Hydrogen Bake-Out???

[QAScott]

Hello,

I would like to find info about Hydrogen bake outs for SA-516 Gr70,SA 285 GrC or any P1. What is happening what you bake-out the Hydrogen? How do you know if it is all removed? Were dose it go?

Thank You,
QAScott

 

[unclesyd]

These are steels that normally don't require H2 bake out procedures. See the thread below for references to bake out procedures after plating.

If you are concerned with diffused hydrogen, like H2 blistering or cracking, from a process standpoint you need to give a little more information. Once you get H2 damage to your materials it's usually not recoverable.

As for checking for H2 diffused in metal, it is very expensive and usually not worth the effort.

So if you can come back with more information on what you are trying to do maybe you can get a little better answer.


thread338-76023

 

[QAScott]

unclesyd,

What I will be doing is welding new P1 Mat'l to old P1 Mat'l (1968) that is in Hydrocarbon service.

I want to know how to do the Hydrogen bake-out(time&Temp) for this full Pen. weld in .500" Nom. Thk. Mat'l. or is this Mat'l to thin to need it?


Thank You,
QAScott

 

[unclesyd]

You material is ok concerning any heat treating requirements for the thickness.

Have you seen any signs of H2 damage in the equipment?

You mention hydrocarbon service or do you mean hydrogen or any acid gases?

If in H2 service there are specific considerations for carbon steel in H2 service, concentration, temperature, and partial pressure of the H2. If your service was H2 come back with the conditions. Again if H2 service has caused damage you can restore some ductility by heat treating.

A little test is to make a one pass filet weld on one side a 1” x 1" x 1/4" or so C/S tab to the old material and attempt to break it off. It should break off in the weld.

We welded both these materials in H2 service all time without any problems. The only consideration was PWHT for thickness considerations. We even used temper bead welding on some very thick sections with no problems.


I think you can weld your material without any bakeout using only the normal welding parameters. Weld above 50°F, i would use 175°F, and use low hydrogen rods. One always has to add a little caveat, if you see any problems during welding stop and ask another question.

Good luck

 

[stanweld]

In addition to the comments from unclesyd, it is also important to know if the steel has been subject to sulfur contamination. At 1/2-inch thick, cracking can easily occur if the process surface is not thoroughly cleaned to remove all sulfur contamination.

For similar vessels in H2S and hydrogen service, I have required 200 F preheat and low hydrogen welding processes with excellent results.

 

[Kerhin]

Scott, we use a post weld hydrogen bake out when performing weld repairs with the temper bead process. We use this controled welding process to avoid PWHT on components that would be adversely affected by a high temperature PWHT.
The ASME Section XI requirement is 450-550 deg. F for a minimum of 2 hrs. after the completion of the weld repair in P1 materials (such as SA515 Gr.70 material) for the SMAW process. When using the GTAW process (inherently more hydrogen free) the weld area shall be maintained at a minimum temperature of 300 deg F for a minimum of 2 hrs. after the completion of the weld repair in P1 materials.

The requirement is to allow the hydrogen to diffuse out of the weld and heat affected zone. Of course it is also a requirement to use low hydrogen electrodes or a hydrogen free process and I recommend a preheat to ensure any moisture is removed fron the joint.