AS 2885-3 Pipelines Gas and Petroleum-Operation & Maint..pdf

AS 2885.3—1997

Australian Standard Pipelines—Gas and liquid petroleum Part 3: Operation and maintenance

This Australian Standard was prepared by Committee ME/38, Petroleum Pipelines. It was approved on behalf of the Council of Standards Australia on 2 April 1997 and published on 5 May 1997.

The following interests are represented on Committee ME/38: Alinta Gas, Australia Australasian Corrosion Association Australasian Institute of Mining and Metallurgy Australian Gas Association Australian Institute for Non-destructive Testing Australian Institute of Petroleum Australian Pipeline Industry Association Bureau of Steel Manufacturers of Australia Co-operative Research Centre for Materials, Welding and Joining Department of Energy, N.S.W. Department of Minerals and Energy, N.S.W. Department of Minerals and Energy, W.A. Department of Mines and Energy, Qld. Department of Mines and Energy, N.T. Department of Natural Resources and Environment, Vic. East Australian Pipeline Epic Energy Operation and Maintenance, S.A. Hazardous Industry Planning Taskforce, Australia Institution of Engineers, Australia Metal Trades Industry Association of Australia Mines and Energy, S.A. Ministry of Commerce, New Zealand Office of Energy, W.A. Welding Technology Institute of Australia

Review of Australian Standards. To keep abreast of progress in industry, Australian Standards are subject to periodic review and are kept up to date by the issue of amendments or new editions as necessary. It is important therefore that Standards users ensure that they are in possession of the latest editi on, and any amendments thereto. Full details of all Australian Standards and related publications wil l be found in the Standards Australia Catalogue of Publi cations; this information is supplemented each month by the magazine ‘The Australian Standard’, which subscribing members receive, and which gives detail s of new publications, new editions and amendments, and of withdrawn Standards. Suggestions for improvements to Australian Standards, addressed to the head office of Standards Australia, are welcomed. Notification of any inaccuracy or ambiguity found in an Australian Standard should be made wit hout delay in order that the matter may be investigated and appropriate action taken.

This Standard was issued in draft form for comment as DR 93007.

AS 2885.3—1997

Australian Standard Pipelines—Gas and liquid petroleum Part 3: Operation and maintenance

Originated in part as AS CB28— 1972. Previous edition AS 2885 — 1987. Revised and redesignated in part as AS 2885.3— 1997.

PUBLISHED BY STANDARDS AUSTRALIA (STANDARDS ASSOCIATION OF AUSTRALIA) 1 THE CRESCENT, HOMEBUSH, NSW 2140 ISBN 0 7337 1192 8

AS 2885.3 — 1997

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PREFACE This Standard was prepared by the Joint Standards Australia/Standards New Zealand Committee ME/38 on Petroleum Pipelines, to supersede AS 2018 —1981, SAA Liquid Petroleum Pipeline Code, and AS 2885— 1987, SAA Pipeline Code, as well as the parts of AS 1697 —1981, SAA Gas Pipeline Code that relate to an MAOP of more than 1050 MPa or a hoop stress of more than 20%, and revising the operation and maintenance related Sections 9, 10, 11, 12, 13 and 14 of AS 2885 — 1987. The major inclusion is that of sections of the Australian Institute of Petroleum (AIP) code of practice for inspection and maintenance of liquid hydrocarbon pipelines (in Victoria) AIP CP18-1991. This Standard is the result of a consensus among Australian and New Zealand representatives on the Joint Committee to produce it as an Australian Standard. The objective of this Standard is to provide minimum requirements for the operation and maintenance of pipelines complying with AS 2885.1 and 2. The review of this Standard coincides with a move to deregulation and as such there may be a need to further review this Standard in the relative short-term future. This Standard is one of the following series, which refers to high pressure petroleum pipelines: AS 2885 2885.1 2885.2 2885.3

Pipelines —Gas and liquid petroleum Part 1: Design and construction Part 2: Welding Part 3: Operation and maintenance (this Standard)

Gas pipelines with a pressure of less than 1050 MPa and a hoop stress of less than 20% are covered by AS 1697. The term ‘normative’ has been used in this Standard to define the application of the appendix to which it applies. A ‘normative’ appendix is an integral part of a Standard.

 Copyright

STANDARDS AUSTRALIA

Users of Standards are reminded that copyright subsists in all Standards Australi a publications and software. Except where the Copyri ght Act allows and except where provided for below no publications or soft ware produced by Standards Australi a may be reproduced, stored in a retri eval system in any form or transmitt ed by any means wit hout prior permission in writ ing from Standards Austr alia. Permission may be conditi onal on an appropriate royalt y payment. Requests for permission and information on commercial soft ware royalt ies should be dir ected to the head off ice of Standards Australi a. Standards Austr alia wil l permit up to 10 percent of the technical content pages of a Standard to be copied for use exclusively in-house by purchasers of the Standard without payment of a royalty or advice to Standards Austr alia. Standards Austr alia will also permit the inclusion of its copyri ght material in computer soft ware programs for no royalty payment provided such programs are used exclusively in-house by the creators of the programs. Care should be taken to ensure that material used is from the curr ent edit ion of the Standard and that it is updated whenever the Standard is amended or revised. The number and date of the Standard should therefore be clearly identif ied. The use of materi al in pri nt form or in computer soft ware programs to be used commercially, wit h or wit hout payment, or in commercial contr acts is subject to the payment of a royalt y. This policy may be varied by Standards Australi a at any ti me.

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CONTENTS Page SECTION 1 SCOPE AND GENERAL 1.1 SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 BASIS OF STANDARD . . . . . . . . . . . . . . 1.3 APPLICATION . . . . . . . . . . . . . . . . . . . . . 1.4 RISK MANAGEMENT . . . . . . . . . . . . . . . 1.5 REFERENCED DOCUMENTS . . . . . . . . . . 1.6 DEFINITIONS . . . . . . . . . . . . . . . . . . . . . 1.7 RECORDS . . . . . . . . . . . . . . . . . . . . . . . .

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SECTION 2 PREPARATION FOR OPERATION 2.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 PROCEDURES AND PLANS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 RESPONSIBILITIES FOR PERSONNEL . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 READINESS FOR OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 DELAYED COMMENCEMENT OF OPERATION . . . . . . . . . . . . . . . . . . . . 2.6 FILLING PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SECTION 3 OPERATING REQUIREMENTS 3.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 NORMAL OPERATING PROCEDURE . . . . . 3.3 SAFETY AND OPERATING PLAN . . . . . . . 3.4 EMERGENCY PLANS . . . . . . . . . . . . . . . . 3.5 VENTING PROCEDURES . . . . . . . . . . . . . . 3.6 PURGING PROCEDURES . . . . . . . . . . . . . .

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SECTION 4 OPERATING CONDITION CHANGES 4.1 DESIGN CONDITION CHANGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 PRESSURE TESTING OF DESIGN CONDITION CHANGES . . . . . . . . . . . 4.3 PIPELINE MODIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 REVIEW OF PRESSURE-CONTROL AND OVER-PRESSURE PROTECTION SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 REVIEW OF DESIGN LIFE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 REVIEW OF MAXIMUM ALLOWABLE OPERATING PRESSURE (MAOP) 4.7 REVIEW OF LOCATION CLASSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 TRANSFER OF OWNERSHIP OR OPERATORSHIP OR BOTH . . . . . . . . . . 4.9 ABANDONING A PIPELINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10 RECORDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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SECTION 5 MAINTENANCE REQUIREMENTS 5.1 PIPELINE INTEGRITY . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 PIPELINE INSPECTION AND ASSESSMENT . . . . . . . . . 5.3 COATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 PIPE WALL DEFECT ASSESSMENT . . . . . . . . . . . . . . . 5.5 ANCILLARY EQUIPMENT ASSESSMENT . . . . . . . . . . . 5.6 CATHODIC PROTECTION CRITERIA . . . . . . . . . . . . . . 5.7 CATHODIC PROTECTION INSPECTION . . . . . . . . . . . .

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Page 5.8 5.9 5.10 5.11

PRESSURE CONTROL AND PROTECTIVE EQUIPMENT INSPECTION PIG TRAP INSPECTION AND MAINTENANCE . . . . . . . . . . . . . . . . . . CASING (SLEEVE) MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . STRUCTURES HOUSING EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 6 PIPELINE REPAIRS 6.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 SUPERVISION . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 COMMUNICATION AND CONTROL . . . . . . . . . 6.4 WORKING ON PIPELINES . . . . . . . . . . . . . . . . . 6.5 REPAIR STRATEGY . . . . . . . . . . . . . . . . . . . . . . 6.6 WELDING ONTO AN IN-SERVICE PIPELINE . . . 6.7 HOT-TAPP ING OPERATIONS . . . . . . . . . . . . . . .

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APPENDIX A LIST OF REFERENCED DOCUMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 B ASSESSMENT OF A CORRODED PIPELINE . . . . . . . . . . . . . . . . . . . . . . 36 INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

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STANDARDS AUSTRALIA Australian Standard Pipelines — Gas and liquid petroleum Part 3: Operation and Maintenance S E C T I O N

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S CO P E

A N D

G E NE R A L

1.1 SCOPE This Standard specifies the minimum requirements for the operation and maintenance of pipelines complying with AS 2885.1 and AS 2885.2. 1.2 BASIS OF STANDA RD It is not the intention of this Standard to prescribe a detailed set of operating and maintenance procedures that will encompass all cases. The operating authority, using its experience and its knowledge of the facilities and conditions under which it operates, shall develop operating and maintenance procedures based on the relevant requirements of the Standard. These procedures shall be adequate with regards to the safety of the public, operating personnel, pipeline and protection of the environment. 1.3 APPLICATION The requirements of this Standard apply to the operation and maintenance of pipelines designed in accordance with AS 2885.1. The requirements of this Standard will also apply to the operation and maintenance of existing pipelines when they are modified to operate under the conditions within the scope of this Standard. This Standard is not intended to be applied retrospectively to existing pipelines that have not been modified. 1.4 RISK MANAGEMENT Risk management during operation and maintenance should be addressed in accordance with AS 2885.1. 1.5 REFERENCED DOCUMENTS The documents referred to in this Standard are listed in Appendix A. 1.6 DEFINITIONS For the purpose of this Standard, the definitions in AS 2885.1 apply. 1.7 RECORDS During the period commencing from the receipt of the materials for the pipeline and its construction until it is decommissioned or removed, the operating authority shall prepare and keep current records of the following: (a)

The identity of all materials and components including all test results and inspection reports.

(b)

All maps, charts, plans, drawings and records that are required to allow the procedures to be properly administered.

(c)

Any modifications to the maps, charts, plans, drawings and procedures that are required to allow the procedures to be properly administered (e.g. exposure to the public, changes in design and operating conditions).

(d)

Charts and maps showing the location of cathodically-protected pipelines, cathodic protection equipment and structures affected by or affecting the cathodic protection system. COPYRIGHT

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(e)

The MAOP that are required by Section 4.

(f)

The condition of the internal and external surfaces.

(g)

Cathodic protection potential readings, cathodic protection unit outputs and interference current readings.

(h)

Details of any corrosion.

(i)

Details of any leaks, ruptures and other damage.

