Does anyone have experience with piping hydrogen at moderate temperatures and pressures? Say, 500 psig and 350 F. What materials did you use and what inspection program did you recommend?

If you do not have external reasons to use SS then ASTM A106B should be OK. I would try to limit flange connections and would not used srewed at all. Check that valves are for hydrogen service. Where possible run the pipe so that it is protected.

You do not want to have leaks. X ray may not show small pinholes. Well run hydrotest should help. If area is critical start looking helium test.

Thanks - I like the idea of a helium leak test! Probably the only gas with atoms on the scale of a hydrogen molecule, although nothing is as small as a dissociated hydrogen nucleus (one proton).

I think we did hydrogen piping going to hygrogen plant for low sulfur deisel project. We used 304 stainless steel pipe and did high-pressure pneumatic test consist of both pressure retention and a leak test, using clean dry nitrogen as test gas.

Goodluck!

Carbon steel is fine for 500psi and 350F. Check with API RP 941 for hydrogen attachs on different materials.

Agree with SSW temps too low to be a problem...

Dears,

Taking cue from Jouko, it's better to limit flange joints in hydrogen service. But, if we use, which flange/gasket combination is suitable for say 900/1500# high temperature hydrogen service - ring or spiral wound or anything else?

regards,

sam

Sam,

for low pressure class you can use spiral wound gaskets, but for high pressure lines (i.e. 1500#) we usually review case by case and commonly we use ring joint RTJ (confined metal) gaskets.

Here is a chart for operating limits for steels in Hydrogen service. The chart is adapted from API 941.

Goodluck!

Thanks to Flexy for so quick response.

regards,

sam

Thanks to all.

As usual, a lot of good ideas.