scope:

This Standard applies to standard designs of new, on-shore, gas supply meter installations (hereinafter referred to as "installations") supplied from a Network pipeline (service) supplying Natural Gas (NG) and having:

• Design Maximum Incidental Pressure (DMIP_u) not exceeding 200 mbar

• Maximum Operating Pressure (MOP_u) not exceeding 75 mbar

• Lowest Operating Pressure (LOP_u) not less than 25 mbar

• Design Minimum Pressure (DmP_u) not less than 19 mbar.

Note 1: NG is a 2^nd family gas as defined by BS EN 437.

Note 2: Experience has shown that 25 mbar is a reasonable inlet pressure (LOP_u) to be used for sizing meter installations for use on networks of MOP ≤ 75 mbar and designed in accordance with IGEM/GL/1.

Note 3: For meter installations of 75 mbar < MOP_u ≤ 38 bar and all installations of MOP_u ≤ 75 mbar that are not standard designs, IGEM/GM/8 applies.

Note 4: For meter installations of MOP_u > 38 bar, IGEM/GM/4 applies and IGEM/TD/13 may be used with respect to the regulation of pressure.

Note 5: IGEM/GM/6 has been produced for primary meters. However, its principles may be applied for other meters, for example appliance check meters and departmental charging meters, etc. when certain requirements may not apply.

Standard designs incorporate either a diaphragm or RD meter of maximum badged capacity exceeding 6 m³ h^-1 but not exceeding 1076 m³ h^-1 and delivering a nominal metering pressure of 21 mbar.

Note 1: The installation design capacity will be less than badged capacity of the meter. e.g., For a meter with a badged capacity of 1076 m³ h^-1 the standard design's installation design capacity is as low as 675 m³ h^-1.

Note 2: For meters of badged capacity ≤ 6 m³ h^-1, intended to carry NG, BS 6400-1 or BS 6400-2 apply, as appropriate for MOP_u.

These standard designs also allow the use of alternative meter technologies, such as, thermal mass or ultrasonic meters. These new technologies have to meet the requirements of this Standard.

Note: Further information is provided in Appendix 9.

The standard designs fall into two categories:

• IGEM/GM/6 designs - conforming to the drawings and component lists in Appendix 5

Note: Normally, the IGEM/GM/6 designs are sourced as a kit of components.

• Manufacturer designed pre-assembled modules complying with the requirements of IGEM/GM/6.

Note: Normally, the modules are supplied as a pre-assembled and tested unit. However, there is no reason why a module may not be dismantled and re-assembled on site, provided it is appropriately tested and is not modified in any way.

This Standard covers meter installations that are wholly downstream of the outlet of the ECV, as recommended in IGEM/G/1, that is, the installation is not part of a network.

Note 1: IGEM/GM/6 does not address the Network pipeline (see IGEM/TD/1, IGE/TD/3, IGE/TD/4 and IGEM/G/5, as appropriate), neither does it address requirements for a pressure regulating installation (PRI) installed in a Network pipeline when IGEM/TD/13 applies.

Note 2: In addition to defining requirements for the meter installation, this standard defines requirements for associated considerations such as its location, housing and notices and labels.

This Standard covers only meter installations that are connected directly to the ECV and which are adjacent to the ECV.

This Standard applies to meter installations that supply a consumer's downstream installation that complies with IGEM/UP/2 and which contains:

• pipework and standard appliances (see Note 2), or

• pipework and appliances that may be standard appliances (see Note 2) and/or appliances that are not standard appliances but that will operate satisfactorily at the limits of supplied gas pressure as given in this Standard.

Note 1: A maximum pressure drop of 1 mbar as specified by IGEM/UP/2 has been assumed for the consumer's installation.

Note 2: Standard IGEM/GM/6 designs have a metering pressure of 21 mbar and provided components are selected appropriately will ensure a suitable pressure to standard appliances. It has been established that standard appliances have the following characteristics (see also Appendix 5 and 6):

STP ≥ 50 mbar

P_max = 25 mbar

OP = 20 mbar

P_min = 17 mbar

P_ign = 14 mbar (70% OP).

This Standard does not apply to installations incorporating a standby regulator stream or installations that incorporate a by-pass. Where twin streams are incorporated (see Figure 47), it is simply to achieve desired capacity i.e., shared load.

Note: Continuity of supply, while not always an essential requirement, may be desirable in some circumstances, in particular where there is risk to life or property; for example, to enable a hospital or a system requiring gas for a continuous process to take gas during maintenance or in the event of a fault. IGEM/GM/8 would then need to be used for the design of the installation.

All references to gas pressure are gauge pressure unless otherwise stated.

Italicised text is informative and does not represent formal requirements.

Appendices are informative and do not represent formal requirements unless specifically referenced in the main sections via the prescriptive terms "must", "shall" or "should".