(j)

A current list of land holders who have been granted easement rights or other operating permits.

(k)

Any approved changes to operating conditions, engineering investigations and any work carried out in connection with any changes to operating conditions.

(l)

Records of pipeline sections or components identified as potentially high risk in an emergency.

(m)

Routine inspections and inspections carried out when cutting a pipeline or making hot taps.

(n)

Repairs and maintenance work to pipelines and stations.

The operating authority shall also prepare and retain for a minimum of 2 years records of the following: (i)

Necessary operational data.

(ii)

Pipeline patrols.

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S E C T I O N

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P RE PA R AT I O N

AS 2885.3 — 1997

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O P ER AT I O N

2.1 GENERAL Preparations for operation shall be deemed complete when the procedures and plans below have been implemented. With the preparation completed and with approval given to start operation, the filling of the pipeline can occur and the pipeline can then be put into operation. 2.2 PROCEDURES AND PLANS The operating authority shall ensure that the following plans and procedures have been prepared and approved as appropriate, and that personnel have been properly trained in their application: (a)

Operating, maintenance and repair procedures.

(b)

Safety and operating plans including emergency plans.

(c)

An environmental code of practice to deal with possible pipeline leaks and ruptures.

2.3 RESPONSIBILITIES FOR PERSONNEL Personnel responsible for the operation and maintenance of the pipeline shall, as applicable to their position; be — (a)

adequately trained and experienced in all aspects of the equipment in their control;

(b)

aware of properties of the fluid, including its hazard level in accordance with AS 3920.1;

(c)

capable of ensuring the safe disposal of any accidentally discharged fluid; and

(d)

capable of arranging for damaged pipelines to be repaired.

2.4 READINESS FOR OPERATION Pipelines shall not be considered ready to commence operation unless, as a minimum, the following checklist has been completed: (a)

The pipeline complies with the requirements of all relevant parts of AS 2885.

(b)

The hydrostatic strength and leak test requirements have been achieved.

(c)

The MAOP has been established.

(d)

The welds of tie-ins to existing facilities have been inspected by an approved nondestructive examination method and are considered to comply with AS 2885.2.

(e)

Components have been tested for satisfactory operation. Where impractical, other appropriate inspection shall be carried out.

(f)

Operating, maintenance and emergency personnel have been trained.

(g)

The pipeline is cathodically protected.

(h)

Third party awareness is established in accordance with Clause 3.2.4.

Additional site specific aspects may need to be evaluated prior to commencement of operation. NOTE: Initial operation may be approved before completion of the field work, provided that the incomplete work does not directly affect the safety of the pipeline, the public or the operating personnel.

2.5 DELAYED COMMENCEMENT OF OPERATION Where a pipeline is to be placed in operation with a time delay after it has been hydrostatically tested and if the fluid is allowed to remain in the pipeline, the test fluid shall be dosed with a corrosion inhibitor or the pipeline filled with a fluid that inhibits corrosion, unless it can be demonstrated that such measures are not warranted.

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If the test fluid is removed, the pipeline shall be dried or purged with inert gas to produce a moisture level which will not promote corrosion during the delay period. Where the pipeline is left filled with a liquid, precautions shall be taken to ensure that no damage is caused by overpressure due, for example, to thermal expansion effects. During the period between the hydrostatic test and the initial operation, the pipeline shall be inspected in accordance with Clause 5.7 to determine whether the corrosion mitigation systems are effective, and shall undergo surveillance in accordance with Clause 3.2.2. Corrective action shall be taken when an inspection reveals that unacceptable corrosion is occurring. 2.6 2.6.1

FILLING PROCEDURES General

The operating authority shall ensure that—

(a)

a pipeline is filled in a safe manner;

(b)

work is undertaken on a pipeline only when all relevant aspects of this Standard have been complied with; and

(c)

an approved procedure is used.

The filling of pipelines shall take into account the following actions: (i)

Controlling the filling rate.

(ii)

Controlling and monitoring the discharge of displaced fluids and venting of gases.

(iii)

Limiting the mixing of fluids at their interface.

(iv)

Preventing the formation of explosive gaseous mixtures at the gas/air interface.

(v)

Removing unacceptable residues from the pipeline.

(vi)

Preventing the discharged fluid from causing unacceptable environmental effects such as damage to crops, excessive erosion, soil contamination or contamination of watercourses or bodies of water.

(vii) Allowing any static electricity that may be generated to be continually discharged by an effective earth. (viii) Minimization of hydrocarbon discharge. 2.6.2 Filling a gas pipeline Where a gas pipeline which is full of air is to be placed in operation, the air may be displaced with gas separated with an inert gas slug provided that an appropriate continuous steady flow is introduced at one end of the pipeline and vented at the other. The flow should not be interrupted until the vented gas is free from air. The vent should then be closed. Where an uninterrupted flow cannot be maintained, the slug of inert gas shall be separated from the air by a pig to prevent the formation of an explosive mixture. When the pipeline has not been designed to allow pigging, alternative procedures shall be developed. 2.6.3 Filling a liquid petroleum pipeline Where air in a pipeline is to be displaced by a hydrocarbon liquid, a slug of water between spheres or batching pigs shall separate the air and hydrocarbon liquid. Where water in a pipeline is to be displaced by a hydrocarbon liquid, a sphere or batching pig shall separate the water from the hydrocarbon liquid. The flashpoint of the initial hydrocarbon liquid introduced into a pipeline shall, where possible, be not less than 61°C to prevent the formation of explosive gas/air mixtures. When the pipeline has not been designed to allow pigging, alternative procedures shall be developed. COPYRIGHT

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2.6.4 Filling a high vapour pressure liquid (HVPL) pipeline Where the HVPL consists of a single hydrocarbon, the pipeline may be filled in the gas phase in accordance with Clause 2.6.2. Where the HVPL is a mixture of hydrocarbons, the pipeline shall be filled first with water or a suitable low vapour pressure hydrocarbon liquid, and that liquid displaced by the HVPL. The two liquids should be separated by suitable spheres or pigs. The pressure shall be maintained at, or above, the bubble point of the HVPL to maintain it in its liquid phase.

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3

O P E R AT I N G

R E Q U I R E M E NT S

3.1 GENERAL The operating authority, using its experience and its knowledge of the facilities and conditions under which they are operated, shall develop procedures based on the relevant requirements of this Standard. Operating personnel shall be suitably qualified, trained and experienced to accepted industry standards. 3.2 3.2.1

NORMAL OPERATING PROCEDURES Operating to design conditions

The operating authority shall —

(a)

operate a pipeline only when it conveys the fluid or fluids under the conditions (including subsequent changes) for which it was designed, constructed, tested, and approved;

(b)

ensure that during normal operation, the operating pressure at any point in the pipeline does not exceed the MAOP, and that transient pressure does not exceed 110% of the MAOP;

(c)

ensure that the operating temperature is such that thermal stress limits used in the pipeline designs are not exceeded;

(d)

have written procedures (controlled document) for the operation and maintenance of the pipeline in accordance with this Standard; and

(e)

operate and maintain the pipeline in compliance with these procedures.

The procedure specified in Clause 3.2.1(d) shall include detailed plans and instructions for persons responsible for the operation and maintenance of the pipeline during normal operations and maintenance. 3.2.2

Pipeline surveillance

3.2.2.1 General Pipeline surveillance shall be carried out by the operator to ensure a pipeline is free from identifiable leaks and to identify any unacceptable risks to the pipeline, particularly unnotified external interference near the pipeline. The type of surveillance and the frequency required for safe pipeline operation varies and is related to the consequences of a hazard and the hazard reduction measures in place, as well as being dependent upon factors which include the following: (a)

Operation of a mandatory ‘One-Call System’.

(b)

Whether the pipeline is above or below ground.

(c)

Other forms of protection against interference.

(d)

Activities by third parties which could affect the pipeline.

(e)

Location in a built-up area.

(f)

Location close to environmentally sensitive areas.

(g)

Provision of a leak-detection system.

(h)

Regularity of use.

(i)

Nature of the fluid carried.

(j)

Design and operating pressure and temperature.

For a pipeline which is not regularly used, a patrol at frequent intervals may be maintained during use only, provided the line is isolated from sources of pressure when not in use. An annual patrol is required as a minimum. COPYRIGHT

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For a pipeline in regular or continuous use, the type of surveillance shall be by at least one of the following, provided the observer can clearly identify the pipeline and observe all the surveillance criteria: (i) Foot patrols. (ii) Vehicle patrol. (iii) Aerial patrol. (iv) Water craft for underwater pipelines. 3.2.2.2 Patrol of route The route shall be patrolled and inspected in an approved manner at approved intervals, and whenever it is considered that damage or threats to the integrity of the pipeline may have occurred or may be expected to occur. The route shall be accessible to authorized personnel and clear access to valve stations shall be maintained. Corrective action shall be initiated immediately a condition requiring such action is detected. Particular attention shall be given to drains or ditches that are maintained and cleaned by an independent party. Surveillance criteria shall include the following: (a) Variations of surface conditions such as erosion or earth movement. (b) Indications of leaks such as dead vegetation or evidence of liquid. (c) Construction activity or evidence of impeding construction activity on or near the route. (d) Impediments to the access to the route, valve stations, pressure regulator stations, compressor stations, pump stations, cathodic protection sites, communication installations and the like. (e) Deteriorating condition, visibility, adequacy and correctness of route markers and signs installed in accordance with the relevant requirements of AS 2885.1. (f) Security of sites and evidence of unauthorized entry. (g) Any other factors affecting the safety and operation of the pipeline. The person conducting the patrol shall— (i) be issued with written patrolling procedures; (ii) know the extent of the pipeline easement and the location of the pipeline; (iii) be in radio/telephone communication with the pumping station/control centre; and (iv) maintain a patrol log. All surveillance patrol records shall be retained for a minimum period of 2 years. 3.2.2.3 Underwater pipelines The pipeline operator will have measures in place such as to remain reasonably assured that, for underwater crossing, the depth of cover if the pipeline is buried remains adequate, that scouring has not caused any part of the pipeline to be unsupported beyond allowable freespan length, and that there is no accumulation of debris or silt that could affect the stability and safety of the pipeline. In the event that the operation is not so assured, further inspections are to be taken. Additional inspections shall be made following severe floods or storms which could have affected the integrity of the crossing. Corrective action should be initiated immediately when inspection reveals an unsafe condition. 3.2.2.4 Tunnels, shafts and valve pits Tunnels and shafts shall be inspected at approved intervals to confirm — (a) the structural integrity of the tunnel or shaft; and (b) the absence of leaks in the pipeline. COPYRIGHT

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Corrective action shall be initiated immediately where the necessity for such action is revealed. Tunnels and shafts accessible by people may be a confined space whereby entry shall be controlled by the confined space entry procedure and permit. A valve pit may be a confined space whereby entry shall be controlled by the confined space entry procedure and permit. The pit shall be kept free of all matter that in any way could interfere with the operation of the valve. 3.2.2.5 Valves Valves including mainline valves and the emergency hand-operated equipment of remotely controlled valves shall be operated at intervals not exceeding 18 months. 3.2.3

Stations

3.2.3.1 General Stations for pumps, compressors, meters, mainline valves, pressureregulators, odorizers and the like shall comply with the following: (a)

The area around stations shall be maintained in a clean and safe condition.

