to a level which will cause any low water safety device to be actuated shall cause complete shutdown and lockout.
(c)
One low water safety device required by Item (b) shall be fitted directly into the steam drum, and shall de-energize the heating circuit on a fall in the water level to a level not less than 50 mm above the level where the topmost heating section of the highest element would be exposed above water. De-energization shall be effected by the opening of the boiler mains contactor or circuit-breaker, which shall have high reliability and be protected to minimize tampering.
(d)
The second low water safety device required by Item (b) shall be a manual reset type. NOTE : Th is device may be an inde pend ent low wat er level cont rol complying wit h Ite m (e) or overtemperature complying with Item (f).
(e)
Where the second low water safety device is an independent water level control, it shall be a float or probe type with its physical attachment to the boiler shell and its electrical circuitry and operation independent of the primary level control system.
(f)
Where the second low water protection, the overtemperature pressure-retaining parts against accordance with Item (i) or Item (i)
safety device is in the form of overtemperature safety devices or safety features used to protect the heating above their design temperature, shall be in (ii), as follows:
Where the boiler has electric elements, which will fail before any pressureretaining part is heated above its design temperature (see Note 1) for boilers with a power output exceeding 20 kW, one overtemperature safety device at least (see Notes 2 and 3) shall be fitted. Where the boiler power output exceeds 500 kW, the device shall incorporate acceptable self-checking features.
(ii)
Where the boiler has electric elements that cannot be assured of failing before any pressure-retaining part is heated above its design temperature (see Note 1) — (A)
for boilers with a po wer output not exceeding 500 kW, two overtemperature safety devices at least (see Notes 2 and 3), completely independent and having different modes of operation, or one safety device at least incorporating acceptable self-checking features shall be fitted; or
(B)
for boilers with a power output exceeding 500 kW, two overtemperature safety devices at least (see Notes 2 and 3), one of which incorporates acceptable self-checking features shall be fitted.
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NOTE S: 1
For compliance with Item (f) (i), calculations or a proof tes t should be carried out to demonstrate the acceptability of the combination of element type, size, location and capacity with the pressure-retaining parts, dimensions and material properties. Where the voltage may fall below 90 percent of rated voltage, an undervoltage lockout device should be fitted.
2
For compliance with Item (f) (i) or Item (f) (ii), one or more of the following safety devices may be used:
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(a)
Where the device is an overtemperature safety thermostat, this thermostat may make use of a thermocouple or capillary tube attached directly to the sheath of the element or of the change in electrical resistance of the element. The sensor of such overtemperature safety device is to be fitted to the uppermost element. It is desirable that this element be the first energized and the last de-energized. Alternatively, where it is desired to have cyclic step control of elements, the sensor(s) should be located and arranged to cause de-energizing of the operating element(s) and complete shutdown and lockout in the event of low water and overheating of any element.
(b)
Temperature sensors attached to the outer shell of the boiler in at least two areas where maximum temperature of the pressure-retaining parts would be expected under any failure condition.
(c)
Temperature relief safety valve located in the top space of the boiler. This relief valve should open to reduce pressure when the steam or water temperature exceeds the boiler design temperature.
Each of the overtemperature safety devices (except that in Note 2(c)) is to be able to remove supply to the element(s) by de-energizing a contactor coil or operating a trippable circuitbreaker, and each should cause complete shutdown. Where the electric elements cannot be assured of failing before the pressure retaining parts exceed their design temperature. It is desirable that the first operating overtemperature safety device de-energize the contactor coil and the other overtemperature safety device trip the circuit-breaker.
3.5.7.3 Feedwater supply
Each electric steam boiler shall be fitted with one water supply at least, which shall be capable of supplying not less than 120 percent of the equivalent water evaporation of the power output of the boiler calculated on the basis of feedwater at 100 C and at design pressure. °
3.6 ELECTRICAL POWER ISOLATION
Each boiler management system shall incorporate a main isolator or circuit-breaker which shall be capable of being locked in the open position and shall be capable of being closed only by manual means. The means of isolation shall be located in a safe and readily accessible location and shall be clearly and prominently labelled. The reset facility shall be located in the vicinity of the boiler to enable a visual inspection of the boiler system to be made, prior to reset, to establish that the operating condition that required the operation of the isolator has been corrected and the boiler is in a safe starting condition. 3.7 POWER FAILURE PROTECTION 3.7.1 Design and construction
The boiler and combustion equipment shall be designed and constructed so that loss of electric power at any time shall cause shutdown and lockout. The combustion chamber, bed or grate system shall be designed and operated to minimize the stored energy in the system upon power failure.
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3.7.2 Hazard of overheating
Where there is a hazard of overheating of pressure-retaining parts, e.g. where the combustion chamber is refractory-lined or there is a bed or grate solid-fuel firing system capable of retaining a large quantity of heat energy, the following means shall be taken to minimize the hazard: (a)
Initially, the main steam or energy outlet valve should be closed. The feedwater control valve shall be opened or bypassed.
(b)
Secondly, an auxiliary water supply shall be started to maintain the feedwater level in the boiler.
A type test, if required, shall be performed by the manufacturer in accordance with Appendix C. The results shall be made available to the designer of the boiler for review. 3.8 CONTROL EQUIPMENT
All control equipment, including wiring and control cabinets for the boiler management system shall comply with this Standard. Where programmable logic controls are used, the program software shall be verified as complying with this Standard independently of the software designer. The software program shall be in the form of a non-volatile memory module. 3.9 ALARMS ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
Each boiler shall be provided with a suitably placed alarm arranged to signal any shutdown and lockout condition. The alarm shall be of the audible type and, if required, have a visual type display. This alarm shall be well located so as to alert the operator of the shutdown or lockout condition. 3.10 VISUAL DISPLAY FOR BOILERS UP TO AND INCLUDING A POWER OUTPUT OF 500 kW 3.10.1 General
A visual display panel shall be provided to indicate the status of all critical operating and safety devices during the various phases of the operating sequence and to indicate any visual alarm (see Clause 3.9). The display shall indicate the presence of electric power to the control cabinet. 3.10.2 Fuel-fired boilers
The display shall facilitate the checking of the start-up sequence and shall indicate the operation of the following: (a)
(b)
For oil-fired, gas-fired, and solid-fuel-in-suspension-fired boilers, as follows: (i)
Main flame.
(ii)
Flame failure safety device (loss of start or main flame).
For solid-fuel-fired (bed or grate) boilers, as follows: (i)
Low draught or combustion chamber pressure safety device.
(ii)
Combustion equipment, e.g. stoker, grate or fluid bed.
3.10.3 Water level security
The visual display shall indicate the operating status of the following: (a)
For steam boilers other than forced circulation types as follows: (i)
Low water level safety device.
(ii)
Extra low water level safety device (if fitted).
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(c)
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For forced circulation type steam boilers as follows: (i)
Circulation pump.
(ii)
Water flow safety device.
(iii)
Overheat safety device.
For hot water boilers, as follows: (i)
Low water level safety device.
(ii)
Extra low water level safety device (where applicable).
(iii)
Low water level in feed tank or expansion vessel safety device.
(iv)
Water flow safety device.
3.11 VISUAL DISPLAY FOR BOILERS EXCEEDING A POWER OUTPUT OF 500 kW 3.11.1 General
A visual display panel shall be provided to indicate the status of all critical operating and safety devices during the various phases of the operating sequence and to indicate any visual alarm (see Clause 3.9). The display shall indicate the presence of electric power to the control cabinet, the initiation or energization of the start-up sequence and, where alternative fuel systems or components, such as pumps, are fitted, the system or component chosen for the operation.
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3.11.2 Fuel-fired boilers
The display shall facilitate the checking of the start-up sequence and shall indicate the operation of the following: (a)
(b)
For oil-fired, gas-fired, and solid-fuel-in-suspension-fired boilers, as follows: (i)
Combustion air-proving device.
(ii)
Spark ignition.
(iii)
Start flame.
(iv)
Low firing rate hold.
(v)
Main flame.
(vi)
Flame failure safety device (loss of start or main flame).
For solid-fuel-fired (bed or grate) boilers, as follows: (i)
Combustion and draught air fan(s).
(ii)
Low draught or combustion chamber pressure safety device.
(iii)
Combustion equipment, e.g. stoker, grate or fluid bed.
3.11.3 Water level security
The visual display shall indicate the operating status of each of the components provided for the control and supervision of the water level or water feeding, as follows: (a)
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For steam boilers other than forced circulation types, the following apply: (i)
Feed water pump.
(ii)
Low water level safety device.
(iii)
Extra low water level safety device.
(iv)
Inadequate feedwater supply (see Clause 3.5.2).
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(b)
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For forced circulation type steam boilers, the following apply: (i)
Circulation pump.
(ii)
Water flow safety device.
(iii)
Overheat safety device.
For hot water boilers, the following apply: (i)
Low water level safety device.
(ii)
Extra low water level safety device (where applicable).
(iii)
Low water level in feed tank or expansion vessel safety device.
(iv)
Water flow safety device.
3.12 COMBUSTION EQUIPMENT FOR FUEL-FIRED BOILERS 3.12.1 General
The combustion system shall comply with this Standard and shall be matched to the requirements and conditions of the boiler design, including the following:
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(a)
Type and grade of fuel.
(b)
Volume and shape of combustion chamber.
(c)
Required volume of purging air.
(d)
Intensity and distribution of heat.
(e)
Ambient temperature.
(f)
Duty cycle, particularly any stand-by conditions.
The combustion equipment shall be such that it will not produce temperatures in the boiler in excess of those for which the boiler is designed. 3.12.2 Alternative firing of main fuels
With the exception of fluidized bed combustion boilers, (see Clause 3.12.3), the combustion equipment and boiler management system may be arranged for use with an alternative main fuel provided that provision is made in the management system to prevent one main fuel from being fired simultaneously with another main fuel except as specified in Clause 3.12.4. The changeover shall be effected by manual selection which is arranged so that — (a)
the safety shut-off valve(s) for any main fuel cannot be opened while the safety shutoff valve(s) for the alternative main fuel is open; and
(b)
the burner management system ensures that purging takes place before starting the alternative main fuel.
3.12.3 Alternative firing of main fuels, fluidized bed combustion boilers
The combustion equipment and boiler management system shall be arranged so that — (a)
the required purging takes place prior to ignition of the preheating flame and bed warm-up gas;
(b)
the main preheating flame management system sense flame establishment prior to the opening of valves for introduction of bed warm-up gas;
(c)
failure to detect the preheating flame will close the preheating gas valves and bed warm-up valves; and
(d)
with preheating flame established and bed warm-up gas valves open, the boiler management system will allow introduction of solid fuel only when bed temperature reaches a minimum temperature nom inated by the designer.
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3.12.4 Supplementary fuel firing
When a supplementary fuel and a main fuel combine in the process of combustion, then the following apply:
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(a)
The supplementary fuel shall not support combustion in the boiler under its own means.
(b)
The supplementary fuel shall be extinguished if the main fuel is stopped at any particular point in the firing rate.
(c)
The main fuel shall ignite the supplementary fuel safely, reliably and smoothly.
(d)
The equipment which controls the supplementary fuel shall satisfy the same criteria as if it was a main fuel, i.e. a liquid supplementary fuel shall satisfy the requirements of oil-fired equipment and a gas supplementary fuel shall satisfy the requirements of gas-fired equipment.
(e)
The oxygen levels shall be monitored constantly while the supplementary fuel and main fuel are in combustion.
(f)
The device which monitors the oxygen levels during combustion shall incorporate internal self-diagnosis capabilities and should the device reveal internal faults, then the boiler shall go to lockout.
(g)
The combustion characteristics which satisfy that the supplementary fuel does not support combustion under its own means shall be set on the oxygen analyser or other suitable control equipment.
(h)
The mixing of the supplementary fuel with the main fuel shall not create any products of combustion which do not meet environmental standards for discharge into the environment.
(i)
Supplementary fuel shall not be introduced until the main flame is established.
(j)
The maintenance program shall include checks on the supplementary fuel interlocks and incorporate the appropriate m aintenance.
(k)
When a limited attendance boiler has provision for supplementary fuel firing, then the maintenance requirements shall be at a frequency of an unattended boiler, i.e. every five weeks.
(l)
The combustion of supplementary fuel shall not cause over-firing of the boiler.
3.12.5 Combustion characteristics
The combustion equipment shall be capable of effecting satisfactory combustion within the designated combustion chamber boundaries. In particular — (a)
ignition shall be smooth and reliable;
(b)
combustion shall be completed within the combustion chamber;
(c)
flames shall be stable and shall show no abnormality, such as floating, lifting or flashback; and
(d)
for gas burners, the CO/CO2 ratio (V/V) in the flue products shall not exceed 0.02.
NOTE: Item (d) relat es to this Standard only and does not take account of requirement s of other authorities such as gas authorities and authorities having jurisdiction over atmospheric pollution. Typical limits for carbon monoxide emission to atmosphere are that the ratio (V/V) of CO to total flue gas should not exceed 0.0002 and that the burner needs adjustment if the ratio exceeds 0.0005.
Excessive combustion noise, pulsation, and vibration should be avoided. Tests shall be carried out to verify the correct matching of the combustion system with the fuel to be used. NOTE : Fo r sol id-f uel -in-su spe nsion burn ers, the analys is and characteri sti cs of the fuel may affect the flame stability, the low firing rate and the ignition characteristics (see also Clause 3.15.4).
