Specification for Fabrication of Subsea Structures

SPECIFICATION FOR FABRICATION OF SUBSEA STRUCTURES WEST NATUNA PIPELINE PROJECT INDONESIA TO SINGAPORE

PREPARED FOR

WEST NATUNA GROUP

INTEC PROJECT H-0879.01 APRIL 1998 0

8-Apr-98

ISSUED FOR CLIENT APPROVAL

B1

31-Mar-98

ISSUED FOR CLIENT REVIEW

REV.

DATE

DESCRIPTION

LSW

CDK

RJP

WNG

RCG

CDK

RJP

WNG

BY

CHKD

APPD

CLIENT

SPECIFICATION NO. 8791/09-FS1

Specification No. 8791/09-FS1 Rev. 0/Page i 8-Apr-98

TABLE OF CONTENTS 1. GENERAL................................................................................................................................1 2. FABRICATION REQUIREMENTS .....................................................................................1 3. STRUCTURAL STEEL MATERIALS.................................................................................2 4. WELDING................................................................................................................................4 5. DIMENSIONS..........................................................................................................................8 6. LINERS TO PIPE CLAMPS..................................................................................................9 7. ANODES.................................................................................................................................12 8. ANTI-CORROSION COATING TO STRUCTURE .........................................................16 9. BOLTED CONNECTIONS ..................................................................................................19 10. DIVER MARKINGS .............................................................................................................19

(This Specification consists of 21 pages)

cw

Specification No. 8791/09-FS1 Rev. 0/Page 1 of 19 8-Apr-98

1.

GENERAL This Specification defines minimum quality and technical standards governing materials procurement, fabrication, testing and inspection of fabricated steel structures used in a subsea environment. This Specification is to be used in conjunction with the following documents:   

2.

Design Basis Memorandum 8791/02-DBM001 General Specification 8791/09-GS1 - Definitions and Specification Directory General Specification 8791/09-GS2 - Quality Assurance / Quality Control

FABRICATION REQUIREMENTS Structure fabrication and materials used shall be in accordance with the CONTRACT Documents, Project Drawings, SPECIFICATIONS and all applicable codes and standards. CONTRACTOR shall furnish shop drawings for COMPANY approval prior to fabrication.

2.1

Documentation CONTRACTOR shall prepare and issue the following documents for COMPANY review and approval:           

Fabrication drawings Fabrication procedures Material datasheets Assembly lifting, handling and storage procedures Welding Procedure Specifications Welding Procedure Qualification and Records Welding Repair Procedures Welding Procedure Qualifications Welding Procedures Weld location plans NDE Procedures and Procedure Qualification Reports

Following completion of fabrication the following documents shall be issued in a single comprehensive databook by CONTRACTOR for COMPANY review and approval.       cw

Construction drawings to as-built status Technical queries and concessions Test and inspection records Calibration records Material certificates Mill Test Certificates


    

Batch certificates for all welding consumables NDE Reports NDE Technicians Qualification Certificates Weld Qualification Test Results Welder Qualification Certificates

CONTRACTOR shall obtain written COMPANY approval for any deviation from this specification before starting fabrication. CONTRACTOR shall ensure that Work shall not be performed when weather conditions prevent satisfactory workmanship, or prevent adequate inspection. As-built drawings, showing field modifications and weld locations shall have a numbering system corresponding to the Non-Destructive Examination (NDE) reports. 3.

STRUCTURAL STEEL MATERIALS

3.1

Procurement, Handling and Storage CONTRACTOR shall provide all materials necessary to fabricate structures in accordance with the design drawings and this Specification. All materials furnished by CONTRACTOR shall be new, unused and undamaged. Temporary bracing, erection aids, scaffolding and testing materials shall be furnished by CONTRACTOR, and shall be demonstrably safe, serviceable and adequate. All material must be manufactured, delivered and stored in accordance with the latest edition of ASTM A-6, ASTM A-20 and ASTM A-700, as applicable.

3.2

Substitutions Substitution of materials by CONTRACTOR shall not be made without prior written approval of COMPANY.