(b)

Entries, exits, and escapes routes shall be kept free from obstruction at all times.

(c)

Fences and gates shall be maintained to ensure the protection of the public and the equipment.

(d)

Start up, operating, and shutdown procedures for all equipment shall be established and followed. The procedures shall include details of the measures required to ensure that all equipment, including any shutdown control or alarm circuits, functions correctly.

(e)

Warning signs shall be maintained to ensure their accuracy, legibility and adequacy.

(f)

When deviations from the normal operating conditions that affect the safety of the pipeline occur, corrective action shall be initiated immediately.

(g)

The necessary firefighting equipment shall be kept on site and maintained in good condition.

3.2.3.2 Controls and pressure protection equipment Controls and protection equipment, including regulators, controllers, relief valves, and the safety devices shall be inspected and tested at regular intervals and serviced, as necessary, to ensure that the equipment is — (a)

adequate from the standpoint of capacity and reliability of operation; and

(b)

set at the required level.

3.2.3.3 Site security secured.

When a station is unattended, the site shall be appropriately

3.2.3.4 Structure A structure housing equipment containing hydrocarbons, such as valve/regulator/metre pits or buildings, instrument rooms and laboratories shall be inspected at approved intervals and shall be maintained in a safe condition. The inspection shall include the following: (a)

Testing of the atmosphere in the structure for toxic and combustible vapour.

(b)

Operation of ventilating equipment.

(c)

Structural integrity of pit covers.

3.2.4

Third party awareness

3.2.4.1 General Consideration shall be given to inform people and organizations that may in any way rely upon the safety of the pipeline detailed as follows: (a)

The appropriate authorities and other relevant bodies shall be informed of the hazardous properties of the fluid and the effects of any accidentally discharged fluid on the safety of the public so that, in the event of an emergency, prompt joint cooperative action can be taken.

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(b)

AS 2885.3 — 1997

Landowners and other occupiers of land through which the pipeline passes shall be informed of the methods of recognizing an emergency. They should be supplied with 24 h contact telephone numbers of the appropriate responsible persons or organizations to be notified in the case of emergency. Warnings should be issued concerning the dangers of interference with the pipeline and its appurtenances.

(c)

Landowners and other occupiers of land through which the pipeline passes shall be visited by staff of the operating authority at approved intervals, and be provided with information to ensure that their activities do not endanger the pipeline and its appurtenances.

To ensure land use planning, development, subdivision and the like does not jeopardize the integrity of the pipeline and the safety of the public and the environment, it is critical that land use planners, property and service designers, developers, owners and operators, construction organizations and the general public take into account the presence of the pipeline in their intended activities. Frequent communication with these groups is recommended. The operating authority should be advised about any changes in planning, development or similar near the pipeline, preferably while they are still in the concept stages, so that work will not interfere with the pipeline or vice versa. Third party development work may require additional protection to be considered such as concrete slab cover, increasing the depth or varying the route of the pipeline. Frequent communication with land use planners, developers, excavators, driller and borers is required to raise or reinforce the awareness of the presence of a pipeline and the constraints with respect to the use of the land on and near the pipeline. Constraints on land use adjacent to the pipeline include maintaining access to the pipeline, prohibition of buildings near the pipeline, restriction on and addition of fill, control of placement of vegetation, power and telegraph poles, fencing and agricultural activities. 3.2.4.2 Access to the pipeline In order to maintain the security and safe operation of the pipeline, regular patrol of the route is mandatory under pipeline regulations and as a condition of the pipeline licence. To meet this requirement, the easement or pipeline route shall be able to be accessed and traversed by pipeline personnel and authorized contractors at any time without delay, except in weather-induced conditions. 3.2.4.3 Prohibition of buildings near the pipeline Where a pipeline easement exists, no building or structure shall be allowed on the easement without approval. 3.2.4.4 Vegetation on and near the pipeline Unless approved, vegetation is to be restricted to allow free passage along the pipeline route. Vegetation in the vicinity of the pipeline whose roots may damage the anti-corrosion coating of the pipeline, is not permitted. 3.2.4.5 Addition of fill on or near the pipeline It is preferred that fill is not added on or near the pipeline as this increased depth increases the cost of excavation and the poor stability of the fill increases the risk of cave-in during subsequent excavation. If fill must be added, the depth and quality is to be advised prior to placement for agreement by the operating authority. Any landscaping should be level within the easement or a minimum of 3 m (but preferably 6 m) either side of the pipeline to permit excavating equipment to operate without having to destroy the adjacent landscaping. The addition of fill on or near the pipeline shall only be clean (preferably the same as the natural soil in that area) and shall not contain ash, salt or chemicals that could have a deleterious affect on the pipeline. COPYRIGHT

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3.2.4.6 Power and telegraph poles, fencing and agricultural activities Proposed new or replacement power and telegraph poles and fencing across or along the easement or pipeline route is to be advised prior to commencement to prevent damage to the pipeline by pole-hole augers or pole drivers. Holes are only to be drilled and poles or posts placed after the exact pipeline location has been marked by the operating authority. Agricultural activities deeper than 300 mm such as deep ripping and the installation of drainage systems are not permitted on the pipeline easement, or when no easement exists, a minimum of 3 m (but preferably 6 m) each side of the pipeline, without the approval of the operating authority. Such works adjacent to the pipeline should be advised prior to commencement to allow marking out the prohibited area. 3.2.5

External interference near pipelines

3.2.5.1 General near pipelines:

The following conditions shall be imposed upon external interference

(a)

A minimum of 48 working hours notice of intended activities near a pipeline should be given to the operating authority or operators so that arrangements can be made to have an operating authority s representative on site during the work. It is the responsibility of the operating authority to bring the requirement to the attention of third parties.

(b)

Where third party works are to be conducted in the proximity of a pipeline so that the integrity of the pipeline is potentially under threat, the site shall be inspected and a work plan specified and approved.

(c)

A representative from the operating authority shall be present during machine excavation which exposes a pipeline, to minimize the risk of pipeline damage.

(d)

No mechanical equipment shall be used within 1 m of the pipeline even after the pipeline location has been proven, except when approved by, and under explicit ‘onsite’ direction from the operating authority’s inspector. Under no circumstances is mechanical equipment to be used closer than 0.3 m to the pipeline.

(e)

The minimum clearance from a pipeline for any buried structure shall be — (i)

0.3 m between the pipeline and the other equipment, if up to 1.5 m wide; and

(ii)

0.5 m between the pipeline and the other equipment, if greater than 1.5 m wide.

NOTE: Separation distances from the metallic structure forming part of electrical power generation, transmission and distribution systems should be determined on an individual basis as large currents can be discharged into the ground under fault conditions.

The minimum clearance for parallel installation shall be such that future maintenance can be conducted, but shall not be less than 0.5 m. (f)

Any accidental damage to the pipeline coating or steel shall be advised to the operating authority.

(g)

All backfill within 150 mm around the pipeline shall be in accordance with AS 2885.1.

(h)

Where boring is to take place under or over a pipeline, methods shall be employed to ensure that the pipeline or its coating will not be damaged and a separation of at least 0.3 m between the pipe and bore is maintained.

3.2.5.2 Explosives The use of explosives shall not be permitted within 30 m of the pipeline without prior approval of the operating authority. 3.2.5.3 One-Call-services Operating authorities shall register their assets with One-Call (or Dial Before You Dig) services, where available, for the benefit of members of the public seeking the location of buried assets prior to excavation. COPYRIGHT

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Third parties excavating in areas for which ‘One Call’ or ‘Dial Before You Dig’ services are available, should be encouraged to seek from that service, information about buried assets, at least 48 hours prior to excavating. 3.2.6 Communications systems Adequate communication systems shall be used to ensure safe pipeline operation under both normal and emergency conditions. Systems allowing multiple simultaneous listening are preferred over one-to-one systems. 3.2.7 Noise abatement A certain amount of noise is inherent in operation and maintenance activities. The best practicable methods and industry standards should be employed to meet statutory requirements for the protection of site personnel and the general public. Special consideration should be given to the following: (a)

Provision of suitable ear protection to site personnel.

(b)

Siting and screening of plant.

(c)

Use of acoustically treated power tools, compressors and generators.

(d)

The timing of all operations and maintenance activities, which should take into account the impact on the environment.

3.2.8 Leakage survey and detection Operating authorities shall provide for leakage detection systems or periodic leakage surveys of the pipeline in its operating and maintenance plan. The types of surveys selected shall be effective for determining whether potentially hazardous leakage exists. The extent and frequency of the leakage surveys shall be determined by the operating pressure, piping age, class location, and whether the pipeline transports gas without an odorant. 3.2.9 Review of procedures Operating and maintenance procedures, and emergency plans shall be reviewed periodically and, if necessary, shall be revised and approved. 3.3

SAFETY AND OPERATING PLAN

3.3.1 General A safety and operating plan shall be established, monitored and maintained by the operating authority. The plan shall detail the policy of protection of personnel, the public and the environment including measures to — (a)

protect the pipeline and associated installations;

(b)

promote public awareness of the pipeline;

(c)

operate and maintain pipeline safety;

(d)

respond to emergencies;

(e)

minimize product leakage; and

(f)

monitor plans in accordance with Clause 5.1.2.

3.3.2 Safety and operating plan requirements include the following:

The safety and operating plan shall

(a)

A description of the pipeline system operation including suitable maps showing the route of the pipeline, the location of associated facilities such as compressor stations, SCADA control centres, transmission towers, cathodic protection points, valve stations, metering points, and launching and receiving stations.

(b)

An analysis of the likely hazards which include — (i)

a systematic identification of hazardous events, their potential causes, and the consequences (in qualitative terms) of such events; and

(ii)

the proposed operational, maintenance and organization safeguards that would prevent such hazardous event from occurring or should they occur, that would protect the plant, its equipment, operating personnel, the community and the environment. COPYRIGHT

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(c)

(d)

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Operational and maintenance safeguards which include — (i)

maintenance schedule;

(ii)

pipeline inspections; and

(iii)

cathodic protection surveys.

Emergency plans covering— (i)

impact events;

(ii)

fire;

(iii)

explosion;

(iv)

leak/spill; and

(v)

natural events.

3.4 EMERGENCY PLANS The following recommendations are given as a general guide with respect to emergency plans: (a)

Both operative and supervisory staff levels should be adequate at all times to respond to reported escapes. Procedures should be established in order to ensure that personnel attend the site of the emergency as soon as possible in the circumstances. An up-to-date contact list of such personnel should be maintained.

(b)

Emergency procedures should be established and all operational personnel should be made aware of them and be fully trained in their application including any action required from them under such procedures.

(c)

Necessary planning and preparation to implement emergency actions to be followed in the event of an accident, a failure or other emergency should be made, and may include the following:

(d)

(i)

Promptly and expediently providing remedial action for the safety of the public and operating personnel, minimizing damage to property and protecting the environment.

(ii)

Liaising with the appropriate authorities and other relevant bodies.

(iii)

Limiting the quantity of and controlling any accidentally discharged fluid.

(iv)

Preventing or controlling the spread of vapour by the use of temporary flares, blow-downs, or other means.

(v)

Giving particular attention to those sections of the pipeline that present the greatest risk to the public or the environment or, because of construction features, have special requirements or extraordinary maintenance requirements.

