Short answer
IGEM/UP/1A is the simplified strength testing, tightness testing and direct purging procedure for smaller natural gas installations: typically volume up to 1 m³, MOP at the ECV outlet up to 40 mbar and pipework up to 150 mm diameter. It uses tables rather than full calculation, so it is quicker to apply on small commercial sites.
When you can use UP/1A
All of the scope limits must be met. If any part of the installation exceeds the volume, pressure or diameter limits, or the gas is outside the scope, the whole job reverts to IGEM/UP/1. Engineers should calculate installation volume before choosing the standard, not after.
Typical UP/1A installations are restaurants, cafés, small offices, shops, churches and school kitchens with a single meter and low pressure supply.
How the procedure differs
UP/1A provides look-up tables for test duration based on installation volume and the gauge type (water gauge or electronic gauge with 0.1 mbar or 0.5 mbar resolution). The permissible pressure drop is read from the table rather than calculated from first principles, and the stabilisation period is fixed.
Purging uses tabulated purge volumes for each pipe size and length, with the purge proven by a gas detector reading at the purge point.
Common mistakes
Underestimating volume by forgetting the meter, large-bore manifolds or appliance internal volumes; using a gauge with too coarse a resolution for the volume; and starting the test before temperature has stabilised after pipework has been handled or run through a cold void.
Figures are typical for UK natural gas. The current edition of the relevant IGEM standard and the manufacturer's instructions always take precedence on site.
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