OGP 471 Underwater Cutting - Burning Report

Oxy-arc underwater cutting Recommended Practice

Report No. 471June 2012

I n t e r n a t i o n a l A s s o c i a t i o n o f O i l & G a s P r o d u c e r s

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Global experience

The International Association of Oil & Gas Producers has access to a wealth of technical knowledge and experience with its members operating around the world in many different terrains. We collate and distil this valuable knowledge for the industry to use as guidelines for good practice by individual members.

Consistent high quality database and guidelines

Our overall aim is to ensure a consistent approach to training, management and best practice throughout the world.

The oil and gas exploration and production industry recognises the need to develop consistent databases and records in certain fields. The OGP’s members are encouraged to use the guidelines as a starting point for their operations or to supplement their own policies and regulations which may apply locally.

Internationally recognised source of industry information

Many of our guidelines have been recognised and used by international authorities and safety and environmental bodies. Requests come from governments and non-government organisations around the world as well as from non-member companies.

DisclaimerWhilst every effort has been made to ensure the accuracy of the information contained in this publication, neither the OGP nor any of its members past present or future warrants its accuracy or will, regardless of its or their negligence, assume liability for any foreseeable or unforeseeable use made thereof, which liability is hereby excluded. Consequently, such use is at the recipient’s own risk on the basis that any use by the recipient constitutes agreement to the terms of this disclaimer. The recipient is obliged to inform any subsequent recipient of such terms.

This document may provide guidance supplemental to the requirements of local legislation. Nothing herein, however, is intended to replace, amend, supersede or otherwise depart from such requirements. In the event of any conflict or contradiction between the provisions of this document and local legislation, applicable laws shall prevail.

Copyright notice

The contents of these pages are © The International Association of Oil and Gas Producers. Permission is given to reproduce this report in whole or in part provided (i) that the copyright of OGP and (ii) the source are acknowledged. All other rights are reserved.” Any other use requires the prior written permission of the OGP.

These Terms and Conditions shall be governed by and construed in accordance with the laws of England and Wales. Disputes arising here from shall be exclusively subject to the jurisdiction of the courts of England and Wales.

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Oxy-Arc underwater cutting recommended practice

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Oxy-arc underwater cutting Recommended Practice

Report No: 471

June 2012

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International Association of Oil & Gas Producers

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Acknowledgements

This Recommended Practice was produced by the OGP Oxy-Arc Underwater Cutting Task Force

Revision history

Version Date Amendments

1 July 2012 First issued

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Table of contents

1 Glossary of terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

4 Risk mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74.1 Alternative cutting methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

4.1.1 Saws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.1.2 Shears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.1.3 Arc water gouging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.1.4 Kerrie cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.1.5 Thermal cutting techniques that use no oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.1.6 Plasma arc cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.1.7 Water jet cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.1.8 Chain feed cutters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.1.9 Orbital pipe cutters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.1.10 Casing cutters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.1.11 Hydraulic hand tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5 Roles, responsibilities & operational control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95.1 The client . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95.2 The diving contractor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 5.3 Client on-site representation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95.4 Dive supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.5 Divers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.6 Dive support crew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

6 Equipment selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.1 Welding power source. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.2 Safety switch or circuit breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.3 Burning leads or burning umbilical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166.4 Ground leads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166.5 Wire splices, connectors and terminations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.6 Continuity check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.7 Oxygen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.8 Oxygen hose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.9 Oxygen regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186.10 Oxygen pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186.11 Torches or electrode holders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7 Consumables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217.1 Tubular steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217.2 Exothermic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217.3 Consumables in general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8 Pre-job considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9 On-site considerations and the burning operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239.1 Proper venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

10 Safety & PPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

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10.1 Diver’s PPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

11 Training requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2511.1 Specification for instructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2511.2 Specification for diver training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

11.2.1 Oxygen-arc cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2511.2.2 Specification for diving supervisor training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

12 Oxy-arc cutting risks & mitigation (a commentary section) . . . . . . . . . . . . . . . . . . . . . . 29

Appendix 1 – Checklists for oxy-arc operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Client diving representative oxy-arc cutting checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Diving contractor oxy-arc prompt list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

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ALARPAs Low As Reasonably Practicable.

BurningUnderwater oxy-arc cutting.

Commercial DiveA logged dive carried out after training when the diver is employed as a commercial diver.

DiverPerson who by qualification and experience is a competent commercial diver.

DMTDiving Medical Technician.

HAZIDHazard Identification. A process of defining all potential hazards on a job by task identification and then identifying all mitigations (barriers) to prevent an incident, as well as recovery efforts defined in the event the incident does occur.

HP and LPHigh Pressure and Low Pressure.

JSAJob Safety Analysis. Developed on-site; a group effort by the responsible crew about to perform a task; to define work roles, safety considerations, and mitigations, prior to a task being performed.

O2 CleanOxygen clean is the verifiable absence of particulate, fibre, oil, grease and other contaminants following appropriate industry guidance.

Safe Work PlanAlso known as a work scope or work plan. It outlines the work required to complete a project. It is not as detailed as a work procedure, but would allow procedures to be developed based on its detail.

ROVRemotely Operated Vehicle.

TendersNewly-qualified divers or apprentice divers that are gaining the worksite commercial experience to be classed as a fully competent diver.

1 Glossary of terms

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Underwater oxy-arc cutting, also commonly referred to as “burning”, is the process of cutting materials (generally ferrous metals) with a tool that combines oxygen and heat to oxidize or melt the parent material, the method has been utilised extensively in the underwater diving environment. The frequency of diver fatalities, injuries, incidents, and asset damage occurring while using this process continues to be unacceptably high within the global diving industry.

Divers engaged in burning need to be competent in the task. This competence is achieved through training, knowledge and experience. This Recommended Practice has been developed to assist with the management of this activity and provide control measures, guidance and processes to ensure the safe execution of this technique. Additional information can be obtained from the documents referenced below.

2 Introduction

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• OGP Report № 411, Diving Recommended Practice• OGP Report № 431, Diving worksite representative roles, responsibilities and training• U.S. Navy Underwater Cutting and Welding Manual, Doc. № S0300-BB-MAN-010• IMCA D 045, R 015, Code of Practice for the Safe Use of Electricity Under Water• IMCA D 003 Rev. 1, Guidelines for oxy-arc cutting• IMCA D 031, Cleaning for Oxygen service• HSE OTH 349, Evaluation, selection & development of subsea cutting techniques

3 References

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4 Risk mitigation

The decision to use burning should always be considered against other methods and the risks identified, assessed and controlled. Many alternative cutting methods are safer and, in some cases, faster and more cost effective than oxy-arc burning. The use of unmanned submersibles or ROVs with power-operated saws can be considered and the choice to use a diver in an oxy-arc burning scenario should be balanced with alternative methods.

An ROV can also be used to assist in oxy-arc cutting by monitoring hoses, vent paths and the operation; this should be identified in the risk assessment.

4.1 Alternative cutting methods

4.1.1 SawsTubular members, pipelines and structural members can be readily cut with various types of underwater saws. Many of these saws are ROV or remotely operable.

