IGEM/SR/25 Edition 2 - Hazardous area classification of natural gas installations

This standard complements BS EN 60079-10-1 by providing detailed requirements for the hazardous area classification of permanent and temporary natural gas installations. It applies to all natural gas installations, although other standards may be more readily applied for installations downsteam of an emergency control valve. In general, it will not be less conservative than these other standards and therefore it may be used for any natural gas installation. It applies to liquid free natural gas within specific property ranges. This standard applies to any potential release of natural gas except those that may be caused by catastrophic failure such as rupture of a process vessel or pipeline, component failure and similar rare events that are not predictable.

Specifically, it contains details of:

  • Legal considerations such as the Health and Safety at Work etc. Act and the Environmental Protection Act
  • Classification of hazardous areas in different environments, such as outdoors, within covered pits, within enclosed spaces
  • Calculation of ventilation levels and zoning distances.

SR/25 Calculator

The SR/25 calculator was developed by GL Noble Denton (now DNV GL) in agreement with the networks (NG, SGN, NGN and WWU) and IGEM.  

IGEM/SR/25 Edition 2 compliments BS EN 60079-10-1 by providing detailed requirements of the Hazard Area Classification of permanent and temporary natural gas installations. A hazardous area is an area in which explosive gas/ air mixtures are, or may expected to be, present in quantities such as to require special precautions for the construction, installation and use of electrical apparatus or other sources of ignition.

The IGEM/SR/25 calculator is a spreadsheet that is based upon IGEM/SR/25 Edition 2 and applies to liquid-free natural gas with a combined proportion of Methane- plus-inerts of greater than 89% by volume; a gross calorific value not exceeding 45 MJ m-3; molecular weight not exceeding 20 kg kmol-1; LFL of not less than 4.4% a temperature range of -20 ˚C to 50˚C and gauge pressure not exceeding 100 bar.

This spreadsheet is not intended for use by persons who are not familiar with IGEM/SR/25.  It is an aid to zoning to compliment the standard and not a substitute of a full understanding of IGEM/SR/25 Edition 2.  

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