H2S Corrosion in Black Sea 1

[gregozo1]

Would like to know if steel springs in equipment about to be put on Black Sea floor will be affected by the H2S in solution in the Black Sea

 

[TVP]

Yes.

 

[gregozo1]

Thanks TVP - we thought it would but what can we do to make the springs reliable - stainless? The springs are quite powerful having to close 3000psi w.p. valves and are open to the sea. How long does the hydrogen embrittlement take to affect steel - weeks, months? Any pointers greatfully recd.

 

[swall]

The Black Sea is saltwater, right? So you have chlorides to worry about in addition to H2S.

 

[gregozo1]

Have used these springs/valves since the seventies sub sea and get some corrosion - they last about 18 months. The thing with the Black Sea is that below +/- 200m water is anoxic hydrogen sulphide soup and we've never used these springs in this environment, just wanted to know if we can expect problems from H2S in solution.

 

[CoryPad]

You should review NACE MR0175/ISO 15156 Petroleum and natural gas industries—Materials for use in H2S-containing environments in oil and gas production

http://www.nace.org/NACE/Content/technical/MR0175/Mr0175index.asp

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[TVP]

gregozo1,

I agree with CoryPad, use the NACE document as a guide for suitable material selection. Even stainless spring steels will be questionable in H₂S environment. I am not sure if nickel-based grades like Alloy X-750 are suitable for sulfide exposure, but titanium alloys definitely are. I would investigate a suitable titanium alloy and re-design the spring to accommodate it. Renton Coil Spring in the USA is a leader vendor of titanium springs.

 

[rorschach]

X-750 would be ok as would Titanium. MP-35N and Elgiloy would also be acceptable. 17-4 and 17-7 would probably be attacked by the chlorides.