OLFNSA Guidelines for Safe Anchor Handling and Towing

OLF/NSA GUIDELINES FOR SAFE ANCHOR HANDLING AND TOWING

Final draft after consultation on 18 December 2002

OLF/NSA Guidelines for Safe Anchor Handling and Towing No.: 061A

Date effective: 25 March 2003

Revision No.: 09 Date revised: 18 December 2003 Page: 2

Contents 1. 1.1 1.2 1.2 2. 3 3.1 3.1.1 3.1.2 3.1.2.1 3.1.3 3.1.4 3.2 3.3 3.4 3.4.1 3.4.2 3.4.2.1 3.4.3 4.4 4 4.1 4.2 4.2.1 4.3 4.4 4.5 5 5.1 5.1.1 5.1.2 5.1.3 5.1.4 6 7 8. 9 9.1 9.2 9.3 9.4

Introduction........................................................................................................................................... 3 Objective ................................................................................................................................................. 3 Application.............................................................................................................................................. 3 Responsibilities ....................................................................................................................................... 3 Definitions and Abbreviations ............................................................................................................. 4 Planning and execution of anchor handling and towing operations ................................................ 7 Preparations and planning of anchor handling........................................................................................ 7 Responsibilities of operating company ................................................................................................... 7 Responsibilities of installation owner ..................................................................................................... 7 When vessels arrive on the field (500-meter zone)................................................................................. 8 Responsibilities of AHTS captain........................................................................................................... 8 Anchoring meeting.................................................................................................................................. 9 Anchor handling operation...................................................................................................................... 9 Securing anchor on deck ....................................................................................................................... 10 Towing operation requirements ............................................................................................................ 10 General towing rules ............................................................................................................................. 10 Planning of towing operation ................................................................................................................ 11 Catinary and towline load curves.......................................................................................................... 12 Towing operation .................................................................................................................................. 12 Reporting............................................................................................................................................... 12 Equipment requirements.................................................................................................................... 13 Permanent chaser pendant (PCP) requirements .................................................................................... 13 Pennant buoy system requirements....................................................................................................... 14 Pennant wire color codes ...................................................................................................................... 14 Vessel working wire/chaser requirements ............................................................................................ 15 Equipment requirements ....................................................................................................................... 15 Piggyback systems ................................................................................................................................ 15 Work specification requirements (scope of work) ........................................................................... 15 Work specification checklists ............................................................................................................... 16 Field information................................................................................................................................... 16 Installation information......................................................................................................................... 16 Requirements related to relevant vessels .............................................................................................. 17 Other information required in the work specification........................................................................... 17 Communication requirements during anchor handling and towing operations ........................... 17 Safe job analyses for anchor handling and towing........................................................................... 18 Competence and manning requirements for anchor handling and towing operations ................ 18 Appendices........................................................................................................................................... 19 Drawing of permanent rig chaser pendant system with and without anchor ........................................ 19 Drawing of pennant buoy system.......................................................................................................... 20 Piggyback system.................................................................................................................................. 23 Recommended design of working wire/chaser termination on vessel .................................................. 25


1.

1.1



Introduction

Objective

The objective of the guidelines is to facilitate safe anchor handling and towing operations on the Norwegian Shelf. The guidelines are intended for those parties that through planning, work procedures or actions influence safe operations in connection with the interaction between operators, owners of installations, installations, vessels, bases and suppliers. These guidelines have been prepared within the framework of "Working Together for Safety". The guidelines are therefore intended for relevant personnel working for owners of installations, operators, and on installations and bases and for the suppliers of towing and anchor handling equipment. This applies in particular to vessel Masters/crew, personnel involved in anchor handling and towing operations, as well as offshore installation managers, crane or winch operators with a special responsibility for safeguarding safety aspects in connection with anchor handling and towing. The guidelines contain a description of what is regarded as good working practices in the Norwegian offshore industry. Even though they are recommendations they should not be deviated from unless alternative solutions or instructions are deemed to be equal or better than those set out in the guidelines and satisfy relevant regulatory requirements for coordination between installations, anchor handling vessels, bases and suppliers.

