1.1  This Specification is part of a series of Institution of Gas Engineers and Managers (IGEM) publications. This document provides the purchasing requirements for diaphragm gas meters, which will be suitable for installation in installations complying with:

• BS 6400-1 
• BS 6400-2 
• IGEM/GM/6
• IGEM/GM/8. 

 
1.2  British Gas and latterly National Grid Metering (NGM), developed a series of specifications for key metering components based on its own product requirements. These documents were subsequently passed to the Network operators at the time of Network sale. 
 
Scotia Gas Networks (SGN) has subsequently taken the decision to transfer ownership of their version of PRS/11 to IGEM to make it available to the wider industry.  
 
1.3    This Specification has been drafted by an Institution of Gas Engineers and Managers (IGEM) Panel, appointed by IGEM’s Gas Measurement Committee, and has been approved by IGEM’s Technical Co-ordinating Committee on behalf of the Council of IGEM. 
 
1.4    This Specification covers the purchasing requirements of the purchaser for diaphragm gas meters (hereafter referred to as 'meters') purchased under contract by the purchaser for use in domestic, commercial and industrial locations. 
 
1.5    Terms such as “maximum operating pressure” (MOP), “maximum incidental pressure” (MIP) and “operating pressure” (OP) are used to reflect gas pressure terminology used in European standards. These terms will arise in all relevant IGEM Standards and, possibly, in other standards. Other terms have been introduced to assist in recognition of design information to be transferred between interested parties. 
 
1.6    This Specification 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 procedure which, it is intended, will be complied with in full and without deviation 
• the term “should” prescribes a procedure 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    It is now widely accepted that the majority of accidents in industry generally are in some measure attributable to human as well as technical factors. People who initiated actions that caused or contributed to accidents might have acted in a more appropriate manner to prevent them. 
 
To assist in the control of risk and proper management of these human factors, due regard should be taken of HSG48 and HSG65. 
 
1.8    New and improved practices may be adopted prior to this Specification being updated. Amendments to this Specification will be issued when necessary and their publication will be announced in the Journal of IGEM and elsewhere, as appropriate. 
 
1.9    Requests for interpretation of this Specification in relation to matters within their scope, but not precisely covered by the current text, should be either: 

• addressed to Technical Services, IGEM, IGEM House, 26 & 28 High Street, Kegworth, Derbyshire, DE74 2DA; or  
• emailed to [email protected]  

 
These will be submitted to the relevant Committee for consideration and advice, but in the context that the final responsibility is that of the engineer concerned. If any advice is given by or on behalf of IGEM, this does not imply acceptance of liability for the consequences and does not relieve the responsible engineer of any of their obligations. 
 
1.10     This Specification was published in January 2024. 
 
       

2.1 This Specification covers the product requirements for primary diaphragm gas meters with a maximum flow rate (Qmax) in the range 6 m³h-1 to 160 m³h-1 that may be purchased for installation in domestic (including semi-concealed), commercial and industrial locations. This Specification supplements the requirements given in BS EN 1359 and conformity with BS EN 1359 is a prerequisite of this Specification.  
 
Note: The principles and relevant requirements of this specification may be applied to other sizes of diaphragm meter. 
 
2.2   Meters conforming to BS EN 1359 meet the requirements for Class 1.5 of the Measuring Instruments Directive (MID) and UK Measuring Instruments Regulations (MIR). 
 
Note: At the time of publication, a temporary derogation is in place to allow CE marked meters to the MID to be used in the UK, and government have recently announced that an amendment is to be made to the UK MIR prior to the expiry of the temporary derogation, which will allow use of meters CE Marked against the MID to be used indefinitely. 
 
2.3 This Specification also covers the requirement for integral gas valves for meters not exceeding 6 m³h-1. 
 
2.4 Meters covered by this Specification are positive displacement diaphragm gas meters for use with 2nd and 3rd family gas at maximum operating pressures not exceeding 75 mbar and a maximum incidental pressure of 200 mbar. 
 
2.5 Meters covered by this Specification are primary meters and will be stamped in accordance with the Gas Act 1986 as amended. 
 
2.6 This Specification covers the requirements for the construction, performance and marking of meters and includes requirements for resistance to high ambient temperatures (see clause 7.1.7). 
 
2.7 This Specification covers the requirements for meters installed indoor or outdoor (in a meter box or kiosk) both with condensing humidity, or with non-condensing humidity. 
 
2.8     Pressures quoted are gauge pressures unless otherwise stated. 
 
2.9     Italicised text is informative and does not represent formal requirements. 
 
2.10 Appendices are informative and do not represent formal requirements unless specifically referenced in the main sections via the prescriptive terms “must”, “shall” or “should”.