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3.12.6 Secure mounting
The combustion equipment shall be securely attached to the boiler in a safe manner using accepted engineering materials and methods. Where part or all of the combustion equipment is designed to be movable from its normal operating position, the following requirements shall apply: (a)
The method of mounting and locating the combustion equipment or part thereof shall be such as will prevent inadvertent movement from the operating position.
(b)
If the fuel supply requires disconnection, a means for preventing significant leakage of fuel shall be provided.
(c)
A means for preventing inadvertent start-up or continued operation in other than the intended operating position shall be provided.
3.12.7 Adverse conditions
The combustion equipment shall be installed so that it will not be adversely affected by the normal heat of operation or by residual heat from the combustion chamber after shutdown. Particular attention should be paid to the effect of such heat on any fuel that may remain within the combustion equipment and to the specified operating temperature limits for the combustion equipment and its associated components.
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Where there is a possibility that fuel retained in the combustion equipment after shut-off could be cracked or ignited by residual heat, means shall be provided for its expulsion or for heat-shielding (see Clause 5.3). 3.12.8 Visual flame-checking provisions
When combustion equipment is installed and operating, it sh all be possible — (a)
to determine safely by visual inspection whether there is a flame from the main combustion equipment or pilot; and
(b)
for maintenance or adjusting personnel to observe flame characteristics either by direct sight or by means of a remote viewing device equivalent to direct sight.
3.13 MULTIPLE-BURNER INSTALLATIONS
Each multiple-burner installation shall comply with the requirements for multiple main burners in AS 1375. 3.14 AIR SUPPLY AND CONTROL SYSTEM 3.14.1 General
The equipment for air supply shall be correctly sized and arranged to ensure that airflow and pressure are adequate for all operating and ambient conditions. 3.14.2 Air inlets
The arrangement of air inlets, ductwork and air preheaters should be such as will minimize contamination of the air supply. 3.14.3 Proportioning
The fuel-air proportioning arrangements for any main combustion equipment or pilot burner shall be such as will ensure that a stable flame and satisfactory combustion is maintained at any input rate at which the combustion equipment or pilot burner will be required to operate.
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3.15 IGNITION SYSTEM 3.15.1 Start flame or pilot ignition
A spark-ignited interrupted gas pilot for oil, gas, or solid-fuel-in-suspension burners, or a low-fire start flame for gas burners, shall be provided for each burner. For solid fuel-fired, bed or grate combustion equipment, any automatic ignition system shall comply with the requirements of Clause 5.3.4. 3.15.2 Ignition electrodes
Electrode mountings shall be designed so that the electrodes can be locked in position after the spark gap and spark location have been set. 3.15.3 High tension components
High tension insulators and high tension leads shall be made of material that is suitable for the temperature, is impervious to oil and moisture, and will resist tracking of the current and loss of ignition spark. 3.15.4 Location and fixing
Every component in the ignition and flame supervision systems shall be located and fixed so that —
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(a)
the flame detector does not indicate the presence of a start or pilot flame unless it is of the correct size and shape, and in the correct position to provide satisfactory ignition for the main burner;
(b)
the position of each component relative to another or the main flame is correctly maintained; and
(c)
the accumulation of carbon or other deposits, and the distortion, dislocation or burning of parts, is minimized.
3.15.5 Start gas rate
The start gas rate shall comply with the requirements of AS 1375 and AS 3814/AG 501 as appropriate. 3.15.6 Main burner to start at a reduced rate
Where a main flame is being ignited from a pilot, the gas rate during the main flame establishment period shall be not more than 1 MW, or the low-fire situation defined i n Clause 3.16, w hichever is the greater, unless the burner is designed specifically for sequential ignition in a multiple burner installation. 3.16 MAIN FUEL FIRING RATE 3.16.1 Low-fire rate operation
Each oil or gas burner or solid-fuel-fired combustion system above 500 kW output shall operate at a low-fire as required by Clauses 3.16.2 and 3.16.3. NOTE : Where more tha n one burner fires into a combustio n space, the tot al low-fi re start rate should relate to the total firing rate of the set of burners rather than to any individual burner. This Clause 3.16 therefore may be subject to qualifications according to the nature of the installation.
3.16.2 Low-fire interlock
The main combustion equipment of a boiler other than a forced circulation boiler shall have its heat output limited as follows:
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(a)
For a steam boiler To its lowest output until the steam pressure reaches at least 1 percent of the maximum operating pressure.
(b)
For a hot water boiler To a heat output not greater than 50 percent of its maximum heat output until the water temperature reaches 20 + 0.33( t o − 30)° C, where t o is the maximum operating temperature in d egrees Celsius.
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3.16.3 Main flame turn down and modulation 3.16.3.1 Main flame turn down
The main combustion equipment shall have a minimum turn-down ratio as follows: (a)
For an oil-fired or gas-fired boiler >500 kW, ≤1 MW............................................2:1.
(b)
For an oil-fired or gas-fired boiler >1 MW, ≤2 MW ..............................................4:1.
(c)
For boilers other than those specified in Items (a) and (b) ........ .......... ......... ......... .5:1.
3.16.3.2 Main flame modulation
The main combustion equipment shall be of the modulating type for boilers exceeding 2 MW power output. 3.16.4 Main flame firing rate
The main flame shall be established at its minimum rate and its firing rate shall not exceed the maximum rate specified by the manufacturer. The minimum firing rate or start firing rate for a solid-fuel-in-suspension fuel shall be matched to the fuel to be used, e.g. coal.
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NOTE : Coal is subject to wide vari ations in ana lys is and charact eristics. A cha nge in the percentage of volatile constituents affects the ignition characteristics of the coal and may affect the safe turndown ratio of a particular boiler design. Coals having a high volatile content, e.g. 28 percent as-fired are easier to igni te than coals having low volatile content, e.g. below 20 percent as-fired. As the volatile content decreases, the safe minimum firing rate may increase significantly. Pulverized coal fineness may also affect the safe turndown ratio. Therefore it is necessary to establish minimum firing rates and start firing rates for the range of volatile contents and fineness expected. A firing rate too low may result in gradual build-up of coke or slag on the burner tip or on the furnace floor and i s to be avoided.
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S E C T I O N 4 A D D I T I O N A L R E Q F O R O I L - F I R E D , G A S - F I R E D A F U E L - I N - S U S P E N S I ON - F I R E D U A N D L I M I T E D A T T E N D A N C E
U I R E M E N T S N D S O L I D N A T T E N D E D B O I L E R S
4.1 APPLICATION
In addition to complying with the applicable requirements in other Sections of this Standard and with Clause 4.2 and Clause 4.3, oil-fired boilers shall comply with Clause 4.4, gas-fired boilers shall comply with Clause 4.5 and solid-fuel-in-suspension-fired boilers shall comply with Clause 4.6. 4.2 OPERATIONAL REQUIREMENT S FOR OIL, GAS AND SOLID-FUEL-INSUSPENSION MANAGEMENT SYSTEMS FOR BOILERS WITH A POWER OUTPUT ABOVE 500 kW 4.2.1 Pre-start safety interlocks
The boiler management system shall prevent energy input or combustion start-up until safe start-up conditions have been established as follows:
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(a)
Electric power supply on all connected phases shall be available.
(b)
Boiler water shall be at the correct level.
(c)
Water in the feedwater tank shall be at a safe level.
(d)
Liquid fuel temperature shall be correct.
(e)
Any necessary atomizing medium shall be available at the correct pressure.
(f)
Any other necessary pre-start condition of the plant shall be established, e.g. dampers or doors correctly set, pressures or temperatures within the correct limits, auxiliaries either operating or ready to start, and the like.
4.2.2 Starting and operating sequence
A safe sequence of operations shall be provided by the control system of a boiler, and shall be in the following sequence unless otherwise approved:
©
(a)
Where appropriate, prove that the gas valves are tight (see AS 3814/AG 501).
(b)
Check that the water flow switch, where fitted, is not in the water-proven condition.
(c)
Check that the feedwater or circulating water pump as appropriate is running and water supply proven.
(d)
Check that the air-proving device is not in the air-proven condition.
(e)
Start of combustion air/purge fan.
(f)
Where full damper opening is used for pre-purge, drive damper to open position and prove, and continue to prove for complete timed purge.
(g)
Prove satisfactory air flow and continue to prove until burner shutdown.
(h)
Commence timed purge.
(i)
Finish timed purge.
(j)
Drive burner to low-fire position and prove fuel control valve or feeder is in low-fire position.
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(k)
Check integral circuitry to prove the system is not in the flame-proven condition prior to ignition.
(l)
Commence ignition spark.
(m)
Supply start gas.
(n)
Establish start flame.
(o)
Cease ignition spark.
(p)
Prove start flame and continue to prove flame until pilot shutdown.
(q)
Supply low-fire main fuel.
(r)
Establish low-fire main flame.
(s)
Where expanding flame gas burner is used, continue to prove flame; where separate pilot is used, shut down the pilot and continue to prove main flame.
(t)
Hold low-fire position for settling down period, then allow modulation when low-fire hold on steam pressure or temperature allows.
(u)
Provide continuous supervision of main flame, combustion air, and fuel conditions during the normal run period.
(v)
Controlled shutdown, including post-purge, where incorporated.
NOTE : A typ ica l firi ng sequence is ill ustrat ed i n Appendix D. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
4.2.3 Fault shutdown and lockout condition for other than forced circulation boilers
The management system of a boiler other than a forced circulation boiler shall shut down and lock out the fuel input in the event of any of t he following operating faults: (a)
Fall in water level below a predetermined level in the highest set level controller/low water device where more than one such device is fitted.
(b)
Failure of low water safety device to pass self-check test.
(c)
Inadequate air for satisfactory combustion or purging.
(d)
Incorrect pressure/temperature in the main fuel supply.
(e)
Start or main flame ignition failure.
(f)
Flame failure.
(g)
Failure of flame detector to pass self-check test.
(h)
Detection of gas leakage during any required gas valve tightness check.
(i)
Fall in the feedwater tank level below a pre-determined level.
(j)
Inadequate feedwater supply or circulating pump flow.
(k)
Phase failure.
NOTE : Co ndit ions e xternal to t he boil er may require addi tio nal shu tdow n i nte rloc ks.
4.2.4 Fault complete shutdown and lockout condition for other than forced circulation boilers
The management system of a boiler shall shut down and lockout the fuel input in the event of an extra low water fault. 4.2.5 Purging
The boiler management system shall incorporate a purge period immediately before the ignition spark period or before any other ignition source is introduced into the combustion chambers.
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NOTE S: 1
The volume of air required for purging is dependent on the needs of the application and the burner may be required to provide part of or all of the air, according to the extent to which other fans on the boiler can contribute. The purge period is therefore an applicationdependent variable.
2
Provision of a second purge period, immediately following controlled shutdown is recommended where a corrosive atmosphere is likely to remain in the boiler.
The purging system shall comply with the following requirements: (a)
Purging air shall be provided by mechanical means.
(b)
Purging shall occur automatically at the correct time(s) in the starting and operating sequence.
(c)
Where, on a multifuel burner a change from one main burner fuel to another is to be made, purging shall occur before introduction of the second fuel.
(d)
The purging air flow rate shall be as high as possible and not less than 25 percent of the maximum combustion air flow rate.
(e)
The purge period shall ensure that not less than 5 times the volume swept by the products of combustion in their flow from the burner to the boiler flue connections has been purged to the atmosphere. NOTE : Th e aut hori ty hav ing jurisdi cti on may all ow som e rel axation of thi s require ment if it is satisfied that the flow through all or part of the volume to be purged is plug flow.
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(f)
The purging air shall be circulated so that its distribution is adequate and no zone within the combustion space remains unpurged. NOTE : It can be assum ed tha t if the open spaces of a comb ust ion chamber are purged adequately, the subsequent flow passages where velocities are higher will also be purged. Therefore, in the calculation of combustion chamber volume for purging purposes, the volume should be calculated up to the first significant decrease in flow area, e.g. the entry to a bank of closely spaced tubes in a water-tube boiler or the first tube pass in a fire-tube boiler.
4.2.6 Flame simulation
If a flame simulation signal is detected at any time before the means of ignition is activated, the start-up cycle shall cease and the lockout condition shall occur. 4.2.7 Fuel admission
No fuel shall be admitted to the combustion chamber before the means of ignition has been energized. 4.2.8 Spark ignition period
The spark ignition system shall comply with the following requirements: (a)
The spark shall not commence before the completion of the purge period.
(b)
Any pre-ignition spark period shall not exceed 6 s.
(c)
The spark ignition period shall cease at the end of the start-flame establishment period.
4.2.9 Flame establishment period for spark ignition
The start-flame establishment period for any spark-ignited pilot shall not exceed 5 s. 4.2.10 Start flame proving
A proving period of not less than 3 s shall be provided at the end of any pilot or low-fire flame establishment period, prior to the opening of any main flame fuel valve.
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4.2.11 Main flame establishment period for start flame ignition
After the main fuel valve has been energized, a period not exceeding the following periods for various fuels shall be provided for main flame establishment: (a)
For oil or gas, 5 s.