1.2

Application

The guidelines apply to anchor handling and towing of mobile installations on the Norwegian Continental Shelf. 1.3

Responsibilities

The operating company has a see-to duty to ensure correct anchoring of installations. The operating company is responsible for ensuring that the installation is correctly positioned when the anchoring operation has been completed. The OIM on the installation is responsible for the anchoring operation, the safety of the installation and personnel on board, as well as operations taking place within the installation's safety zone. The OIM is the rig owner's senior representative on board the platform. The Master is responsible for safety on board the anchor handling/towing vessel, for the crew and equipment at all times. This means, for example, that the Master has the authority, if necessary, to stop operations that threaten the safety of the vessel and/or its crew. The Master shall obtain permission from the OIM or the person assigned authority for maritime operations on his/her behalf before entering the safety zone. This is to ensure the necessary coordination with planned and ongoing operations on the installation and/or within the installation's safety zone.


2.



Definitions and Abbreviations

1.2 Definitions Working wire

Wire in working winch including termination, for example socket

Work winch

Winch for hoisting and setting anchors. Power, length, width and diameter determine the area of application of the working winch.

Bollard pull

The towing vessel's pull normally specified as maximum continuous pull.

Bridle towing arrangement

Two wires/chains of equal length arranged as a triangle that connects the installation to the towing vessel.

Catenary curves

Specification of towline and anchor line curvature (bow height) for various loads.

Deck crane on vessel

Crane for lifting and assembling equipment on deck.

Shark jaw

Device for connecting/disconnecting chains/wires.

Stern roller

Large stern roller for guiding chains and wires primarily, but also anchors.

Installation

Submersible platforms, jack-ups, barges, etc.

J-chaser

Hook used by anchor handling vessels to "fish" the installation's anchor lines.

Gypsy

Wheel with machined pockets for hoisting chains fitted on a winch.

Kenter link

Device for linking two chain lengths.

Chain tail

A short piece of chain consisting of two or more links.

Fairlead for chain

Device that guides chains towards gypsy and chain lockers.

NavTug

Navigation equipment placed on board the individual anchor handling vessel in connection with an anchoring operation which functions as an interface with the installation's (MOU) main navigation equipment.

Pear link

Device for linking two different chain dimensions.

Pennant wire

Buoy wire; wire from the seabed up to a buoy on the surface.




Pendant

Wire hanging permanently attached to the installation used for chasing out anchors. PCP (Permanent Chain Pendant)

Permanent chaser

Ring fitted over the anchor line connected to the pendant wire. Used by anchor handling vessel when hoisting or setting the installation's anchors.

Pigtail

Short chain/wire with open end links.

Piggyback anchor

Anchor connected to primary anchor with wire/chain in case of insufficient holding power.

Towing winch

Winch of the same design as a working winch, but often with different gears. On newer vessels, the towing winch has a smaller drum than the working winch.

Towline

Wire on towing winch used for towing.

Spooling gear

Arrangement to guide wire onto drum.

Socket

Cast anchoring termination on wire.

Swivel

Connecting link/device used to prevent wire rotation.

Towing pins/guide pins

Device for guiding towline/pennant wire, e.g. towards stern roller.

Tow eye/towline guide

Arrangement for keeping towline in centre line/midship area.

Tension control A type of constant tension control; may be set to pull in or pay out at a specified tension. Tugger winch Used for pulling equipment on deck during anchor handling, delivered with remote control on newer vessels, may also be controlled from the bridge on some vessels. Tugger wire Steel or fibre wire used for tugger winch. Weather criteria Specification of maximum allowed weather (wind, waves, etc.) when performing the operation. Weather window Specification of maximum allowed weather (wind, waves, etc.) when performing the operation for a specific time period. Weak link Weak link in a rigging arrangement.

2.2 AHTS:

Abbreviations Anchor Handling Tug Supply vessel



AHV: DP: IMDG: IMO: ISM: MBL: MUF: NPD: ORQ: PCP ROV REH RUH: NMD: SJA: SOW: STCW:

Anchor handling vessel Dynamic Positioning International Maritime Dangerous Goods Code International Maritime Organization International Safety Management Code Minimum Breaking Load Notification of undesired conditions Norwegian Petroleum Directorate Oil Rig Quality, chain quality designation Permanent Chaser Pendant Remotely Operated Vehicle Reporting after incident Reporting of undesired incident Norwegian Maritime Directorate Safe Job Analysis Scope of Work International Convention on Standards of Training, Certification and Watchkeeping for Seafarers Safe Working Load Ultra High Frequency Very High Frequency

SWL: UHF: VHF:

2.3


References

References that apply in full or partially as agreed with the operating company: Normative references: • OLF/NSA Guidelines for Safety and Emergency Preparedness Training •

OLF/NSA Acceptance Criteria for Offshore Service Vessels

•

Norwegian Maritime Directorate's rules for passenger and cargo vessels, etc.