Guillotine saws use a reciprocating hacksaw blade to make a cut. Each stroke sets the saw deeper in the cut. They can be diver or ROV deployed.

Diamond wire saws use a continuous loop of diamond embedded wire rotating around a guide-wheel frame to make a cut. They can be diver or ROV deployed.

Hydraulic ring saws are of particular value for cutting thick cross sections.

4.1.2 ShearsShears have proven to be valuable tools for remotely cutting large diameter components. Where there is stored residual energy in the component to be cut this method creates a risk to the diver.

Pyro-mechanical systems are generally a shear and these devices use a small low-powered explosive charge to operate the cutter as opposed to hydraulics. It can be used to cut any shaped structural member that will fit between the shear jaws. It can be deployed by an ROV.

4.1.3 Arc water gougingCarbon arc gouging utilises a copper coated carbon electrode that melts the steel in a controllable puddle and a low pressure water jet sweeps the molten metal from the cut area. This method is particularly suited for small cross-sections, 1-inch thick or less. It does not completely eliminate the hydrogen gas build-up due to electrolysis, but the lack of pure oxygen in the process reduces the risk significantly. It also provides a very controllable cut depth and thicker cross-sections can be cut by first gouging a bevel before making the through cut. This process works well with non-ferrous metals as well.

4.1.4 Kerrie cableKerrie cable is a flexible exothermic cable suited to cutting large components. This will require a dedicated additional training course before use.

4.1.5 Thermal cutting techniques that use no oxygenThese are electrodes manufactured for cutting underwater that use no oxygen in the process. This method can be much slower than oxy-arc cutting and can also produce hydrogen as a by-product of electrolysis.

4.1.6 Plasma arc cuttingA process whereby material is removed with heat from a high-energy plasma stream created in a hand held torch and usually propelled with an inert gas. This method can be much slower than oxy-arc cutting and can also produce hydrogen as a by-product of electrolysis.

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4.1.7 Water Jet CuttingThe cutting of metal is achieved by pumping high pressure water through a small diameter nozzle. This process is generally not a diver operated device and is used for inside or outside cuts made on tubular structural members where the cutting machine is set up and held in place on the member as it tracks around the member while cutting. An abrasive material is sometimes used in the high pressure water jet to aid in the cutting.

4.1.8 Chain feed cuttersThis machine tracks around a tubular member with the aid of a tensioned belly chain and guide wheels that encircle the tubular member. The traveling cutter is hydraulically powered and a blade cuts the pipe as the machine travels around the pipe on the chain.

4.1.9 Orbital pipe cuttersThese consist of a pipe clamp, guide ring and a pair of geared cutter heads. The cutters revolve around the clamp and each rotation sets the cutter deeper, automatically producing a finished cut on tubular members. These can either be hydraulic or air operated.

4.1.10 Casing cuttersGenerally used for cutting pipe or casing from the inside; these cutters are deployed hydraulically and have several cutters that revolve on an axis and open outward as the cutting is done. Tungsten carbide cutters mill away the pipe from the inside and can be used for cutting pilings on offshore structures.

4.1.11 Hydraulic hand toolsTools such as hydraulic grinders with cutting discs may be used to cut underwater effectively. Grinding should be considered “hot work” as sparks and friction may raise the metal temperature to the ignition point of any trapped flammable material. Hand-held reciprocating saws which use a reciprocating hacksaw blade can be used to make a cut. Hole saws are used to cut access holes for rigging underwater as well as being a good choice for cutting first vent holes in an area where burning will be required.

Other methods of cutting are known to exist, many of them using explosives that will not be reviewed in this document.

For a comprehensive list of alternatives, please refer to: HSE (OTH 349) Evaluation, selection & development of subsea cutting techniques.

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5 Roles, responsibilities & operational control

Roles and responsibilities for diving-related projects are found at length in OGP Report № 411, Diving Recommended Practice. In addition to all provisions of Report № 411 the following requirements are specific to a burning operation:

Note: all personnel on a project have the right, authority and obligation to Stop Work if they consider anything unsafe about the operation.

5.1 The client

The client is required to provide information in order to assist the contractor in planning and preparing for an underwater cutting operation; this will include but not be limited to the following:

• Current drawings of worksite and areas specific to the burning operation, which include: pipeline drawings; platform plan and elevation drawings; P& ID drawings; detailed deck layout drawings.

• A detailed Scope of Work to allow the contractor to produce workscope procedures.• The burning operation is executed according to the requirements of this Recommended Practice.• Any changes to the approved burning procedure shall be controlled by a Management of

Change (MOC), which is approved by client and contractor representatives.• Concerned parties, or approvers, shall be pre-determined and documented, a list generated and

included in the diving project plan.• Approvers may include client, project engineer, on-site rep, contractor management, vessel

master, diving superintendent and supervisors.• The client’s authorised representative shall participate in the contractor’s project risk assessments.• A Permit-To-Work is in place for control of this activity.

5.2 The diving contractor

The diving contractor is responsible for the following:

• The Diving Project Plan detailing the operational workscope and how it will progress from start to finish.

• The HAZID and risk assessment should be specific to underwater burning (provide documentation of the trained and qualified divers identified for the operation (see Chapter 11 – Training requirements)).

• Providing equipment that is suitable for the burning operation.• Location-specific procedures for burning based on a review of all drawings and inspection

reports.• Location-specific risk assessment/JSA developed for the planned activities of that shift. If

planned activities for that shift’s risk assessment change additional risk assessments will need to be performed.

5.3 Client on-site representatives

Knowledge and understanding is essential. Client on-site representatives should:

• Be knowledgeable of burning operations, the primary risks, applicable controls and compliance with this document.

• Be familiar with the worksite location, either through drawing review or diver inspection and assessment.

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• Verify that tools are available to assess electrical current and gas pressure/flow during the burning operation.

– Contractor shall provide these verification tools.• Participate in the risk assessment process and ensure that mitigation measures are implemented

during the operation.

5.4 Dive supervisor

A dive supervisor is responsible for the diver’s overall safety and ensures that all control measures identified through the risk assessment process are implemented. They should:

• Be competent in the management of burning operations; including knowledge of the primary risks, their controls and compliance with this Recommended Practice.

• Be familiar with the worksite, through procedural review, diver inspection and assessment.• Maintain physical control of the dive, burning operation and management control over the

knife switch or circuit breaker controlling the electrical current to the burning torch. The circuit breaker/safety switch shall be in easy reach of the supervisor.

• Participate in the risk assessment specific to the burning operation. Shall not take over, or hand-over, an operation to the next shift supervisor without a thorough exchange of information as entered in the operational log, equipment status, and location of diver and earthing/grounding point prior to leaving the radio or assuming control of the diver.

If a diving superintendent is present on the job, he should also be involved in this hand-over and ensure that control measures are being complied with. It shall be determined in the risk assessment process whether a second diving supervisor is required on each shift. If there is only one supervisor per shift no burning will be performed during shift handover.