3.3

Structural Sections Structural steel plates, pipe, fabricated pipe and shapes shall comply with the design drawings and the requirements of API RP 2A Class C steels.

cw


3.4

Bolts, Nuts and Washers All bolts and nuts for structural connections shall be Unified Standard Coarse-Thread Series and shall conform to ASTM A-325 unless otherwise noted, and shall be of the heavy hex-head type. All bolts, nuts and washers shall be or Teflon coated. Round washers shall conform to ASTM F-436. The diameter of washer holes shall be 1/16 inch greater than the bolt size for bolts not larger than one (1) inch, and 1/8 inch greater than the bolt size for bolts larger than one (1) inch.

3.5

Mill Certificate CONTRACTOR shall furnish COMPANY with copies of all mill certificates for all pipe, structural shapes, and plate 3/8 inch or greater before the material is worked. CONTRACTOR’s stock material shall bear mill heat numbers for identification. In order to facilitate material inspection efforts, CONTRACTOR shall include with each mill certificate the following information: a.) b.) c.) d.) e.)

3.6

CONTRACTOR’s job number Item to be used (e.g., W36X150) Quantity to be used (e.g., number of feet) Area of structure for material (e.g., deck truss) Plate stock to be used for CONTRACTOR-rolled steel pipe. (Pipe diameter and wall thickness of pipe to be made.)

Material Marking All high-strength and special steels shall be color coded or otherwise marked upon delivery to CONTRACTOR’s yard. The steel shall be marked such that the identity of the type of piece steel, heat number, and special tests can be immediately recognized. The color code shall be renewed as necessary throughout the fabrication process until the material enters its final location in the structure. All heat numbers or other identification marking shall be stenciled with 3/8-inch low stress concentration dyes on both ends of each item. CONTRACTOR shall maintain all markings through the life of the project. CONTRACTOR shall steel stencil the heat numbers on all component parts of lifting padeyes.

cw


3.7

Imperfections and Repairs

3.7.1

General In the event that laminations, split ends or other defects are discovered in any material, this specification will govern the extent to which the material can be rejected, accepted, tested and repaired.

3.7.2

Cracks Any crack, including surface cracks, in any structural material shall be rejected. Any material in which surface cracks are discovered shall be subject to magnetic particle and dye penetrant testing. Any material, notwithstanding prior acceptance, in which cracks are discovered, shall be removed from the fabrication and worksite and replaced. Material, other than joint cans, which contain laminations with a transverse dimension larger than 1/2 inch internal to the material or 1/4 inch on the beveled edges shall be rejected. Materials, other than joint cans or materials where through thickness material properties are critical, which contain laminations with transverse dimensions larger than 1/4 inch, shall be rejected.

3.7.3

Surface Defects and Imperfections Defects in the finished material which are not deeper than 5% of the specified nominal wall thickness (up to maximum depth of 1/16 inch) need not be removed. However, their extent must be determined. Shallow imperfections shall be ground to sound metal, the ground area shall be well joined, and the thickness of the ground plate shall not be reduced more than 7% of the nominal thickness, but in no case more than 1/8 inch. If the depth of the defect exceeds the above limits, but is not more than 20% of the nominal thickness, welding repairs may be performed with COMPANY approval, otherwise the section must be rejected. Repair of defects deeper than 20% of the nominal wall thickness or repair of defects with length and/or width more than 20% of nominal diameter is not acceptable. For tubulars made from thermally treated plate, repair by welding shall be permitted only with prior written approval of COMPANY.

3.7.4

Inspection Should laminations, split ends or other defects be discovered in CONTRACTORsupplied materials, the materials shall be tested by ultrasonic, radiographic, magnetic particle, and dye penetrant examination.

4.

WELDING Structural welding shall conform to COMPANY-approved CONTRACTOR welding procedures, and to the types, sizes and extent detailed on CONTRACTOR’s shop

cw


drawings. Unless otherwise stated, all welding shall conform to API RP2A and AWS D1.1. Welding and Weld Repair Procedure Specifications (WPSs) shall be in accordance with AWS D1.1, and shall be approved by COMPANY prior to fabrication. Approved procedures shall be adhered to during construction, and any changes must be resubmitted for COMPANY approval. CONTRACTOR shall maintain copies of procedures in each fabrication area and provide supervision to ensure adherence to procedures. 4.1

Welder Qualifications Welder qualification shall be in accordance with API RP 2A and AWS D1.1. COMPANY retains the right to require re-testing of any welder or welding procedure at any time. During fabrication, a file shall be maintained of welder performance certificates, available for COMPANY review.

