scope:

This Standard covers the stress analysis and calculation of loadings for welded and flanged pipework used in gas industry installations on or connected to pipelines.

In general, an installation on a pipeline comprises one or more of the following:

• compressor station

• line valve

• branch connection

• meter installation (see also IGEM/G/1, IGEM/GM/8 and/or IGEM/GM/4, as appropriate)

• multi-junction station with or without in-line metering and which may include pig traps and/or line valves

• overhead pipe crossing

• pigging station

• PRI controlling gas flow and/or pressure from one system to another

• terminal

• other offtakes.

This Standard applies to pipework (as outlined in Sub-Section 2.1) on land. For pipework offshore, additional or alternative guidance may be required. However, many of the requirements in this Standard will remain valid.

Note: Offshore pipework is on the seaward side of the low water mark or special boundaries drawn at bays and estuaries.

This Standard is entirely dependent upon the application of other relevant codes and standards, appropriate to the system being designed, e.g., IGEM/TD/1, IGEM/TD/13, etc., to ensure overall plant integrity.

Note: The information covering materials (pressure testing and construction) is included to qualify the stress analysis recommendations and draw attention to important areas of consideration.

This Standard is entirely dependent upon the correct selection of materials compatible to the appropriate duty. This Standard is not intended for general application to pipelines, which are covered by IGEM/TD/1, IGEM/TD/3 and IGE/TD/4 respectively. Where larger diameter pipework is above ground for a significant distance, these requirements may be relevant.

This Standard covers stress analysis for pipework carrying gas at a maximum operating pressure (MOP) not exceeding 100 bar and at a temperature between -25 oC and 120 oC inclusive. Some pipework such as venting pipework could be subjected to lower than -25 oC in certain conditions. IGEM/TD/12 can still be used for the assessment of this pipework, but the designer is to ensure that the material remains ductile under these lower temperatures.

Note: Specifically, this Standard applies to the range of conditions expected to be encountered in the types of plant specified in Sub-Section 2.1.

This Standard covers pipework handling 1^st and 2^nd family gases as defined in BS 1179, odorised or unodorised.

This Standard applies only to carbon and austenitic steels whose permanent elongation at tensile fracture at room temperature is greater than 14% when measured using the method outlined in BS EN ISO 6892-2.

Note 1: The use of pipe manufactured from non-metallic, cast metallic or other brittle material is not within the scope of this Standard.

Note 2: Materials operating above their creep threshold are not covered.

This Standard applies to pipework containing gas at a positive gauge pressure, i.e., internal pressure not less than external pressure.

Pipes with a diameter to wall thickness ratio (D/t) of less than 10 require special consideration.

For pipes of D/t greater than 96, the possibility of buckling of the pipework needs to be considered.

All pressures are gauge pressures 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".