5.5 Divers

Divers participating in burning operations shall be qualified in accordance with this Recommended Practice. Competence levels shall be demonstrated and based on the following levels:

Diver Competence Level Criteria Restrictions

1 – Advanced

Completed 30 logged commercial dives using oxy-arc as level 2. Plus a minimum of 150 commercial dives. For offshore this may be a combination of 100 offshore and 50 carried out inland. For inland diving only, this can be a minimum of 150 commercial inland dives.

• Evaluate diver competence requirements as part of risk assessment for intended operation.

• No other restrictions.

2 – Intermediate Completed 10 logged commercial dives using oxy-arc as level 1, plus 100 commercial dives.

• Only perform cuts with no residual energy in the component to be cut.

• No potential for gas entrapment.• No grout or mud behind the cut location.• No depth limitation.• Only cut component with less than 2 inches

wall thickness.

3 – Entry Passed training and assessment.

• Only perform cuts with no residual energy in the component to be cut.

• Water visibility not less than 2 feet.• No potential for gas entrapment.• No grout or mud behind the cut location.• Only cut component with less than 1.5

inches wall thickness.

• Divers shall have a comprehensive knowledge of the burning equipment being used and the scope of work.

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• The diver shall be able to identify a problem during the process, i.e. torch malfunction, incomplete electrical circuit (poor burning), oxygen/hydrogen build up (improper venting), etc.

• Diver shall initially confirm the vent path using a secondary supply such as the pneumofathometer prior to commencing the cutting operation. Thereafter the diver shall continually verify the gas vent path and have proven to himself and the supervisor that a clear vent path exists and is maintained, and there is no potential for gas entrapment adjacent or above the work site.

• Shall have reviewed the HAZID, risk assessment, dive procedures and work plans or MOC, prior to making a dive to burn.

5.6 Dive Support Crew

• One experienced member of the crew shall be designated by the diving supervisor for burning equipment oversight and to monitor equipment while in use.

• They shall be responsible for maintaining the burning equipment during the operation.• They shall monitor equipment during use to spot trouble, with particular attention to welding

leads and chaffing and to check for hot spots in the wires i.e. lead coating producing steam, smoke, or a slick wetted appearance. Hot spots indicate possible conductor breakdown within the lead.

• Report equipment status to the supervisor.

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6.1 Welding Power Source

The power source used to supply electrical current shall be installed at the dive site, vessel or structure and brought into service within the restrictions and requirements of any relevant vessel classing society, such as ABS, DNV or Lloyds. Machine grounding issues shall be addressed prior to hook-up.

The two most widely used types of welding machines used in burning are motor generators and electric inverter machines. The motor generators are pure DC current machines run with a diesel engine, or electric motor, driving a DC generator (newer machines may actually be AC rectified to DC). The inverter machines are AC rectified to DC machines utilising 220V or 480V, 3-phase input.

The following considerations should be noted before the use of any welding power source for underwater burning:

• DC output only machines shall be used. No machine that can be switched from DC to AC shall be used.

• No machine which has been modified in any way from manufacturer’s specification shall be allowed.

• Machine polarity shall be set to electrode negative or straight polarity (DCEN).• During machine selection, failure path and consequences must be considered.• Machines must be designed to fail in the open circuit mode.• Machines used for burning should be isolated from other welding machines on the vessel

(within the rules of vessel classification). On some vessels a common ground is used for all machines that can allow stray electrical current to enter the circuit specific to the burning.

• Any machine that is specifically designed for welding processes other than stick electrodes (GMAW, GTAW, etc.), should not be considered unless it is DC output only.

• Machines in constant use should be 400-600-amps or greater with a 100% duty cycle for the amperage setting being used. Some machines may be rated at 60% for max amperage and 100% for amperages less than maximum. Machines rated at 60% duty cycle should be regularly monitored during use for overheating and pauses in the burning monitored. (A 60% duty cycle means that the machine can be used at rated capacity for 6 minutes out of 10 minutes) On jobs requiring day to day burning activity, a 100% duty cycle machine is highly recommended. These machines are much more robust and fit for maximum usage.

• Exothermic electrodes require less amperage and a correspondingly lower amperage machine can be used for this type of application. If a combination of tubular steel, and exothermic electrodes, are planned for use, the machine should be rated for the higher amperage requirements of the tubular steel rods.

• Amperage control may be remote and controlled by the Supervisor in dive control.• Amps/Volts may be remotely monitored by Supervisor from dive control.• Amperage may be verified by calibrated instrumentation at or in the vicinity of the torch.

6.2 Safety Switch or Circuit Breaker

A circuit breaker, such as a “knife switch”, is the power disconnect switch in the electrical circuit going to the diver; it is used to prevent electrical shock when the diver is not actually cutting. A manual knife switch, or single pole/ single throw electrical switch is not recommended for diving operations. The preferred form of safety switch is a remote electrical contactor and must be a double pole/single throw switch or two single pole/single throw switches wired in parallel that interrupts the current flow through both the torch lead and the ground lead.

6 Equipment selection

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Figure 1 - Basic oxy-arc cutting system

Figure 2 - Preferred circuit breaker arrangement

Oxygen

Oxygen

Oxygen

-Ve

+Ve

Dive controlLeast preferable set up is with a twin pole knife switchHandle hinge position lowest

Dotted line would be the cable set up for ‘Single Pole’ switch

DC Welding Machine

Oxygen

Oxygen

Oxygen

-Ve +Ve

Dive control

Remote control of weld machine

DC breaking contactor

DC Welding Machine

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In addition:

• The switch must be rated greater than the maximum amperage of the welding machine powering the burning.

• The knife switch shall be mounted to a non-conducting stand.• The knife switch shall not be mounted in an area where oxygen could accumulate, such as an

enclosed, non-ventilated dive van.• Mounted in such a way that if the knife blade should fall it would fall to the open position and

not close the circuit.• The switch shall be covered with a non-conductive housing to safeguard the operator from

electrical shock for reasons as described in the warning below.• Local governmental or client requirements of explosion proof equipment may be required

on offshore platforms, refinery loading docks or chemical plant docks where ignitable concentrations of flammable gases, vapours or liquids are present within the atmosphere during normal operating conditions.

Warning: a manual knife switch produces a large arc when being connected or disconnected. This arc carries high energy and can cause electrical burn or shock. It is also a large ignition source.

The preferred mode of circuit interruption is through a remote circuit breaker that is housed in its own breaker box and operated through an on/off switch in the dive control. There are breakers specifically designed for use in burning operations and feature remote switching from the operator location. This type of switch is typically permanently mounted in a safe location outside the dive control van. These breakers shall always fail to the open circuit. It should be noted that the rocking motion of a dive vessel can affect the operation of some breakers and these breakers should be selected on “fitness for purpose” basis and the design carefully evaluated. Inverter type machines are generally equipped to support remote contractor switching.

Figure 3 - Voltage drop over distance

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6.3 Burning leads or burning umbilical

All cables providing a current path in the burning system shall be copper, and sized in accordance with the chart found below. All cables, including in-line connectors that are exposed to the water or a wet environment shall be fully insulated and watertight. Wet mate-able connectors of the proper size may be used only with their locking caps secured and a strength member installed to prevent separation.