4.2

Primary Connections Welded connections shall be full penetration continuous seal welds, to protect members against corrosion. Structural members, beams and shapes shall have edges prepared in accordance with API RP 2A and AWS D1.1, and any damaged beveled edges shall be restored to minimum tolerances. Structural members shall be properly aligned and spaced to provide joint configurations conforming to AWS D1.1 requirements and qualified CONTRACTOR welding procedures. Welding joint details, as shown in API RP 2A and AWS D1.1 for plates, pipes and structural shapes, shall be used wherever practical. When transition from one basic groove detail to another basic groove detail, or to a fillet weld, is required in otherwise continuous welded connections, CONTRACTOR shall describe the boundaries and contour changes developed in the transition zone. All structural welds shall be continuous and properly sized to develop the full strength of the smaller of the two members being joined. All splices shall be continuous V-butt joints (single or double depending on the member size) and of sufficient size to develop the full member strength. All surfaces to be welded shall be free of loose scale, oil or foreign material. Cleaning shall be performed by grinding, power wire brushing or sandblasting.

cw


Materials may be cut and shaped by machining, grinding, chipping, shearing, flame or plasma-arc cutting, using mechanically guided equipment where applicable. Sheared edges that are not to be welded shall be trimmed by grinding or machining to a minimum 3-mm (1/8-inch) depth, to ensure complete removal of cracked or cold work metal. Plate edges or pipe ends to be welded shall be examined for lamination before welding using Ultrasonic Testing (UT) techniques, in accordance with API RP 2A and AWS D1.1. Pre-heat and interpass temperatures shall conform to those in API RP 2A and AWS D1.1 or qualified CONTRACTOR welding procedures. No welding shall be performed when base metal temperatures are above 260 oC (500oF). Welding shall not be performed when prevailing weather conditions, including airborne moisture, blowing sand, or high wind, that would impair weld quality. Windshields shall be used when required. Arc-air gouging shall be acceptable for random metal removal and back gouging, however, gouged surfaces shall be ground before welding. Temperature and weather limitations specified above shall apply to all arc-air gouging. Low hydrogen flux-coated electrodes shall be handled and stored in the manner recommended by the electrode manufacturer. Butt welded joint and fillet weld contour details shall conform to API RP 2A and AWS D1.1 requirements. Partial or full penetration groove-welded "tee" joints shall be contoured smoothly into upstanding members by building up filler reinforcement in the inner corner with a transition radius equal to 50% of the thinner member’s thickness, but no more than 4.5-mm (3/16-inch), unless specified otherwise. Welding joint root openings wider than permitted by API RP 2A and AWS D1.1, but less than the thinner member thickness, shall be built up by welding to specified groove dimensions before the parts are joined. Such weld build-up shall be subject to Magnetic Particle Inspection (MPI) before welding. Welding joint root openings less than permitted by API RP 2A and AWS D1.1 shall be cut or gouged to maintain specified groove dimensions. If "arc-strikes" occur, grinding or weld repair followed by Magnetic Particle Inspection (MPI) will be required to ensure that no cracks exist in the metal. 4.3

Seal Welds All attachments, such as pipe supports, packaged equipment, tubular members, structural shapes, stiffeners, connections, gussets, and miscellaneous plate materials shall be seal

cw


welded in place to minimize corrosion. Non-structural seal welds shall be fillet welds or partial penetration groove welds no larger than 3-mm (1/8-inch). 4.4

Temporary Welds and Repairs When temporary welds are necessary, they shall be performed with the same care, materials, electrodes, preheat, and procedures as permanent weld installations. Temporary welding shall not be removed by arc-air gouging, and shall be removed without any parent metal damage. Any damage (gouges, tears, etc.) shall be repaired in accordance with COMPANY-approved procedures. CONTRACTOR shall repair weld deposit defects only with prior COMPANY approval. Defect removal may be by any method producing uncontaminated weld repair surfaces. Weld repairs shall be performed in accordance with approved weld repair procedures, which may be developed for multiple repair defect types, but shall provide for maximum adherence to essential Qualified Welding Procedure requirements.