•

Norwegian Maritime Directorate's rules for mobile installations (most recent edition)

• •

Norwegian Maritime Directorate's Safety Notification No. 9 dated 3 April 2001 on incorrect use of shark jaws OLF/NSA 061 Guidelines for Safe Operation of Offshore Service Vessels

•

NPD’s regulations

Informative references • NORSOK Marine Operations (J-003 Marine Operations) •

DNV Rules for Planning and Execution of Marine Operations




3

Planning and execution of anchor handling and towing operations

3.1

Preparation and planning of anchor handling

3.1.1

Responsibilities of the operating company

The operating company is responsible for obtaining the information needed to anchor an installation in a field. The operating company is responsible for chart data and verifications/approval of position charts. The operating company shall: • Obtain an overview of infrastructure on the seabed • The operator shall specify horizontal/vertical minimum distances to installations and pipelines on the seabed for anchors and anchor lines. • Make available any HAZOP studies that have been carried out • Obtain information on sea bottom conditions and any obstructions • Provide weather and wave data • Provide information on simultaneous operations • Provide charts with positions • Carry out a briefing with the owner of the installation • The operating company shall normally make the vessels available for briefing on the base • Organise rig move meeting well in advance of the start-up • Obtain both hard copies and electronic versions of charts • Verify the work specification prepared by the owner of the installation • Obtain or determine who is to obtain vessels and mobilise according to plans • Obtain positioning equipment and positioning personnel • Evaluate the need for own representative on the rig • Determine logistics needs (deck cargo, bulk) • Ensure anchor handling equipment is shipped • Inform vessel and installation about the status of the operation at all times 3.1.2

Responsibilities of owner of the installation

The owner of the installation shall: • Prepared a work specification or "Scope of Work" that covers the entire anchor handling or towing operation in accordance with the guidelines of Chapter 5. The work specification shall be in English unless otherwise agreed. • Obtain valid approval from the Norwegian Maritime Directorate in case of asymmetric anchoring. This also applies to symmetrical anchoring, if there is no permanent approval from the Norwegian Maritime Directorate of anchor analyses for symmetrical line patterns. • Normally organise an information/operation meeting with the AHTS no later than the day before the anchor operation • Supervise the operation in the field • Communicate any changes to the work specification • Ensure that the Scope of Work has been reviewed with vessel and key personnel that participate in the operation, that the SOW is understood and that a Safe Job Analysis has been performed


• • • • • • • • • • • • •



Ensure that that the communication between all parties involved in the operation works Prepare anchor patterns to be verified by the operating company Ensure that satisfactory anchoring analyses have been prepared in compliance with Norwegian Maritime Directorate requirements Send notification of expected departure and arrival to defined recipients a minimum of three weeks before the operation Obtain necessary anchoring equipment in accordance with the anchor handling work specification, Chapter 5 Obtain spares (pins, shackles, etc.) Obtain extra personnel as required (OIM, personnel manager, winch operators, etc.) Send notice of departure to defined recipients Allocation of frequency for helicopter beacon (Radio Inspectorate TELENOR) Identify potential backload Ensure the crew is rested Verify that a Safe Job Analysis has been performed for all parties involved in accordance with the work specification, see also Chapter 7 Hold briefing with vessel and installation

3.1.2.1 When vessels arrive in the field (500-metre zone) It is the responsibility of the OIM to: • Ensure distribution of anchoring equipment • Distribute TugNav pack • Update the work specification • Provide status of the operation and weather report • Perform a communication check

3.1.3

Responsibilities of Master of the AHTS

The Master of the AHTS is responsible for: • Ensuring that the manning on board is sufficient based on working hour provisions, anchoring description and that the crew is rested • Ensuring that equipment meets the work specification • Ensuring compliance with the minimum competence requirements • Ensuring that a Safe Job Analysis has been performed in accordance with the work specification, cf. Chapter 6 on communication requirements in connection with anchor handling and towing operations • Inspecting received equipment (visual inspection of technical condition) Ensuring use of personal safety equipment/rescue equipment • • Having sufficient bunkers for the planned operation • Having the necessary towing and anchoring equipment Reference is made to the OLF/NSA 061 Guidelines for Safe Operation of Offshore Service Vessels