In addition:

• Generally, no wire smaller than 2/0 (9.26mm) should be used for burning in water depths to 100-fsw (30m). 1/0 (8.25mm) wire is shown in the chart above to show amperage/voltage loss over distance as example only. As a rule, for water depth over 200-fsw (60m) the wire size should increase one size per 100-fsw (30m). 4/0 (11.7mm) and greater wire should be used for any burning in excess of 400-fsw (122m). Doubling the wire should be considered for extreme depths over 600-fsw (183m).

• All leads must be copper and properly sized for the application.• Due consideration should be given to the fact that the burning umbilical loses efficiency and

voltage when coiled, and heat is generated. The leads or umbilical should be laid out across a deck to prevent the formation of an electromagnetic coil.

• The circuit of the burning system starts and ends at the power source. All leads to the safety switch from the power source must be considered in the circuit length.

• If large size (4/0 or 11.7mm) wire is unavailable an alternate means of carrying high amperage is to double the leads throughout the circuit (power and ground).

• A strength member (synthetic and non-conductive rope) should be incorporated into the umbilical to reduce strain on the leads. The leads are not manufactured to hold their own weight over any length greater than ~50-ft (15.24m).

• Cable construction should be considered when procuring the leads. Cables with insufficient thickness of insulation may chaff and the insulation could become compromised.

• A tougher, more durable option is double insulated wires with PVC as the inner core cover and neoprene over the PVC. Insulation coating is critical to safe burning. Water ingress into the wire core creates resistance and electrolysis will corrode the wires severely in a short time. Welding cable utilising paper as an insulator should be avoided due to water absorption.

• An even more robust cable for burning application is Diesel Locomotive Cable (DLO) it has a 24 strand wire core versus the 30 strand wire core for welding cable. In a permanent application such as aboard a DSV this may work well between power source and safety switch. The reduced flexibility may make it difficult to deploy and retrieve from the water.

6.4 Ground leads

Ground wires shall be constructed of the same size and length as the lead wire to the torch. Usually the ground wire is married into the lead wire and oxygen hose to form an umbilical but this is not always the case for surface supplied diving, and therefore, the ground lead may be separate from the torch lead. The end is coiled to allow the diver to place it in the immediate area of the cut. The following recommendations apply to the ground lead:

• No through-water grounding. The ground wire must be attached to the item being cut in an effort to keep stray current from the diver and other equipment such as impressed current protection systems. A solid and well established ground produces a more reliable circuit.

• The ground should have a brass or high Copper alloy clamp arrangement on the diver’s end to allow the ground to be securely attached to the work.

• Ground lead attachment locations should be cleaned to bare metal.

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• The position of the ground in relation to the diver must be such that at no time does the diver or his equipment become positioned between the ground and the electrode. The diver must avoid becoming part of the electrical circuit.

6.5 Wire splices, connectors & terminations

Splices in the cutting leads should be kept to a minimum. A wire continuity check will determine whether a spliced lead is fit for service. Wire manufacturers may have guidance as to the maximum number of splices a wire can have and still function within intended parameters. When splices are required the following recommendations shall be adhered to:

• Wire splice kits designed for underwater service shall be used.• Never use termination lugs that are bolted together as a means of splicing as this is not their

intended purpose.• Insulation provided by a waterproof moulded casting, applied within manufacturer’s

instructions, as a splice cover is the preferred means of restoring insulation over a repair or splice.• Rubber, vinyl tape, and electrical sealant, as an insulator is not recommended as the sole means

of insulation for long term use, due to chaffing and possibility of arcing through the chaffed area.

• Underwater wire connectors shall not be of the twisted together type. A more positive connection is recommended to reduce resistance in the connector resulting in amperage loss. Above water connections may be a lug and bolt type, or twist lock connectors that can be disconnected. These connections must be insulated. All termination points should be cleaned to bright copper prior to their use.

6.6 Continuity check

Burning leads must be regularly checked, including visual examination, functional test of unit, including protective devices, plus continuity and resistance testing of cables. Continuity must be checked and logged by the use of an appropriate “insulation resistance tester to determine if the leads are fit for service. High resistance creates heat and may damage equipment, including the power source and also creates a large voltage loss between power source and electrode. Water logged and degraded leads must be replaced.

6.7 Oxygen

Oxygen used in a burning operation should be industrial quality (greater than 99%). A percentage reduction in oxygen purity will result in a reduction in cutting speed. Oxygen pressure and flow requirements should be based on the manufacturer’s recommendations for the material thickness to be cut.

6.8 Oxygen hose

The following should be considered when selecting oxygen hose:

• Recommend 0.375-inch (9.53mm) inside diameter hose, minimum (for depths greater than 200-ft a ½-in (12.7mm) hose I.D. may be required).

• Thermoplastic hose shall not be used in oxygen service for burning.• Oxygen hose shall be non-collapsible.

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• The hose shall be routinely maintained for oxygen use (O2 clean is the verifiable absence of particulate, fibre, oil, grease and other contaminants).

• Restrictions through hose fittings shall be minimised where possible. Full bore valves and full port regulators should be used for burning applications.

• In the cutting of non-ferrous materials air is sometimes used as a medium to move the molten metal from the cut. If air is used in an oxygen hose then the hose must be cleaned prior to returning to oxygen service. Air from HP cylinders is preferred to minimise or eliminate the oil contamination that can occur with LP or HP air produced by a compressor.

6.9 Oxygen regulators

Oxygen regulators used for burning shall be high pressure/high flow regulators. Regulators should be designed to work at maximum pressure and flow against a backpressure; these regulators have larger ports within the regulator body.

A flashback arrester and pressure relief valve should be incorporated into the regulator on the downstream (low pressure) side.

6.10 Oxygen pressure

Oxygen pressure requirements should be verified by the diving supervisor on the job site. Using pressures greater than required will increase the probability of an explosion by introducing more oxygen than is needed or producing a build-up behind the cut. The high volume, high pressure, two stage regulator shall be capable of delivering 70 CFM.

Oxygen pressure should be reduced to 40 bars or less at source.

The pressure and volume of oxygen is critical to efficient cutting. To calculate the required gauge pressure at any depth, always use the manufacturer’s recommendations.

6.11 Torches or electrode holders

Torch heads require regular maintenance and shall be marked with an identification number. Maintenance should be logged in the Equipment Maintenance System (EMS) to track the life of a torch and burning umbilical.

A new torch shall be inspected following the manufacturer’s recommendation prior to use. Torches shall be inspected before and after each burning operation. A checklist of inspection is as follows:

• Torch manufacturers should provide a schematic breakdown and recommended maintenance program to the consumer.

• Check all threaded pieces for contamination or slag in the threads; clean accordingly.• Check electrode collet for electrolysis erosion or arc damage. Replace as required for tight

electrode fit.• Inspect all rubber washers and O-rings for damage.• Inspect flash arrestor for serviceability.• The oxygen delivery system (field check):

– A flash arrestor shall always be installed in the torch.• Prior to use, the torch shall be inspected and assembled in accordance with the manufacturer’s

specification.• Manufacturer’s specification for pressure testing the torch and system shall be followed.