4.5

Quality Control CONTRACTOR shall furnish Quality Assurance and Quality Control Procedures in accordance with COMPANY Specification 8791/09-GS2. Weld inspection shall include but not be limited to, DPI, MPI, radiographic and UT inspection methods. CONTRACTOR shall furnish all necessary testing equipment, and shall submit complete descriptions of the procedures required to COMPANY, for each type of test performed. In addition to other inspection methods used, joints shall be visually inspected prior to welding, including checking fit-up for proper alignment, groove angle, root face, and root opening to conform with weld procedure requirements. CONTRACTOR shall visually inspect completed welds, after weld spatter has been removed, for their size, configuration, appearance, undercut and surface flaws to ensure that all welds conform with applicable codes. Electrode care and storage procedures shall include storage conditions prior to opening containers, holding temperature after opening and any reconditioning procedures for electrodes exposed to atmospheric conditions for periods exceeding the manufacturer's recommendations. CONTRACTOR shall also establish positive wire and electrode identification methods. Submerged-arc flux condition procedures shall include methods to assure flux dryness before and during use, flux recovery systems after use, screening of foreign materials and flux storage methods used to prevent contamination. Procedures shall be established for post heat or stress relief temperature control.

cw


Procedures shall be established to assign each qualified welder a unique identifying number, used to identify all welds performed by him. Procedures shall be established for color coding each grade of steel used with paint that may be used on unprimed material. If materials are primed, paint compatible with the final coating system shall be used. Lumber crayon or wax sticks are unacceptable and shall not be used. Procedures shall be established to identify all welds by number and welder. Welds not clearly identified, prior to weld acceptance, are subject to repair or rejection by COMPANY at CONTRACTOR sole cost. Procedures shall be established in accordance with API RP 2A and AWS D1.1 to prevent warping. Welders and weld areas shall be provided with protection during periods of inclement weather and / or excessive wind conditions. Procedures shall include electrode, wire, fluxes, etc. protection methods. 4.6

Non-Destructive Examination Inspection methods and extend of inspection shall be in accordance with API RP 2A and referenced sections of AWS D1.1.

4.7

Inspection Personnel Qualifications SNT-TC-1A Level II or III inspectors are permitted to read and interpret inspection results. Level I inspectors may perform, and assist in, inspection operations, only in the presence of a Level II or III inspector. Inspection of certified materials, welding and structural fabrication by SNT-TC-1A Level I inspectors is subject to rejection by COMPANY. Radiography inspectors shall have had an eye examination within the previous twentyfour (24) months; otherwise they shall not be allowed to review films.

5.

DIMENSIONS CONTRACTOR shall submit a dimensional control report every two weeks giving at least overall structure dimensions to effectively control vital structural dimension fabrication tolerances. Final fabrication tolerances shall be in accordance with API RP 2A.

cw


Pipe clamps shall be fabricated with an internal diameter of –0 mm to +6 mm of the pipe outside diameter. 6.

LINERS TO PIPE CLAMPS

6.1

Introduction This section details the minimum requirements for materials, manufacturing, installation and testing of the polychloroprene lining to be used for the subsea structures pipe clamps.

6.2

General Requirements It is CONTRACTOR’s responsibility to add to these SPECIFICATIONS other requirements, such as tolerances needed to be fulfilled to allow for subsequent subsea installation of fittings.

6.3

Material Requirements

6.3.1

General The liners shall be manufactured using polychloroprene.