3.1.4



Rig move meeting

The operating company shall issue invitations to a rig move meeting, if possible, approximately two weeks before the operation starts. The work specification shall be distributed approx. one week before the meeting, if possible. This meeting is intended to identify any needs in connection with: • • • •

Anchor handling equipment Navigation and positioning Advance inspection of materials Selection of components

The following should attend the rig move meeting: • • • • • • • • • •

OIM (preferably the one on board during the operation) Representative from owner installation's operations department Onshore drilling supervisor for operating company Onshore logistics manager operating company Person responsible for positioning operating company/contractor Representative from operating company's marine operations group Captain on vessel if relevant (for special jobs) Equipment supplier if relevant (chains, wires, etc.) Warrenty surveyor if relevant Representative from owner/operator of pipeline/other installation if relevant.

The rig move meeting shall have the following agenda (as a minimum): • • • • • • • • • • • • • • • 3.2

Review of HAZOP for anchor handling in the field, if one has been prepared (in particular for fields with pipelines) and transfer of experience Weather limitations and definition of operational criteria Charts Area inspection with ROV Anchoring analysis, anchor pattern and work specification (scope of work) Pre-installation of anchor Vessel requirements; quantity and technical specifications Drawings and sketches of anchoring equipment in the sea Manning on installation Manning on boats Safe job input for boats and installation Schedules and drilling operation Equipment lists for AHTS equipment to the individual vessels Sea bottom conditions Communication lines (VHF channels, telephone nos.). Executing the anchor handling operation

Anchor handling shall be executed in accordance with the work specification. The OIM has the authority to make the necessary changes to the work specification. Significant changes shall be verified by the operating company. All changes shall be logged.


3.3



Securing the anchor on deck

Securing means preventing that a single component failure results in the anchor dropping uncontrollably off the stern. Recommended safety measures: • Anchor completely disconnected + wire connected to anchor chains • Use of separate safety wire (backup) • When running chains to the installation, the anchor is secured using a shark jaw and work winch • Reference is made to the Norwegian Maritime Directorate's Safety Notification No. 9 dated 3 April 2001. 3.4

Towing operation requirements

The following responsibilities apply to towing operations: • The operating company is responsible for ensuring that the entire towing operation for the contracted installation has been planned. • The owner of the installation, represented by the OIM, is responsible for planning and securing the necessary approvals of the towing operation. • If more than one vessel will be towing, the offshore installation manager shall designate a main towing vessel. • The Master on the main towing vessel is responsible for navigation of the towing operation. • The main towing vessel is responsible for complying with the prepared plans. • Other towing vessels are responsible for following the stipulated plans.

The maximum bollard pull shall not exceed the SWL for the towing equipment on the installation. Correct use of tension control on the vessel will make this easier to handle. Important factors that shall be taken into consideration during the towing operation: • The size of the object towed: length, width, and draft • Hull shape and condition (any marine fouling) • General conditions such as seaworthiness and stability. 3.4.1

General towing rules:

Special attention must be paid to the towline; particular attention must be paid to preventing any chafing and friction. • Fiber protection may be used, alternatively regular adjustments of the wire length. • Major dynamic tension must be avoided. • Changes in towing speed shall be done very slowly and in a controlled manner. • When heaving in or paying out the towline, the engine thrust shall be reduced correspondingly to avoid damage to the towline. • Wire connections shall be used when appropriate, but this wire shall have a breaking strength of at least 90% of the towline. Shock absorbers may be used carefully, if other circumstances make it necessary to use a short towline. • Avoid abrupt and major changes in heading. If the heading is changed, one must ensure sufficient room for the intended manoeuvre and take into consideration any other tows in progress in the same area. • Major changes in heading with a long towline shall be avoided as the wire could become slack and become damaged through touching the bottom.


• • • 3.4.2



Preferably use the tow eye or "eye-and-eye wire" to control the towline; avoid using the towing pins for this purpose. Maintain focus on the use of tension control in relation to bridle. Shorten the length of the towline when towing with reduced power and in shallow waters. Planning the towing operation

See Chapter 3.4 for details regarding the responsibility for planning towing operations. The sailing plan for the tow shall be planned carefully by the towing vessel in cooperation with the installation with regard to water depth, offshore installations, subsea installations and emergency anchorage. •

Keep a safe distance from any offshore installations; preferably five nautical miles in the open sea. Pass on the side that provides the best assurance that the tow will drift away from the installation in case of a black-out or the towline breaks.