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• The welding cable or torch lead should be inspected at the connection to the torch body. Electrolysis will result in this connection becoming loose over time. It should be re-tensioned according to manufacturer’s specification.

Warning: electrolysis can produce hydrogen as a by-product of the process. This hydrogen may build up in the torch head voids if dead space exists.

• Check for work hardened areas in the welding cable adjacent to the torch handle. Work hardened cable may indicate the presence of broken conductor strands inside the insulation.

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In oxy-arc cutting there are two basic electrode (rod) designs, Tubular Steel Electrode and Exothermic Rod. Each rod type has its inherent strong points and also its weaknesses. Both types are commonly used and the equipment is the same for each type of rod, with the exception of higher amperage machine requirements for tubular steel electrodes. It is not uncommon to see both types of rod on a job and being used for the same work. A brief definition of each rod is as follows:

7.1 Tubular steel

Tubular steel rods are composed of a hollow, solid steel tube that is coated with a flux or waterproof coating. Some designs are covered with a waterproof coating over the flux. The typical rod is a 5/16-in (7.9mm) diameter tube with a concentric through-hole that is approximately 1/8-in (3.17mm) in diameter. Tubular steel rods can only be used for cutting when the electrical circuit is energised (hot). Tubular steel rods require more amperage (~300 amps) to perform efficient cutting and work very well on clean steel of any shape or design. Because of the need for electrical continuity the tubular steel rods cannot burn through heavy corrosion or marine growth efficiently; however, they can be more accurate, and because constant electrical contact is required, when burning close to another member which must not be damaged, rubber matting or insulation can guard against arc strike. Typical rod travel during a cut is usually more than that of an exothermic rod. Generally, tubular steel rods work better than exothermic rods on steel thicknesses in excess of 1-in (25.4mm), making a cleaner cut with less chance of an unburned section (hanger) being left behind. Tubular steel rods produce a higher arc temperature than exothermic rods. Arc temperature can be as high as 20,000°F, depending on amperage.

Note: exact amperage requirements should be established by testing. Examples given only suggest a range for use.

7.2 Exothermic

Exothermic rods are comprised of an insulated thin sheet steel outer cover over several small diameter alloy wires used as fuel wire. The small diameter wires are alloyed with materials that exhibit exothermic properties. The rod is typically 3/8-in (9.5mm) in diameter and the inner wires are arranged to form a hollow centre as an oxygen path. These rods require much less amperage or no electrical current at all after ignition. Once the rod is ignited the electrical current can be shut off, the heat is maintained by thermo-chemical reaction sustained by the exothermic materials. Some burning may require a low amperage (~150-amp) boost, especially in thicker materials. Once the oxygen is shut off the reaction stops.

Note: exact amperage requirements should be established by testing. Examples given only suggest a range for use.

Oxygen must be shut off from the rod to stop the burning process once started.

7.3 Consumables in general

Burning rods must be kept in a dry storage area and not exposed to extreme climatic conditions or contaminates that may have a reaction with oxygen.

Rusted rods should be disposed of and rods that have been in the water and returned to the surface unused should be considered unfit for service and disposed of.

Rods must never be oiled to reduce corrosion effects. Oil and oxygen may produce an explosion.

For large burning projects the electrodes should be qualified by testing to establish the best fit for purpose.

7 Consumables

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8 Pre-job considerations

9 On-site considerations & the burning operation

All burning operations shall be risk assessed.This will follow the contractor’s process and in addition to the support requirements for this process. Only divers and supervisors that comply with the training and competence requirements of this document should be used.

No burning operation shall be executed unless planned and managed in accordance with the requirements of this RP. The metal in the cut area should be thoroughly cleaned before burning begins. Metal should be cleaned of all corrosion scale, calcareous growth (barnacle bases) and paint or coating. Cleaning should be done on both sides of a cut when practical. Paint or other petroleum based coatings can produce a flammable gas when not completely burned; mixed with oxygen this can create an explosive environment. Proper cleaning prior to cutting will reduce the amount of oxygen consumed while making a cut.

If areas of material requiring cutting are in places where effective cleaning cannot be achieved the selection of electrode/rod types should be considered. Using an exothermic rod that does not require constant electrical contact may be the preferred choice in this case.

An accurate assessment of the burning requirements is always required. This shall include inspection dives or ROV to trace out gas paths, possible impact to adjacent structures or piping. The material to be cut must also be known. Any material, other than carbon steel, may not be easily cut with the oxy-arc process. Non-ferrous metals are cut by melting not oxidation and unsuited to the oxy-arc process. Materials such as aluminium, magnesium, or zinc shall not be cut with the oxy-arc process. These metals will actually burn on their own in the presence of high temperature and oxygen. These materials are very dangerous to the diver doing the burning. These materials shall be cut using alternative means.

9.1 Proper venting

It is a mandatory requirement that a suitable gas path for the elimination of volatile gases from adjacent to and above the cut is achieved prior to commencing the oxy-arc cutting operation.

The diver and supervisor must ensure that this gas is being removed from the area and not building up in pockets. This gas path confirmation can be accomplished in several ways:

• Vent holes can be drilled, or cut, above the intended cut line. If the content of the void behind a cut is not known, the holes must be drilled or saw-cut into the material. Vent holes made by drilling should be made with a drill using a reduced RPM to prevent the cutting edge of the drill bit from creating enough heat to ignite a combustible gas.

• Circular saws and grinders with cutting blades may produce sparks and heat which have been known to ignite combustible gas.

• Hydrocarbon presence shall always be assumed until proven otherwise.• Once penetrative holes are drilled windows should then be enlarged to allow adequate flow to

vent properly.• Prove the vent path by flowing secondary gas, such as from pneumofathometer.• What is behind the cut shall be considered, and verified, before any vent holes are made.• Stored energy may shift the material being cut. Differential pressure may create a problem.

Concrete-filled structures create a new set of problems to be considered.

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• Mud, grout or other material built up behind a proposed cut shall be removed. If it is not possible to remove the background mud, alternative cutting methods shall be used.

• Oxygen or other combustible gases may naturally rise away from the cut area and be of no consequence. This shall be verified. Internal structural braces within a structural member such as a tubular diagonal brace with internal stiffener rings shall be considered a possible gas entrapment. If gas introduced into the member does not vent in a predictable amount of time, it shall be considered as blocked and alternate venting schemes considered.

• Burning on an incline or vertical position should be done from the top moving down to reduce or eliminate the possibility of burning into a gas pocket. More than one vent should be made when burning in the horizontal directions.

• When cutting into a tubular tank or enclosed space vent holes will be needed.• Burning on a pipeline, vessel, storage tank, or anything having previously contained a

hydrocarbon product shall not be performed. Residual hydrocarbons in any amount can become quite explosive when mixed with oxygen.

Other hazards to consider when establishing a vent hole are:

• Differential pressure.• Residual forces in material causing load shifting.• Internal structural bracing within a closed member, such as an internal ring stiffener in a

tubular member.• Marine growth that can trap gases.• External coatings.

The process to verify flow path and identify any potential pockets should be in three phases:

• Identification.• Mitigation.• Verification which includes continuous monitoring as the cut progresses or locations changed.