(b)
For solid-fuel-in-suspension, as determined during commissioning.
NOTE : The mai n flam e e sta blishm ent period r equired for start fla me sta bility with a s oli d-fu el- insuspension system may need to be varied to suit the fuel used. The period should be as short as possible, subject to the achievement of a safe and stable ignition of the main flame.
At the end of this period, the start flame shall be turned off and only the m ain flame shall be monitored by the flame supervision system. If the main flame is not detected when the start flame is shut off, lockout shall occur. The shutting off of the flame concludes the start-up cycle. 4.2.12 Ignition failure
If the flame that is being ignited, i.e. start or main flame, has not been detected by the end of its particular flame establishment period, the fuel shall shut off within 3 s of the end of the flame establishment period and lockout shall occur. 4.2.13 Flame failure response
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In the event of flame failure during operation, the flame safeguard controller shall shut off power within 2 s and lockout shall occur. A period of 3 s shall be allowed to include the combined time for the responses of the flame supervision system and the closing of its associated valves. 4.2.14 Controlled shutdown
The shutdown procedure for controlled shutdown shall leave the fuel and control equipment in a safe condition and shall be in the following sequence: (a)
Shut off the fuel supply.
(b)
Operate any post-purge system.
(c)
Shut down any other systems or controls as necessitated by the nature of the shutdown signal.
(d)
Signal any appliance function to assume the shutdown position, e.g. flue dampers.
NOTE : It is importa nt tha t an adequat e supp ly of comb ust ion air be mai ntained whi le the las t of the fuel is being cleared from the burner.
4.3 OPERATIONAL REQUIREMENT S FOR OIL, GAS AND SOLID-FUEL-INSUSPENSION MANAGEMENT SYSTEMS FOR BOILERS UP TO AND INCLUDING A POWER OUTPUT OF 500 kW 4.3.1 Pre-start safety interlocks
The boiler management system shall prevent energy input or combustion start-up until safe start-up conditions have been established as follows: (a)
Boiler water shall be at the correct level.
(b)
Liquid fuel temperature shall be correct.
(c)
Any necessary atomizing medium shall be available at the correct pressure.
(d)
Any other necessary pre-start condition of the plant shall be established, e.g. dampers or doors correctly set, pressures or temperatures within the correct limits, auxiliaries either operating or ready to start, and the like.
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4.3.2 Starting and operating sequence
A safe sequence of operations shall be provided by the control system of a boiler, and shall be in the following sequence unless otherwise approved:
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(a)
Check that the water flow switch, where fitted, is not in the water-proven condition.
(b)
Check that the feedwater or circulating water pump as appropriate is running and water supply proven.
(c)
Check that the air-proving device is not in the air-proven condition.
(d)
Start of combustion air/purge fan.
(e)
Where full damper opening is used for pre-purge, drive damper to open position and prove, and continue to prove for complete timed purge.
(f)
Prove satisfactory air flow and continue to prove until burner shutdown.
(g)
Commence timed purge.
(h)
Finish timed purge.
(i)
Check integral circuitry to prove the system is not in the flame-proven condition prior to ignition.
(j)
Commence ignition spark.
(k)
Supply start gas.
(l)
Establish start flame.
(m)
Cease ignition spark.
(n)
Prove start flame and continue to prove flame until pilot shutdown.
(o)
Supply main flame.
(p)
Where expanding flame gas burner is used, continue to prove flame; where separate pilot is used, shut down the pilot and continue to prove main flame.
(q)
Provide continuous supervision of main flame, combustion air, and fuel conditions during the normal run period.
(r)
Controlled shutdown, including post-purge, where incorporated.
4.3.3 Fault shutdown and lockout condition for other than forced circulation boilers
The management system of a boiler other than a forced circulation boiler shall shut down and lock out the fuel input in the event of any of t he following operating faults: (a)
Fall in water level below a predetermined level in the highest set level controller/low water device where more than one such device is fitted.
(b)
Inadequate air for satisfactory combustion or purging.
(c)
Incorrect pressure/temperature in the main fuel supply.
(d)
Start or main flame ignition failure.
(e)
Flame failure.
(f)
Inadequate feedwater supply or circulating pump flow.
NOTE : Co ndit ions e xternal to t he boiler may require addi tional shutdown and lockout int erlo cks.
4.3.4 Flame simulation
If a flame simulation signal is detected at any time before the means of ignition is activated, the start-up cycle shall cease and lockout shall occur.
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4.3.5 Fuel admission
No fuel shall be admitted to the combustion chamber before the means of ignition has been energized. 4.3.6 Spark ignition period
The spark ignition system shall comply with the following requirements: (a)
The spark shall not commence before the completion of the purge period.
(b)
Any pre-ignition spark period shall not exceed 6 s.
(c)
The spark ignition period shall cease at the end of the start-flame establishment period.
4.3.7 Flame establishment period for spark ignition
The start-flame establishment period for any spark-ignited pilot shall not exceed 5 s. 4.3.8 Start flame proving
A proving period of not less than 3 s shall be provided at the end of any pilot or low-fire flame establishment period, prior to the opening of any main flame fuel valve. 4.3.9 Main flame establishment period for start flame ignition
After the main fuel valve has been energized, a period not exceeding the following periods for various fuels shall be provided for main flame establishment: ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
(a)
For oil or gas, 5 s.
(b)
For solid-fuel-in-suspension, as determined during commissioning.
NOTE : The mai n flam e e sta blishm ent period r equired for start fla me sta bility with a s oli d-fu el- insuspension system may need to be varied to suit the fuel used. The period should be as short as possible, subject to the achievement of a safe and stable ignition of the main flame.
At the end of this period, the start flame shall be turned off and only the m ain flame shall be monitored by the flame supervision system. If the main flame is not detected when the start flame is shut off, lockout shall occur. The shutting off of the flame concludes the start-up cycle. 4.3.10 Ignition failure
If the flame that is being ignited, i.e. start or main flame, has not been detected by the end of its particular flame establishment period, the fuel shall shut off within 3 s of the end of the flame establishment period and lockout shall occur. 4.3.11 Flame failure response
In the event of flame failure during operation, the flame safeguard controller shall shut off power within 2 s and lockout shall occur. A period of 3 s shall be allowed to include the combined time for the responses of the flame supervision system and the closing of its associated valves. 4.3.12 Controlled shutdown
The shutdown procedure for controlled shutdown shall leave the fuel and control equipment in a safe condition and shall be in the following sequence: (a)
Shut off the fuel supply.
(b)
Operate any post-purge system.
(c)
Shut down any other systems or controls as necessitated by the nature of the shutdown signal.
(d)
Signal any appliance function to assume the shutdown position, e.g. flue dampers.
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4.4 SPECIFIC REQUIREMENTS FOR OIL-FIRED BOILERS 4.4.1 Oil fuel pretreatment
Any system for the pretreatment or preparation of oil fuel that may be incorporated in the burner shall comply with the relevant requirements of AS 1940. 4.4.2 Gas pilot
Each gas pilot on an oil burner shall comply with the requirements of AS 3814/AG 501 and AS 5601/AG 601. 4.4.3 Controls and safety devices
The automatic oil burner shall be fitted with t he following controls and safety devices:
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(a)
Automatic means for ensuring temperature and pressure of the oil is within the operating range specified for the burner.
(b)
Two power-operated fuel shut-off valves of the fail-safe, spring close, power open type shall be fitted in series.
(c)
Fuel flow-rate control valve or fixed orifice.
(d)
Where gas pilot ignition is employed, two gas pilot safety shut-off valves shall be fitted in series.
(e)
Oil filter of sufficient free filtering area to permit operation at the maximum firing rate (see Note 2).
(f)
Fuel pump, which, if required to draw oil from a lower level tank, should be capable of applying a minimum suction to suit the installation. For light oil systems, the fuel pump shall operate only when the combustion fan is in operation.
(g)
Excess-pressure-relief valve. NOTE S: 1 Typical oil supply and control systems are illustrated in schematic form in Appendix E. 2 Detailed requirements f or filters are given in BS 799: Part 4, and should be read in conjunction with AS 1853, which provides information on the filtration of oil fuels. 3 The valve in Item (g) may be the same valve as that provided in compliance with Item (a).
4.4.4 Fuel bypass valve
Each oil supply system shall include a bypass power-closing valve connected between the delivery side and the suction side of the burner pump so that, when the main burner fuel valves are shut, the bypass valve shall be open thereby minimizing the oil pressure to the main burner fuel valves. The bypass valve shall remain fully open throughout pre-purge or post-purge periods of cycles. 4.4.5 Steam air-atomized burners
Where a steam/air-atomized burner is used, a suitable atomizing steam/air pressure interlock shall be fitted in the system. 4.4.6 Fuel oil installation
The fuel oil installation shall be designed and arranged so that fuel shall not be able to gravitate to the burner. 4.5 SPECIFIC REQUIREMENT S FOR GAS-FIRED BOILERS
The gas system AS 5601/AG 601.
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4.6 SPECIFIC BOILERS
REQUIRE MENTS
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AS 2593 — 2 004
SOLID-FUEL-IN-S USPENSION-FIRED
4.6.1 General
Guidance for the design and operation of solid-fuel-in-suspension firing and handling systems may be found in ANSI/NFPA 8502 and ANSI/NFPA 8503. 4.6.2 Controls and safety devices
The automatic solid-fuel-in-suspension firing system shall be fitted with the following controls and safety devices:
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(a)
Automatic means to ensure correct primary air supply.
(b)
Loss-of-fuel interlock. One device at least, which will activate on loss of fuel, shall be fitted.
(c)
A combination of such devices is preferred.
(d)
Raw fuel feeder isolation system.
(e)
If the system includes a pulverizer, the pulverizer to have failure interlock.
(f)
Two start or pilot burner safety shut-off valves fitted in series.
(g)
Primary air flow interlock.
(h)
Primary air flow control damper.
(i)
Means of venting the primary air and solid-fuel-in-suspension stream to a safe container on lockout or normal shutdown of the solid fuel feed system.
4.6.3 Valve and piping arrangement
The valve and piping arrangement shall — (a)
be such as to prevent the hazardous accumulation of fuel within the system;
(b)
provide a positive direction of flow, flow rate, and velocity of the transport medium to avoid fuel deposition within the piping system;
(c)
provide sufficient access points for the clearing of all fuel lines;
(d)
provide dust-tight safety shut-off (barrier) valves at each burner inlet and at the pulverizer outlet;
(e)
provide a positive means of isolating the transport medium;
(f)
be designed to withstand an internal explosion of 4.4 times the absolute operating pressure;
(g)
employ long radius bends and have a smooth flow path; and
(h)
be adequately supported to allow for any vibration and the combined stresses in the system.
4.6.4 Fuel quality
The fuel type and characteristics shall be specified by t he manufacturer as being suitable for the equipment supplied. The fuel shall be of reasonably uniform quality and of appropriate particle size distribution for the firing equipment and the automatically controlled combustion system. The fuel grading should be in accordance with the manufacturer ’s recommendation for the combustion system.
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S E C T I O N 5 A D D I F O R S O L I D - F U E L U N A T T E N DE D O R B
36
T I O N A L R E Q U I R E M E N T S F I R E D ( B E D O R G R A T E ) L I M I T E D A T T E N D A NC E O I L E R S
5.1 APPLICATION
In addition to complying with the applicable requirements in other Sections of this Standard, solid-fuel-fired (bed or grate) boilers shall comply with Clauses 5.2 and 5.3. 5.2 OPERATIONAL REQUIREMENT S FOR SOLID FUEL (BED OR GRATE) MANAGEMENT SYSTEMS 5.2.1 Pre-start interlocks
The boiler management system shall prevent combustion start-up until safe start-up conditions have been established including the following:
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(a)
Electric power supply on all connected phases shall be available.
(b)
Boiler water shall be at the correct level.
(c)
Water in the feedwater tank shall be at the correct level.
(d)
Fuel supply system shall be in the start position.
(e)
All other necessary pre-start conditions of the plant shall be established, e.g. dampers or doors correctly set, pressures or temperatures within the correct limits, and auxiliaries either operating or ready to start.
NOTE : The pre- sta rt checks of the plant may be carried out by the oper ator whe re the ini tial s tart up is to be controlled by an operator.
5.2.2 Start-up
A safe sequence for start-up shall be provided by the control system, an operator or a combination of automatic and operator control and shall be in the following sequence unless otherwise approved: (a)
Purge boiler, where required by Clause 4.2.5.
(b)
Start ignition fire.
(c)
Check initial ignition establishment.
(d)
Start air supply system.
(e)
Check that combustion air flow has been established.
(f)
Start fuel input at low-fire rate.
(g)
Check combustion for ignition stability.
(h)
Supervise firing until start-up complete.
(i)
Change control to fully automatic control.
The time interval for each stage of start-up shall ensure safe operation. 5.2.3 Controlled shutdown
The shutdown procedure for controlled shutdown shall leave the fuel and control equipment in a safe condition and shall occur in the following sequence:
©
(a)
Shut off the fuel input and combustion system, e.g. stoker.
(b)
Shut down the air supply system fans.
(c)
Shut down other systems or controls, as necessary.
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5.2.4 Fault shutdown and lockout
The boiler management system shall shut down and lockout the combustion system, the fuel input and the draught system in the event of any of the following operational faults occurring: (a)
Fall in boiler water level below a predetermined level in the low water safety device.