•

Weather reports shall be obtained regularly. The weather criteria and necessary weather window for the tow shall be defined.

•

The need for support vessels shall be evaluated.

The following applies with regard to the use of any support vessels along the towing route for traffic control and assistance through trafficated waters. (The installation's standby vessel may be used as a support vessel, if available, or an anchor handling vessel that has to follow the tow to the next anchorage.) If a support vessel is used its tasks should include, but not be limited to: •

Monitoring and plotting all ship traffic along the towing route.

•

Intercepting any vessel that moves too close to the tow.

•

Checking that the anchoring site is clear and free of permanent fishing gear before the installation arrives.

•

Functioning as a back-up towing vessel, if the vessel is rigged for this type of job.

•

Handling tasks that the standby vessel normally would handle during a normal operation.

The following shall be prepared before connecting the installation's towing gear to the vessel: • • • •

Description of capacity of bridle and weak link Description and dimension of end termination of the installation's equipment Communication lines shall specified (UHF/VHF/mobile telephone), also see Chapter 6 on communication For towing vessel requirements, see Chapter 5.1.3.




3.4.2.1 Catenary and towline tension curves The following applies to catenary and towline tension curves: •

Exercise great caution and respect the dynamic forces at play when towing in adverse weather. The length of towline paid out may be critical to the tension the towline can handle. Excercise great caution when waves come in astern (leeward side).

•

The length of the towline is critical to its elasticity and ability to absorb dynamic forces. The longer the towline, the greater its capacity to handle dynamic tension. Of course, water depth and other water-related circumstances will also determine the length of the tow.

•

For longer ocean-going tows the length of the towline should be as long as possible, i.e. approximately 1200 -1300 metres or longer.

•

Calculation models (with spreadsheet and tables) should be prepared for catenary curves for vessels and installation.

3.4.3

Towing operation

Reference is made to Chapter 3.4 for details regarding responsibility for execution of the tow.

3.5

•

The vessels are normally equipped with a quick release. As a safety precaution any vessel without such a device shall have cutting equipment accessible and ready for immediate use.

•

When towing other vessels, the anchor chains are often the best place for hooking up the towline. A good towline catenary is ensured if the vessel towed can pay out a couple of shackles of anchor chain.

•

A tow journal, tow log or an IT-based maintenance system shall be used to document the hours the towing equipment is used. A deck log is not adequate.

•

Relevant bodies shall be notified in connection with rig moves, cf. Chapter 3.1.4

•

Towing vessels should issue navigational warnings at specified intervals (1 hr.)

•

During towing work should not be performed on the towing vessels and installation over the open sea. Reporting

The owner of the installation shall make sure that the following reporting is done immediately after anchoring up. The reporting shall be done in cooperation with and involve the vessels: • Issue notification of arrival to defined recipients when the first anchor is on the bottom • Prepare an overview of equipment in use (including rental equipment) • Report near misses and incidents (RUH-REH-MUF) • Report any damaged equipment and its condition (also rental equipment), see also Chapter 4.4


•



Report all remaining equipment to the owner of the installation/operating company (remember numbering).

4

Equipment requirements

4.1

Permanent chaser pendant (PCP) requirements

The requirements below apply to PCP components. In general a swivel should not be used in the pendant system, only on the working wire. See figure in Appendix 9.1 for further details on the system. Requirements related to chaser: certification-recertification-repairs-discarding • The original chaser certificate shall be on board and any repairs shall be documented • Routines shall be in place that ensure periodic inspection • The inspections shall focus on geometrical dimensions and wear and tear. Requirements related to shackles between chain tail and chaser: • Shall be a minimum of 110 tonnes (corresponding to super green pin). Chain tail requirements: • Minimum requirement is ORQ and a 400-tonne breaking load • The chain shall be certified • Minimum length 12 metres • Dimension 3” or 76 mm • There shall be an open common link at both ends. Requirements related to shackles between chain tail and pendant wire: • Shall be a minimum of 120 tonnes. Pendant wire requirements: • Eye towards chaser shall be PeeWee/CR socket • The wire shall be a minimum of 3” or 76 mm • Possibility for connecting a minimum 3" kenter link • The wire shall be galvanized and its quality certified • The length of the pendant wire shall be 200 foot or 61 metres. • Eye towards vessel/shark jaw: • Use a PeeWee/CR socket with an option for connecting a minimum 3" kenter link. It is recommended that a 3" chain tail is connected as shown below, to ensure that the chain tail is grabbed by the shark jaw on board to avoid damage to the pendant wire. Connector requirements (kenter link or pear link) • As a minimum the length shall be four links, for example: - Kenter link with a minimum of four links with stud and one open common link The quality shall maintain ORQ standard as a minimum • Minimum dimension is 3" or 76 mm • Shall be certified.