Identification of flow paths and potential gas pockets shall be investigated using drawings, inspection dives performed, and any other information available to the project planning team. This team should be composed of personnel that have experience and competence in the type of burning to be accomplished and knowledge of the structure being burned.

Mitigation of the risk by establishing vent holes or windows to allow escape of explosive gases, removing potential barriers to gas flow behind the cut and be aware of trapped gases above vent windows that may ignite.

Caution: Hot slag encased in an oxygen bubble can travel up several atmospheres in the water column past the venting window and ignite gases or hydrocarbons trapped above the vent location.

Verification of venting to prove it is adequate shall be accomplished. One recognised method is to introduce a burst of air/inert gas into a drilled hole at the potential cut location and record the time elapsed until it exits the vent window.

Venting should be monitored and also verified when conditions, location, or when divers or supervisors are changed.

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10.1 Diver’s PPE

In addition to the standard PPE required for all diving, the following should be worn by the diver for the burning operation:

• Non-conductive gloves. The diver’s gloves should not become saturated with or entrap gas• Eye protection for arc flash in clear water. A #4 shaded lens or darker.• Protective clothing to protect the diver and dive suit from damage or burns from hot slag.• Personal jewellery should not be worn during burning. Gold is a highly conductive material and

can increase the chances of the diver becoming a part of the electrical circuit.

11.1 Specification for instructors

Instructors shall be trained to the requirements of this RP, experienced to Level 3, with 10 years commercial diving experience.

The instructor should be able to demonstrate the process in the training tank, or have a diver qualified to level 3 available who can perform this task.

11.2 Specification for diver training

11.2.1 Oxy-arc cuttingTraining establishment Diving Safety Standards to follow OGP Report № 411 Appendix 3, and this OGP oxy-arc RP.

Training and assessment in the hazards and controls of conducting oxy-arc cutting:• Risk Assessment and MOC

– Hazards – Mitigation – Controls

• Principles of Operation: – Theory of Burning – Oxygen system – Safe materials and their correct application – Venting – Grounding – Circuit breakers – Lifting – Rigging – Dropped objects – Lift bag use – Residual energy

10 Safety & PPE

11 Training requirements

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– Differential pressure – Hydrocarbons – Visibility – SimOps – Types of material, ferrous and non-ferrous – Configuration (tubular, wire, structural) – Slag – Bell position – Gas migration – Confined space burning – Dredging and below mudlines – Surface cleaning – Contaminated water – Tides, currents, splash zone – Electrical risks – Alternative cutting – Water depth – Diver position – Diver stance

• Underwater Cutting Rods – Tubular steel electrodes – Exothermic rods – Cutting rod amperage requirements – Tubular steel electrode amperage – Exothermic rod amperage – Other rod options

• Oxygen requirements – Oxygen delivery pressure – Oxygen purity – Oxygen safety – Burning oxygen segregation from main gas stores

• Cutting technique – Tubular steel electrode – Exothermic rod – Other rod options

• Troubleshooting – Symptoms – Probable causes – Identification and problem solving

• Post-Dive Maintenance

Training schedule each diver – Classroom instruction and assessment – 3 days. – Practical equipment setup – 1 day. – Dry burning – 0.5 days. Student will practice the necessary techniques with each type rod. – Wet tank training – 2 days. Each student will burn 50 rods of each type.

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Level 1 will be required to satisfactorily demonstrate safe and successful burning technique as follows:• Exothermic rod

– Burn 6 inch Schedule 80 pipe using no more than 3 rods. No Hangers. 4 minutes start to finish.

– Burn 1 inch clean steel for a distance of 18 inches using no more than 5 rods. No Hangers. 12 minutes start to finish.

– Burn 2 inch clean steel for a distance of 18 inches using no more than 9 rods. No Hangers. 15 minutes start to finish.

• Tubular steel electrode – Burn ½ inch clean steel for a distance of 18 inches using no more than 3 rods. No Hangers.

4 minutes start to finish. – Burn 1 inch clean steel for a distance of 18 inches using no more than 5 rods. No Hangers.

6 minutes start to finish. – Burn 2 inch clean steel for a distance of 18 inches using no more than 9 rods. No Hangers.

10 minutes start to finish.

The diver should maintain competence by using oxy-arc for 5 hours in water per annum. Where this is not achieved, tank top-up training should be considered by the client.

11.2.2 Specification for diving supervisor training

(Without diver burner qualifications following this guidance)

Training and assessment in the hazards and controls of conducting oxy-arc cutting:• Risk assessment and MOC

– Hazards – Mitigation – Controls

• Principles of Operation – Theory of burning – Oxygen system – Safe materials and their correct application – Venting – Grounding – Circuit breakers – Lifting – Rigging – Dropped objects – Lift bag use – Residual energy – Differential pressure – Hydrocarbons – Visibility – SimOps – Types of material, ferrous and non-ferrous – Configuration (tubular, wire, structural) – Slag – Bell position – Gas migration

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– Confined space burning – Dredging and below mudlines – Surface cleaning – Contaminated water – Tides, currents, splash zone – Electrical risks – Alternative cutting – Water depth – Diver position

• Underwater Cutting Rods – Tubular steel electrodes – Exothermic rods – Cutting rod amperage requirements – Tubular steel electrode amperage – Exothermic rod amperage – Other rod options

• Oxygen Requirements – Oxygen delivery pressure – Oxygen purity – Oxygen safety – Burning oxygen segregation from main gas stores

• Cutting Technique – Tubular steel electrode – Exothermic rod – Other rod options

• Troubleshooting – Symptoms – Probable causes – Identification and problem solving

• Post-Dive Maintenance

Classroom theoretical instruction, assessment and equipment setup -1 day

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The following commentary represents best industry practice and safety warnings in regard to using the oxy-arc underwater cutting process. Many of these comments are taken from documents referenced in this document, but are important enough to be mentioned again within the body of this work.

• Underwater burning produces a combination of pure oxygen and hydrogen gases as a by-product of electrolysis and heat generated over 2000°F. When trapped in a confined, or unvented, area this gas mixture will produce a serious explosion when ignited.

• Holes in the outer insulation cover of a burning lead may “bleed” a red copper oxide from the electrolysis in the wire core if the lead has been submerged in water.

• Never burn where there is a pressure differential from one side of the cut to the other. A differential that causes either a pressure release or a vacuum is an extreme danger to a diver.

• The diver must ensure that there are no hydrocarbons present that can ignite during the burning process.

• Never burn into an area that is not vented.• In order to flush out any hydrogen gas pockets in the equipment, oxygen must be flowed through

the torch and rod prior to energising the circuit.• Always follow the manufacturer’s instructions when using oxy- arc cutting equipment.

12 Oxy-arc cutting risks & mitigation (a commentary section)

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Two checklists have been added for use and to give a quick reference as to what is required both pre-operation and pre-dive.

The pre-operation checklist will provide a quick reference of compliance for project managers of both the client organisation and the contractor’s organisation and is primarily to assist the OGP Diving Client Representative(s).

