Aug 2013
by Institution of Gas Engineers and Managers

IGEM/G/1 +A: 2013 - Defining the end of the network

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This standard defines various important terms within natural gas systems and provides a basic guide to the arrangement of the components required in such a system.

It provides a framework and standard approach or new gas distribution mains, services, primary meter installations and installation pipework and include:

Definitions for the end of the gas network, the primary meter installation (including any associated regulator) and installation pipework

Illustrations of a range of recommended arrangements and those which, for historical reasons, are not recommended with respect to their design or layout and are 'legacy' arrangements

Identification of boundaries and interfaces.

It is applicable to all natural gas systems and defines the boundaries and interfaces between the end of the Network, a primary meter installation and installation pipework and, in addition, provides a definition of recommended gas supply arrangements which will simplify any new arrangements that are required to ensure a safe and secure supply of gas to a consumer.



1.1     This Standard provides a framework and a consistent approach for the 
arrangement of Natural Gas distribution mains, services, primary meter installations and installation pipework.  
IGEM/G/1 Edition 2 supersedes the 1st, 2nd, and 3rd Impressions (Communication 1733), of IGEM/G/1 which are obsolete. 
1.2 For the purposes of this Standard, definitions have been agreed between parties involved in the introduction of competition into metering activities in Great Britain. The Institution of Gas Engineers and Managers (IGEM) consulted appropriate regulatory bodies (HSE, Ofgem and Gas Safe Register), associations of gas transporters (GTs), suppliers and shippers, meter asset managers (MAMs), installation pipework owners and installers and manufacturers of pipe, meters, regulators and other equipment associated with gas systems at the end of networks. 
1.3 Arising from the provision in the Gas Act 1986 (as amended) (see clause 3.1.2), metering services and, in particular, the provision of gas supply meters at gas consumers’ premises are provided by competitive service providers under the revision of gas metering arrangements (RGMA). 
In order to facilitate the operation of the market and to provide necessary controls, a number of industry documents have been published which include:  

  • OFGAS Gas Metering Definitions 
  • OFGAS Codes of Practice, CoP1/a, 1/b and 1/c, which specify standards and processes applicable to meter installations  
  • MAM Code of Practice (MAMCoP) 
  • OFGAS Meter Competition Focus Group – Definitions Expert Group Final Report, June 2000, which defines the competitive area for meter installations. 

Work dataflows across the industry need to conform to the relevant parts of the Review of Gas Metering Arrangements (RGMA) processes managed by Supply Point Administration Agreement (SPAA Ltd). 
IGEM/G/1 Edition 2 builds on the above documents to provide additional and supplementary detail to assist parties who have statutory duties under legislation in the development of arrangements and to assist in the provision of a safe and secure supply of gas to consumers.  
1.4 In defining the end of the network, there are repercussions with respect to the boundaries of responsibility between a GT/gas conveyor with network management responsibilities, the meter installation owner/MAM and the installation pipework owner/operator. Notwithstanding the Notes (below), the document is, to IGEM’s best knowledge, consistent with the current editions of: 

  • Gas Safety (Management) Regulations (GS(M)R) 
  • Gas Safety (Installation and Use) Regulations (GS(I&U)R) 
  • Pipeline Safety Regulations (PSR)
  • Pressure Systems Safety Regulations (PSSR). 

Note 1: This Standard contains specific terminology which may differ from the legal meaning. 
Note 2: This Standard does not include all possible configurations, and the law may allow deviation from the common practices shown. For example, the designation of an “emergency control” in a particular situation will, ultimately, rest on the facts of the case, that is primarily on intended use by a consumer of gas. 

1.5 This Standard recognises inconsistency between relevant official CoPs, guidance to legislation, and national and industry standards. They attempt to consolidate the varied use of different terms across such publications, to provide a base for their future amendment and to represent current best practice. These publications include: 

  • HSL56 
  • HSL80 
  • HSL81 
  • HSL82 
  • HSL122 
  • HSL144 
  • OFGAS Gas Metering Definitions  
  • OFGAS CoPs: 1/a, 1/b and 1/c (see Sub-Section 1.3) 
  • IGEM/GM/5  
  • IGEM/GM/6 
  • IGEM/GM/7A 
  • IGEM/GM/7B  
  • IGE/GM/8 
  • IGE/UP/1  
  • IGE/UP/1A  
  • IGEM/UP/1B
  • IGEM/UP/1C 
  • IGEM/UP/2 
  • IGEM/TD/1 
  • IGE/TD/3  
  • IGE/TD/4  
  • IGEM/TD/13 
  • IGEM/G/5 
  • BS 6400-1 
  • BS 6400-2 
  • BS 6891. 

 Appendix 2 provides detail of these publications. 
Any definitions relating to this Standard but not contained within it are given in IGEM/G/4, which is free to access and download from 
1.6 This Standard makes use of the terms “must”, “shall” and “should” when prescribing particular requirements.  Notwithstanding Sub-Section 1.7: 

  • the term “must” identifies a requirement by law in Great Britain (GB) at the time of publication 
  • the term “shall” prescribes a requirement which, it is intended, will be complied with in full and without deviation 
  • the term “should” prescribes a requirement which, it is intended, will be complied with unless, after prior consideration, deviation is considered to be acceptable. 

Such terms may have different meanings when used in legislation, or Health and Safety Executive (HSE) Approved Codes of Practice (ACoPs) or guidance, and reference needs to be made to such statutory legislation or official guidance for information on legal obligations. 
1.7 The primary responsibility for compliance with legal duties rests with the employer. The fact that certain employees, for example “responsible engineers”, are allowed to exercise their professional judgement does not allow employers to abrogate their primary responsibilities. Employers must: 

  • have done everything to ensure, so far as it is reasonably practicable, that “responsible engineers” have the skills, training, experience and personal qualities necessary for the proper exercise of professional judgement 
  • have systems and procedures in place to ensure that the exercise of professional judgement by “responsible engineers” is subject to appropriate monitoring and review 
  • not require “responsible engineers” to undertake tasks which would necessitate the exercise of professional judgement that is not within their competence. There should be written procedures defining the extent to which “responsible engineers” can exercise their professional judgement. When “responsible engineers” are asked to undertake tasks which deviate from this, they should refer the matter for higher review. 

1.8     This Standard was published in August 2013. 


2.1 This Standard is applicable to all Natural Gas systems and provides a framework for the arrangement of gas distribution mains, services, primary meter installations, installation pipework and includes: 

  • definitions for the end of the gas network, the primary meter installation (including any associated regulator) and installation pipework 
  • illustrations of a range of standard arrangements which are deemed appropriate for the gas industry as it currently operates and which will simplify any new arrangements that are required, to ensure a safe and secure supply of gas to a consumer 
  • illustrations of a range of legacy arrangements, which are not recommended with respect to their design or layout
  • identification of boundaries and interfaces. 

Note: The definition of these boundaries and interfaces is essential so that relevant information can be exchanged between organisations and persons who have a duty to ensure a safe and secure supply of gas to premises.  
2.2    The term “regulator” is intended to mean “meter regulator” unless otherwise stated. 
2.3    All pressures are gauge pressures unless otherwise stated. 
2.4    Italicised text is informative and does not represent formal requirements. 
2.5    Appendices are informative and do not represent formal requirements unless specifically referenced in the main sections by the terms “must”, “shall” or “should”.