Meaning of full vacuum operating condition of pipes?

[tsarbomba_imported]

Pressure in pipes during operating condition is full vacuum. How do we input the pressure value for pipe stress analysis? Should it be zero Mpa or we should use atmospheric pressure?

 

[TugboatEng]

To simplify your analysis use absolute pressures. Full vacuum is zero absolute.

 

[1503-44]

Gage pressure would be -14.7 psig or -1 Barg, if the pipe is Sea level.
If its a subsea pipeline, you must also subtract the water pressure at the pipeline's depth.
If it is buried, you must also subtract the pressure of the soil.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

Depends on your program.

Could be a pressure of -1 barg or internal pressure of 0 barg and an external pressure of 1 barg assuming this is above ground. As Mr44 says if this is subsea then it's probably easier to add 10m to the water level and have 0 barg inside.

Either way for most pipes it's a very small stress.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Krausen]

Section VIII clearly defines "Full Vacuum" as -15 psig. I'm not certain if the B31 codes have adopted this exact definition though, but I would advise to use that.

Tolerance is the virtue of the man without convictions -GK Chesterton

 

[tsarbomba_imported]

Thank you everyone for the reply. -15psig seems correct for my situation.