(vi)

Critically reviewing the actions and revising them at approved intervals.

(vii)

Revising the actions whenever there is a change in the fluid, the operating conditions along the route or the equipment.

(viii)

Carrying out periodic ‘mock-up’ exercises to determine the procedural correctness and personnel understanding of the emergency procedures.

(ix)

Having emergency equipment, pipe and fittings in good working order.

Emergency plans should consider the necessity of the following: (i)

Attendance at the emergency site to assess the situation.

(ii)

Reduction of the pressure in the pipeline.

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(iii)

Closure of any valves on each side of any dangerous or potentially dangerous situation.

(iv)

Establishment of a control centre from which emergency activities may be coordinated.

(v)

Instruction to the appropriate authorities and other relevant bodies of the action to be taken.

(vi)

Evacuation of any endangered members of the public and unauthorized personnel.

(vii)

Prohibition of any road and rail traffic, low-flying aircraft and isolation of electrical power, in any areas that may be hazardous to safety, to reduce any risk of ignition and resultant dangers.

(viii)

Expeditious transport of repair equipment, materials and personnel to the site.

(ix)

Additional prudent action that particular circumstances may make necessary.

VENTING PROCEDURES

3.5.1 Precautions to prevent an explosion Precautions shall be taken to prevent the accidental ignition of a possible hazardous concentration of flammable vapour or gas. Appropriate precautions may include the following: (a)

The display of suitable signs to advise the public about the extent of the hazardous area.

(b)

Where a cut in a pipeline is to be made by means other than a cutting torch, the installation of a metallic bond around that location.

(c)

Only electrical equipment, including radios, flashlights, and hand lanterns, that are safe for use in a Zone 1 hazardous location as defined in AS 2430.1 should be used.

(d)

When two flanges are to be separated, the installation of a metallic bond across the proposed break. Any impressed current cathodic protection system should be isolated but should be restored as soon as the work is complete.

(e)

The safe discharge of any static electricity (see AS/NZS 1020).

(f)

The prohibition of —

(g)

(i)

smoking and the presence of matches, lighters, and naked flame; and

(ii)

all sources of ignition from the work area, e.g. spark-ignition engines, motor vehicles and mobile phones.

Electrical safety (see AS 2885.1)

3.5.2 Venting gas In cases where venting of gas is to take place, reference should be made to the Recommendations IGE/SR/23 and the guidance contained therein should be applied as appropriate. 3.6

PURGING PROCEDURES

3.6.1 General Hydrocarbon fluids shall be purged from a pipeline when operating procedures dictate the need and before a pipeline is abandoned. Any purging of pipelines shall be in accordance with an approved procedure. 3.6.2 (a)

Gas

When a pipeline is to be purged of gas after depressurization —

a continuous steady flow of air shall be introduced at one end of the pipeline and vented at the other end, until the vented fluid is free of gas; or

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(b)

a slug of inert gas such as nitrogen or carbon dioxide shall be introduced between the air and the gas, to prevent the formation of an explosive mixture at the interface; or

(c)

the requirements of AGA 1975 shall be met.

Dissimilar fluids should be separated by suitable spheres or batching pigs. Discharged gas shall be disposed of in an approved manner. 3.6.3 Hydrocarbon liquid Where a pipeline is to be purged of hydrocarbon liquid, the purging fluid shall be water, air or a non-flammable gas. Where the hydrocarbon has a flashpoint equal to or less than 61°C and is being purged with air, a batching sphere, a batching pig or slug of water between two spheres should be introduced between the air and the hydrocarbon liquid. Where the hydrocarbon has a flashpoint greater than 61°C and is being purged with air, a batching sphere or a batching pig should be introduced between the air and the hydrocarbon liquid. Where the hydrocarbon is being purged with water, an assessment should be made of the need to separate water from the hydrocarbon liquid with batching spheres or batching pigs. 3.6.4 Purging an HVPL Where an HVPL is to be purged from a pipeline the pressure in the pipeline shall be maintained at a value greater than the bubble point at all points in the pipeline until the purging is compete. The liquid phase purging operation shall be in accordance with Clause 3.6.3. Gas phase purging shall be used only where the pressure in the pipeline has accidentally fallen to less than the bubble point or where the HVPL is deemed to be a single hydrocarbon. The gas phase purging operation shall be in accordance with Clause 3.6.2. Dual-phase conditions shall be avoided. 3.6.5 Trapped hydrocarbon Where a pipeline or auxiliary equipment that has been in service is to be filled with air and there is a reasonable possibility that the inside surfaces are wetted with a volatile combustible liquid or a volatile combustible liquid may have accumulated in low places, a procedure designed to purge such liquids shall be used. NOTE: Transmission pressure may be trapped in valve body cavities and other blind off-takes.

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S E C T I O N

4

O P E R AT I N G C H A N G E S

AS 2885.3 — 1997

C O ND I T I O N

4.1 DESIGN CONDITION CHANGES The operating authority shall ensure that where any changes to the originally approved design conditions occur or are proposed, these changes are fully assessed to ensure the integrity of the pipeline is not impaired and that safety of the public, operating personnel or protection of the environment is not diminished. The changes may require the modification and re-approval of operating, maintenance and emergency procedures and to the MAOP and design life. The following list is given as a guide to items of change that would initiate an assessment: (a)

Process fluid.

(b)

Pressure and temperature.

(c)

Land use location class.

(d)

Pipeline damage or deterioration.

(e)

Pipeline modification.

(f)

Pipeline raising/lowering.

(g)

Pipeline route relocation.

(h)

Pressure control and protection systems.

(i)

Design life extension.

The assessment shall include as appropriate a review of the following: (i)

The location class.

(ii)

The boundaries of the location class and the location of physical barriers or other features that could restrict the movement of these boundaries.

(iii)

Management of risk to the public, property, environment or to the pipeline in accordance with AS 2885.1.

(iv)

The protection measures required against third-party damage in accordance with AS 2885.1.

(v)

The physical characteristics of the pipeline, including the diameter, wall thickness, SMYS, fracture toughness properties, strength test pressure and leak test pressure. NOTE: These may be determined from records or, in the absence of records, by testing.

(vi)

The physical condition of the pipeline as determined from records of the operation and maintenance and from reports of examinations, inspections and monitoring, including those pertinent to corrosion mitigation.

(vii) The design pressure. (viii) The action that is required for the approval of a revised MAOP. The results of the investigation shall be used as the basis for the confirmation of or the need to review the MAOP, and shall be documented and approved. 4.2 PRESSURE TESTING OF DESIGN CONDITION CHANGES Where a change in a design condition occurs, and where a pipeline which has been strength-pressure tested previously to an appropriate pressure is in good physical condition, the results of that strength test shall be used to determine the MAOP. COPYRIGHT

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Where a pipeline has not been strength-pressure tested previously to the pressure appropriate to the location or is in a poor condition, the pipeline shall be tested in accordance with AS 2885.1 and the results to that pressure test used to determine the MAOP. The condition of the pipeline shall be determined through a formal engineering investigation. 4.3 PIPELINE MODIFICATIONS Where a pipeline is modified and the modifications may result in a change to the MAOP, (e.g. the addition of a branch line or the inclusion of a pressure-containing component) the MAOP of the modified pipeline shall be determined in accordance with AS 2885.1, and approved. 4.4 REVIEW OF PRESSURE-CONTROL AND OVER-PRESSURE PROTECTION SYSTEMS Pressure-control and over-pressure protection systems, including compressor supplier packages control software, shall be suitable for and effective at the operating pressure and at the MAOP. Any changes to pressure-control and over-pressure protection systems shall be approved. Suitability of systems shall be reviewed at approved intervals and in conjunction with changes to supply capacity. 4.5 REVIEW OF DESIGN LIFE Where it is intended to operate a pipeline beyond its design life, then prior to the expiry of the design life, an engineering investigation shall be made of the design, operating conditions and history of the pipeline, and an engineering investigation shall be made to determine its condition and any limits for continued safe operation. The pipeline shall only be operated under the conditions and the limits so established and approved. 4.6 REVIEW OF MAXIMUM ALLOWABLE OPERATING PRESSURE (MAOP) The MAOP of each pipeline shall be reviewed at approved intervals not exceeding 5 years and, if necessary, amended whenever there are changes (including corrosion or damage) that could adversely affect the safety of the public, the operating personnel or the integrity of the pipeline. Investigations, tests and calculations shall be made during the review to establish the current condition of the pipeline and to determine an MAOP in accordance with Appendix B. 4.7 REVIEW OF LOCATION CLASSES At approved intervals not exceeding 5 years and at any time when patrolling indicates the possibility of a need to change the classification of a location, the classification of the locations along the route of the pipeline shall be reviewed and if necessary changed, and appropriate corrective action shall be taken. 4.8 TRANSFER OF OWNERSHIP OR OPERATORSHIP OR BOTH The new owners or operators or both shall satisfy themselves of the integrity of the pipeline prior to takeover, by examination of the previous owner s or operator s records or by conducting an assessment of integrity. 4.9 ABANDONING A PIPELINE When a pipeline is abandoned, it shall be disconnected from all sources of hydrocarbons that may be present in other pipelines, meter stations, control lines and other appurtenances, and shall be purged of hydrocarbons and vapour with a non-flammable fluid. Disposal of the purging fluid shall meet all relevant environmental and safety requirements. When abandonment in place is approved, the ends of the pipeline shall be sealed on completion of purging and any warning signs along the route shall be removed.

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Consideration is to be given to filling the pipeline with a cementitious slurry, or alternatively applying cathodic protection to prevent the eventual collapse of the pipeline and consequent ground subsidence. In the event that cathodic protection is applied, the responsibility for ownership will remain with the pipeline operator and appropriate records will be kept. 4.10 RECORDS A record of approved changes of operating conditions, all engineering investigations and work carried out in connection with any change in the operating conditions shall be maintained until the pipeline is abandoned or removed. A record should be kept of all abandoned pipelines that remain in situ, to prevent possible mistakes in identifying an abandoned pipeline as an operational pipeline.

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S E C T I O N 5.1

5

M AI N T E N AN C E

R E Q UI R E M E N T S

PIPELINE INTEGRITY

5.1.1 General For the purpose of integrity assessment, the MAOP of a pipeline is equivalent to the allowable maximum pipeline pressure under the requirements of AS 2885.1. In order to maintain the integrity, a pipeline shall have the following: (a)

Sufficient wall thickness, at all locations, to contain hydrocarbons at the system MAOP. The minimum allowable wall thickness shall be assessed as follows: (i)

For a new pipeline, and for an in-service pipeline containing no corrosion defects or uniform general wall thickness loss, the minimum wall thickness shall be calculated in accordance with AS 2885.1.

(ii)

For a pipeline with physical damage, the minimum wall thickness shall be assessed in accordance with Clause 5.4.1 or other approved method.

(iii)

For a pipeline with corrosion defects, the minimum wall thickness shall be assessed in conformance with Clause 5.4.2 or another approved method.

(b)

Sufficient integrity at joints to prevent leakage at the design conditions and at the MAOP.

(c)

An appropriate pressure control system to ensure that the pipeline pressure does not exceed the MAOP during normal operation.