4.2



Requirements related to pennant buoy system

See Appendix 9.2 for further details on design of the pennant buoy system. The recommended length of the entire system (from piggyback to pigtail) should be the water depth plus 60 metres. Recommended maximum length is 75 metres more than the water depth. Buoy requirements: • Reference is made to general regulatory requirements: • Shall be able withstand a collision with a vessel • The load bearing capacity of the buoy shall be dimensioned based on the water depth and weight of the equipment • Shall have sufficient buoyancy in relation to the weight • Markings in accordance with applicable regulatory requirements • The pigtail shall be fixed to the buoy • The shackle shall be rated a minimum of 110 tonnes • The pigtail length shall be 20 feet with a minimum dimension of 2 ¾" • An open common link is recommended for pigtail eyes at the bottom end of the pigtail • The pigtail is connected to a kenter link at the bottom Kenter link requirements: • Shall as a minimum be ORQ quality and 3". Shackle requirements: • Minimum 110 tonnes. Requirements related to pennant wire for buoy: • Colour code markings (for example talurite socket) based on length, see 4.2.1 • Use preferably metric measuring units • Should have a soft eye or PeeWee/CR-socket with a chain tail of four chain links (3"). Requirements related to chain tail on anchor. May be piggyback or primary anchor, but in case of piggyback the following applies: • 12-metre chain tail at both ends (towards primary anchor and towards buoy/piggyback) • Chain tail shall be 3" or 76 mm • Minimum requirement is ORQ and a breaking load of approx. 400 tonnes • The chain shall be certified • There shall be an open common link at both ends • Lifting yoke for the piggyback shall follow the piggyback anchor. There is an option to use either a kenter link or 120-tonne shackle in the system, as long as the shackle is placed so that it can not enter the winch on the anchor handling vessel. 4.2.1

Pennant wire colour codes

The following colour codes shall be used on the socket to identify the length of the pennant wire 600 ft. Orange 500 ft. Blue



400 ft. 300 ft. 200 ft.

Green Red Yellow

4.3

Vessel working wire/chaser requirements • • • • • • •

4.4


A swivel shall be used in the working wire to prevent the wire spinning. It should be capable of handling 7000 kN and be of a concave design A PeeWee/CR socket is recommended for the working wire The minimum thickness of the working wire should be in relation to the winch (breaking load 300 tonnes) A pear link of an approved make shall be used The correct wire length in relation to the water depth shall be used, i.e. 1 ½ times the water depth It is a demand to keep up-to-date with new swivel designs being developed and to qualify these for use in working wires. See Appendix 9.4 for further details. Equipment requirements

The original certificates shall always accompany rental equipment. It shall be possible to track the equipment based on adequate labelling. Equipment that is shipped out shall be accompanied by a condition report and history. The person/organisation renting the equipment is responsible for ensuring that the supplier has complied with all requirements. When renting out kenter shackles and swivels, the equipment shall be greased and function tested. 4.5

Piggyback systems

The wire between the piggyback anchor and primary anchor shall have a breaking load of a minimum of 70% of the holding tension of the primary anchor. The wire between the piggyback and primary anchor shall be fastened to pad eye or bridle. The piggyback anchor shall be adapted to the sea bottom conditions based on the site survey. Reference is made to Chapter 9.3 for further descriptions of the piggyback system.

5

Work specification requirements (scope of work)

A work specification shall be prepared that provides the necessary background information on the anchor handling/towing operation and describes the operation at the required level of detail. The purpose of the work specification is as follows: • Ensure a safe operation for personnel, the environment and the economics • Provide common guidelines for standardising the relocation of the installation and anchor handling • Provide an brief outline of the topics to be covered • Must be brief and outline framework conditions without getting wordy • Is intended for use during the planning, execution, verification and demobilisation during relocation of the AHTS/installation



•


Shall be in English, unless otherwise agreed.

