I have been working with several clients who are on a Hydrogen Fuel journey. It is fun to get deep into process safety protection schemes regarding NFPA 2 and ASME B31.12 and see the similarities and extra code requirements when dealing with large H2 gas systems. One of the interesting items regarding H2 piping is a “Leakage Survey,” which applies to “Industrial Plants.”
There is an ongoing debate about this “problem” with GH2 tubing and piping, and such the industry is attempting to make the argument that pressure and leak testing should be done with GH2. However, the AMSE B31.12 committee did not buy into this argument and still requires pressure and leak testing to be done with a NON-FLAMMABLE gas…
IP-10.7.3 Test Fluid
The gas used as test fluid, if not air, shall be nonflammable and nontoxic.
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GR-5.4 LEAKAGE SURVEYS Each operating company shall provide for periodic leakage surveys of the facility in its operating and maintenance plan. The types of surveys selected shall be effective for determining if potentially hazardous leakage exists. The extent and frequency of the leakage surveys shall be determined by the operating company, considering the operating pressure, hoop stress level, piping age, class location, and whether the transmission line transports hydrogen without an odorant. In no case shall the interval between surveys exceed 12 months. |
Since GH2 is more prone to leakage than other industrial gases, it is essential to periodically survey your hydrogen piping and pipelines with a hydrogen detector. Hydrogen piping should be surveyed between 1 and 4 times per year, depending on the area’s population density and as defined by national regulations. You must pay particular attention to flanged connections, valve stems, and compression fittings.
The methods to perform these “leak surveys” include:
1) Subsurface gas detector survey
You must sample the subsurface atmosphere with a gas detector or other devices capable of detecting 0.5% hydrogen gas in air at the sample point. You must survey by performing tests with a gas detector in a series of available openings (enclosed spaces and small substructures) and/ or bar holes over and/or adjacent to the hydrogen gas facility.
2) Surface hydrogen gas survey
If you have buried hydrogen piping, sampling of the atmosphere shall take place, where practical, at a height of no more than 2 in. above the ground surface.
3) Ultrasonic leakage test
You can test your exposed piping facilities using an instrument that detects the ultrasonic energy from escaping gas.
4) Bubble leakage test
You can use soapy water or other bubble-forming solutions on exposed piping to determine the existence of a leak.
5) Pressure drop test
Using this test, you can determine if an isolated segment of hydrogen piping or pipeline loses pressure due to leakage.
References:
1- ASME B31.12-2019, Hydrogen Piping and Pipelines
2- EIGA IGC Doc 121/14, HYDROGEN PIPELINE SYSTEMS