6.3.2

Specification for Polychloroprene Material The material specification of the polychloroprene shall satisfy the following minimum requirements and shall be tested using the methods specified on the Standards as indicated.

cw

     

Hardness Tensile Strength Tear Strength Elongation at Break Compression Set Abrasion Resistance



Ozone Resistance Test data to be as follows: Ozone concentration Elongation Temperature Duration of Test

65 + 5 Shore A 17.2 N/mm2 min 45 N/mm min. 400% min. 30% max. Akron - 0.3 g/1000 revs. max.. No cracking 50 pphm 20% 40oC 96 hours

ASTM D 2240-81. ASTM D 412-80. ASTM D 624-73 ASTM D 412-80 ASTM D 395-78 DIN 53516

DIN 53509, ASTM D 1149




Volume Increase

5% maximum

70oC 70 days

Variation after Aging Hardness Tensile Strength Elongation at Break

+ 5 Shore A, Max -15% of Variation, Max -25% of Variation, Max

Test data to be as follows: Temperature Aging

70oC 168 hours

 

Limit Low Temperature Adhesion to Steel

- 25oC 10 N/mm2 Minimum



Cathodic Disbonding



Operating Temperature Range

No Disbonding with potential - 1.5 V from -20oC to 70oC



6.3.3

Seawater Resistance Test data to be as follows: Temperature Duration of Immersion

UNI 5405 or equivalent

Metal and Elastomer Bonding Agents CONTRACTOR shall prepare metal and elastomer bonding agents as recommended by the polychloroprene material supplier for COMPANY approval.

6.4

Manufacturing and Testing Specification The polychloroprene lining shall be prepared by specialized manufacturers with proven capability and experience. The manufacturing procedure shall be based on the following minimum requirements and shall be submitted to COMPANY for approval.

6.4.1

Clamp Linings The manufacturing and application procedure shall be based on the following:

cw


 

The steel fabrication shall be planned in such a way that no welding that would otherwise influence the performance or properties of the lining takes place after the linings have been applied. The method to be adopted for the bonding of the polychloroprene linings to the steel surface shall be based on the technique of hot cure in autoclave.

The manufacturing and application procedure shall fulfill the following minimum requirements: 6.4.2

Surface Preparation Prior to applying any liners, CONTRACTOR shall ensure that the steel surface and the liner surface have been suitably prepared. The steel surface shall be cleaned by solvent washing to dispel all grease, oil and contamination. The steel surface shall then be heated to a temperature between 25-60oC. The steel surface shall be blasted to SSPC-SP10 and all residual dust removed from surface. The surface profile shall be 50-100 microns. The polychloroprene shall be applied within 6 hours of surface preparation.

6.4.3

Application of Polychloroprene Two coats of bonding agent shall be applied to the surface of the steel. The first coat of bonding shall be completely dry before applying the second coat. Two coats of similar bonding agent shall be applied on the liner surface. The liner surface shall then be brought into contact with the steel surface, rolled down, impacted and all excess polychloroprene dressed off. No air gaps shall exist between the liner and the steel surface. It shall be demonstrated to COMPANY, with test pieces if required, that the bonding process can be achieved leaving no air gaps between liner and steel surface. All production applications shall be left to cure in autoclave at the suitable temperature and pressure conditions and for the required time (indicatively 1.5 hours) as specified by manufacturer after the full pressure has been reached.

6.4.4

Laboratory Testing In addition to the test carried out in Section 6.4.5, the following tests shall be carried out on representative test pieces.   

Bond Test Hardness Test Spark Test

The testing procedures shall be submitted for COMPANY approval before any testing is carried out. All tests shall be completed, with satisfactory results as determined by COMPANY, prior to any production bonding taking place. cw


6.4.5

Inspection and Testing on the Installed Linings The following inspection and function tests shall be carried out on the installed polychloroprene:     

Visual appearance inspection of the installed polychloroprene. Visual bond inspection of the installed polychloroprene. Hardness test of the installed polychloroprene. Spark Test of the installed polychloroprene. Ultrasonic examination of the installed polychloroprene.