Deviation from the work specification is permitted by the cooperation of the parties involved in the operation. Reference is also made to OLF's guidelines for acceptance criteria for offshore service vessels. 5.1

Work specification checklists

The work specification shall have an introduction that describes its purpose in accordance with the items listed above. The description shall be based on a step-by-step approach with five phases: hoisting anchor, transit, setting anchor, pre-tension and final tension. The work specification shall contain the following items to be checked: 5.1.1 1.1

Field information Position

1.2 Water depth 1.3

Sea bottom conditions

1.4

Infrastructure (pipelines, templates etc.)

1.5

A minimum of field-specific requirements (such as simultaneous operations, buoyancy buoys, moorings, pre-positioned equipment/arrangements, changes in anchor lines). The appendix should show the anchor pattern with line lengths and operations manual for running anchor issued by the supplier.

5.1.2

Information on installation

•

Chain type and length (numbering of anchor lines and anchor pattern)

•

Anchor type, weight and quantity

•

Recommended PCP length, dimension, socket type and any chain tails (both ends)

•

Fluke angle on anchor

•

Towing gear SWL

•

Various propulsion systems (size and type thrusters, DP on installation)

•

VHF-UHF working channel, see Chapter 6

•

Telephone numbers (vessels and installation)

•

Crane radius and lifting capacity


5.1.3



Requirements related to relevant vessels

The work specification shall define the following: •

Bollard pull

•

Winch capacity (pull, drum capacity, diameter and number of drums)

•

Gypsies, number and dimensions

•

Chain lockers, number and capacity

•

Secondary winches, number and capacity

•

Guide pins/shark jaws (minimum 2)

•

Requirements related to wire terminations (see Chapter 4.3 for further details)

•

Stern roller: single or double for special needs

•

System for removal of clay

•

Spooling gear

•

Minimum freeboard requirement for safety on deck

•

Requirements related to crane on aft-deck for handling of equipment

5.1.4

Other information required by the work specification

If there are any special operations, it is recommended that drawings are prepared describing the operation step-by-step using words and images. Other relevant information: •

A drawing should be available of the anchoring arrangement when it is more complex than chains with PCP

•

Any catenary curves for relevant water depths showing the various tensions

•

Draught of the installation during the anchor handling operation (transit draught/operations draught, survival draught)

•

List of equipment to be ordered, as required

•

Weather criteria and weather window

•

Time estimate.

6

Communication requirements during anchor handling and towing operations

Good communication during the planning and execution phases of the anchor handling and towing operations is a precondition for a safe operation. Reference is made to communication in Chapter 3.3 of OLF's Guidelines for Safe Operation of Offshore Service Vessels.


• • •

7



VHF output power: 1 watt There is to be UHF communication between the crane operator and vessel deck during the operation. In the event UHF is not used, one of the seamen shall have VHF if the crane uses VHF. Before the operation is initiated a Safe Job Analysis shall be prepared or there shall be a dialogue between the parties involved (crane/vessel), see Chapter 7.

Safe job analyses for anchor handling and towing

The installation and vessel shall perform a Safe Job Analysis (SJA) before the anchor handling operation starts. If there is a change in the operation originally planned, and which was covered by an SJA before the operation started, it is important that the hazards of the changed operation are reviewed by the personnel involved. This requires a time-out and a review with the personnel involved. This review is carried out at the place of work using the established communication system on board the vessel. In contrast to an SJA, a time-out requires no fixed agenda, nor will it be necessary for the participants to sign out. Changes to the operation after the completed time-out are documented in the deck log. Reference is made to Chapter 9.8 of OLF's Guidelines for Safe Operation of Offshore Service Vessels for further details.

8.

Competence and manning requirements for anchor handling and towing operations

In principle the competence requirements stipulated in OLF/NSA 061 Guidelines for Safe Operation of Offshore Service Vessels apply.




9 Appendices

9.1 Drawing of permanent rig chaser pendant system with and without anchor Enclosed is a drawing of the recommended design of the installation's pennant wire system with and without anchor and with associated equipment. NOTE: Open end link here means open common link




9.2 Drawing of pennant buoy system Recommended design of a pennant buoy system with associated equipment: soft eye or socket. NOTE: Open end link here means open common link.










9.3 Drawing of piggyback system Recommended design of piggyback system - with associated equipment. NOTE: Open end link here means open common link







9.4 Recommended design of working wire/chaser termination on vessel

PeeWee/CR socket

Pear link

Pear link

Swivel 7000 kN Concave

Two chain links- with stud

Open common link

OLFNSA Guidelines for Safe Anchor Handling and Towing

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