Regarding to ANSI B31.8 You can only test the gas pipeline for one minute at a pressure given by them. Here in Venezuela, the pipeline is tested for an 8 hours period.
You really need to have the latest issue of the Code if you are to be responsible for design of these piping systems.
Tests required by B31.8 to prove strength:
B31.8, Paragraph 841.321
All pipelines and mains operated at a hoop stress of 30 percent or more of specified minimum yield strength of the pipe shall be given a test for at least 2 hr to prove strength after construction and before being placed into operation.
The test pressure depends upon location Class and varies from 1.1 times the maximum operating pressure to 1.4 times the maximum operating pressure.
Paragraph 841.33 - Tests Required to Prove strength for Pipelines and Mains to Operate at less than 30 percent of the SMYS of the Pipe but in Excess of 100 psi.
Steel Piping that is to operate at stresses less than 30 percent of the SMYS in class 1 locations shall at least be tested in accordance with 841.34 (841.34 describes leak testing). In class 2, 3, and 4 locations, such piping shall be tested in accordance with tabel 841.322(f), except that gass or air may be used as the test medium within the maximum limits set in table 841.33
Leak Tests.
841.341
Each pipeline and main shall be tested after construction and before being placed in operation to demonstrate that it does not leak. ............
841.342
The test procedure used shall be capable of disclosing all leaks in the section being tested and shall be selected after giving due consideration to the volumetric content of the section and to its location. This requires the exercise of responsible and experienced judgement, rather than numerical precision.
Leak test pressures vary with circumstances.
For leak tests they are asking for the application of good engineering practices.
This post reflects only my opinion and is not necessarily the opinion of ANSI, ASME or any Code Committee.