(d)

A documented system for pipeline maintenance and corrosion prevention.

5.1.2 Monitoring plan As part of the safety and operating plan (as required in Clause 3.3), the operating authority shall prepare, document and follow a plan detailing the inspections and tests that are necessary to allow the quality and integrity of completed pipelines to be monitored, to ensure that they continue to comply with the engineering design. 5.1.3 Audit A operating authority shall periodically assessment of each pipeline to—

conduct

a full audit and

(a)

assess the integrity of the pipeline;

(b)

review the operational and maintenance procedures of the pipeline; and

(c)

implement, integrity.

if necessary, appropriate measures to ensure continuing pipeline

Inspections shall be carried out to identify actual or potential problems that could affect the integrity of the pipeline. The operator shall plan and perform any maintenance required to rectify any such problems. Inspections shall be carried out by appropriately qualified and experienced personnel. 5.2 5.2.1

PIPELINE INSPECTION AND ASSESSMENT General

The inspection and assessment of a pipeline shall include the following:

(a)

A full visual survey of all above ground sections of the pipeline, including supports and associated equipment, to locate and assess any defects.

(b)

An audit of corrosion control facilities to assess their effectiveness. This includes cathodic protection systems, pipeline coatings, surge protection systems, static earth systems, and inhibitor dosing facilities.

NOTE: Where available, intelligent pigging results should also be considered in assessing pipeline integrity. COPYRIGHT

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5.2.2 Regularity of assessment The regularity of assessment should be based on the past reliability of the pipeline, current knowledge of its condition, the rate of deterioration (corrosion rates, coating degradation and the like), and statutory requirements. 5.2.3 Assessment results and appropriate action If the integrity of a pipeline is assessed as being inadequate or at immediate risk, the operator shall immediately take steps to rectify the problem until the integrity of the pipeline is restored. Measures shall be taken to mitigate the risk of a leak to the minimum. This may be by a reduction in pressure, bypassing, or carrying out temporary repairs and appropriately adjusted surveillance. 5.2.4 Internal surfaces Where a part of any pipeline is removed for any reason, the internal surface shall be inspected to confirm integrity, (such as corrosion) with appropriate action taken. 5.2.5

External surfaces

5.2.5.1 Above-ground pipelines Above-ground pipelines shall be inspected for evidence of corrosion or damage to or deterioration of any anti-corrosion coatings at intervals of not more than 12 months, and the rate of corrosion shall be assessed. Where the rate of corrosion will reduce the design life, remedial action shall be taken. NOTE: Suitable action may include a reduction of the design life.

5.2.5.2 Buried and submerged uncoated pipelines Uncoated pipelines that are buried or submerged shall be surveyed using approved techniques at intervals of not more than six months. Pipelines shall be inspected at positions that are not more than 1 km apart and wherever the most corrosion is expected to occur. 5.2.5.3 Buried and submerged anti-corrosion coated pipelines Whenever any part of a buried or submerged anti-corrosion coated pipeline is exposed, it shall be inspected for corrosion and evidence of damage to or deterioration of any anti-corrosion coatings. Cathodic protection systems on coated buried pipelines shall be inspected in accordance with Clauses 5.6 and 5.7. The effectiveness of the cathodic protection system on submerged coated pipelines shall be established within a period of not more than 12 months after installation. The system shall be monitored at intervals of not more than five years. The interval may need to be shortened towards the end of the design life. 5.3

COATINGS

5.3.1 Above-ground pipework The coating of above-ground pipework should be repaired or renewed if external corrosion is occurring, which will compromise the integrity of the pipework within the period between integrity assessments. The coating should be assessed in particular at crevice areas like pipe supports and on the underside of the pipework. The pipe wall should also be inspected for corrosion at areas of blistered or disbonded coating. Insulation where installed shall be maintained in a condition such that — (a)

water cannot reach and collect next to the pipe surface; and

(b)

the requisite thermal insulation performance is maintained.

NOTE: Corrosion under insulation can be a severe problem, especially if the pipeline is in intermittent service (i.e. subject to fluctuating temperatures encompassing the water vapour dewpoint). Inspection for corrosion under the insulation should be a regular feature of assessment surveys.

Records of the coating condition shall be kept.

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5.3.2 Below-ground pipework All below-ground pipework should be coated to prevent external corrosion and be cathodically protected. The coating system used shall be appropriate for underground service and the operating conditions. The coating shall be applied in conformance with the appropriate industry standards including proper pipe surface preparation, controlled application and quality testing of the final coating. The coating shall be maintained to a standard such that — (a)

the cathodic protection system effectively maintains protection at all coating holidays; and

(b)

coating disbondment is minimized.

Assessment of the coating condition on below-ground pipework should be achieved by evaluation of some or all of the following: (i)

Cathodic protection data.

(ii)

Special coating defect surveys (eg. Pearson or DC pulsed method surveys).

(iii)

Visual inspection at selected locations of bellhole excavations and where the pipeline is exposed for other reasons.

Records of the coating condition shall be kept. 5.4

PIPE WALL DEFECT ASSESSMENT

5.4.1 Damaged pipework Unless detailed analysis has been carried out to confirm the acceptability of the defect, defects in excess of the following criteria shall be removed, replaced or otherwise repaired: (a)

Dents, as described in AS 2885.1 except that maximum depth shall be 6% of the pipe diameter.

(b)

Gouges, grooves and notches which are outside the criteria described in AS 2885.1.

Pipework with wall thickness loss due to grinding should be treated as corroded pipework. 5.4.2

Corroded pipework

5.4.2.1 General Where corrosion is detected, it shall be investigated to determine its nature, extent, depth and cause. The corrosion shall be evaluated and the current MAOP shall be confirmed. In the event that the MAOP is determined to have been compromised, a safe operating pressure shall be determined by assessment in accordance with Clause 5.4.3 and if necessary a new MAOP established or the corroded portion of the pipeline repaired or replaced. Corroded pipelines shall be protected against further corrosion in accordance with AS 2885.1. NOTE: Figure 5.1 provides a flow chart for assessing corrosion defects .

5.4.2.2 Safety precautions Great care shall be taken when work is carried out on a corroded portion of pipeline. The operating pressure should be maintained or reduced to a safe level (usually 80% of normal operating pressure), until such time as the corroded area has been cleaned and inspected, the extent and depth of corrosion has been determined and an assessment has been made of the corroded portion of the pipeline. Where the contents of the pipeline are liquid and locked in between valves, consideration shall be given to any increase in pressure that may be caused by changes in temperature.

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NO TES: 1 The design pressure Pd shall be calculated as follows:

where Pd = design pressure, in megapascals Fd = design factor δ dp = wall thickness for design internal pressure, in millimetres σ y = yield stress, in megapascals D

= nominal outside diameter, in millimetres

2 Test pressure = 1.25 × Pd

FIGURE 5.1

FLOWCHART FOR ASSESSING CORROSION DEFECTS

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5.4.3

26

Assessment of corroded pipework

5.4.3.1 General The assessment required by Clause 5.4.2 shall be made by one of the following methods: (a)

Pressure testing, in accordance with Clause 5.4.3.2.

(b)

Calculation, in accordance with Appendix B, Paragraph B3.

(c)

AGA Project PR3-805.

NOTE: This program is based on the calculation method given in Appendix B, Paragraph B3 but is slightly less conservative.

(d)

Any other approved methods.

5.4.3.2 Assessment by pressure testing The section of any pipeline containing corrosion shall be pressure tested in accordance with AS 2885.1 and its MAOP determined in accordance with Appendix B, Paragraph B2. The normal maximum pressure, recorded or determined for the corroded section over the six months prior to the discovery of the corrosion, may be deemed to be a test pressure for the purposes of recalculating the MAOP in accordance with this Clause. Where the original design included an allowance G (refer to AS 2885.1) and it can be shown that the original allowance is not required for the corroded section of pipe, a revised value for G may be used in the re calculation of MAOP. The revised value shall be approved. 5.5

ANCILLARY EQUIPMENT ASSESSMENT

5.5.1 General In addition to the pipeline itself, equipment ancillary to the pipeline, and in particular the items listed in this Clause 5.5, shall be regularly maintained. 5.5.2 Valves Valves require regular usage and maintenance to ensure they are functioning correctly. They should be inspected at approved intervals to ensure that — (a)

each valve is properly supported and that corrosion problems at support points are not occurring;

(b)

valves are secured to prevent unauthorized access and usage;

(c)

valve pits are structurally sound, and that corrosion on fittings is not occurring;

(d)

valves are not leaking; and

(e)

valves are fully operable.

5.5.3 Pipe supports All pipe supports, for above-ground portions of lines, shall be inspected at approved intervals. The inspections shall establish the physical condition of each support, and verify that they are providing the required support for the pipe at that point. Where applicable the interface between the carrier pipe and the pipe support shall be inspected for corrosion. 5.5.4 Ground entry locations Severe corrosion can occur at the point where pipelines enter and leave the ground. Such points shall be regularly inspected for coating deterioration and associated corrosion. The inspection intervals are dependent on the coating type applied to the line. 5.6

CATHODIC PROTECTION CRITERIA

5.6.1 General For pipeline cathodic protection criteria, including the effects of pipe and soil potentials, foreign structure interference, stray current and telluric effects, the requirements of AS 2832.1, local pipeline regulations and local electrolysis committees shall apply.

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5.6.2 Steel-cased crossings Where electrically isolated from the pipeline.

possible,

AS 2885.3 — 1997

steel

casings

shall

be maintained

If electrical isolation is lost, it shall be restored or other measures taken to prevent corrosion occurring on the pipe inside the casing. 5.7

CATHODIC PROTECTION INSPECTION

5.7.1 Inspectors The parties responsible for the survey, inspection, testing and maintenance of the cathodic protection system shall have the requisite experience and qualifications in cathodic protection as approved by the operating authority. 5.7.2 Measuring equipment cathodic protection testing.

Only approved measuring equipment shall be used for

5.7.3 Inspections The operating authority shall carry out inspections to ensure the correct operation of transformer and rectifier units, stray current control and drainage bonds at an interval not exceeding two months in accordance with AS 2832.1. The operating authority shall, at intervals not exceeding twelve months, carry out cathodic protection inspections, including pipeline potential surveys in accordance with AS 2885.1 and tests for stray current electrolysis. The inspections shall ensure that the cathodic protection system is operating satisfactorily in conformance with the design criteria and Clause 5.6. If variations are found, action shall be taken to rectify the deficiencies. 5.7.4 Records Information should be recorded in accordance with AS 2832.1, to cover the following major areas: (a)

Commissioning and installation.

(b)

Inspections undertaken and results of pipe to soil potential testing.

(c)

Equipment maintenance.

5.8 PRESSURE CONTROL AND PROTECTIVE EQUIPMENT INSPECTION All pressure control and protective equipment shall be subjected to systematic inspection and testing to determine if they are — (a)

in good electrical, mechanical or hydraulic condition;

(b)

set to function at the correct pressure;

(c)

properly installed and protected from foreign material or other conditions that might prevent proper operation;

(d)

installed in a manner so as to prevent unauthorized operation or alteration; and

(e)

operating correctly.

