IGEM/UP/1B Edition 4 calculator
First time here? Show me how
- Pipework: enter the lengths in metres. Include the whole section you are calculating. Leave unused sizes blank.
- Valves and fittings: add their calculated internal volume. If it cannot be calculated, select the 10% option and we will add it.
- Meter: choose the meter included in that section, then answer the gas and scope checks.
- Calculate: get installation and purge volumes. Tick the optional pressure-drop box only if you want that guidance too.
Entering numbers: inputs support up to eight decimal places.
This explains the form. It does not replace the testing or purging procedure.
A) Pipe volume
Survey the whole section being calculated, including existing pipework and any new extension. Enter only the sizes used and leave unused fields blank. For inaccessible pipework with unknown lengths of different sizes, use the largest visible diameter for the maximum length (Appendix 7).
Copper
Steel / stainless steelShow pipe sizes15, 20, 25 and 32 mm
Includes pliable corrugated stainless steel.
PE SDR11Show pipe sizes20, 25 and 32 mm
Other pipe sizes or materials
Leave this blank if all your pipework is covered by the sizes above. For other pipework, enter its calculated internal volume in m³, using reliable internal dimensions or manufacturer data. Do not enter a pipe length here.
B) Valves and fittings
Valves and fittings hold gas too. Include any extra internal volume that has not already been counted in the pipework. If you cannot calculate that extra volume, choose the 10% option below and we will add it for you.
What does this mean?
We already calculate the gas space inside the pipe from the lengths above. This section adds the gas space inside valves and other fittings that has not already been counted. Use reliable dimensions or manufacturer information where available.
If that extra volume cannot be calculated, choose the 10% option. The calculator will add it for you. It adds 10% of the pipe volume, not the meter volume.
C) Meter
D) Gas and gas-smell check
Check with the occupier where relevant. If there is a smell or indication of gas, or you have not confirmed there is none, this calculator will not provide a purge quantity. Follow the applicable investigation procedure.
E) Check this calculator applies
Check that the installation meets the limits in Section 2.2 of IGEM/UP/1B:
- Gas and installation: check the gas and installation type are covered.
- Pipe size: nominal bore no greater than 35 mm (DN32).
- Meter capacity: no greater than 16 m³/h.
- Pressure: check the applicable supply and operating pressure limits.
The calculator checks the installation volume from your entries.
Not covered: boats and LPG service pipework.
Separate guidance: legacy medium-pressure arrangements without a meter inlet valve need Appendix 4.
Need pressure-drop guidance?
Optional. Answer a few extra questions to include it in your results.
Pressure-drop guidance
If the initial test has no perceptible movement and no smell of gas, the appliance-isolation retest is not triggered by pressure loss. Where perceptible loss is observed, the allowance applies only to existing appliances after the meter and pipework have been proved gas tight. A new section must meet the no-perceptible-movement criterion.
Check with the occupier where relevant. Choose ‘Known or suspected escape’ for any known or suspected gas escape, including an installation isolated following a report. A pressure-drop allowance cannot override a smell of gas. A known or suspected escape investigation requires no perceptible movement and no smell of gas (Section 5.5). Follow the applicable gas escape and unsafe-situations procedures.
Interpret “no perceptible movement” using the standard and your gauge: at most 0.25 mbar, or 0.2 mbar on an electronic gauge reading to one decimal place. This calculator does not assess gauge readings or replace the complete test procedure.
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