The pre-dive checklist has been created as a reference to assist the diving contractor in managing the operation.

Client Diving Representative oxy-arc cutting checklist

No. Criteria Yes/No Comments

1Has a risk assessment been carried out to establish whether alternative methods of cold cutting are more appropriate?

2

Have site-specific procedures for oxy-arc cutting been created for the task? (Including material composition, thickness, configuration, surface condition, internal pressure, hydrocarbon content, identified cutting lines and venting positions, measurement/proving of venting and PTW & isolations?)

3Are there sufficient competent divers and supervisors trained to meet the requirements of this RP?

4Has a site-specific risk assessment been carried out on the work procedures with client personnel, diving contractor personnel, including supervisors & divers?

5Have all necessary isolations been identified and the PTW issued?

6 PTW Number added to this list. PTW No.:

7Have the cut areas been confirmed with the procedures? Have vent hole locations and cut lines been marked on the material?

8Is the burning equipment set-up, tested and maintenance compliant with this RP?

9Can the diver and supervisor confirm that there are no areas for gas entrapment in the cutting vicinity?

10Confirm that the bell set-up position and trunking have been located to avoid any potential for bell atmosphere contamination.

11Has the material to be cut been cleaned of coatings and marine growth?

12Confirm that the diver is to cut vent holes on instruction from the supervisor using the methods at the locations stated in procedure.

13Ensure that the supervisor and diver have confirmed all vent paths are functioning and monitored.

14Confirm that the diver is now ready to undertake oxy-arc cutting operations safely.

Appendix 1 Checklists for oxy-arc operations

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Diving contractor oxy-arc prompt list

YES NO

Equipment Oxygen cylinders Marked according to IMCA

Oxygen warning signs in place

Oxygen purity certificate from the gas supplier

Oxygen cylinders marked for Industrial Gas• Do not connect to BIBs lines• Do not connect to metabolic make up gas lines

Cylinder pressure test certificate in-date

Quad framework in good condition (look for pits painted over &/or filler)

Check under the frame for corrosion that may affect structural integrity

Check cylinders for corrosion on the base (contact area with quad frame)

Quad Lifting Pad Eyes - pull test & MPI in-date

Quad Slings & Shackles - fit for purpose & in-date load test certificates

Cylinder security

Cylinder paint & security

Cylinder neck valves blanked & capped

Cylinder neck valves in good condition

Cylinders & neck valves grease free

Dropped object protection in place

Burning oxygen segregated from DDC gas• Fire concern• Non-medical gasses connection to gas for human consumption

concern

Quads sea-fastened securely

Fire detection in place

Fire suppression in place

Fire hose nearby

Burning oxygen is not stored below deck

Quad electrically grounded to hull of vessel

Quantity - sufficient for the job

Quantity - burning gas is not included in treatment mix or metabolic - check/confirm on LSS gas board

Quantity - quad can easily be changed out

Oxygen manifold (on the quad)

Fit for purpose

Integral with the quad

Fabricated from suitable materials rated for oxygen (Swagelok catalogue or similar)• Should not be carbon steel, copper or iron tube• Should not contain galvanised or cadmium coated fittings

Pressure test certificate

Oxygen cleaned to an internationally recognised standard & certified by a competent person

Valves - must be rising stem type

Valves - fit for purpose - i.e. rated for oxygen use by the manufacturer

Valves - oxygen clean

Visually check metallic pig tails for: crush, crimp, twist, buckle, cracked joints, inappropriate fittings, excessively tight radiusIf the pig tails are silver soldered to a main tube request a pressure test certificate (Hydro test of pipe work is usually 1.5x WP) (200 bar WP requires a TP of 350 bar)

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YES NO

Equipment (continued)

Oxygen manifold (on the quad)

(continued)

Purpose-built oxygen distribution manifold shall be:• Designed to a recognised international standard• Constructed from materials designed for oxygen use• Capable of withstanding upstream pressure or a relief valve shall be

fitted to protect LP components• Certified by a competent person• Oxygen cleaned and tested• Pressure tested to an internationally recognised standard

Regulator Fit for purpose (high pressure & high flow)

Oxygen cleaned

HP & LP gauges fitted and operational (scale appropriated)

HP filter in place

Protected from dropped objects

Bull nose is the correct type for the cylinder

Pressure relief valve - to protect downstream components

“Burn back” (automatic device designed to sever the connection between the hose/regulator in the event of internal hose fire)

Relief valve fitted (downstream component protection)

Generally set at 90 psi over bottom, pressure reduced to 40 bar or less at source

Hoses & tube runs Oxygen hose:• From quad regulator to the top-side burning umbilical connection

must not be wire reinforcedSuch hoses shall be constructed from non-conductive materials

Oxygen hose shall be fit for purpose and designated for oxygen transport by the manufacturer

Hydraulic hose:• From hydraulic power pack to the burning umbilical reel connection

must not be wire reinforcedSuch hoses shall be constructed from non-conductive materials

Burning umbilical: oxygen hose shall be fit for purpose and designated for oxygen transport by the manufacturer

Oxygen hoses shall be pressure tested and certified by a competent person

Oxygen cleaned to an internationally recognised standard & certified by a competent person

Whip checks shall be used where required

Oxygen carrying hose/tube specifically related to thermal cutting operations shall not be bundled with life support gas, electrical, communications or other services critical to the diver, bell or DDCs life support functions

Oxygen carrying hose/tube shall not pass through machinery spaces or other areas that contain flammable substances or may promote or enhance combustion (such as hydraulic power pack rooms etc.)

Umbilical winch Designated SWL must be marked on the frame

Securely sea-fastened

Load tested and deck tie-down joint ND inspected

Primary brake - should be automatic when the lever returns to neutral

Secondary brake - may be manual

Maximum heave force to be entered in the risk assessment

Oxygen hose connection should be on the opposite side from the hydraulic connections

Oxygen hose to have a double block and bleed facility

Valves - should be rising stem type

Valves - fit for purpose - i.e. rated for oxygen use by the manufacturer

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YES NO


Umbilical winch(continued)

Valves - oxygen clean

Electrical connections must be designed for the application intended and fit for purpose

Umbilical winch lifting pad eyes in pull test & MPI date

Umbilical winch slings & shackles - fit for purpose & in-date

Must be electrically grounded to the vessel with heavy duty cable

Welding machine AC welding current output machines are unacceptable

Only Direct Current (DC) output machines shall be used

DC negative to the torch is the industry norm

400 to 600 amp range

Duty cycle 60 to 90 per cent depending on the type of rods used

The machine must be certified as fit for purpose by a competent electrical technician

Safety devices such as ground fault detection systems must be operational

The machine shall be electrically grounded to the vessel hull

Remote voltage and amperage read out is an advantage (in dive control)

Remote amperage control is an advantage (in dive control)

Test the output current is as indicated (Tong test or amp clamp)

Warning signs and barriers

Fire monitoring & suppression should be considered

Consider engine exhaust location

Welding machine lifting pad eyes - pull test & MPI in-date

Welding machine slings and shackles - fit for purpose & in-date load certificates

Cutting umbilical Should, at a minimum, contain a positive and negative cable with an oxygen hose

Consider a strength element of non-stretch rope such as Spectra

Consider the fitting of “D” rings as lift points or chain stops

Cable cross-section should be commensurate with the length of cable and the anticipated voltage drop. See a welding cable selection guide or low voltage electrician

Cable insulation should be of a robust nature. Consider sheathing in areas likely to sustain damage from structure or marine growth.It is likely that robust sheathing incurs a flexibility penalty.Consider the last three to five meters be “extra” flexible welding cable.

