4645-2005

AS 46452005

Australian Standard

Gas distribution network management

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This Australian Standard was prepared by Committee AG008, Gas Distribution. It was approved on behalf of the Council of Standards Australia on 8 December 2004. This Standard was published on 21 February 2005.

The following are represented on Committee AG008:

Australian Liquefied Petroleum Gas Association

Energy Networks Association

Energy Retailers Association of Australia

Gas Technical Regulators Committee

Welding Technology Institute of Australia

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AS 46452005

Australian Standard


Originated as AG 6031978. Previous edition 1982. Revised and redesignated as AS 46452005.

COPYRIGHT

Standards Australia

All rights are reserved. No part of this work may be reproduced or copied in any form or by

any means, electronic or mechanical, including photocopying, without the written

permission of the publisher.

Published by Standards Australia, GPO Box 5420, Sydney, NSW 2001, Australia

ISBN 0 7337 6465 7

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AS 46452005 2

PREFACE

This Standard was prepared by the Standards Australia Committee AG-008, Gas

Distribution to supersede AG-603. This Standard is a fully restructured and revised edition

of AG 603, Gas Distribution Code that was published in 1978 (and last revised in 1982).

The 1982 edition needed fundamental updating for a reformed industry environment.

The Committee primarily addressed the safety aspects of managing a fuel gas distribution

network. It maintained a close liaison throughout with the Standards Australia Committee

ME-038.

Users of the Standard should note that AS 1697 has been revised by AG-008 in parallel

with the revision of this Standard. AS 1697 which is now titled Installation and

maintenance of steel pipe systems for gas, (and AS 3723, Installation and maintenance of

plastics pipe systems for gas, now under revision) have a supporting relationship with

AS 4645 as depicted in Figure 1.1

A Standard finalized by the Committee in 1997, AG 606 (to become AS 4568), Code of

practice for the preparation of a safety and operating plan for gas networks, deals with

safety and operating plans (also known as safety cases) for regulatory authority purposes.

AS 4645 gives safe management and safe operating requirements intended to be specified in

safety and operating plans.

LP Gas distribution networks are included.

The terms normative and informative have been used in this Standard to define the

application of the appendix to which they apply. A normative appendix is an integral part

of a Standard, whereas an informative appendix is only for information and guidance.

The Standard is not a design handbook, nor a manual on distribution practices. It does not

remove the need for qualified and experienced engineering design, installation and

operation or for competent engineering judgement, and does require interpretation and

implementation by competent engineers.

AG 606Code of practice for the preparation of a

safety and operating plan for gas networks

AS 4645Gas distr ibution network management

AS 1697Instal lat ion and maintenance of

steel pipe systems for gas

AS 3723Instal lat ion and maintenance of

plast ics pipe systems for gas

FIGURE 1.1 RELATIONSHIPS BETWEEN STANDARDS

NOTES:

1 AG 606 (to be AS 4568) is used for preparation of SOP/SC as required by technical regulator

(advisory only).

2 AS 4645 specifies safety management of a gas distribution network for its life cycle. Refers

to AS 1697 for steel and AS 3723 for plastics (see Note 3).

3 AS 1697 and AS 3723 specify material specific requirements for construction and installation

(and operation/repair where material specific).

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3 AS 46452005

The Standard was prepared to provide an adequate risk based framework for management of

a gas distribution system, by specifying performance requirements and avoiding detailed

prescription as much as is possible. Where appropriate, detailed requirements (which tend

to be prescriptive) are provided in AS 1697 for steel pipes and AS 3723 for plastic pipe.

The Standard relies on a risk management approach, as needed to meet regulatory

requirements in most States. Risk management processes and criteria were initially

developed in AG 606 (to be AS 4568), in anticipation of new regulatory regimes for gas

distribution systems. AG 606 (to be AS 4568) will be reviewed and if necessary refined to

meet the evolving needs.