(b)
Fall in boiler water level below a predetermined level in the extra-low water safety device, where fitted.
(c)
Fall in feedwater tank level.
(d)
Inadequate circulating pump pressure or flow (water heating boilers).
(e)
Inadequate air for satisfactory combustion or purging.
NOTE : Co ndit ions e xternal to t he boiler may require addi tional shutdown and lockout int erlo cks.
5.2.5 Purging
Where there is a possibility of accumulation of explosive gas or vapour, e.g. from interconnected boilers, the requirements for purging in Clause 4.2.5 shall be incorporated into the boiler management system. 5.3 SPECIFIC REQUIREMENTS FOR SOLID-FUEL-FIRED (BED OR GRATE) BOILERS ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
5.3.1 General
Each component used in a solid-fuel-fired (bed or gate) boiler shall be designed and constructed so as to prevent a hazardous condition arising. 5.3.2 Fuel quality
The fuel type and characteristics shall be specified by t he manufacturer as being suitable for the equipment supplied. The fuel shall be of reasonably uniform quality and of appropriate particle size distribution for the firing equipment and the automatically controlled combustion system. The fuel grading should be in accordance with the manufacturer ’s recommendation. 5.3.3 Combustion equipment
The fuel shall be burnt on a grate, hearth or fluidized bed. The equipment shall be designed to minimize the formation of clinker. 5.3.4 Ignition of bed fuel
Where ignition of the bed of a solid-fuel-fired combustion system is by automatic means, the automatic pilot ignition system shall comply with the relevant requirements in Sections 3 and 4 for a gas pilot or a low -fire gas start flame system. Where ignition of the bed is by manual means, the operator shall ensure that the combustion of the main fuel is stable before starting the supply of the main fuel to the bed or grate. The bed warm-up gas of a fluidized bed system shall comply with the relevant requirements for a low-fire gas start flame system (see Clauses 3.12.3 and 3.15). 5.3.5 Controls and safety devices
Each automatic solid-fuel-fired system shall be fitted with the following controls and safety devices: (a)
Automatic means of regulating the flow of fuel to the bed, grate or hearth.
(b)
Automatic means to stop the supply of fuel to the combustion equipment.
(c)
Start flame burner shut-off valve.
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5.3.6 Burn-back protection
The fuel feeding system of each solid-fuel-fired boiler shall be designed to prevent burnback in the bun ker in accordance with AS 3892. This shall be achieved by one of the following methods: (a)
The fuel-feeding system shall be provided with two independent steam, water or other fire-extinguishing fluid spray systems, independent of the boiler management system, fitted in the fuel feeder or chute to extinguish any fire caused by a burn-back of the fuel. The sprays shall be automatically controlled by thermostats to operate upon temperature rise in the fuel feeder, chute or hopper.
(b)
The fuel supply chute or duct shall have an air break between the bunker and the combustion equipment hopper which will prevent a burn-back into the fuel storage bunker.
(c)
Means shall be provided to isolate the fuel feed in the event of an emergency arising. NOTE : The i solati ng devi ce sho uld be a s clos e as pr act icable to t he c ombust ion equi pment.
(d)
Other acceptable methods, see Clause 1.3.1.
5.3.7 Power failure protection 5.3.7.1 General
The boiler shall comply with the relevant requirements of Clauses 3.7 and 5.3.7.2. 5.3.7.2 Draught safety device
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A damper that automatically closes on loss of electric power or fault shutdown (see Clause 5.2.4) shall be fitted to the air supply. 5.3.8 Solid fuel and residue handling plant
The solid fuel and ash handling, storage and dust collection equipment for each boiler shall be in accordance with AS 3892.
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S E C T I O N 6 C H E C K I N G , T E S T I N G A N D M A I N T E N A N C E F O R U N A T T E N D E D A N D L I M I T E D A T T E N D A N C E B O I L E R S 6.1 GENERAL
The continued safety and reliability of an unattended or limited attendance boiler during its operation is directly dependent on the regularity and quality of the checking, testing and maintenance carried out on the boiler. The checking, testing and maintenance of each unattended or limited attendance boiler shall comply with this Section. 6.2 ORGANIZATION AND PERSONNEL
The contractor and the owner, where maintenance is carried out by the owner, shall be qualified and experienced in all facets of the boiler and its combustion equipment controls and safety systems. The persons who carry out the testing and maintenance shall be thoroughly familiar with all operating procedures and equipment functions and shall be capable of rendering sound judgement on whether the equipment is in a reliable operating condition. NOTE : Or ganizations and pers onne l who carry out tes tin g and mai nte nance should have qualifications and experience in accordance with Appendix B. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
6.3 RESPONSIBILITIES CHECKING, TESTING AND MAINTENANCE 6.3.1 Program and procedures
Procedures to ensure reliability and maximum safety conditions of the boiler shall include, appropriate to the attendance status, the checking, testing and maintenance requirements specified in Clauses 6.4, 6.5 and 6.6, and shall include the following: (a)
Limited attendance checking in accordance with Clause 6.4.1.
(b)
Daily checking of each boiler in accordance with Clause 6.4.2.
(c)
Weekly checking of each boiler in accordance with Clause 6.4.3.
(d)
Periodic testing and maintenance of each boiler in accordance with Clause 6.4.4.
(e)
Yearly inspection, maintenance and testing of each boiler in accordance with Clause 6.5.2.
NOTE S: 1
During initial operation of the boiler, more frequent checking, adjusting, cleaning, and the like, will be required.
2
For stand-by boilers, emergency boilers and other boilers subject to periods of non-operation, the program is to include provision for the frequency of checking, testing and maintenance to be varied.
6.3.2 Periodic and yearly testing and maintenance
Periodic and yearly testing and maintenance shall be performed by the contractor under a maintenance contract (see Clause 6.7) or by the owner. 6.4 CHECKING AND TESTING 6.4.1 Intermediate checking—limited attendance operation
In order to meet the requirements of Table 1, the supervision of this type of attendance shall — (a)
ensure the boiler is still operating correctly;
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(b)
examine all glands, flanges and connections to ensure that there is no substantial leaks; and
(c)
examine all locks and seals to ensure that there has been no unauthorized tampering.
6.4.2 Daily checking — unattended and limited attendance operation
The daily checking shall include the following: (a)
Visually check operation of the water level controls on steam boilers.
(b)
Test boiler water for the levels of total dissolved solids.
(c)
Check operation of each automatic blowdown system, where appropriate.
(d)
Examine all glands, flanges and connections to ensure that there are no substantial leaks.
(e)
Examine all locks and seals to ensure that there has been no unauthorized tampering.
(f)
Blow down water gauge glasses and check for correct water level all in accordance with AS 3873, where appropriate.
(g)
For boilers other than water-heating boilers, blow down any external water level safety device and check operation interlock.
Where the daily checking reveals the need for maintenance or adjustment, such maintenance shall be carried out as soon as practicable in general in accordance with Clause 6.5.1.
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6.4.3 Weekly checking — unattended and limited attendance operation
In conjunction with the daily checking procedure (see Clause 6.4.2), additional checks shall be made at regular intervals not exceeding seven days and s hall include the following: (a)
Check operation of flame failure detection system to shutdown energy input and boiler in correct order.
(b)
For each boiler other than water-heating boilers, operate intermittent (manual) blowdown while the boiler is off-line. NOTE : Wa terw all headers sho uld only be blow n d own whi le the boil er is off -li ne.
(c)
For boilers other than water-heating boilers, blow down any external water level safety device and check operation of interlock.
(d)
Reset any manual reset interlocks, check water level in gauge glasses and restart boiler.
(e)
Check start-up sequence and visual sequence indicator operation.
(f)
Check that all management systems are operating, all valves are correctly set and water level is correct before leaving boiler.
(g)
Check that feedwater pump operating sequence has changed in accordance with Clause 3.5.3.3.
(h)
For hot water boilers incorporating a pressurized expansion system, check that the system is functioning correctly and check levels in the expansion system are in accordance with the manufacturer ’s recommendations.
6.4.4 Periodic testing
Periodic testing of the boiler operating and safety systems, in addition to daily and weekly checking, shall be carried out at intervals not exceeding the applicable period given in Table 1.
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The procedure shall include the following checks: (a)
Lower the boiler water level to check the operation of the low water and extra low water devices.
(b)
Check the operation of fan and airflow interlocks.
(c)
Check safety shut-off valve(s) for leakage.
(d)
Check fire start interlock.
(e)
Check steam pressure interlock.
(f)
For oil: check fuel pressure and temperature interlocks.
(g)
For gas: check main gas filter, and high and low fuel pressure interlocks.
(h)
Clean and check fuel filters.
(i)
Clean and check water filters.
(j)
In areas with hard or contaminated water, check the effectiveness of the water treatment. NOTE : I n ot her area s, thi s c heck ing may tak e place every three or s ix months .
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(k)
Check combustion efficiency and flue gas analysis through the normal operating range.
(l)
Check flame failure detection system whilst boiler is operational to shutdown the energy input and the boiler in a correct sequence, then clean the flame detection sensors.
(m)
Other examinations and tests as required by the contractor or authority having jurisdiction.
The following information shall be recorded at the time of testing: (i)
Date and times of arrival and departure of the person performing the testing.
(ii)
Each test and examination performed and the results thereof prior to any adjustment or maintenance work.
(iii)
Particulars of any malfunction.
(iv)
Details of maintenance work required, if outside the scope of the maintenance contract.
(v)
The name of the person performing the testing.
6.4.5 Changes to procedures
Where the testing reveals the need to change the maintenance procedures or equipment adjustment, appropriate changes shall be made in the procedures specified in Clause 6.3.1 and, where relevant, to the maintenance contract (see Clause 6.7). 6.4.6 Log
All the checks prescribed in Table 1 shall be recorded in a suitable log . The log shall contain — (a)
date and time of checking;
(b)
each check and examination and its results;
(c)
the printed and signed name of the person who performed the checks;
(d)
the date and time of any lockout or equipment malfunction;
(e)
results of tests on boiler or feed water; and
(f)
changes in operation.
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6.5 MAINTENANCE 6.5.1 Periodic maintenance
Where maintenance that is not specifically covered in the maintenance procedure is required, such maintenance shall be carried out as soon as practicable, account being taken of the safety of the boiler. Where any doubt exists as to the safety of the boiler system because of the need for maintenance, the boiler shall not be re-started until such maintenance has been completed. 6.5.2 Yearly maintenance
At least once per year, the boiler and its operating and safety systems shall be thoroughly checked and overhauled in accordance with the procedure for annual maintenance specified in Clause 6.3.1. The procedure shall include the inspection of all pressure parts, valves and fittings, and the following:
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(a)
Open boiler for periodic inspection as required by AS/NZS 3788, when appropriate.
(b)
Clean and examine boiler internally (where appropriate to the type of vessel) for scale or corrosion (forced circulation boilers normally cannot be inspected internally).
(c)
Clean and test every interlock and safety system.
(d)
Check electric equipment and wiring.
(e)
Check all instruments.
(f)
Start-up and check operation of all components for — (i)
correct operation and sequence;
(ii)
leaks or loose connections; and
(iii)
correct calibration and adjustment.
6.5.3 Records
All maintenance work on the boiler and its systems shall be recorded as follows: (a)
The names of the persons and organizations performing the maintenance and testing and the work date where required by relevant Standards and regulations.
(b)
Details of any maintenance work performed in conjunction with daily or periodic testing shall be recorded on the documentation for the relevant testing.
(c)
Details of yearly maintenance, or any additional maintenance shall be recorded in a separate report.
(d)
Particulars of any malfunction.
6.6 RETENTION OF RECORDS
Records of all testing shall be retained by the owner for a period of not less than 18 months. Records for all maintenance, repairs and conversions shall be retained for the operating life of the boiler. Such records shall be made available for maintenance purposes. 6.7 MAINTENANC E CONTRACT
The maintenance contract shall include the f ollowing:
©
(a)
The periodic testing of the boiler as specified in Clause 6.4.4.
(b)
The maintenance of the boiler as specified in Clause 6.5.
(c)
Any other maintenance specifically detailed on the maintenance contract.
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(d)
Specific details pertaining to the contract, e.g. contract period and supply of replacement parts.
(e)
Determination of agreed times to allow the maintenance requirements of Table 1 to be met.
(f)
Supply of records in accordance with Clause 6.5.3.
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S E C T I O N
7
A T T E N D E D
B O I L E R S
7.1 GENERAL
Boilers exceeding the limits for limited attendance or unattended operation for the boiler type in Table 1, and all boilers that do not include the special features within the control, management and supervision requirements of this Standard for limited attendance or unattended operation, shall be regarded as attended boilers. In addition, boilers that have not had an appropriate attendance-category certificate of compliance issued in accordance with Clause 10.5 for either unattended or limited attendance operation shall be regarded as fully attended boilers. 7.2 MANAGEMENT SYSTEM
Each boiler shall be equipped with a manual or automatic management system which consists of controls, safety devices, instruments and indicating devices sufficient to enable safe operation of all functions of the boiler combustion (including air supply and flue gas exhaust) or energy input, water level security and pressure or temperature regulation. Such controls may be manual or automatic, or both. The management system may be fitted as part of the installation, i.e. site fitted, or it may be fitted to the boiler prior to delivery. The boiler management system shall comply with this Clause, Clauses 7.3 or 7.4, as appropriate, and with the relevant requirements of Clauses 7.5 and 7.6.
