Last year I broke down the pressure and leak test requirements found in ASME B31.5 for those of you in the Ammonia Refrigeration industry, and at the time, I promised I would do the same for those of you that use ASME B31.3 in all the other process industries. And as I got busy with other things, I forgot to follow up until my PSM SeminarFest course this weekend, when a student got access to the website and could not find this information. So here are the pressure and leak testing requirements found in ASME B31.3, our PSM/RMP RAGAGEP for our process piping.
General Requirements for Leak Tests (Section 345)
The test pressure may be reduced to the maximum pressure that will not exceed the piping’s yield strength at the test temperature. If a pressure test is to be maintained for a period of time AND the test fluid being used can expand under the test conditions (including ambient atmospheric conditions, the code requires that precautions be taken to avoid excessive pressure from the thermal expansion.
The code allows for a preliminary “pressure test” using regular air at no more than 25 psig. This preliminary “pressure test” is intended to be done prior to hydrostatic testing to locate any major leaks in the piping circuit being tested. The code calls for the test pressure to be maintained for at least 10 minutes. After successfully completing the pressure test, we can reduce the pressure in the pipe circuit and examine/inspect ALL joints and connections for leaks.
These tests MUST be conducted AFTER any heat treatment has been completed.