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AS 46452005 4

CONTENTS

Page

SECTION 1 SCOPE AND GENERAL

1.1 SCOPE ........................................................................................................................ 6

1.2 EXCLUSIONS ............................................................................................................ 6

1.3 RETROSPECTIVE APPLICATION OF STANDARD ............................................... 8

1.4 REFERENCED DOCUMENTS .................................................................................. 9

1.5 PRESSURE CLASSIFICATIONS............................................................................... 9

1.6 DEFINITIONS ............................................................................................................ 9

SECTION 2 NETWORK SAFETY

2.1 GENERAL ................................................................................................................ 12

2.2 SAFETY AND OPERATING PLAN ........................................................................ 12

2.3 SYSTEM MANAGEMENT ...................................................................................... 12

2.4 COMPETENCIES ..................................................................................................... 12

2.5 RECORDS................................................................................................................. 12

SECTION 3 NETWORK PLANNING

3.1 GENERAL ................................................................................................................ 14

3.2 FUNCTIONAL REQUIREMENTS........................................................................... 14

3.3 BASIS OF DESIGN .................................................................................................. 14

SECTION 4 NETWORK DESIGN

4.1 GENERAL ................................................................................................................ 15

4.2 DESIGN PRESSURES.............................................................................................. 15

4.3 NETWORK DESIGN DETAILS............................................................................... 15

4.4 DESIGN ELEMENTS OF MAINS AND SERVICES, AND ASSOCIATED

PIPEWORK............................................................................................................... 19

SECTION 5 CONSTRUCTING, TESTING, COMMISSIONING

5.1 GENERAL AND DOCUMENTATION .................................................................... 22

5.2 SEPARATION FROM OTHER UNDERGROUND STRUCTURES........................ 22

5.3 COATING FOR BURIED METAL PIPE.................................................................. 22

5.4 PIPE INSTALLATION METHODS.......................................................................... 22

5.5 TESTING .................................................................................................................. 23

5.6 COMMISSIONING OF GAS MAINS....................................................................... 24

SECTION 6 OPERATING AND MONITORING

6.1 PRE-OPERATING REQUIREMENTS ..................................................................... 25

6.2 OPERATING AND MONITORING ......................................................................... 26

6.3 REVIEWS, REPORTS AND ANALYSIS................................................................. 28

SECTION 7 MAINTAINING AND REPAIRING

7.1 GENERAL ................................................................................................................ 30

7.2 REPAIR OF COATING OF BURIED METAL PIPE................................................ 30

7.3 MAINTENANCE AND REPAIR OF COATING ON ABOVE-GROUND

PIPEWORK............................................................................................................... 30

7.4 STEEL-CASED CROSSINGS................................................................................... 30

7.5 WORK ON GAS MAINS.......................................................................................... 30

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5 AS 46452005

Page

SECTION 8 MODIFYING

8.1 DESIGN OF MODIFICATIONS............................................................................... 32

8.2 CONSTRUCTION, TESTING AND COMMISSIONING OF MODIFICATIONS... 32

SECTION 9 DECOMMISSIONING

9.1 MAKING SAFE ........................................................................................................ 33

APPENDICES

A LIFE-CYCLE OF NETWORK .................................................................................. 34

B REFERENCED DOCUMENTS ................................................................................ 35

C MATERIALS, COMPONENTS, AND DESIGN CONDITIONS GUIDELINES...... 36

D CONTROL OF GAS PRESSURE ............................................................................. 38

E MARKERS AND MARKING................................................................................... 43

F EMERGENCY PLANS ............................................................................................. 44

G CLASSIFICATION OF LEAKS................................................................................ 46

H PIPE IDENTIFYING, LOCATING AND WARNING SYSTEM ELEMENTS ........ 48

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AS 46452005 6

Standards Australia www.standards.com.au

STANDARDS AUSTRALIA

Australian Standard


S E C T I O N 1 S C O P E A N D G E N E R A L

1.1 SCOPE

This Standard specifies requirements for safe management of a fuel gas distribution

network throughout the life cycle of all elements of that network.

NOTE: Appendix A describes life-cycle phases.

The requirements apply to the life cycle of new assets in new or existing systems, but the

Sections on operations, maintenance, repair and decommissioning are suitable for

application to existing assets in existing systems.

Gas distribution networks within the scope of this Standard comprise of all facilities

between the outlets of all city gate supply points or equivalent (being wherever pressure is

reduced to below 1050 kPa), or for an LP Gas network the point of entry to the network

operators facility, and the outlet of the consumers meter assemblies, as detailed in

Figure 1.2.

Detailed requirements for design and materials, construction, testing and commissioning of

steel and plastic mains and services within a network, are specified by reference to

(a) AS 1697 for steel mains and services; and

(b) AS 3723 for plastic mains and services.