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7.3 MANUAL OPERATION
Where a control function is to be operated manually, the boiler management equipment shall provide the operator w ith adequate facilities for the control and operation of the boiler in accordance with the relevant procedures set out in AS 3814/AG 501, AS 5601/AG 601 or AS 1375. 7.4 AUTOMATIC OPERATION 7.4.1 General
Where the boiler is intended to be automatically operated, the boiler management system shall embody the necessary interlocks and alarms to provide a safe integration with the energy input and water level management systems required in Clause 7.2 and this Section (7). The management system and operating procedures for other than electric boilers shall comply with AS 3814/AG 501, AS 5601/AG 601 or AS 1375. Each boiler shall be equipped with sufficient indicating devices necessary for the safe operation and supervision by certificated boiler attendant. 7.4.2 Automatic water level management
Each boiler, with an automatically-controlled energy input system, shall be fitted with an automatically-controlled water feeding system. 7.4.3 Alarms
Each boiler shall be fitted with a water level system which activates an audible alarm should the water fall below a pre-determined level. The alarm shall sound while the water level is still visible in the water gauge glass. If a visual alarm is fitted, the audible alarm may be of a manually-muted type which self-resets on restoration of the water level. A high level alarm may be required, depending on the nature of the installation. The audible alarm shall be located in a position where it can be heard by the person in charge of the boiler. ©
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7.4.4 Controls and boiler mountings
In addition to the safety valves, water level gauges, pressure gauges, blowdown valves and other thermal controls, attended automatic boilers shall have at least the following: (a)
One low-water cut-out and alarm.
(b)
Automatic feedwater control.
(c)
One safety valve on the outlet side any superheater.
7.5 LOW-WATER CUT-OUT AND ALARM
One independent low-water cut-out and alarm shall be fitted to the drum or shell. On a lowwater condition, the heat source shall be cut off and an audible and visual alarm activated. The cut-out shall be of the lock-out type requiring manual resetting. This does not apply to once-through coil boilers where a steam drum is not fitted. The low-water cut-out and alarm shall be set to actuate while the water level is still visible in the water level gauges. 7.6 WATERFEED CONTROL 7.6.1 General
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Automatic water level controls shall be so arranged that they positively control the boiler feed pumps or regulate the water supply to the boilers and effectively maintain the level of water in the boiler between certain predetermined limits set by the boiler manufacturer. 7.6.2 Modulating water control
Modulating water level controls are required for boilers of 3 MW output and above. 7.7 OPERATIONAL SUPERVISION
An attended boiler shall be attended by an appropriately certificated boiler attendant at all times that it is being operated. The owner shall ensure that there are no aspects of the boiler attendant ’s duties which will impede their supervision and checking of the boiler, including start-up, shutdown and periodic testing. The duties of the attendant shall be such that they are at all times within hearing distance of the boiler's alarm systems and can respond to any alarm(s) within a reasonable period of time which does not endanger the boiler or persons working within the vicinit y. 7.8
TESTING AND CHECKING PROGRAMS
7.8.1 General
Testing and checking programs shall comply with AS 3873. A certificated boiler attendant shall carry out routine operation tests and observations on at least a daily basis. 7.8.2 Checks
The extent of checking specified in the instructions shall be in accordance with the service manual and owner and user’s requirement in addition to any regulatory requirements or applicable Standard. Basic regular checks shall include, where appropriate — (a)
the blowing down of the water gauge glasses; and
(b)
the operation of any water-level security equipment, i.e. a low water device.
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The following additional checks should be included: (i)
Check start-up and shutdown for correct sequences (automatic boilers).
(ii)
Check operation of flame failure detection system for automatic shutdown.
(iii)
Examine all glands, flanges and connections to ensure that no substantial leaks have occurred.
(iv)
Examine all locks and seals to ensure that no unauthorized tampering has occurred.
Where the checking reveals the need for maintenance or adjustment, such maintenance shall be carried out as soon as practicable, account being taken of the safety of the boiler. 7.8.3 Log
A log shall be kept. Typically, this should include the following:
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(a)
Date and time of check.
(b)
Each check, examination and observation.
(c)
Any abnormalities in operation.
(d)
The name of the person performing the checking.
(e)
Results of tests on boiler or feedwater.
(f)
Changes in operation.
7.9 PROGRAMMABLE LOGIC CONTROLLER (PLC) MANAGEMENT SYSTEMS
Where programmable logic controls are used, the program software shall be verified as complying with this Standard independently of the software designer. The software program shall be in the form of a non-volatile memory module. 7.10 NOTICES
Suitable notices shall be displayed at the boiler or boiler control station giving instructions on periodic testing, internal cleaning, and maintenance of controls. In conjunction with the notices a logbook, as detailed AS 3873, shall be retained. The logbook shall be lodged securely near the boiler to record the required maintenance when and by whom this maintenance was performed. The notices shall also include the following note: AUTOMATIC CONTROLS AND EQUIPM ENT ARE CAP ABLE OF MAINTAINING THE REQUIRED WATER LEVELS, FIRING RATES AND SIMILAR CONDITIONS, BUT IT SHOULD BE NOTED THAT AUTOMATIC CONTROLS REQUIRE REGULAR MAINTENANCE BY COMPETENT PERSONNEL DEPENDING LARGELY ON THE QUALITY OF THE BOILER WATER. WHERE THIS QUALITY MAY SERIOUSLY AFFECT THE AUTOMATIC CONTROLS, FEE DWATER TR EATM ENT IS ESS ENTI AL.
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S E C T I O N 8 W A T E R L E V E L M A N A G E M E NT A N D S E C U R I T Y F O R A L L T Y P E S O F B O I L E R S 8.1 WATER LEVEL DEVICES AND INTERLOCKS 8.1.1 General
The water management, i.e. control sequencing, interlocks and instrumentation of each boiler (other than a main boiler in a power station), shall comply with this Section. 8.1.2 Electrical requirements
Electrical requirements shall comply with Clause 9.7 and the wiring shall be arranged so as to permit inspection and maintenance of each level device. 8.2 WATER LEVEL INDICATORS 8.2.1 Number and type
The number, type and installation of water level indicators shall comply with the following requirements provided that for main boilers in power stations, or process boilers with similar automated boiler control systems, some other arrangement suitable for the intended duty may be used (see Note): ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
NOTE : Ag ree ment betwee n relevant part ies , e.g . man ufacturer, purc haser, ins pecting authori ty, on the proposed water level indicators would usually be required.
(a)
Each boiler, except a once-through type and electric heater type, shall be fitted with at least one water gauge directly connected to the drum at the water level and of a type which makes the water level directly visible. Such a gauge will normally be one of three types: (i)
Tubular glass type (maximum operating pressure 2.5 MPa).
(ii)
Through-vision or reflex type embodying continuous flat plates.
(iii)
Through-vision type having a number of independent circular ports. NOTE :Where prac ticable, the visibil ity of thi s gauge should not be obst ructed othe r than by equipment permitted in Item (e).
(b)
Each boiler other than one electrically heated with a power output of 100 kW or more shall in addition to the requirements of Item (a) have either — (i)
another gauge similar to that required in Item (a); or
(ii)
two independent remote water level indicators each having its own independent connections to the drum.
(c)
Each direct reading water gauge shall be placed so as to be readily accessible and so located that the water level is clearly visible from a safe and accessible location.
(d)
When the water level in the gauge glass is not readily visible from the normal operating position, two dependable indirect indications shall be provided by transmission of the gauge glass image, e.g. mirrors, closed circuit TV, or by remote level indicators. The two methods need not be identical, e.g. one mirror system and one manometric gauge in an acceptable arrangement.
(e)
Each electric boiler, having an internal volume exceeding 150 L or a power output exceeding 100 kW, shall be equipped with at least one water gauge glass and each electric boiler having a power output exceeding 2 MW shall be equipped with at least two water gauge glasses.
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NOTE S: 1
Any boiler other than one electrically heated of less than 100 kW power output may, in lieu of the requirements of Item (b), be provided with at least two test cocks fitted directly to the drum or shell and located within the range of the visible length of the gauge.
2
Small boilers or closed heating units, where the steam is generated within the unit using it, or where the heating unit is connected direct to the boiler without any shut-off valves between heating unit and boiler, and where there is no other steam connection from the boiler, may be fitted with one glass water gauge or two test cocks placed in positions acceptable to the inspector.
3
Boilers using media other than water and operating in a closed circuit system may be fitted with only one gauge glass.
4
Boilers may be fitted with two independent remote water level indicators of the compensated manometric type, with each having its own independent connection to the boiler, in place of one of the two glass water gauges otherwise required.
8.2.2 Length of gauge glass on boilers other than water-tube type
The minimum visible length of the gauge glass used on boilers shall be as given in Table 2. For a water-tube boiler other than a once-through type, the visible length of the gauge glass shall be not less than the g reater of —
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(a)
150 mm; and
(b)
one-half the inside diameter of the drum or 300 mm, whichever is less. TABLE 2 MINIMUM VISIBLE LENGTH OF GAUGE GLASS FOR BOILERS OTHER THAN WATER-TUBE BOILERS Type of boiler
Size of boiler mm
Horizontal
Vertical
Diameter
> 600 ≤ 900
Minimum visible length of gauge glass mm 150
Diameter > 900
200
Height ≤2 000
200
Height
300
>2
000
8.2.3 Glass diameter
The diameter of any tubular glass water gauge shall comply with AS 1271. 8.2.4 Visibility and accessibility
Each glass water gauge shall be so placed as to be readily accessible and so located that the water level is clearly visible from a safe and accessible location. 8.2.5 Drains
A drain cock or valve and pipe shall be fitted to each water gauge. The drain shall lead the discharge clear of all places where it would be likely to cause a hazard to personnel. The discharge should be visible to the operator. 8.2.6 Guards
All tubular glass water gauges shall be adequately guarded so as not to cause a hazard to personnel near the operating area. Guards shall not detract from the required visibility of the gauge glass.
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8.2.7 Water level gauge connections and location 8.2.7.1 General
Water level gauges may be fitted direct to the shell or end of a boiler or be connected to the boiler by extended pipes. Connections shall be arranged so that an accurate water level is indicated. Water level gauges shall not be fitted to chambers used for any control or alarm fitting. 8.2.7.2 Hollow support connections
Where a boiler is fitted with hollow support tubes for the gauge glasses, the following requirements shall be met: (a)
The boiler operating pressure and output shall be not less than 3.5 MPa and 20 MW, respectively.
(b)
The nominal inside diameter of the support tube shall not exceed 40 mm.
(c)
A valve shall be fitted between the boiler and the support tube and also between the support tube and the water gauge, on both legs as shown in Fig ure 1.
NOTE : The man ufactu rer to supply a cle arly wri tte n correct proc edur e for blowdown and gau ge checking.
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NOTE: A t empera ture e qual izi ng val ve is usuall y only fit ted on h igh pre ssu re boiler s.
FIGURE 1
TYPICAL VALVE ARRANGEMENT FOR HOLLOW SUPPORT TUBE WATER LEVEL GAUGE
8.2.7.3 Electric boilers
On each electrode boiler, the water gau ge glass, where fitted, shall be located to indicate the water level from 50 mm below the electrodes to 50 mm above the electrodes, or recommended water level for maximum rated steam load, whichever is the greater. An indicator plate shall be attached to the gauge glass and shall be clearly marked with the levels of the bottom and top of the electrodes. The water level recommended by the manufacturer for maximum rated steam load shall also be clearly marked. On each element boiler, the lowest visible part of the water gauge glass, where fitted, shall be above the top of the electric resistance heating element.
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8.2.7.4 Connections for two sets of gauges
Two sets of water gauges may be fed by one set of connecting pipes provided that the minimum bore of the pipe is 38 mm or greater but, where the size of the boiler reasonably permits, two independent connections are recommended. 8.2.7.5 Isolating valves
Separate isolating valves (as distinct from integral water gauge valves or cocks) should not be fitted in the pipes connecting water gauges. Where fitted, such valves shall be locked or sealed open. Isolating valves shall be of through-flow construction and shall have sufficient area to prevent stoppage by deposits of sediment, the position of the operating mechanism shall clearly indicate whether the valves are in the open or closed position. Levers or handles shall be permanently fastened and cocks shall be plainly marked with a deep line to indicate the direction of the passageway through the plug. Where plug cocks are used they shall be of a type where the plug is held in place by a guard or gland. 8.2.7.6 Vertical installation
Water gauges shall be installed in a substantially vertical position and, except for electric boilers, located so that the lowest visible part of the gauge glass is at least 50 mm above the lowest water level at which there will be no danger of overheating any part of the boiler which is designed to be water-cooled when in operation at that level. 8.2.7.7 Connections
Water gauge connections, with the exception of steel connections, shall be of the flanged type for design pressures in excess of 750 kPa. Steel connections may be welded. All water gauges shall be securely mounted. The hole in the shell or end plate shall be at least equal to the size of the bore of the connecting pipe.