Inspection and testing procedures shall be submitted for COMPANY review and acceptance before any inspection/testing is carried out. COMPANY shall be informed immediately should any part of the polychloroprene fail an inspection or test, and CONTRACTOR shall submit full details of proposed remedial work and subsequent re-inspection. 6.4.6

Bonding Failure Should any areas of bond failure occur in the production bonding, then the complete lining shall be removed either by cutting the bond with solvent or by applying heat, and then the surface of the steel and liner shall be re-prepared in accordance with Section 6.4.2. The liner bonding face shall be visually inspected for damage caused by its removal and the liner shall be replaced if in the opinion of COMPANY sufficient damage has been sustained to impair its performance. The liner will then be re-applied to the steel in accordance with Section 6.4.3. Should any local areas of edge bond failure be found, then, these bond failures may, on approval from COMPANY be repaired by further application of the bonding agent to both the liner and steel surface. CONTRACTOR shall ensure that both liner and steel surfaces are clean and free from contamination. Further bonding agent shall be applied to both surfaces and the surfaces brought together, impact and further pressure applied if necessary.

6.4.7

Curing Period CONTRACTOR shall ascertain the minimum time required before the liners can be put in service and the time required to achieve the ultimate bond strength. CONTRACTOR shall observe such prescriptions during the assembly and loading of the pipe clamps.

7.

ANODES

7.1

Introduction This section defines the minimum technical requirements for the supply of sacrificial stand off anodes for the cathodic protection of the subsea structures.

cw


7.2

Anode Design CONTRACTOR shall prepare detailed dimensional fabrication drawings of the anode design for COMPANY review prior to commencement of production. CONTRACTOR may propose an equivalent standard size anode subject to COMPANY review and approval, provided specified mass and surface area are satisfied.

7.3

Anode Construction Anodes shall be of the stand off type supplied complete with tubular insert extensions for direct welding to the structure. Insert shall provide support for the anodic material throughout the design life of 50 years and the anode shall achieve a minimum utilization factor of 0.9.

7.4

Anode Material The sacrificial anode material shall be an Aluminium-Zinc-Indium type alloy, which shall exhibit the following electrochemical properties in seawater when tested in accordance with Appendix A of DnV RP B401.  

Capacity (minimum) Closed circuit potential

2500 Ahr/kg. -1.05V wrt Ag/AgCl.

Test data demonstrating that the performance of the anode material complies with the above requirements shall be provided by CONTRACTOR. CONTRACTOR shall submit the chemical composition of the proposed alloy to COMPANY for approval. 7.5

Insert Material The insert shall be fabricated from API 5LGrB material or similar Group I Class C material in accordance with API RP 2A. Mill certificates for steel insert materials shall be supplied for approval by COMPANY.

7.6

Anode Fabrication

7.6.1

Manufacturing Procedures CONTRACTOR shall submit an anode fabrication procedure for COMPANY approval. The description shall include the following: a.) b.)

cw

Insert fabrication Preparation of insert for anode casting


c.) d.) e.)

Anode material sampling and analysis methods Casting procedure Anode marking and inspection procedure

7.7

Steel Insert

7.7.1

Fabrication The welding of steel inserts, if applicable, shall be in accordance with qualified procedures using welders qualified to AWS D1.1.

7.7.2

Preparation The insert shall be blast cleaned to SSPC-SP 10 a maximum of 12 hours prior to casting. The steel inserts shall be clean, dry and free from rust blooming when the anode is cast.

7.8

Anode Casting The chemical composition of the furnace melt for each anode shall be determined by spectrographic analysis of representative samples taken at the beginning and end of each melt. The quantity of each element specified shall be determined and shall be within the limits approved by COMPANY.

7.9

Insert Position The anode insert shall be within + 5% of the nominal position in the anode.

7.10

Inspection and Testing

7.10.1 Anode Material Performance Testing One test from each melt required for the anodes shall be made to confirm that the electrochemical capacity of the anode material complies with Section 7.4 of this Specification. 7.10.2 Anode Weight At the start of anode casting, CONTRACTOR shall determine the average weight of the steel inserts by weighing. This average shall then be used as the basis for calculating the anode net weights. The total and net weight of each anode shall be accurately determined and the net weight shall be within - 3% of nominal net weight. The net weight of the complete order shall be -0% of the total nominal net weight.

cw


7.10.3 Dimensions The anode tolerance width and height shall be +5%, and the anode tolerance length shall be +25 mm. Straightness shall be subject to a maximum deviation of 2% of the nominal length from the longitudinal axis of the anode. 7.10.4 Anode Casting Each anode casting shall be visually inspected for any defects exceeding the requirements of this Specification. Shrinkage depressions and cavities shall not exceed 10 mm. The topping up of irregularities shall be allowed only if the additional material is fully bonded to the bulk anodic material. The casting shall be generally free from non-metallic inclusions. Cold shuts or laps shall not exceed a depth of 10 mm or extend over a total length of more than 3 times the width of the anode. Longitudinal cracks are not permitted. Transverse cracks or closely spaced clusters of cracks are only acceptable if: a.) b.) c.)

