Recalling the process of finalizing the pressure for the airtightness test of the gas system in an overseas project

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The last edit to this post was made by we11we11 on 2021-7-12 at 19:23. Seventeen years ago, before the commissioning of a gas-fired power generation project abroad, it was necessary to prepare a plan for the airtightness testing of the gas treatment system. As the main person responsible for drafting the procedural documents and encountering airtightness testing for the first time, I reviewed a large amount of literature, including domestic standards as well as ASME31.3, 31.4, and 31.8. Yet I was still confused regarding the pressure levels required for such tests; so I simply followed conventional practices and prepared a draft version of the plan using the design pressures of each subsystem as the airtightness test pressures. Upon closer inspection of the PID drawings, it was found that the design institute had set the setting pressure for the safety valves of each subsystem to be equal to the design pressure of that subsystem. This means that if the design pressure is used as the pressure threshold for ensuring airtightness, the safety valves will activate; in such cases, it is necessary to remove the safety valves and send them to a local factory for re-calibration. This not only takes a lot of time but also disrupts the integrity of the system after the safety valves are removed and reinstalled – wasn’t all the work done to ensure airtightness in vain? Feeling confused, I consulted the owner (a world-renowned oil company); the manager in charge of commissioning told me that the pressure to be used for the airtightness test should be 1.1 times the maximum operating pressure (MOP) of each subsystem. After doing the calculations, it turned out that the pressures resulting from multiplying MOP by 1.1 did not exceed the design pressures, so there was no need to calibrate the safety valves. (Of course, in the end I didn’t see any official documents provided by the owner; P) Additionally, the gas turbine generators at that time were manufactured by GE, and the turbines came equipped with a gas treatment skid. According to GE’s own commissioning documents, a gas-tightness test was to be carried out on this skid. The instructions stated, “Keep increasing the system pressure up to the value expected during normal operation,” which means that the maximum operating pressure should be used, without needing to raise it to 1.1 times that value. Of course, as a major company, GE’s documents were naturally accepted by the owner. I drafted several versions of the plan back and forth, drew numerous diagrams for sub-system testing, and eventually had it approved by the client; the airtightness test was carried out on site as well. I suppose this can be considered one of the gains from my efforts to study the relevant standards.