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8.2.8 Connecting pipes for water gauges
Extended pipes connecting water gauges to boilers shall have a minimum bore as specified in Table 3. Steam connecting pipes shall be so arranged that there is no pocket or bend in which water may lodge. They shall, where practicable, be connected direct to the boiler shell or ends and be adequately supported. Connecting pipes should not pass through flues or other gas passages but where this condition cannot be complied with they may pass through a passage open to ventilation, at least 50 mm clear all round. TABLE 3 MINIMUM SIZE OF EXTENDED CONNECTING PIPES FOR WATER GAUGES millimetres Distance between boiler and water gauge > 600 > 600 >2
000
≤1
200
Minimum bore
18 24 38
8.2.9 Safety devices
Safety balls shall be fitted in accordance with Clause 2.1.3.
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8.3 FEED SYSTEMS 8.3.1 Design pressure
The design pressure of all valves, fittings and pipes, forming feed supply systems from the pump up to and including the feed stop valve or cock on the boiler shall comply with AS 4041. 8.3.2 Design temperature
The design temperature of feed check valves and cocks and feed shut-off valves shall comply with AS 4041. 8.3.3 Feedwater arrangements 8.3.3.1 General
The requirements of Clause 8.3.3.2 shall be met. However, in the case of main boilers in power stations or similar large process boilers, some other arrangement suitable for the intended duty shall be used (see N ote). NOTE : Ag ree ment bet wee n rel evant parties, e.g. manufa ctu rer and purchaser, on the proposed feedwater arrangement would be required.
8.3.3.2 Specific requirements
The following requirements shall be complied with: (a) ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
Every boiler shall be provided with at least one method of pressurizing the feedwater supply to the boiler. Any boiler having a power output exceeding 500 kW shall be provided with two means of pressurizing the feedwater supply to the boiler. If either or both methods of feedwater supply, are common to two or more boilers, then each method of supply shall be capable of providing a minimum of 120 per cent of the total feedwater requirements of all connected and operating boilers. Both methods to feed through a common system to one connection on a boiler. All automatically controlled systems shall be capable of manual control.
(b)
Each feed pipe to a boiler shall be provided with a non-return valve fitted as closely as possible to the boiler and a stop valve or cock fitted between the non-return valve and the boiler. The stop valve or cock shall be attached direct to the boiler after taking access and internal feed distribution into consideration. Where two or more boilers are fed from a common source, there shall be a manual regulating valve on the branch to each boiler between the non-return valve and the source of supply (a typical arrangement is shown in Figure 2). Wherever regulating valves are used on feed piping, the inlet shall be under the disc of the valve. NOTE : A combinati on stop /non-re turn val ve with two body sea ts and two dis cs and in which the disc and seat serving the function of a non-return valve are accessible while the boiler is under pressure, may be used in place of two separate valves.
(c)
A combination stop/non-return valve in which there is only one body set and one disc, and in which a stem is provided to close the valve, shall not be considered as complying with the requirements of the separate non-return valve and stop valve required in Item (b). NOTE : It may, howeve r, be regarde d eit her as a stop val ve or a non- return valve and the relevant additional valves supplied and installed as required by this Clause.
(d)
Where an economizer or other feedwater heating device is connected directly to the boiler without intervening valves, the stop v alves and non-return valves required shall be placed at the inlet to the economizer or feedwater heating device.
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52
Any feed-regulating device automatically actuated from the liquid level in the boiler shall be additional to all the preceding requirements of this Clause with bypass capacity sufficient to meet the operating requirements specified by the purchaser. Additional valves shall be installed for the purpose of stopping flow through the automatic valve and bypassing it. If more than one automatic regulating device is installed, one means of bypassing water to the boiler directly and under manual control shall be sufficient. NOTE S:
(f)
1
The bypass may be installed in parallel with the feed regulating valve where fitted.
2
Sufficient valves are recommended to be installed to provide complete isolation of each automatic regulating valve (see Figure 2).
For boilers other than the water-tube type, or electric heated boilers, the lowest point of discharge of any feed valve opening in the boiler or of any opening in the internal feed pipe shall be not less than 50 mm above the waterside of the highest part of any heating surface provided by furnaces, combustion chamber crowns or tubes.
8.3.3.3 Operating positions
Feed-regulating valves shall be so arranged as to enable them to be satisfactorily operated from the firing floor or other convenient position.
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FIGURE 2
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S E C T I O N
9 O F
AS 2593 — 2 004
I N S T A L L A T I O N R E Q U I R E M E N T S A L L T Y P E S O F B O I L E R S
9.1 STATUTORY REQUIREMENTS 9.1.1 Gas installations
Gas installations shall comply with the requirements of AS 5601/AG 601 as appropriate. 9.1.2 Fuel oil installations
Fuel oil installations shall comply with AS 1940, this Standard, and any other regulatory requirements. 9.1.3 Solid fuel installations
Solid fuel installations shall comply with this Standard and any other regulatory requirements. 9.1.4 Electrical installations
The electrical installations shall comply with AS/NZS 3000 and the requirements of the relevant electricity authority. 9.2 HOUSING, ACCESS AND SECURITY ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
Boilers, other than electric boilers with a power output of 500 kW or less, shall be installed in accordance with AS 3892. 9.3 FEEDWATER SUPPLY
Each boiler shall have sufficient feed water supply and storage capacity in compliance with AS 3892. 9.4 WATER TREATMENT
Each boiler shall be operated with water treated in accordance with AS 3873. 9.5 BLOWDOWN
Each boiler shall be provided with blowdown facilities. (For unattended and limited attendance, see Clause 3.5.1.) 9.6 FLUES AND CHIMNEYS
Each boiler shall be fitted with flues and a chimney in accordance with and AS 3892, AS/NZS 1170.2 and AS 1768. 9.7 ELECTRICAL EQUIPMENT 9.7.1 Electrical requirements
All control equipment shall be installed in accordance with AS/NZS 3000, with the requirements of the appropriate authority and any other applicable regulations. All circuits and controls shall be arranged to fail-safe upon the failure of the energizing supply and to require manual reset. Control circuits shall also fail-safe upon the development of any electrical fault in the circuit. The wiring of the boiler management system shall comply with AS/NZS 3000 except as varied by the following:
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(a)
Wiring to any control or switch in or on the top half of a boiler drum or shell shall be a heat-resisting thermal grade not inferior to Type V90 or equivalent of AS/NZS 3187.
(b)
Wiring other than as specified in Item (a) shall be of a specification suitable for the exposure to heat from the boiler installation.
(c)
Wiring inside control panels shall be neatly loomed or enclosed in ducting and terminated at approved terminals which shall be identified to correspond to the circuit diagram. Wiring to components of the boiler shall be identified with approved markers to correspond to the schematic circuit diagram.
Wiring of a boiler may be any of the following:
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(i)
Armoured cable.
(ii)
Mineral-insulated metal-sheated (MIMS) cable.
(iii)
Cables enclosed in galvanized screwed c onduit (AS/NZS 2053.7) or screwed galvanized steel pipes or flexible metal conduit.
(iv)
Orange circular pvc cable on a cable tray or ladder where the cable temperature rating is not exceeded.
(v)
For instrument wiring, single or multi-pair double insulated instrument cable with overall and individual screening as required, run in enclosed galvanized sheet metal or open galvanized steel ladder type rack.
Notwithstanding Items (i) and (iii) above, where the wiring is subject to vibration or where movement for adjustment, repair or inspection of equipment is necessary, MIMS cable shall not be used and the wiring shall be enclosed in flexible metal conduit. 9.7.2 Control cabinets
Control cabinets shall comply with AS/NZS 3000.
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S E C T I O N 1 0 F O R
M A R K I N G A L L T Y P E S
AS 2593 — 2 004
A N D I N S T R U C T I O N S O F B O I L E R S
10.1 MARKING
In addition t o the requirements of AS 1228 or AS 3814/AG 501 as appropriate, the manufacturer’s nameplate or subsidiary plate attached to the boiler shall be legible and indelibly marked with the following information: (a)
Electrical data, as required by the electricity authority.
(b)
Fuel type, and minimum and maximum input rate.
(c)
Power output in kilowatts and letters ‘kW’ thereafter.
(d)
Boiler type (in accordance with Table 1).
10.2 ELECTRICAL DATA
The manufacturer shall provide sufficient information on the electrical control system to permit safe operation and maintenance of the boiler. The information shall include the following:
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‘Schematic wiring diagrams shall identify each major item of equipment and its rating. The means of identification used shall correspond to that used for labelling the control panel and for the identification of switches, contactors, relays circuit breakers, resets, indicators, terminals and cables.’ All symbols used shall comply with the relevant Australian Standard for graphic symbols for electrotechnology unless otherwise agreed by the owner. 10.3
INSTRUCTIONS
The manufacturer (or representative) of the boiler shall provide instructions that are sufficient to permit safe and satisfactory installation, maintenance and operation of the complete boiler installation. Instructions shall include a programmed schedule of checks of safety equipment (see also Section 6). NOTE : The nature and extent of the ins truc tions should be dete rmi ned by agreement bet wee n the purchaser and the supplier.
10.4 LANGUAGE AND UNITS
Markings, diagrams, and instructions shall be in the English language, and values shall be in SI units (see AS ISO 1000). 10.5
CERTIFICATES
The owner shall ensure that an appropriate attendance-category certificate of compliance with this Standard is issued by an organization independent of the boiler owner and the installer, prior to operation of the unit.
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1 1 E N E R G Y I N P U T S Y S T E M S A L L T Y P E S O F B O I L E R S
F O R
11.1 COMBUSTION SYSTEMS 11.1.1 Suitability
The combustion system shall be correctly matched to the requirements and conditions of the boiler design, including the following: (a)
Type and grade of fuel.
(b)
Volume and shape of combustion chamber.
(c)
Required volume of purging air.
(d)
Intensity and distribution of heat (see Note).
(e)
Ambient temperature.
(f)
Duty cycle, particularly any standby conditions. NOTE : AS 3 873 giv es inf ormation boiler/combustion equipment.
on
poss ible
probl ems
due
to
mis mat chi ng
of
11.1.2 Combustion heat flux limitation
Changes or modifications to the combustion system or fuel that could vary the combustion intensity or distribution of heat energy shall not be made without rigorous analysis of the thermal conditions, including consultation with the boiler manufacturer where appropriate.
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Means shall be provided within the combustion control, management and safety systems to limit the energy input to suit the design output rate of a boiler and prevent any overtemperature conditions from developing. NOTE : See AS 1228 for heat f lux limitation in fire-tube boil ers.
On/off type equipment shall not be used for the main combustion equipment for boilers with a heat output exceeding 500 kW. 11.1.3 Automatic oil and gas firing equipment
The design and construction of automatic oil-fired and gas-fired burners and management systems for single and multiple applications shall comply with AS 1853, AS 3814/AG 501 and AS 5601/AG 601. 11.1.4 Other oil, gas or solid-fuel-in-suspension firing equipment
The design, construction and installation of oil, gas or fuel-in-air suspension firing systems, other than that specified in Clause 11.1.3, shall comply with AS 1375, AS 3814/AG 501 and AS 5601/AG 601. NOTE : Fo r addi tional informati on on fue l firing of boil er equipme nt, it is reco mme nded tha t reference be made to ANSI/NFPA 8502.
11.1.5 Solid-fuel firing systems 11.1.5.1 General
Solid-fuel firing systems of other than the fuel-in-suspension type shall be designed and constructed to meet the specific application and site conditions.
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11.1.5.2 Suitability
In addition to complying with Clause 11.1.1, the combustion equipment and management system shall be matched to fuel type, fuel characteristics, and particle size (distribution). The fuel type, characteristics or size shall not be changed without the approval of the equipment manufacturer or a competent combustion engineer. 11.1.5.3 Solid-fuel firing systems
Solid-fuel firing systems, other than that described in Clause 11.1.5, should have a feeding mechanism which permits fully automatic control. The feeding system should provide a proper bed contour at all firing rates, without airholes or thin spots, over the entire grate area. 11.1.5.4 Power failure protection
The boiler, combustion equipment and management systems shall be designed and constructed so that loss of electric power at any time during the operating cycle will minimize the possibility of any hazard arising. The combustion chamber, bed or grate system should be designed and operated to minimize the stored energy in the system upon power failure. 11.1.5.5 Piping
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All fuel-conveying pipelines and flexible hoses shall be constructed from materials that resist heat and combustion. Combustible material should not form any part of such pipelines. 11.2 WASTE HEAT ENERGY RECOVERY SYSTEM 11.2.1 Input control
Each system shall be equipped with the means to control the heat energy input to provide interlocks to shut off or by-pass the waste heat input in the event of a loss-of-water or overpressure condition in the boiler. 11.2.2 Input location
Where the waste heat energy is introduced into a section of the boiler not designed for radiant heat transfer, provision shall be made to avoid overheating of the boiler metal. For example — (a)
where the waste heat is introduced directly onto the tubeplate of a fire-tube or shell boiler, the tubeplate surface and edges of the tube should be protected by insulation; and
(b)
spiral-wound water tubes should not be exposed to radiant heat and should be protected.
11.3 ELECTRIC ENERGY INPUT SYSTEMS NOTE : This Sta ndard is not int ended to appl y to elec tric boil ers whe re an ele ment is in contact with, or is close to a pressure-retaining part.
