316/316L stainless steel and UNS N08825 for Sour Environment

[onrush]

Dear member,

In project piping material specification, client specified "SOUR" in item descriptions of 316/316L stainless steel and UNS N08825 piping components including valves to meet the requirements of NACE MR0175/ISO 15156.

I think that 316/316L and UNS N08825 basically meet the requirements of NACE MR0175/ISO 15156. So the item descriptions of those materials for both "SOUR" and "Non-SOUR" services shall be same.

Am I correct?

If not so, please give me the details....

Thanks.......

 

[SJones]

Provided that your client has ensured that selection of 316/316L complies with the environmental restrictions of ISO 15156-3, then the material will be required to have a maximum hardness of 22 HRC, be solution annealed and be free of cold work designed to enhance properties in order to qualify for H2S service. It is not required to have these restrictions for non H2S service; so, there are your first differences that you will have to be very clear about. There could also be similar differentiators for 825. Why don't you get a copy of ISO 15156-3 and check the specific materials restrictions for H2S service?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[TomEun]

Onrush,

I believe you have the correct answer from Steve.

Basically they (in sour and non-sour) should be different specs because the different requirements of the valve components (probably due to sour and/or other corrosion mechanisms) as well as the different hardness requirements of the base metals (due to sour service) are expected.

Once the 316/316L/825 are selected, there are some other corrosion mechanisms in these services.

 

[rneill]

As mentioned by SJones there are some fairly significant restrictions with regards to the service environments in which different corrosion resistant alloys can be used in NACE MR0175/ISO 15156 and so it is recommended that you review ISO 15156-3 (as well as the technical circulars and corrigendum's that have been issued).

Unfortunately, this document can be a little confusing and difficult to follow if you're not familiar with it so feel free to post again if you need some help interpreting.

 

[strider6]

316 has a limit of Chloride concentration of 50 ppm. below this value there are no limit in terms of pH2S and temperature but above there is a limit of 60°C and 1 bar of partial pressure of H2S. also 316 is not resistant in case you've elemental sulphur...

S

Corrosion Prevention & Corrosion Control