Maximum width is 2 mm Maximum length is less than 75% of the anode width. The depth of these cracks, measured from the anode outer surface may not exceed half the distance to the core as measured by feeler gauge. Maximum number is 5

Cracks less than 0.5 mm width shall be ignored. Cracks shall not be permitted for sections of anodic material not wholly supported by the anode insert. 7.10.5 Anode Internal Defects CONTRACTOR shall show that for the anodes cast from the same melt, transversely cut faces contain not more than: a.) b.) c.) 7.11

4% of any one surface area as gas holes or porosity and the total shall not exceed 2% of the total surface area 2% of any one surface area as non-metallic inclusions and the total shall not exceed 1% of the total surface area 5% of the insert perimeter with voids adjacent to the insert or lack of bond.

Marking and Handling

7.11.1 Marking Each anode shall be dye stamped with the following information: a.) cw

Supplier’s mark


b.) c.)

Melt number from which the anode was cast Inspection stamp

The format of the dye-stamping shall be submitted to COMPANY for approval. 7.11.2 Handling CONTRACTOR shall take all necessary precautions to protect the anode material and steel inserts against damage during handling and storage. Any anodes distorted outside the tolerances detailed in this Specification shall be replaced. 8.

ANTI-CORROSION COATING TO STRUCTURE

8.1

General All surfaces inaccessible after assembly shall be cleaned and coated prior to assembly. All surfaces except for the following items, and unless noted on the drawings, shall be coated:    

8.2

Threaded connections Equipment, name or special instruction plates attached to or included as part of any unit. Valve stems, movable linkages or any similar surfaces that are normally lubricated or have close working tolerances. Anodes (anode structural supports shall be coated).

Equipment and Materials Air for blasting and conventional spraying shall be available in sufficient quantity and at adequate pressure. It shall be substantially free from water and oil and be provided with adequate and efficient filters and traps which shall be regularly cleaned and/or emptied. The paint to be used shall be a two-component, high build epoxy system of one layer of primer, plus a minimum two layers intermediate/topcoats with minimum D.F.T. 300 microns. The different paints forming a specific coating system shall all be supplied by the same manufacturer. All paints shall be COMPANY-approved prior to use. All coating materials shall be furnished in original, unopened containers bearing the manufacturer's label and instructions. The date of manufacture and shelf life, where applicable, shall be shown. All containers of paint shall remain unopened until required for use.

cw


Paints shall be colored as follows: Finished Color - Structure: Finished Color - Padeyes: Finished Color - ROV Grab Bar: Finished Color- - Paint Markings: 8.3

Yellow (RAL 1004) Orange (RAL 2004) Orange (RAL 2004) Black (RAL 9017)

Surface Preparation All laminations, burrs, fins, weld spatter, sharp edges, excess weld metal, etc., considered detrimental to the protective coating systems shall be removed. Contaminants such as oil and grease shall be removed prior to any surface preparation. Heavy deposits shall be scraped or wiped off, prior to cleaning with a COMPANYapproved emulsifying solvent, and the surface washed down with clean water. The surface shall then be re-checked for contamination. Final cleaning shall be by abrasive blasting to SSPC-SP-10. Particular attention shall be paid to welds, rivet heads, corners, joints and crevices. The surface profile shall be as recommended by the paint manufacturer and checked in random positions selected by COMPANY with Testex Press-O-Film and a calibrated micrometer. Surfaces susceptible to particle contamination shall be screened to COMPANY satisfaction prior to commencement of abrasive blasting. All surface defects revealed by blast cleaning shall be properly dressed to a degree that will not be detrimental to coating performance or structural integrity. The area shall then be re-blasted to the required standard. All dust, grit, shot, etc. shall be removed before coating application by using an air lance or COMPANY-approved equivalent.