11.3.1 General
Electric boilers shall be of either the electrode type or the element type and shall comply with the relevant requirements of — (a)
this Standard; and
(b)
AS/NZS 3000, and in particular the requirements for electrode boilers therein.
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11.3.2 Electricity supply
Electric boilers shall be operated only on an a.c. supply. Each electrode boiler shall be fitted with at least one ammeter to indicate the current taken by the boiler. A red line shall mark the full-load current on each ammeter. 11.3.3 Load adjustment
For electrode boilers, the following load adjustment requirements shall apply: (a)
Means shall be provided by which the electrical loading can be adjusted between the agreed minimum load and the nominal rating at the operating steam boiler pressure or, for hot water boilers at any water temperature between 65 °C and the boiling point at the designed pressure, the water in the boiler having the specific resistance as stated by the manufacturer.
(b)
It is recommended that the load adjustment also permits satisfactory operation where the specific resistance of the water in the boiler is up to 50% greater than that recommended by the manufacturer.
(c)
Where means are provided to control the load automatically, a manual control shall also be fitted.
(d)
Automatic load adjustment shall be capable of maintaining the set load within 10% of full-load current.
11.3.4 Electrodes, elements and internal parts ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
Electrodes and elements shall be made of materials suitable for use under the working conditions of the boiler. Moving parts liable to wear shall be made of materials resistant to corrosion and erosion. The electrical insulating materials used shall not be liable to deterioration under the conditions to which they are exposed when the boiler is in o peration. Elements shall be of the electrical resistance sheath type. The sheath shall be of nickel-ironchromium alloy, e.g. Incoloy alloy 800 or 825, or copper, or other appropriate metal. The layout, configuration and location of elements shall be such that, under norm al working conditions, the elements shall have an adequate cover of water not less than 50 mm. Elements shall be supported and located so that any feasible deterioration or sagging of the element will not result in the element contacting the shell of the boiler. Vertical clearance between horizontal elements and pressure-retaining parts shall not be less than 30 mm for elements with an unsupported length exceeding 300 mm or 10 mm for elements with an unsupported length not exceeding 300 mm. 11.3.5 Pressure and temperature control
Each steaming-type electric boiler shall be fitted with a pressure controller which controls the pressure to a predetermined pressure not exceeding the design pressure of the boiler. Hot water-type electric boilers shall be fitted with a temperature controller which controls the temperature to a predetermined value not exceeding boiling point, corresponding to the operating pressure, minus 6°C. 11.3.6 Access
Openings and clearances shall be provided for removal of electrodes and elements. Openings for electrodes or elements may be used to comply with the inspection and cleaning access requirements in AS 1228.
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12.1
1 2
V A L V E S F O R B O I L E R S
AS 2593 — 2 004
A L L
T Y P E S
O F
GENERAL
All valves and fittings shall be installed in the boiler system in such positions as to be accessible for operation, examination and o verhaul. 12.2 SIZE, NUMBER AND LOCATION OF SAFETY VALVES FOR BOILERS 12.2.1 General
Each boiler, which has a designed maximum power output n ot exceeding 2.35 MW, shall be fitted with at least one safety valve. Each boiler with a designed maximum power output exceeding 2.35 MW shall be fitted with at least two safety valves. Each superheater shall have at least one safety valve on the outlet side. When a boiler is fitted with an integral superheater without an intervening stop valve, the safety valves fitted on the superheater may be included in determining the number and size of the safety valves on the boiler, provided that at least 75% of the safety valve capacity is achievable from the safety valves fitted to the boiler drum.
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Each reheater shall have at least two safety valves with a total capacity not less than the maximum steam flow for which the reheater is designed. One or more safety valves having a combined capacity of not less than 20% of the required total capacity shall be located on the reheater outlet side. Reheater safety valves shall not be considered as a part of the safety valve equipment of the b oiler or superheater. Once-through steam generators with no fixed steam or waterline equipped with automatic controls and protective interlocks responsive to steam pressure shall be fitted with safety valves suitable for the intended duty. Economizers separated by a shut-off valve from the boiler shall be fitted with at least one relief valve. The size and location of each safety valve should be selected so as to minimize lifting of the water in the boiler. 12.2.2 Discharge capacity 12.2.2.1 Unvented systems
The total rated discharge capacity of all the safety valves mounted on a boiler (and integral superheater) shall be at least equal to the maximum evaporative capacity of the boiler in the case of steam boilers or the maximum rating of the boiler in the case of hot water boilers, for which 1 kW of rated boiler output shall be taken as equivalent to an evaporation of 1.55 kg/h. Where the feedwater temperature, and hence the actual evaporative capacity of the boiler is not known, the required safety valve capacity shall be based on the specified peak load evaporation ‘from and at 100°C’. NOTE : The term ‘from and at 100° C’ is an abbrevi atio n indicatin g the evaporat ion from feedwater at 100°C to steam at 100°C at atmospheric pressure and as such is the basis of determining the peak load equivalent evaporation of a steam boiler.
12.2.2.2 Open-vented systems
The rating of a safety valve, R (in kW), mounted on a fully-flooded hot water boiler in an open-vented system shall have the value determined from equation — R
= 2(0.0329 pAKdr )
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where p
= the actual relieving pressure (absolute), in megapascals = (set pressure × 1.06) + 0.1
A
= the minimum flow area through the discharge system, in square millimetres
Kdr = the derated coefficient of discharge, as defined in AS 1271 Where the safety valves on a hot water boiler are required to discharge either steam or water, the minimum total discharge capacity of the valves shall be sufficient for either the maximum steam or water discharge. 12.2.2.3 Integral superheater discharge capacity
The minimum discharge capacity of safety valves on an integral superheater shall be equal to that portion of the boiler evaporation which, it is intended, shall be catered for by the superheater valves (see Clause 12.2.2.1). Superheaters shall be fitted with safety valves having a capacity not less than 20% of the maximum evaporation of the boiler. The basis for evaluating the discharge capacity for integral superheater safety valves shall be the set pressure of the highest set drum safety valve which is to be used also for calculating the required area for superheater safety valves. 12.2.2.4 Independently-fired superheater discharge capacity
The minimum discharge capacity of safety valves on independently-fired superheaters, which is shut off from the boiler and permits the superheater to become a fired pressure vessel, shall be equal to 8 grams of steam per second per square metre of superheater surface measured on the side exposed to the hot gases. Where an independently-fired superheater is constructed for a maximum permissible working pressure lower than the boiler or boilers in which the steam it receives is generated, it shall be fitted with safety valves havi ng a capacity not less than the maximum total evaporation of such boilers and which shall lift before the drum valve.
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12.2.2.5 Reheater discharge capacity
The minimum total discharge capacity of safety valves on each reheater shall be equal to the maximum steam flow for which the reheater is designed, see Clause 12.2.1. 12.2.2.6 Economizer discharge capacity
For economizers separated by a shut-off valve from the boiler, the minimum discharge capacity of relief valves shall be equal to the maximum amount of steam which can be generated when so shut off but with full gas flow. 12.2.3 Accumulation
Notwithstanding the requirements of Clause 12.2.2, the safet y valves fitted to each boiler (and integral superheater) shall have sufficient total capacity to discharge the steam generated during maximum p eak load evaporation of the boiler with a rise in pressure to not more than 106% of the design pressure. The same limitations of maximum p ressure rise shall apply to superheaters and economizers which can be separated from the boiler, and to reheaters. 12.2.4 Reseating pressure
Safety valves shall comply with reseating (blowdown) requirements as follows: (a)
On each boiler with a power output not exceeding 20 MW, each safety valve shall be set to reseat, after blowing off, at a pressure not lower than 93% of the set pressure for valves larger than 32 mm size, or 90% of the set pressure for valves 32 mm size or less. (See Note 2.) In no case shall the blowdown be less than 14 kPa.
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(b)
AS 2593 — 2 004
The minimum blowdown in any case shall be 14 kPa. For spring-loaded full-lift safety valves for pressures b etween 690 kPa and 2.1 MPa, both inclusive, the blowdown shall be not less than 2% of set pressure.
NOTE S: 1
In the case of assisted operation valves discharging with the assisting devices inoperative, the requirement of this Clause may be varied.
2
Where more than one valve is installed on a single boiler, all valves may be set to reseat at a pressure not lower than 93% of the set pressure of the lowest set valve.
3
On each boiler with a power output greater than 20 MW, each safety valve should be set to reseat at a pressure not lower than 96% of its set pressure, except that all drum valves installed on a single boiler may be set to reseat at a pressure not lower than 96% of the set pressure of the lowest set drum valve.
12.2.5 Valve settings
One or more drum valves shall be set at or below the design pressure. The setting of additional valves, where used, shall not exceed the design pressure by not more than 3%. In order to avoid damage to integral superheaters fitted to boilers, at least one superheater valve shall be set to lift before the drum valves. Similarly, in order to avoid simmering on boilers fitted with superheaters, all of the drum safety valves shall be set s o as to reseat before any of the superheater safety valves reseat. 12.2.6 Connections to shell ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
Boilers shall have proper outlet connections for the required safety valves independent of any other connection to or from such boiler. Each opening in a boiler shell or drum for safety valves shall have an area of bore at least equal to the total inlet area of the valve or valves which it serves. No obstruction in the safety valve opening of the boil er and no shut-off valve shall be placed between a boiler and its safety or water-pressure relief valves. Discharging steam shall have direct access to the safety valve without flowing through internal pipes. The nozzles of fittings for the attachment of full-lift valves to the boiler shall be designed to permit the certified discharge capacity to be obtained and shall have a machined, rounded leading edge on the inlet side, and the bore, whether taper or parallel, shall be machine finished. More than one safety valve may be fitted in a chest. The chest shall be separate from any other valve chest and shall be connected as directly as possible to the boiler shell. The passage through such chest shall have a combined cross-sectional area at least equal to the sum of the inlet areas of the valves it serves. Safety valves shall be mou nted with the valve spindle vertical. 12.2.7 Expansion joints
Where the layout of a discharge pipe imposes excessive stress on the safety valve or restricts the expansion or movement of the valve, a waste steam p ipe shall be fitted between the valve outlet and the discharge pipe and a suitable expansion joint shall be provided at the junction of the waste steam and discharge pipes. 12.2.8 Pilot pipes
Where the outlets from discharge pipes are not visible from the operating floor or where two or more pipes are combined, pilot pipes should be fitted to enable ready determination as to which valve is blowing.
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12.2.9 Safety valve discharge system
The safety valve discharge system, including a muffler (where fitted), shall be so designed that, under maximum discharge conditions, the maximum back pressure at the outlet flange of the safety valve does not interfere with the operation or rated capacity of the valve. The bore of the discharge pipe shall not be less than the bore of the outlet connection of the safety valve. Safety valve discharge piping shall comply with AS 3892. 12.2.10 Discharge restriction
No shut-off valve, cock, or obstruction of any kind shall b e fitted on the discharge side of a safety valve. This does not preclude the use of a muffler. 12.3 BLOWDOWN VALVES
Blowdown valves fitted to all boilers shall be of the full-bore or ¼ turn single-action design. Design pressure and temperature limitations shall be in accordance with AS 4041. Valves greater than DN 40 or where the working pressure is greater than 1.2 MPa shall not be screwed. Blowdown valves shall also comply with requirements of AS 1271. 12.4 MAIN STEAM ISOLATING VALVE
Main steam isolation valves fitted to all boilers shall be of the globe or gate design and have a valve leakage classification not less than ANSI B16.104 Class IV at the maximum design pressure and temperature limitations of the boiler.
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12.5 MAIN FEEDWATER ISOLATION VALVE
Main feedwater isolation valves fitted to all boilers shall have a valve leakage classification not less than ANSI B16.104 Class IV at the maximum design pressure limitation of the feedwater pump(s) and the design temperature limitations of the boiler.
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AS 2593 — 2 004
S E C T I O N 1 3 I N T E G R A L A N D B O I L E R P R E S S U R E P I P I N G F O R A L L T Y P E S O F B O I L E R S 13.1
GENERAL
Integral piping shall comply with requirements of AS 1228. NOTE : An e xample of int egral pipi ng for a w ater-t ube boiler is sho wn in Appe ndix F.
13.2 WATER-HEATI NG BOILER SYSTEM DESIGN 13.2.1 General
For each water-heating boiler and associated system, provision shall be made to cater for the fluctuations in total water volume and pressure which occur during operation. Pressurization should be obtained by the use of an inert-gas-filled section or steam-filled or by a pumping and relief valve arrangement. 13.2.2 Expansion vessels 13.2.2.1 General
Expansion vessels subject to pressurization shall comply with AS 1210. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 5 1 0 2 l u J 0 3 n o Y R A R B I L Y T I S R E V I N U H S A N O M y b d e s s e c c A
13.2.2.2 Minimum requisite fittings
Each expansion vessel shall be provided with the following fittings: (a)
Safety valve (pressurization steam or gas).
(b)
Water gauge.
(c)
Drain valves.