Details for design and maintenance of gas control plant and equipment associated with the

distribution network are specified by reference to

(i) AS 4041 for design of above ground steel pipework and facilities; and

(ii) AS 3873 for maintenance of above ground facilities.

NOTES:

1 Some requirements of this Standard are suitable for consumer piping operating at >200 kPa,

being not otherwise provided in AS 5601. The operator of such piping should decide which

requirements are appropriate, and should obtain any necessary agreement from the regulator

having jurisdiction over the operation of that piping.

2 The relevant technical regulator may regard this Standard as appropriate for other than fuel

gas.

3 AG 606 (to be AS 4568) provides guidance for preparation of a Safety and Operating Plan for

gas networks.

1.2 EXCLUSIONS

This Standard does not apply to the following:

(a) Piping from the outlet of the meter that measures gas to a consumer, and any other

piping covered by AS 5601.

NOTE: Requirements for pipes downstream of the consumers meter are generally provided

in AS 5601, but where the operating pressure of the downstream pipe will be higher than

provided for in AS 5601, the piping requirements of this Standard are appropriate according

to the pressure (or AS 2885.1 for even higher pressures).

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AS 4645-2005 GAS DISTRIBUTION NETWORK MANAGEMENT - GAS DISTRIBUTION NETWORK MANAGEMENT PREFACECONTENTSSECTION 1 SCOPE AND GENERAL 1.1 SCOPE 1.2 EXCLUSIONS 1.3 RETROSPECTIVE APPLICATION OF STANDARD 1.4 REFERENCED DOCUMENTS 1.5 PRESSURE CLASSIFICATIONS 1.6 DEFINITIONS 1.6.1 Actual thickness 1.6.2 Approved 1.6.3 Authority 1.6.4 Casing 1.6.5 Consumer piping 1.6.6 Fuel gas 1.6.7 Inspector 1.6.8 Internal design pressure 1.6.9 Liquefied petroleum gas/LP Gas 1.6.10 Main 1.6.11 Maximum allowable operating pressure (MAOP) 1.6.12 Monitoring regulator 1.6.13 Network 1.6.14 Network operator 1.6.15 Nominal thickness 1.6.16 Odorization 1.6.17 Pressure 1.6.18 Pressure design thickness 1.6.19 Pressure-limiting station 1.6.20 Pressure-regulating station 1.6.21 Pressure-relief station 1.6.22 Regulator 1.6.23 Required thickness 1.6.24 Service 1.6.25 Service regulator 1.6.26 Shall 1.6.27 Should 1.6.28 Specified minimum yield stress (SMYS) 1.6.29 Statutory authority 1.6.30 Thickness

SECTION 2 NETWORK SAFETY 2.1 GENERAL 2.2 SAFETY AND OPERATING PLAN 2.3 SYSTEM MANAGEMENT 2.4 COMPETENCIES 2.5 RECORDS

SECTION 3 NETWORK PLANNING 3.1 GENERAL 3.2 FUNCTIONAL REQUIREMENTS 3.3 BASIS OF DESIGN

SECTION 4 NETWORK DESIGN 4.1 GENERAL 4.2 DESIGN PRESSURES 4.3 NETWORK DESIGN DETAILS 4.3.1 Safety assessment of route 4.3.2 Materials and components 4.3.3 Pressure control 4.3.4 Meter/regulator specification 4.3.5 Pipe wall design thickness 4.3.6 Design of depth of cover and underground protection 4.3.7 Pipe identification and warning system, and contents identification 4.3.8 Design for natural hazards, and crossings 4.3.9 Additional requirements for LP Gas systems

4.4 DESIGN ELEMENTS OF MAINS AND SERVICES, AND ASSOCIATED PIPEWORK 4.4.1 Mains 4.4.2 General design of internal service lines and risers 4.4.3 Associated pipework 4.4.4 Corrosion mitigation of buried steel pipe

SECTION 5 CONSTRUCTING, TESTING, COMMISSIONING 5.1 GENERAL AND DOCUMENTATION 5.2 SEPARATION FROM OTHER UNDERGROUND STRUCTURES 5.3 COATING FOR BURIED METAL PIPE 5.4 PIPE INSTALLATION METHODS 5.4.1 General 5.4.2 Trenched installation 5.4.3 Trenchless installation 5.4.4 Insertion