5.9 PIG TRAP INSPECTION AND MAINTENANCE Maintenance of all components of pig traps (including end closure seals, bleed locks, electrical bonds, locking rings, pig signallers and fasteners) should be undertaken just prior to use, after painting or at approved intervals. In addition, for temporary or removable pig traps, the traps should be inspected before use for mechanical damage (due to handling) and for evidence of corrosion. 5.10 CASING (SLEEVE) MAINTENANCE Schedules for pipeline maintenance should include appropriate checks on casings and attachments (e.g. checks for pipe to casing contacts or resistive bonds and sniffing of annulus vents for hydrocarbon).

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5.11 STRUCTURES HOUSING EQUIPMENT A structure housing equipment shall be inspected at intervals of not more than 3 months, and shall be maintained in good condition. The inspection shall include the testing of the atmosphere in the structure for toxic and combustible vapour. Leaks of these types shall be located and repaired. Ventilating equipment shall be maintained in a satisfactory operating Ventilation ducts shall be cleared of any obstruction.

condition.

A pit cover shall be examined to determine that it does not constitute a risk to the public, and that no damage to the equipment can result from unexpected loads on the cover.

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S E C T I O N

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AS 2885.3 — 1997

P IP E L I N E R E PA I R S

6.1 GENERAL Where a pipeline is damaged or corroded to the extent that continued operation would be unsafe, the pipeline shall be shut down or the operating pressure reduced to a safe level until such time as a repair is effected. 6.2 SUPERVISION Before any work is carried out on a pipeline, the area shall be declared safe by a competent person in accordance with Clause 6.4. The person responsible for declaring the area safe or an equally competent stand-in shall remain alongside workers in that area until all work of a hazardous nature has been completed. 6.3 COMMUNICATION AND CONTROL A reliable communication system and procedure shall be established between the work site and all locations from which pipeline conditions can be controlled. 6.4

WORKING ON PIPELINES

6.4.1 General When any work is to be carried out on a pipeline, the formation of mixtures of flammable vapour or gas and air shall be prevented. This may be achieved by the exclusion of — (a)

air from spaces filled with hydrocarbon fluid; or

(b)

hydrocarbon fluid from spaces filled with air.

A safe condition shall be established. The area should be tested continuously to prove the absence of hazardous concentrations of flammable vapour or gas. The person responsible for declaring the area safe shall remain alongside workers in that area until all work of a hazardous nature is completed. 6.4.2 Tunnels, shafts, and casing The atmosphere in a tunnel, shaft, or casing, including those which are too small for human access, shall be declared safe by a competent person before any work is carried out on the pipeline within that tunnel, shaft, or casing. 6.4.3 Precautions to prevent an explosion To prevent an accidental ignition of possible hazardous concentrations of flammable vapour or gas, appropriate precautions shall be taken and, where relevant, the following requirements shall apply: (a)

The work area shall be monitored, using approved and correctly calibrated and tested flammable gas detectors prior to and during the work, to determine the presence and concentration of flammable gas.

(b)

Work shall be suspended whenever a flammable gas concentration within the explosive range is detected.

(c)

The perimeter of hazardous areas shall be determined and delineated.

(d)

Suitable signs to indicate to the public the extent of any hazardous areas shall be displayed.

(e)

The following shall be prohibited in hazardous areas: (i)

Smoking.

(ii)

The presence of matches, lighters and naked flame.

(iii)

The access of any sources of ignition to the work area (e.g. spark-ignition engines, motor vehicles and mobile phones).

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(f)

Electrical equipment, including radios, flashlights and hand lanterns, shall be safe for use in Zone 1 hazardous locations as defined by AS 2430.1.

(g)

Adequate training and instruction shall be given to operating and maintenance personnel about the possibility of electric surges (sparks) occurring across insulated joints.

(h)

Static electricity shall be safely discharged (see AS/NZS 1020).

(j)

Where two joining flanges are to be separated, an electrical connection shall be installed across the proposed separation.

(k)

Prior to making a cut in a pipeline the pipeline shall be electrically earthed on each side of the location for the cut.

NOTE: High voltages and currents can occur in pipelines as a consequence of lightning or a fault condition in nearby powerlines. Adequate precautions to prevent accidental injury or the creation of a source of ignition during any pipeline alteration work should be considered, such as the use of grounding mats or earth rods.

6.4.4

Pipelines filled with hydrocarbon gas

6.4.4.1 Where gas is escaping Where gas is escaping and a live repair is being carried out, thermal cutting, welding and other work shall only be carried out on the pipeline, when the following conditions, where practical and appropriate, prevail: (a)

Prior to commencement and throughout the process a slight flow of gas within the pipeline is kept moving past any thermal cutting process and any welding process that is being undertaken.

(b)

The gas pressure is controlled by suitable means.

(c)

Any slots or open ends are sealed, as soon as they are made, with tape, tightly fitted canvas or other suitable means.

(d)

Only one opening is uncovered at any one time. NOTE: This is particularly important where the two openings are at different elevations.

(e)

Any escape of gas at the working location is ignited and kept burning.

(f)

Where the gas is toxic, adequate precautions are taken to protect the public and the workmen.

6.4.4.2 Where gas is not escaping Work to be carried out on a pipeline containing gas from which gas is not escaping shall be in accordance with Clause 6.7. 6.4.5 Pipelines filled with liquid petroleum or HVPL Any cutting of pipelines that contain or have contained liquid petroleum or HVPL that has not been purged shall only be cut by non-sparking mechanical means and any heat generated shall be controlled below the product flashpoint. Welding shall not be carried out on a pipeline filled with liquid petroleum or HVPL, unless liquid and vapour is prevented from escaping from the pipeline. 6.4.6 Purged pipelines Where a pipeline has been purged in accordance with Section 3, is filled with air and is connected to a source of hydrocarbon fluid that cannot be completely isolated, welding, thermal cutting or repair operations shall not be permitted unless the flow of hydrocarbon fluid toward the work site is prevented and the pipeline contents at the work site are tested continuously to ensure that an unsafe concentration of hydrocarbon fluid does not occur. This may require — (a)

the generation of airflow away from the work within the pipeline, by the operation of air movers at suitable locations; or

(b)

the installation of stopples or spheres with bleed vents on each side of the work site, taking care that this does not prevent adequate airflow that may be required in Item (a) above. COPYRIGHT

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REPAIR STRATEGY

6.5.1 Initial response Immediately a leak is detected, corrective action shall be initiated. Damage should be evaluated promptly. Where a pipeline is damaged or corroded to the extent that continued operation would be unsafe, the pipeline shall be shut down or the operating pressure reduced to a safe level, until necessary repairs have been completed and inspected and it is safe to resume normal operation. 6.5.2 Repair strategy flowchart The operating authority shall plan a repair strategy taking into account the process shown in Figure 6.1. 6.5.3 Temporary repairs Temporary repairs shall exclude any method which involves welding. Temporary repairs may only be made when immediate shut down is not practicable, provided that as soon as possible they will be made permanent in accordance with Clause 6.5.4. 6.5.4 Permanent repairs following conditions:

Permanent repairs shall be made to a pipeline, subject to the

(a)

On a liquids pipeline, the defect has been sealed to prevent leakage during repair.

(b)

The internal pressure is at a low enough level to ensure safety during the repair operation.

(c)

Grinding in the area containing the defect is limited to a depth that will ensure safety during the repair operation.

(d)

Safety precautions comply with Clauses 6.2 to 6.4.

(e)

Cutting and welding comply with Clauses 6.6 and AS 2885.2. Welding procedures shall ensure that pipe walls are not reduced in thickness or weakened.

(f)

Where a section of pipe or reinforcement containing a defect is replaced, the replacement pipe shall be pre-tested and have a wall thickness and a SMYS of not less than that of the replaced section. The repaired section shall not impede the passage of the type of pig for which the pipeline was designed.

(g)

Pressure-containing full-encirclement welded split sleeves and other approved mechanical devices that are used to effect repairs shall have design pressures determined in accordance with AS 2885.1, subject to the MAOP of the pipeline not being reduced.

(h)

The carbon equivalent for materials which are to be welded into the pipeline shall conform to that specified in the certified weld procedure in accordance with AS 2885.2.

NOTE: Guidance on methods for the repair of pipelines is given in WTIA Technical Note 20.

6.6

WELDING ONTO AN IN-SERVICE PIPELINE

6.6.1 General Welding onto an in-service pipeline shall be in accordance with the relevant requirements of AS 2885.2. 6.6.2 Monitoring of operating conditions Whilst any welding is in progress, the pressure and flowrate of the fluid shall be monitored continuously. Welding shall be discontinued at any time when the pressure or the flowrate is outside the limits specified in the approved procedure. 6.6.3 Resumption of normal operation The pressure in a pipeline following a repair shall not be increased, until the repair has been inspected in accordance with this Standard and AS 2885.2 and the inspection has demonstrated that it is safe for normal operation to be resumed.

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FIGURE 6.1

REPAIR STRATEGY FLOWCHART COPYRIGHT

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6.7

AS 2885.3 — 1997

HOT-TAPPING OPERATIONS

6.7.1 General A hot-tapping operation shall be carried out by trained and experienced persons and in accordance with an approved written procedure which incorporates the appropriate emergency procedures and safety precautions. The detailed procedure shall be based on shop tests, experience, practice runs and other relevant information. This procedure shall be followed throughout the operation. Operating personnel should be thoroughly familiar with the procedure before the hot-tap operation is commenced. 6.7.2 Location of connections Welds for hot-tap connections shall not be located close to any other weld where the heat applied in making one of the welds may adversely affect the integrity of the other weld. Where this could happen, procedure tests shall be made and the results approved; alternatively, welds should be separated by a distance not less than 6 times the thickness of the pipe wall. 6.7.3 Design A branch connection shall be designed in accordance with AS 2885.1. To ensure that longitudinal welds of an encirclement sleeve are not welded to the pressurized pipeline, backing strips shall be used. 6.7.4 Pipe support prior to drilling Before connecting the drilling machine to the hottap fitting, the fitting and valve shall be adequately supported to prevent excessive strain or vibration on the connection and pipeline during the entire operation.

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APPENDIX A

LIST OF REFERENCED DOCUMENTS (Normative) A1 IDENTIFICATION OF DOCUMENTS The name of the issuing body of documents is identified by the prefix letters in the number of the document as follows: AGA

American Gas Association

ANSI

American National Standards Institute

API

American Petroleum Institute

AS

Standards Australia

AS/NZS Standards Australian/Standards New Zealand ASME

American Society of Mechanical Engineers

ASTM

American Society for Testing and Materials

IGE

Institutions of Gas Engineering, UK

WTIA

Welding Technology Institute of Australia

A2 REFERENCED DOCUMENTS The following documents are referred to in this Standard: AS 2430 2430.1

Classification of hazardous areas Part 1: Explosive gas atmospheres

2832 2832.1

Guide to the cathodic protection of metals Part 1: Pipes, cables and ducts

2885 2885.1 2885.2

Pipelines —Gas and liquid petroleum Part 1: Design and construction Part 2: Welding

3920 3920.1

Assurance of product quality Pressure equipment manufacture

AS/NZS 1020

The control of undesirable static electricity

AGA PR3-805 1975

A modified criterion for evaluating the remaining strength of corroded pipe (RSTRENG) Purging principles and practices

ANSI/ASME B31G Manual for determining the remaining strength of corroded pipelines API 5L ASTM A53 A106

Specification for line pipe Specification for pipe, steel, black and hot-dipped, zinc-coated welded and seamless Specification for seamless carbon steel pipe for high-temperature service

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Specification for metal-arc-welded steel pipe for use with high-pressure transmission systems.

