Pressure testing requirements

[markzu3]

For a power piping designed to B31.1, is it mandatory to do a pressure testing (either hydrostatic or gas)? Under what conditions is one allowed not to do pressure testing. For example if the welds are radiographed, can the pressure testing be waived?

Thanks

 

[ApC2Kp]

markzu,

The B31.1 Code has several levels of requirements for pressure testing to ensure leak tightness.
1). Para 137.3.1 Boiler External Piping shall be hydrotested ... in presence of the AI.
2) Nonboiler External Piping shall be hydrotested,or when specified by owner, alternative test of pneumatic, halide leak, or initial service testing is accepted.
3) Lines open to the atmosphere, such as vents or drains past the shutoff valve, are not required to be tested.

The B31.3 Process Piping Code has provisions for alternative leak testing, again to be specified by owner, which include an option for radiogragraphy supplemented by sensitive leak test plus stress analysis, in lieu of a hydrotest.

The B31.1 Power piping Code does not have specific limitations for the initial service testing, as does the B31.3 Code limits for service testing. The only B31.1 Power Code limit for initial service testing is that it does not apply to boiler external piping. I would suggest considering the fluid service hazards, and the difficulty of repairs for leaks found by initial service tests. If the piping is to be insulated, then the welded and flanged joints need to be left uncovered for initial service testing. If the fluid is flammable, then a pneumatic test could possibly be applied on smaller piping systems. If the piping system is for higher pressures, say CL300 and above, then take extra precautions for restricting personnel in area during an initial service test. If weld repairs on a piping leak would require cleaning and decontamination of a pipe line, then do the leak test before line is put into service.

 

[pm66209]

Will soon be UT testing boiler feedwater piping.

The Power Piping Code has an 'A' factor (corrosion/erossion/mechanical strength allowance). Is this just to be used for a new piping installation calculation or should there be some 'A' amount considered to determine minimal thickness for existing piping?

Weld Joint Efficiency 'E'. We have seamless pipe but I don't know how it was previously welded at the fittings and in the pipe runs. What is a good value to use for 'E' in such a case?

With the previous inputs determined would you consider the minimum thickness calculated to be strictly adhered to for pipe that has been in service for quite a while? That is, would you replace pipe and fittings whose thickness was measured to be below the minimum thickness as calculated from the Power Piping Code or would you allow pipe thicknesses some % below the minimum thickness calculation but no thinner? Where do you draw the line?