5.5 TESTING 5.5.1 Mains and Services 5.5.2 Over-pressure protection

5.6 COMMISSIONING OF GAS MAINS 5.6.1 General 5.6.2 Planning

SECTION 6 OPERATING AND MONITORING 6.1 PRE-OPERATING REQUIREMENTS 6.1.1 Completion of preparations 6.1.2 Plans and procedures 6.1.3 Responsible personnel 6.1.4 Hazards, and safe practices 6.1.5 Venting procedures

6.2 OPERATING AND MONITORING 6.2.1 Maximum allowable operating pressure 6.2.2 Damaged pipe or component 6.2.3 Odour 6.2.4 Public reporting of leaks 6.2.5 Leakage surveys 6.2.6 Response to leak reports and surveys 6.2.7 Network pressure and flow control monitoring 6.2.8 Route monitoring 6.2.9 Locality monitoring, and asset location information 6.2.10 Valve operability monitoring 6.2.11 Monitoring of system performance, growth, pressures, flows and fringe points 6.2.12 Inspection of structures housing gas equipment 6.2.13 Special inspections

6.3 REVIEWS, REPORTS AND ANALYSIS 6.3.1 Leakage reports, review and analysis 6.3.2 Corrosion protection review 6.3.3 Incident reporting, review and analysis 6.3.4 Risk reviews

SECTION 7 MAINTAINING AND REPAIRING 7.1 GENERAL 7.2 REPAIR OF COATING OF BURIED METAL PIPE 7.3 MAINTENANCE AND REPAIR OF COATING ON ABOVE-GROUND PIPEWORK 7.4 STEEL-CASED CROSSINGS 7.5 WORK ON GAS MAINS 7.5.1 General 7.5.2 Purging mains and services

SECTION 8 MODIFYING 8.1 DESIGN OF MODIFICATIONS 8.2 CONSTRUCTION, TESTING AND COMMISSIONING OF MODIFICATIONS

SECTION 9 DECOMMISSIONING 9.1 MAKING SAFE

APPENDIX A - LIFE-CYCLE OF NETWORK A1 PLANNING A2 DESIGN A3 CONSTRUCT, TEST AND COMMISSION A4 OPERATE, MONITOR, MAINTAIN, REPAIR AND MODIFY A5 DECOMMISSION

APPENDIX B - REFERENCED DOCUMENTS APPENDIX C - MATERIALS, COMPONENTS, AND DESIGN CONDITIONS GUIDELINES C1 GENERAL C2 MATTERS THAT SHOULD BE INCLUDED FOR CONSIDERATION C2.1 Materials comprising active metals C2.2 Materials in associations resulting in bi-metallic corrosion C2.3 Designs and configurations leading to crevice corrosion C2.4 Components in plastics C2.5 Materials adversely affected by solvents C2.6 Materials comprising passive alloys C2.7 Materials that are free machining alloys C2.8 Materials that are dezincification resistant alloys C2.9 Designs and configurations leading to stress concentrators

APPENDIX D - CONTROL OF GAS PRESSURE D1 GENERAL D2 MAXIMUM ALLOWABLE OPERATING PRESSURE OF SYSTEM D3 PROTECTION FROM EXCEEDING MAOP D4 REGULATING CAPACITY D5 LOCATION OF PRESSURE CONTROL EQUIPMENT D6 DESIGN OF REGULATING DEVICES D7 DESIGN OF VENTS D8 NOISE CONTROL D9 PRECAUTIONS AGAINST FREEZING D10 PROTECTION OF REGULATORS FROM SOLID MATTER IN GAS D11 INTEGRAL OVERPRESSURE SAFETY DEVICES D12 TYPES OF OVER-PRESSURE SAFETY DEVICE D13 PREVENTION OF UNAUTHORIZED OPERATION D14 SERVICE REGULATOR INSTALLATIONS D15 SERVICE REGULATORS D16 FAILURE OF EQUIPMENT

APPENDIX E - MARKERS AND MARKING APPENDIX F - EMERGENCY PLANS F1 GENERAL

APPENDIX G - CLASSIFICATION OF LEAKS G1 GENERAL G2 CLASSIFICATION G2.1 Class 1 G2.2 Class 2 G2.3 Class 3

APPENDIX H - PIPE IDENTIFYING, LOCATING AND WARNING SYSTEM ELEMENTS

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