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Hw to pressure test lines

Hw to pressure test lines

Hw to pressure test lines

(OP)
If you are pressure testing lines to 1.5 of the working pressure but this exceeds the test pressure of valves then you cant put blanks on if the valve is welded. How do you usually blank off and test on a fully welded system but have to take the valve out to test?

RE: Hw to pressure test lines

Test the pipe without the valve, weld neck flange & blind welded to end of pipe in place of valve. Weld up the valve with pups in a separate assembly. When the pipe test is complete, cut off weld neck-blind, cut valve-pups assembly to fit and weld that into place of the removed weld neck-blind assembly.

Independent events are seldomly independent.

RE: Hw to pressure test lines

BigInch's technique works fine, but I was wondering why you would install a valve that is apparently adequate for the system MAWP, but not for the test? I have never seen that actually installed. In fact, the valves tend to be the strongest part of a system. Have you installed ANSI 150 valves in an ANSI 300 system because the normal operating pressure is well under 280 psig? I saw a design once where someone was proposing that and I laughed at him till he spent the extra $500 on the valve instead of $2000 on welders to do a process similar to what BigInch described.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: Hw to pressure test lines

Explanatory Note: We often test a long, flat terrain, pipeline straight through a valve or pump station plot plan using a length of pipe as a substitute for the block valve, tie-in, or suction/pump/discharge, or station connection/bypass assembly. That is regardless of pressure ratings, or required test pressures of components. Then we drop in the prefabricated, pretested assembly, radiograph the cut-in point welds and move on to the next station to do it again. It's a scheduling thing as some connection points to pump stations may not be completed as the pipeline construction passes by.

Independent events are seldomly independent.

RE: Hw to pressure test lines

It is common practice to test through open valves at 1.5x design pressure. The limit for closed testing is less.

RE: Hw to pressure test lines

Agree C2it, but apparently in this case it's the other way around, "1.5 of the working pressure (of pipe) exceeds the test pressure of valves".

Independent events are seldomly independent.

RE: Hw to pressure test lines

I wonder if there could be some misunderstanding of what "test pressure of valves" is referred to in/by the OP? Actually, as inferred by other posts, there can be two different "test pressures" of some valves, one being a test against the closed valve/seat, and one testing through the valve with the valve open (the latter is sometimes much higher) -- if not sure, you might want to check with the valve manufacturer to clarify.

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