Each valve, water gauge, low-water device and fitting shall comply with the requirements of this Standard. 13.2.2.3 Gas safety valves
Each pressurized expansion vessel shall have at least one safety valve located in the gas space and set to operate at 35 kPa below the setting of the boiler safety valves. The total discharge capacity of such safety valve or valves shall be at least equal to the maximum gas input rate with a pressure rise of not more than 14 kPa. 13.2.2.4 Low-water device
Each expansion vessel shall be fitted with a low-water safety device. Where magnetic devices are fitted, they shall be fitted so that the magnetic components are not in the water space. The operation of this device shall cause a lock-out of the energy input system and the device shall be of the type that requires manual resetting before the energy input system can be reactivated. 13.2.2.5 Boiler safety valves
Where boiler safety valves are fitted to the expansion vessel, such valves shall comply with the relevant provisions of Section 12 for the maximum designed capacity of all boilers connected to the vessel. For duplicate expansion vessels, where the plant can be operated with only one in use, each vessel shall be fitted with sufficient safety valves to cater for the total design output of the plant.
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13.2.3 Piping system 13.2.3.1 Design
The pipe connecting each boiler to an expansion vessel or open-vented head tank shall be designed so that the rise of pressure in the boiler due to the maximum expansion rate of the water is not more than 106% of the design pressure. When a boiler safety valve is fitted to the expansion vessel, the connecting pipe shall be designed so that under maximum discharge conditions of the safety valves the boiler pressure does not rise to more than 106% of the design pressure. Expansion or vent pipes shall be taken from the top of the boiler. Vent pipes shall be separate from the pipe supplying the make-up water from a head tank. Where necessary, precautions should be taken against freezing. 13.2.3.2 Flow restriction
No shut-off valv e, cock, or other obstruction to flow shall be fitted between the boiler and an open-vented head tank or expansion vessel, unless the boiler safety valves (and where required by the inspecting authority, a low-water device) are fitted directly to the boiler. Care shall also be exercised to ensure that during installation no obstruction to this open vent pipe is made accidentally. 13.2.4 Make-up water systems
Provision shall be made for the supply of make-up water to the system. Where a pump is provided for filling while the boiler system is pressurized, precautions shall be taken to avoid a water hammer situation during filling with cold water. Where automaticallycontrolled pumps are used, an effective alarm shall continue to operate while make-up water is required.
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13.2.5 Energy input interlock
For continuously controlled boilers, the system water shall be circulated continuously through the boiler while the boiler is in operation. The energy input system shall be interlocked to prevent ignition or combustion in a liquid, gas or suspension-fired boiler (using pulverized fuel) or the supply of combustion air in a solid-fuel-fired boiler, unless the water is circulating.
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APPENDIX A
LIST OF REFERENCED DOCUMENTS (Normative)
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AS ISO 1000
The international system of units (SI) and its application
1210
Pressure vessels
1228
Pressure equipment — Boilers
1271
Safety valves, other valves, liquid level gauges, and other fittings for boilers and unfired pressure vessels
1375
Industrial fuel-fired appliances (known as the SAA Industrial Fuel-fired Appliances Code)
1768
Lightning protection
1853
Automatic oil and gas burners — Mechanical draught
1940
The storage and handling of flammable and combustible fluids
3814/AG 501
Industrial and commercial gas-fired appliances
3873
Pressure equipment — Operation and maintenance
3892
Pressure equipment — Installation
3920 3920.1
Assurance of product quality Part 1: Pressure equipment manufacture
4041
Pressure piping
4343
Pressure equipment — Hazard levels
4942
Pressure equipment –– Glossary of terms
5601/AG 601 Gas installations AS/NZS 1170 1170.2
Structural design actions Part 2: Wind actions
1200
Pressure equipment
2053 2053.7
Conduits and fittings for electrical installations Part 7: Rigid metal conduits and fittings
3000
Electrical installations (known as the Australian/New Zealand Wiring Rules)
3187
Approval and test specification — Mineral-insulated metal-sheathed cables
3788
Pressure equipment — In-service inspection
ANSI/NFPA 8502
Prevention of furnace explosions/implosions in multiple burner boilers
8503
Pulverized fuel systems
B16.104
Control valve seat leakage
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BS 799 799-4
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Oil burning equipment Part 4: Specification for atomizing burners (other than monobloc type) together with associated equipment for single burner and multi-burner installations
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APPENDIX B
ACCEPTABLE CRITERIA FOR ORGANIZATIONS AND PERSONNEL UNDERTAKING BOILER CONTROL DESIGN, TESTING AND SERVICING FOR UNATTENDED AND LIMITED ATTENDANCE BOILERS ONLY (Informative) B1 GENERAL
The continued safety and reliability of an unattended or limited attendance boiler during its operation is directly dependent on the quality and skill of the organization to supply the maintenance required in Section 6 and on the competency of maintenance and testing personnel. Criteria for the maintenance and testing organizations and personnel are given in Paragraph B2 and Paragraph B3, respectively. B2 ORGANIZATIONAL COMPETENCIES
Each organization should be —
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(a)
a boiler manufacturer with at least three years experience in the design and construction of boiler management, combustion or energy input, and safety systems complying with this Standard; or
(b)
an organization which — (i)
has had at least three years experience in the maintenance and operation of automatic boilers, particularly in regard to the safety systems such as water level systems, combustion or energy systems, safety valves and pressure controls; or
(ii)
has a person or persons with competencies in accordance with Paragraph B3.
B3 MINIMUM COMPETENCIES FOR PERSONNEL B3.1 General
The intent of criteria is to set into place the minimum competencies applicable to the particular job function. All personnel should have knowledge and experience in all of the following areas: (a)
The basic boiler structure, including the location of valves and fittings, water and steam flow and pressure controls, blowdown and safety valve operation, water level controls and indicators.
(b)
Other than for electric boilers, combustion systems and their controls, fuel storage and handling facilities, air and flue gas flow and discharge facilities.
(c)
Inspecting and testing procedures for checking of safety systems for compliance with this Standard.
The above competencies are considered the minimum requirements for a person to verify that a boiler complies with this Standard. In addition, all personnel should have the competencies listed in Paragraph B3.2 or B3.3, whichever is applicable.
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B3.2 Designer
The minimum competencies should be one of the following: (a)
A qualification equal to the Bachelor award in engineering or science, together with two year’s experience in the design of unattended/limited attendance boiler control systems or an Associate Diploma award in engineering or science, together with, 4 year’s experience in the design of unattended/limited attendance boiler control systems.
(b)
All of the following competencies below: (i)
Steam Boiler Attendant’s Certificate of Competency.
(ii)
Combustion Other than for electric boilers, practical and theoretical knowledge of gas, oil or coal-fired burners and combustion equipment appropriate to the design of the boiler proposed.
(iii)
Electrical Unrestricted electrical licence plus competency in industrial control.
(iv)
Experience Together with the above competencies, the designer should have a minimum of three year’s experience on unattended/limited attendance boilers.
The above competencies should be the minimum level for a person to verify that the design of a boiler complies with this Standard. B3.3 Commissioning body
The minimum competencies, other than for electric boilers, should be one of the following:
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(a)
Compliance with Item B3.2(a).
(b)
All of the following competencies: (i)
Steam Boiler Attendant’s Certificate of Competency.
(ii)
Combustion Practical skills and theoretical knowledge of gas, oil or coal-fired burners and combustion equipment appropriate to the design of the boiler proposed.
(iii) Electrical Unrestricted electrical licence plus competencies in industrial control. (iv)
Experience Together with the above competencies, the commissioning body should have a minimum of three year’s experience on unattended/limited attendance boilers.
The above competencies should be the minimum level for a person to verify that the commissioning of the boiler complies with this Standard. B3.4 Servicing
The servicing of unattended/limited attendance boiler systems, other than for electric boilers, should be divided into two categories, mechanical and electrical, as follows: (a)
©
Competency requirements for mechanical service category Competencies should be as follows: (i)
Steam Boiler Attendant’s Certificate of Competency.
(ii)
Mechanical Completed an appropriate trade course.
(iii)
Operation Received special training in the functions and procedures to be employed with a statement as to the extent and level of training received from the principal boiler contractor.
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(iv) Experience Together with the above competencies, it will be necessary to provide a statement of experience from the current employer that the servicing person has sufficient experience performing mechanical maintenance on boilers. This specialized training should include an understanding of the effects of the mechanical category components service on the control and safety systems. (b)
Electrical service category Competencies should be as follows: (i)
Steam Boiler Attendant’s Certificate of Competency or equivalent.
(ii)
Combustion Practical and theoretical knowledge of gas, oil or coal-fired burners and combustion equipment appropriate to the design of the boiler proposed.
(iii) Electrical One of the following:
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(iv)
(A)
Unrestricted electrical licence plus competencies in industrial control.
(B)
A restricted electrical license plus a minimum of three year ’s experience and training in the service and maintenance functions of electrical circuitry with a principal boiler contractor.
(C)
Completion of an apprenticeship or trade course in the electrical field plus a minimum of five years experience and training in the service and maintenance of functions of electrical circuitry with a principal boiler contractor.
Experience Together with the above competencies, it is recommended that a statement of experience from a principal boiler contractor be provided showing that the servicing person has a minimum of one year ’s (full time) experience on unattended/limited attendance boilers. Upon satisfying the above competencies in the electrical category, the servicing person should have demonstrated sufficient mechanical aptitude to perform the mechanical component of the maintenance of unattended/limited attendance boilers.
B3.5 Commissioning and servicing of electric boilers
Requirements for commissioning and servicing electric boilers should be as follows: Compliance with Paragraph B3.4, Items (a)(ii), (iii) and (iv), together with (b)(iii) and (iv).
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APPENDIX C
TYPE TEST FOR A BOILER SUBJECT TO POWER FAILURE (Normative) C1 GENERAL
This Appendix specifies a procedure and acceptance criteria for a type test for checking the ultimate safety of the design of a boiler that may be subject to a power failure. It is intended to be used for a boiler where a potential hazard may exist due to stored heat energy in the system, e.g. where the combustion chamber is substantially refractory-lined or the boiler is a solid-fuel-fired, bed or grate type, and the boiler is not fitted with an independent auxiliary water supply pump that would automatically operate when a power failure occurs. C2 TYPE TEST
Provided that the boiler tested is representative of a manufacturer ’s standard product range for the boiler type, including combustion equipment arrangement, fuel type, refractory content and installation, the test shall be representative of other boilers in the standard product range. C3 TEST PROCEDURE
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The procedure for the test shall be as follows: (a)
Identify each critical part of the boiler. NOTE : A cri tic tical al part is a part whi ch wou would ld fir st beco me hea heated ted abo above ve its des design ign tem pera tur turee in the event of loss of water by boiling off due to stored heat energy in the boiler system.
(b)
Attach a temperature temperature sensing device temperature/time relationship is indicated.
to
each each
critical critical
part
such
that the
NOTE : Re cord cordss may be nec ess ary as evi denc e, if req require uire d by the aut hori hority ty hav having ing jurisdi jur isdi cti ction. on.
(c)
Fire the boiler at maximum capacity capacity for a minimum period of 30 30 min.
(d)
Leave the main steam or energy outlet outlet in the normally open position.
(e)
Simulate a power failure by opening the main power switch. switch. The The shutdown shutdown of the water supply, combustion system, fan and draught system shall be complete.
(f)
Monitor and log the temperature of the boiler metal at each each critical critical part for at least 30 min after the shutdown of power. Record the maximum metal temperature. If the metal temperature of any part exceeds its design temperature during the course of the test, the test shall be aborted and the following steps taken: (i)
Close the main steam or output valve.
(ii)
Re-establish the power supply to the boiler.
(iii)
Shutdown any fuel supply system and, for a solid-fuel-fire bed or grate grate boiler, rake over the fuel bed to minimize radiation to the boiler heating system.
C4 ACCEPTANCE CRITERIA
Provided that the metal temperature of any part monitored in the test does not exceed its design temperature, the boiler shall have passed the test, notwithstanding the fact that it is likely that, for a steam boiler, the water level will drop below the level visible in the water level gauge glass, due mainly to evaporation of steam as the pressure decays. ©
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APPENDIX D
TYPICAL OIL OR GAS BURNER FIRING SEQUENCES (Informative) Figure D1 illustrates typical control system sequences as outlined in Clause 4.2.2.
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FIGURE D1
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TYPICAL BURNER FIRING SEQUENCE—GAS PILOT
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APPENDIX E
TYPICAL OIL SUPPLY AND CONTROL SYSTEMS (Informative) Figure E1 lists the symbols used in oil supply and control s ystems. Figure E2 shows the diagrammatic arrangement of the components detailed in Clause 4.4. Figure E3 shows the diagrammatic arrangement of the components detailed in Clause 4.6.
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FIGURE E1
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LIST OF SYMBOLS
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FIGURE E2
AS 2593 — 2004 2 004
SCHEMATIC DIAGRAM OF HEAVY FUEL PRESSURE ATOMIZED ATOMI ZED SYSTEM SYSTEM WITH WITH PILOT PILOT IGNITIO IGNITION N
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FIGURE E3
SCHEMATIC DIAGRAM OF HEAVY FUEL/AIR OR
STEAM ATOMIZED SYSTEM WITH PILOT IGNITION
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APPENDIX F
EXAMPLE OF INTEGRAL BOILER PIPING COVERED BY AS 1228 AND THIS STANDARD (Informative)
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AMENDMENT CONTROL SHEET AS 2593—2004
Amendment No. 1 (2007)
REVISED TEXT
SUMMARY: This Amendment applies to Clause 3.5.3.2.1. Published on 1 February 2007.
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NOT ES
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