ASME B31.4 Ch XI Operating vs Design Pressure ambiguity with respect to hydrotest requirements

[tomecki]

ASME B31.4 C437.4.1(a) "Portions of piping systems to be operated at hoop stress of more than 20% of the specified minimum yield strength of the pipe shall be subjected at any point to a hydrostatic proof test equivalent to not less than 1.1 times the internal design pressure at that point.."

I'm wondering what is the interpretation of the word "operated". It very ambiguous to me. The line could be "operated" at a lower pressure, but see higher transients at some point. Parts of the line could be "operated" at a lower pressure than others. To be safe, I'm calculating the hoop stress based on the design pressure, but I'm wondering what the right interpretation is.

Thanks

 

[LittleInch]

You seem to be mixing two separate sections

437.4.1A actually says
"(a) Portions of piping systems to be operated at a
hoop stress of more than 20% of the specified minimum
yield strength of the pipe shall be subjected at any point
to a hydrostatic proof test equivalent to not less than
1.25 times the internal design pressure at that point (see
para. 401.2.2) for not less than 4 hr.

437.4.3 says
"A 1-hr hydrostatic or pneumatic leak test may be used for piping systems to be
operated at a hoop stress of 20% or less of the specified
minimum yield strength of the pipe. The hydrostatic
test pressure shall be not less than 1.25 times the internal
design pressure.

Which do you mean?

Operated means the pressure you would normlly expect to see, i.e. it's MOP as limited by devices, alarms or ability of the pumps or whatever to create pressure.

It's not "to be safe" that you calculate hoop stress based on design pressure - it's called following the design Code.

Don't think you're doing yourself a favour here - that's the way it is done.


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