Cable and hose should be taped every meter

Cable should show no visible defects - look for “blisters”, cuts and tears, wire protrusion, “green” staining (copper/salt residue)

Both cables should be resistance & continuity checked prior to immersion

Electrical tests may be problematic due to water salinity, salt build-up on the umbilical, water penetration of the cable sheath

Visual inspection is likely to be the best infield method of fault detection• If necessary lay the entire cable out and have it inspected• Whilst the cable is flaked out, set up for “welding”. Test the cables by

having a number of welds run. If it is difficult to weld on deck there are brakes in the copper wires and strands inside the cable sheath. High resistance brakes may boil internal water generating steam and “blisters”.

Areas of high resistance (caused by copper wire cable thinning) will get hot very quickly

The torch should be in good condition (see torch section)

The ground clamp should be in good condition

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Cutting umbilical(continued)

Umbilical deployment method - pad eyes - pull test & MPI in-date

Umbilical deployment method - slings and shackles - fit for purpose & in-date load test certificates

Cables Cable cross-section should be commensurate with the length of cable and the anticipated voltage drop. See a welding cable selection guide or low voltage electrician.

Fit for purpose

Shall be supported

Shall be protected from dropped objects

“Ground” (positive) shall not be through the vessel hull

Cables shall not pass through areas that contain flammable substances

Cable connectors Treat all styles with caution (Lenco style). They often wear out due to internal arcing eroding the contact faces.

If they get hot during operation then the joint may be high resistance. Check the internal faces of the male & female unit for corrosion and arc pitting also the grub screw that locks the copper wire in the connector body. (Grub screw is likely to be low quality steel and subject to corrosion.)

Stab (Lenco style) connections should not go subsurface unless specifically designed to be immersed in salt water

Joints should be waterproofed using approved materials and process

Cutting & welding switch

Direct Current (DC) rated

Twin pole - solenoid operated

Amperage range to suit the type of rods being used

Should be located as close to the welding machine as possible• Remote activation by the diving supervisor is preferred mode of

operation

Certified fit for purpose by a competent person

Contained in a box that prevents arc flash

Should not be in a location that is subject to elevated concentrations of oxygen or combustible gases or vapours (hydrocarbon, acetylene)

Knife switch style (in dive control)• Mounted in a box (arc flash suppression)• Handle “down” to “open” the circuit• Twin pole• Oxygen analyser in dive control if “Rich Mix” is being used• Consider positive ventilation of dive control• Rated for the current loading of the rods being used• Dive control must be “grounded” with a cable equal to the size of the

welding cable• Welding Cable Bulkhead cable connectors shall be mounted on a

non-conducting board (such as Paxolin)FMEA electrical welding ground faults: considerations may be, but not limited to:• Metallic/conducting pipe work with life support functions• Electrical equipment overload (analysers)• Fire• Oxygen rich atmospheres

Planning Is the current burning work planned?

Is there a client document detailing the work scope?

Has the contractor prepared a burning procedure?

Has a risk assessment been conducted using the procedure as a guide?

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Planning(continued)

Have the correct personnel been identified and represented at the risk assessment?Representatives may be (but not limited to):Client Project Team Representation, Engineer, Diving Contractor Project Team Representation, Client Diving Rep, OIM, Vessel Master, Vessel Chief Engineer, ROV, Crane Operators, third party groups such as other asset owners in the same field.

Has the contractor prepared generic burning risk assessments?

Do the generic RA adequately cover the work scope?

Have the documents been reviewed?

What is the current document revision status?

Has the project plan been issued “for construction”?

Have the divers undergone training for the specific job?

Level 1 HIRA (onsite) to review findings of Level 2 HIRA? Do the conditions remain the same?

Can variations to the HIRA be managed onsite?

Are variations managed by the contractor MOC process?

Execution Pre-dive checks Hot work permit in place for vessel

Hot work permit in place for platform

Supervisor or engineer drafts a dive plan

Divers & “others” have read the “dive plan”

Tool box talk - includes divers & others

Knife switch “open”

Sufficient oxygen

Regulator set

Oxygen hose pre-charged - pressure noted

Inspect the torch for condition:• Large rubber washer• Rod rubber washer• Flash arrestor• Collet condition• Collet contact face condition• Condition and security of the extra flexible copper cable• Collet nut threads• Collet nut

Torch trigger leak & function tested

Generator online and set to the amperage required

Generator polarity test. Electrode should “negative”.• Bubble test can be made by immersion of a small plate attached to

the ground lead & a rod in the torch (remove the insulation on the test rod. Apply current - the larger bubble generation will occur at the cable connected to the negative terminal.

Test the knife switch & torch with a “rod test”• Note the amperage range

Visor in place on helmet• Lens to suit water clarity - No. 4, 6 or 8

Quiver full and tied shut

Spare quiver full and tied shut

Spare collets & washer on a safety pin tied 3 meters back from the torch

Diver has gauntlets and rubber gloves

Spare gloves tied back beside the collets

DDC checked

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Execution(continued)

Pre-dive checks(continued)

Cleaning equipment inspected & power equipment tested prior to deployment:• Water blaster• Power or hand wirebrush• Grit blaster• Chipping hammers• Scrapers

Small tools available• Hammers• Dot punches• Drills• Hole saws• Grinders• Paint sticks & markers• Tape measure

Dive check Diver confirms the conditions are as predicted, or not.• Review of the dive plan may be required

Burning gear is deployed “switch open”, generator “cold”

Work cut site is cleaned & marked out• Clean to a bright surface offers the best cutting quality & speed

Clean the back side of the cut if possible

Vent hole location(s) verified prior to cutting

Vent holes are cut & proven to the process identified in the HIRA

Ground clamp is connected at a location safe for the diver• Diver is not to be between the ground clamp and the cutting face

Set oxygen flow by adjusting the oxygen jet from the rod to about 150mm horizontal flow• Do not place hands in front of the rod to test oxygen pressure• Do not energise cutting torch before flowing oxygen through to purge

any possible hydrogen build up

Test cut is made on a dummy plate• Supervisor verifies the current settings are within normal limits

Do not burn the rod shorter than 75mm

Do not allow oxygen pressure to drop below 90 psi over bottom• Hose burn back may occur at low oxygen pressure

Check load is supported

Safety of diver and asset is identified in the direction of cut

Assess retained energy - inspect for distortion, buckling, twisting etc.

Umbilical clear

Post-dive checks Electrolysis can adversely affect the integrity of the metallic parts, especially on long burning campaigns.Frequency of inspection of the dive hat & burning equipment should be increased.

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Documents

OGP 471 Underwater Cutting - Burning Report