IGE SR/23

Safety recommendation—Venting of natural gas

WTIA TN20

Repair of steel pipelines

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APPENDIX B

ASSESSMENT OF A CORRODED PIPELINE (Normative) B1 SCOPE This Appendix sets out approved methods that may be used when the suitability for service of a pipeline having corrosion damage is being assessed. The methods in this Appendix are relevant to assessments based on pressure testing or calculation. A logic diagram for a calculation method is shown in Figure B1. NOTE: The methods described in this Appendix are used for assessing individual corrosion anomalies. For complex corrosion, including closely linked corrosion anomalies, engineering judgement and experience should be used.

B2 ASSESSMENT BY PRESSURE TESTING The MAOP of a pipeline that is corroded, but is otherwise satisfactory, may be determined by re-testing that section of the pipeline hydrostatically to a pressure that would not cause the pipe to leak or loose its integrity. This would be carried out only after the appropriate safety measures had been taken and an estimate of the appropriate test pressure made. Following a successful re-test, the MAOP for the pipeline is established by dividing the re-test pressure by 1.25 (1.1 for appropriate parts of telescoped pipelines). Where a pipeline that is corroded has been operating successfully, the recent operating history at the time and place where corrosion has occurred may be used as a successful test pressure and it is not necessary to re-test the pipeline. The MAOP for the pipeline is determined by using the operating pressure as the re-test pressure and dividing this by 1.25 (1.1 for appropriate parts of telescoped pipelines). Where the thickness of the pipeline is reduced by corrosion, and corrosion is expected to continue, an allowance shall be made. In the analysis which follows, the MAOP is used in place of the test pressure as in the relevant equation (B4 or B5). One is expressed as a proportion of the other and any common multipliers would cancel out. B3

ASSESSMENT BY CALCULATION

B3.1 General As an alternative to the determination of a MAOP from a pressure test, it may be preferable to calculate the pressure at which the pipe is expected to fail. This can be carried out by using a method of hoop stress analysis. One method is shown in Paragraph B3.2. The pressure at which the corroded pipe would fail occurs when the pressure causes the sound metal beneath the corrosion to fail. If the test pressure calculated from the hoop stress analysis is equal to or greater than the original test pressure, the MAOP need not be reduced. If this calculated pressure is lower than the original test pressure, the MAOP is determined by dividing the calculated pressure by 1.25 (1.1 for appropriate parts of telescoped pipelines). B3.2

Hoop stress analysis

NOTE: This method is derived from the information in ANSI/ASME B31G.

B3.2.1 General This method of hoop stress analysis begins with the calculation of the critical length of the corroded area which is appropriate to the measured depth and the original MAOP. If the projected length is less than the critical length, further calculations are not necessary and the MAOP is confirmed. Where the projected length is greater than the critical length, further calculations are necessary. COPYRIGHT

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A systematic approach is given in Steps 1 to 8. Steps 1 to 5 give verifications or otherwise of the original MAOP, by calculation of the critical length of the corrosion. Steps 6 to 8 give the method for the calculation of a new MAOP. Step 6 is the appropriate method for relatively long or shallow corrosion as it overestimates the area of corrosion. Consequently, the new MAOP is not dependent on the length of the corrosion. In the limiting case where shallow corrosion occurs, i.e. dc/δN is not greater than 0.1 no reduction in the original MAOP is necessary. The use of Figure B3, Figure B4, and Figure B5 is recommended as the graphical solution is sufficiently accurate. The limitations on the use of the equations are shown graphically. Where the corroded pipe has a wall thickness greater that the pressure design wall thickness and this is to be used in the analysis, formal calculations, rather than a graphical method, should be used to justify the final recommendation. Eight solutions are presented to illustrate a range of typical corrosion depths and lengths. The derivation of the method shown in this Appendix, and a review of the test program that confirmed the method and discussion on the Folias factor are given in the American Gas Association, 5th Symposium on Line Pipe Research Catalogue No L30174— Chapter L, 1974. B3.2.2 Limitations limitations:

The method described in this Paragraph B3.2 has the following

(a)

Is limited to corrosion on weldable pipeline steels categorized as carbon steels or high strength low-alloy steels. Typical of these materials are those described in ASTM A 53, A 106, and A 381, and API 5L.

(b)

Applies only to defects in the body of line pipe which have relatively smooth contours and cause low stress concentration (e.g., electrolytic or galvanic corrosion, loss of wall thickness due to erosion).

(c)

Should not be used to evaluate the remaining strength of corroded girth or longitudinal welds or related heat affected zones, defects caused by mechanical damage, such as gouges and grooves, and defects introduced during pipe or plate manufacture, such as seams, laps, rolled ends, scabs, or slivers.

(d)

The criteria for corroded pipe to reman in service are based only upon the ability of the pipe to maintain structural integrity under internal pressure. It should not be the sole criterion when the pipe is subject to significant secondary stresses (e.g. bending), particularity if the corrosion has a significant transverse component.

(e)

Does not predict leaks or rupture failures.

B3.2.3

Review of corrosion parameter

Step 1: Depth of corrosion —measure the depth of corrosion (d c) and express it as a ratio of the nominal wall thickness (δN) for the pipe. Evaluate this ratio as follows: (a)

Where dc/δN is equal to or less than 0.1, the MAOP (po) need not be reduced.

(b)

Where dc/δN is equal to or greater than 0.8, the corroded pipe is to be repaired.

(c)

Where dc/δN is greater than 0.1 but less than 0.8, proceed to Step 2.

Step 2: Length of corrosion —measure the projected length of corrosion (L p). Step 3: Consultant Kf — calculate the value of the constant K f from the following: (a)

Where dc/δN is less than or equal to 0.18, the value of the constant K f is 4.

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Where dc /δN is greater than 0.18, the value of the constant K f is to be determined from Figure B3 or calculated from the following equation: . . . B1

Step 4: Critical length of corrosion — calculate the value of the critical length(L c) from the following equation: . . . B2 Step 5: Evaluation of the MAOP of corroded pipe pipe as follows:

Evaluate the MAOP of corroded

(a)

Where the critical length (L c) is greater than the projected length (L p), the MAOP (po ) need not be reduced.

(b)

Where the critical length is less than or equal to the projected length, the value of the constant K c is to be calculated and compared with 4 and a new MAOP (p c) calculated.

Step 6: Constant Kc — calculate the value of the constant K c from the following equation: . . . B3 Step 7: Value of K c less than or equal to 4 — where the value of the K c is less than or equal to 4, the new MAOP (pc ) is to be determined from Figure B4 or calculated from the following equation: . . . B4 Step 8: Value of K c greater than 4 — where the value of the K c is greater than 4, the new MAOP (p c) is to be determined from Figure A5 or calculated from the following equation: . . . B5 B3.2.4 Example: Determine the MAOP of a corroded pipe having an outside diameter (D) of 762 mm, nominal wall thickness (δN) of 6.35 mm, and the maximum depth of the deepest pit in the corroded area (d) of 3.2 mm in Case (i) and 0.5 mm in Case (ii). The measured length of the corroded area projected onto the longitudinal axis of the pipe (Lp) is, in each case, (a) 25 mm, (b) 100 mm, (c) 300 mm, and (d) 1000 mm. CASE (i) —DEPTH OF CORROSION 3.2 mm Step 1: Depth of corrosion —express the depth of corrosion as a ratio of the nominal wall thickness, i.e. d c/δN = 3.2/6.35 = 0.5. Assessment As d c/δN is greater than 0.1 but less than 0.8, the critical length has to be calculated and the MAOP evaluated. Step 2: Length of corrosion —the length of projected corrosion is given in this example. Step 3: Constant K f — as dc/δN is greater than 0.18, calculate the value of the constant K f from equation A1 as follows:

= 0.74

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Step 4: Critical length of corrosion — calculate the value of the critical length (L c) from equation A2 as follows:

= 57.65 mm. Step 5: Compare Lc with Lp —Compare the value of the critical length (L c) with the projected length (L p): millimetres Example: Case (i)

Lc

Lp

(a) (b) (c) (d)

57.65 57.65 57.65 57.65

25 100 300 1000

Evaluation of MAOP of corroded pipe In example Case (i)(a), where L p is 25 mm, which is less than 57.65 mm (the value of L c), the corroded pipe may be operated without any reduction in the original MAOP established previously for the non-corroded pipe, i.e. pc is equal to po. In examples Case (i)(b), (c), and (d), where Lp is 100 mm, 300 mm and 1000 mm, all of which are greater than 57.65 mm, the value of Lc and a new MAOP (pc) are to be calculated. Step 6: Constant K c — calculate the values fo the constant K c, where L p is 100 mm, 300 mm, and 1000 mm, from equation B3 as follows: millimetres Example: Case (i)

Lp

Kc

(b) (c) (d)

100 300 1000

1.28 3.85 12.84

In examples Case (i)(b) and (c), the value of K c is less than 4. In example Case (i)(d), the value of K c is greater than 4. Step 7: Value of Kc less than or equal to 4 — calculate the value of a new MAOP (pc ) for values of K c equal to 1.28 and 3.85 from equation B4 as follows:

In example case (i)(b), where Lp = 100 mm and K c = 1.28, pc = 0.92po. In example Case (i)(c), where Lp = 300 mm and K c = 3.85, pc = 0.80po. Step 8: Value of K c greater than 4 — calculate the value of a new MAOP (pc) for the value of K c equal to 12.84 from equation B5 as follows:

In example Case (i)(d), where Lp = 1000 mm and Kc = 12.84, pc = 0.55 po.

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CASE (ii) —DEPTH OF CORROSION 0.5 mm. Step 1: Depth of corrosion —express the depth of corrosion as a ratio of the nominal wall thickness, i.e. d c/δN = 0.5/6.35 = 0.08. Assessment As dc /δN is less than 0.1, the MAOP need not be reduced, i.e. pc is equal to p o. Step 2: Length of corrosion —Step 2 and subsequent steps are unnecessary; however, as a further example, Steps 3 to 8 are shown as follows: Step 3: Constant K f — as dc /δN equals 0.08, which is less than 0.18, the value of K f is 4. Step 4: Critical length of corrosion — calculate the value of the critical length (L c) from equation A2 as follows:

= 311.6 mm. Step 5: Compare L c with L p —compare the value of the critical length (L c ) with the projected length (L p): millimetres Example: Case (i)

Lc

Lp

(a) (b) (c) (d)

311.6 311.6 311.6 311.6

25 100 300 1000

Evaluation of MAOP of corroded pipe In examples Case (ii)(a), (b), and (c), where L p is 25 mm, 100 mm, and 300 mm, which is less than 311.6 mm (the value of L c), the corroded pipe may be operated without any reduction in the original MAOP established previously for the non-corroded pipe, i.e. pc is equal to po. In examples Case (ii)(d), where L p is 1000 mm, which is greater than 311.6 mm (the value of Lc ), a new MAOP (pc) is to be calculated. Step 6: Constant K c — calculate the value of the constant K c , where L p is 1000 mm from equation A3 as follows:

= 12.84. Step 7: Value of K c less than or equal to 4 —as K c is not greater than 4 this Step is not required. Step 8: Value of Kc greater than 4 — calculate the value of a new MAOP (pc ) for a value of K c equal to 12.84 from equation B5 as follows:

In example Case (ii)(d), where Lp - 1000 mm and K c = 12.84, pc = po; and therefore original MAOP is acceptable.

