316SS piping for hydrogen gas service

[RJPabbv]

I am reconfiguring the hydrogen gas supply lines to several vessels in a hydrogenation pilot plant. The new pipe will be 316 SS with an operating pressure up to 1100 psig, at ambient temperatures (-10 to 110 F). I know H2 gas generated during passivation of SS can cause hydrogen embrittlement and that heat treating can remove the hydrogen gas in the metal. But considering this pipe will be under hydrogen gas service, I'm curious if the passive layer is needed. Would migration of hydrogen gas into the metal be hindered, assisted, or not affected by the passive layer?

 

[Metalguy]

Should be OK. Atomic H, usually generated by corrosion, will pass right thru both 316 and a passive layer, but you shouldn't have any. Your 316 will already have a very thin passive layer.

316 is better than 304 because the higher Ni makes the austenite more stable during any cold-working.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[EdStainless]

Just make sure that it is well annealed before you use it.
Put a limit on how magnetic it is (max permeability of 1.04).
You won't hydrogen embrittle the 316, just places with excessive ferrite or martensite.

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Plymouth Tube

 

[metengr]

I would strongly advise before doing anything else to review ASME B31.12.

http://www.asme.org/products/codes---standards/hydrogen-piping-and-pipelines

 

[RJPabbv]

For references I have been using NFPA Hydrogen Technologies Code NFPA-2, 2011 edition and Hydrogen Piping and Pipelines ASME B31.12-2001, as well as B31.3-2008, B16.9-2007, B16.34-2009 and B31.12-2001.

Our corporate engineering standards reccommend passivation for stainless steel lines that will handle liquids, but our standards do not call for passivation of systems carrying gases. It appears passivation of the new pipe would not provide any added benefit.

 

[EdStainless]

The purpose of passivation if to clean the surfaces. This is always a good ides in gas service.

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Plymouth Tube

 

[RJPabbv]

For general cleaning after installation, we typically use an alkaline cleaning solution. My understanding is that passivation is intended to remove residual iron particles, either as free iron or imbedded tool steel particles, from the surface and quickly create a passive oxide film.

 

[Metalguy]

You are correct. If you want to passivate, you can pump a citric acid solution thru the installed piping--beside using the traditional nitric and nitric/HF mixes. The citric acid must be heated, but it's a lot safer than the others.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[EdStainless]

There are commercially available Citric acid mixtures (with surfactants and chelatingn agents in them) for this purpose.

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Plymouth Tube

 

[moltenmetal]

At a max temp of 110 F and a pressure of 1100 psig, you don't even need stainless steel. You certainly do not need to passivate 316SS if you use it, unless some corrodent other than hydrogen is a concern.