8.4

Coating Application Coating shall be applied using airless spray techniques. Coating shall not be carried out when the temperature of the ambient air is less then 5º C; when the relative humidity is greater than 85%; or when the temperature of the surface to be painted is less than 3º C above the dew point. Any steel that has been left more than 4 hours between blasting and coating or shows signs of surface deterioration shall be reblasted. When coating is being undertaken outdoors and the areas being coated are unprotected from the elements, work shall not be carried out during rain, fog, mist, snow or hail.

cw


Coating shall not be carried out when the temperature of the surface to be painted is below the recommended paint minimum curing temperature. Coating shall not be carried out in dusty conditions. Edges (other than those to be welded) along with corners, crevices, nuts, bolts and washers, etc are to receive an extra stripe coat of all coats to ensure adequate cover. The completed coating system shall be free from defects. Any defective areas shall be made good prior to the application of any subsequent coat. All surface contaminants shall be removed. Each coat of paint shall be of a contrasting shade or color to that preceding and compatible with the final finish color. The paint used for stripe coating, shall generally be the intermediate coat material and shall be of a contrasting shade of color. Coating layer thickness and overcoating times shall be in accordance with paint manufacturer’s recommendations. 8.5

Coating Repair Damage to the coated surfaces shall be assessed according to: a.) b.)

Sub-coat exposed Bare steel exposed and repaired as follows:

Where the sub-coat only is exposed, the topcoat shall be chamfered back and abraded for a distance of at least 50 mm from the edge. A layer of finish paint shall be applied to obtain the required thickness. Where bare steel is exposed, the area shall be abrasive blasted as detailed in Section 8.3 over a distance of at least 100 mm from the damaged edge. Contrasting shades of paint shall be applied to obtain the required thickness. The finish coat color shall match that of the original finish coat. 8.6

Mixing and Thinning Two-pack materials shall be mixed by mechanical methods only and according to the paint manufacturer’s instructions. Before mixing, both base and activator shall be thoroughly mixed separately in their original containers. The paint manufacturer’s recommend induction/reaction times shall be strictly observed. No thinner shall be added to the coating unless recommended by the manufacturer and required for proper application. Thinning shall not exceed the limitations established by the manufacturer and the type of thinner shall comply with the Manufacturer’s instructions.

cw


8.7

Grated Area Coating If steel grating is used on the subsea structures, this should not be galvanized, but should be coated with similar or equivalent coating to the structure. However, in view of the difficulty of achieving full coverage of the grating, the quality of the coating can be reduced to allow for the equivalent of 80% of the fully coated finish.

9.

BOLTED CONNECTIONS Bolted connections shall conform to AISC “Manual of Steel Construction”, Part 5, unless specified otherwise. Finished bolts and nuts shall be Teflon coated (Standcote or COMPANY-approved equal). Holes shown on Project Drawings, for bolted connections, shall be 1.6-mm (1/16-inch) larger diameter than the bolts used, and shall be drilled at right angles to the metal surface. Holes shall not be enlarged by burning. They shall only be enlarged by reaming and with COMPANY approval. Holes shall be drilled and reamed prior to application of protective coating(s). Bolts and studs shall extend entirely through the nut, but no more than 6.4-mm (1/4-inch) beyond the nut unless the bolted assembly is designed for hydraulic tensioning equipment. Bolts and studs shall be inserted into holes without driving or damaging the threads. Bolt heads and nuts shall be square to the metal and shall be drawn tight against the metal. Shear bolts shall be threaded such that no more than one thread will be within the surfaces of the structural members. Uncoated bolts and nuts may be temporarily used during construction in main members, or permanently in secondary members, but shall not be used permanently in main members. Provision shall be made to prevent nuts loosening due to structural vibration. A lock nut system, using either two nuts or a nut and lock washer, shall be used to join structural components that may be removed later for maintenance or operation.

10.

DIVER MARKINGS Subsea structures shall be provided with COMPANY approved marine anti-fouling diver markings which clearly indicate the subsea structure designation and face elevation, i.e. SSTI-S North Face.

cw

Specification for Fabrication of Subsea Structures

Recommend Documents