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FIGURE B1

REVIEW PROCEDURE FOR CORRODED PIPE COPYRIGHT

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FIGURE B2

ILLUSTRATION OF NOTATIONS L p AND d c/δ N

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FIGURE B3

AS 2885.3 — 1997

RELATIONSHIP BETWEEN K f (BETWEEN THE VALUES 0.448 AND 4) AND THE RATIO d c/δ N (BETWEEN THE VALUES 0.18 AND 0.8)

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NOTE: Other values of Pc may be interpolated FIGURE B4 RELATIONSHIP BETWEEN p c AND p o IN TERMS OF VALUE OF THE RATIO d c/δ N BETWEEN THE VALUES 0.18 AND 0.8 AND THE CONSTANT K c WHERE K c IS EQUAL TO OR LESS THAN 4.

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FIGURE B5 RELATIONSHIP BETWEEN p c AND p o IN TERMS OF VALUE OF THE RATIO d c/δ N BETWEEN THE VALUES 0 AND 0.8 WHERE THE CONSTANT K c IS GREATER THAN 4

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INDEX Clause abandoning a pipeline . . . . . . . . . . . . above-ground pipework . . . . . . . . . . . access to the pipeline . . . . . . . . . . . . . agricultural activities . . . . . . . . . . . . . ancillary equipment assessment . . . . . . application of Standard . . . . . . . . . . . assessment of corroded pipeline . . . . . audit . . . . . . . . . . . . . . . . . . . . . . . .

.. .. .. .. .. .. .. ..

basis of Standard . . . . . . . . . . . . . . . . . below-ground pipework . . . . . . . . . . . . buildings near the pipeline . . . . . . . . . . buried anti-corrosion coated pipelines . . buried uncoated pipelines . . . . . . . . . . .

. . . . . . . . . 4.9 . . 5.2.5.1, 5.3.1 . . . . . . 3.2.4.2 . . . . . . 3.2.4.6 . . . . . . . . . 5.5 . . . . . . . . . 1.3 . . . Appendix B . . . . . . . . 5.1.3

.. .. .... .... .. . . ....

.. . . .. ... ... ...

. . . 1.2 . . 5.3.2 3.2.4.3 5.2.5.3 5.2.5.2

casing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.2 casing maintenance . . . . . . . . . . . . . . . . . . . . . . . . 5.10 cathodic protection, criteria . . . . . . . . . . . . . . . . . . . 5.6 cathodic protection, inspection . . . . . . . . . . . . . . . . . 5.7 coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 communications systems . . . . . . . . . . . . . . . . . . . . 3.2.6 control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 controls equipment . . . . . . . . . . . . . . . . . . . . . . 3.2.3.2 corroded pipeline, assessment by calculation . . . . . . . B3 corroded pipeline, assessment by pressure testing . . . . B2 corroded pipework . . . . . . . . . . . . . . . . 5.4, Appendix B corroded pipework, assessment of . . . . 5.4.3, Figure 5.1, Appendix B damaged pipework . . . . . . . defect assessment, pipe wall definitions . . . . . . . . . . . . . design condition changes . . design life . . . . . . . . . . . . . documents, identification of

.. .. .. .. .. ..

.. .. .. .. .. ..

.. .. .. .. .. ..

.. .. .. .. .. ..

.. .. .. .. .. ..

. . . . . .

. . . . . .

.. .. .. .. .. ..

. . . . . .

. . . . . .

. . 5.4.1 . . . 5.4 . . . 1.6 4.1, 4.2 . . . 4.5 . . . A1

emergency plans . . . . . . . . . . . . . . . . . . . explosion, precautions to prevent . . . . . . . explosives . . . . . . . . . . . . . . . . . . . . . . . . external interference near pipelines . . . . . .

.. .. .. ..

. . . . . . 3.4 3.5.1, 6.4.3 . . . 3.2.5.2 . . . . . 3.2.5

fencing . . . . . . . . . . . . . . . . . . . . . . . . . . fill on or near the pipeline . . . . . . . . . . . . filling a gas pipeline . . . . . . . . . . . . . . . . filling a high vapour pressure liquid (HV PL) filling a liquid petroleum pipeline . . . . . . . filling procedures . . . . . . . . . . . . . . . . . . .

. . . . . 3.2.4.6 . . . . . 3.2.4.5 . . . . . . . 2.6.2 pipeline 2.6.4 . . . . . . . 2.6.3 . . . . . . . . 2.6

ground entry locations . . . . . . . . . . . . . . . . . . . . . . 5.5.4 hot-tapping operations . . . . . . . . . . . hot-tapping, connection location . . . . housing equipment . . . . . . . . . . . . . . HV PL, pipelines filled with . . . . . . .

. . . .

. . . .

. . . .

.. . .. .. ....... .. .. .. . .......

. . 6.7 . 6.7.2 . 5.11 . 6.4.5

integrity inspection . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 integrity of pipeline . . . . . . . . . . . . . . . . . . . . . . . . . 5.1

Clause leakage detector . . . . . . . . . . leakage survey . . . . . . . . . . . liquid petroleum, pipeline filled location classes . . . . . . . . . . .

...... ...... with . . ......

. .. .. .. . . .. .. .. . .. .. . .. ... . .. .. .. . ..

. . . .

3.2.9 3.2.8 6.4.5 . 4.7

maintenance, casing . . . . . . . . . . . . . . . . . . . . . . . . 5.10 maintenance, pig trap . . . . . . . . . . . . . . . . . . . . . . . . 5.9 maintenance, sleeve . . . . . . . . . . . . . . . . . . . . . . . . 5.10 maximum allowable operating pressure (MAO P) . . . . . 4.6 modifications of pipeline . . . . . . . . . . . . . . . . . . . . . 4.3 monitoring plan . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 noise abatement . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.7 one-call-services . . . . . . . . . . . . . . . . . . . . . . . . 3.2.5.3 operating condition changes . . . . . . . . . . . . . . Section 4 operating plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 operating procedure . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 operating requirements . . . . . . . . . . . . . . . . . . . . . . . 3.1 operating to design conditions . . . . . . . . . . . . . . . . . 3.2.1 operation, delayed commencement of . . . . . . . . . . . . . 2.5 operation, general . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 operation, plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 operation, procedures . . . . . . . . . . . . . . . . . . . . . . . . 2.2 operation, readiness for . . . . . . . . . . . . . . . . . . . . . . 2.4 operatorship, transfer of . . . . . . . . . . . . . . . . . . . . . . 4.8 over-pressure protection system . . . . . . . . . . . . . . . . . 4.4 ownership, transfer of . . . . . . . . . . . . . . . . . . . . . . . 4.8 patrol of route . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2.2 permanent repairs . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.4 personnel, responsibilities for . . . . . . . . . . . . . . . . . 2.3 pig trap, inspection . . . . . . . . . . . . . . . . . . . . . . . . . 5.9 pig trap, maintenance . . . . . . . . . . . . . . . . . . . . . . . . 5.9 pipe support prior to drilling . . . . . . . . . . . . . . . . . . 6.7.4 pipe supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.3 pipe wall defect assessment . . . . . . . . . . . . . . . . . . . 5.4 pipeline filled with HVPL . . . . . . . . . . . . . . . . . . . . 6.4.5 pipeline repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 pipeline surveillance . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 pipelines filled with hydrocarbon gas . . . . . . . . . . . . 6.4.4 pipelines filled with liquid petroleum or HV PL . . . . . 6.4.5 power poles . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.4.6 pressure control inspection . . . . . . . . . . . . . . . . . . . . 5.8 pressure-control system . . . . . . . . . . . . . . . . . . . . . . 4.4 pressure protection equipment . . . . . . . . . . . . . . . 3.2.3.2 pressure testing, assessment by . . . . . . . . . . . . . 5.4.3.2 procedures, review of . . . . . . . . . . . . . . . . . . . . . . . 3.2.9 protective equipment inspection . . . . . . . . . . . . . . . . 5.8 purged pipelines . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.6 purging an HV PL . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.4 purging of gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.2 purging of hydrocarbon liquid . . . . . . . . . . . . . . . . . 3.6.3 purging of trapped hydrocarbon . . . . . . . . . . . . . . . 3.6.5 purging procedures . . . . . . . . . . . . . . . . . . . . . . . . . 3.6

COPYRIGHT

47

AS 2885.3 — 1997

Clause records . . . . . . . . . . . . . . . . referenced documents . . . . . . repair, initial response . . . . . repair of pipeline . . . . . . . . . repair strategy . . . . . . . . . . . repairs, permanent . . . . . . . . repairs, temporary . . . . . . . . risk management . . . . . . . . .

. . . . . . . . . . . . . . . . . . 1.7 . . . . . . . . . . . . . . . 1.5, A2 . . . . . . . . . . . . . . . . . 6.5.1 . . . . . . . . . . . . . . . . . . 6.1 . . . . . . . . . . 6.5, Figure 6.5 . . . . . . . . . . . . . . . . . 6.5.4 . . . . . . . . . . . . . . . . . 6.6.4 . . . . . . . . . . . . . . . 1.5, 1.4

safety plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 safety precautions . . . . . . . . . . . . . . . . . . . . . . . 5.4.2.2 scope of Standard . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2.4, 6.4.2 site security . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3.3 sleeve maintenance . . . . . . . . . . . . . . . . . . . . . . . . 5.10 stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3.4 structures housing equipment . . . . . . . . . . . . . . . . . 5.11 submerged anti-corrosion coated pipelines . . . . . . 5.2.5.3 submerged uncoated pipeline . . . . . . . . . . . . . . . 5.2.5.2 supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2

Clause telegraph poles . . . . . temporary repairs . . . . third party awareness . transfer of operatorship transfer of ownership . tunnels . . . . . . . . . . .

...... ...... . .. . .. .. .. . . .. . .. ......

...... . .. ... ...... ...... ...... .. .. ..

. . . . . . . . 3.2.4.6 . . . . . . . . . . 6.5.3 . . . . . . . . . . 3.2.4 . . . . . . . . . . . 4.8 . . . . . . . . . . . 4.8 . . . . 3.2.2.4, 6.4.2

underwater pipelines . . . . . . . . . . . . . . . . . . . . . 3.2.2.3

valve pits . . . . . . . . . . . . . . . . . . . . . . . . . valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . vegetation on and near the pipeline . . . . . . . venting gas . . . . . . . . . . . . . . . . . . . . . . . . venting procedures . . . . . . . . . . . . . . . . . . .

. . . . 3.2.2.4 3.2.2.5, 5.5.2 . . . . 3.2.4.4 . . . . . . 3.5.2 . . . . . . . 3.5

welding onto an in-service pipeline . . . . . . . . . . . . . . 6.6 working on pipelines . . . . . . . . . . . . . . . . . . . . . . . . 6.4

COPYRIGHT