High Pressure H2S/ CO2 Pipeline Material
High Pressure H2S/ CO2 Pipeline Material
(OP)
We are designing a buried 3" gas line some 200 m long to carry 70% H2S, 29% CO2, 0.0059% H2O, and the balance of C1 and C2, all in mol fractions. Design pressure is 1800 psig,(ANSI 900# RTJ flanges chosen) and design temp is 54C. Looking at NACE requirements and the fact that corrosion inhibition injection is uneconomical, we are chosing 316 SS pipe and valves.Is this the best solution or are there better alternatives?





RE: High Pressure H2S/ CO2 Pipeline Material
RE: High Pressure H2S/ CO2 Pipeline Material
S:
http://www.corrosionist.com
RE: High Pressure H2S/ CO2 Pipeline Material
Thanks for your input. But please refer to Table A2 of NACE MR0175/ISO 15156-3:2003 Technical Corrigendum 2, dated 2005-09-01. This corrigendum has removed the pp H2S restiction on the use of Austenitic SS for sour service.
Thanks
RE: High Pressure H2S/ CO2 Pipeline Material
David
RE: High Pressure H2S/ CO2 Pipeline Material
NACE didn't remove the pH2S limits on SS 316. It has introduced the concept that if the Chloride conc is below 50 mg/l then there are no limits on pH2S , temperature and in situ pH, no limits are set on individual parameters but some combination of these parameters might not be acceptable.
These means that you've to assess if your combinations of parameters is acceptable making test or based on previous experience or you accept the possibility of a failure.this is up to you......
And regarding the moisture, if a gas is dry didn't means that the requiremnts on Sour Service go away because you've to consider also the upset and shutdown conditions when water can condense.
S.
http://www.corrosionist.com
RE: High Pressure H2S/ CO2 Pipeline Material
In theory it could all be carbon steel because there will be no freewater to corrode the line at the temperature and pressures you indicated. In practcal terms, during upsets you can get freewater.
RE: High Pressure H2S/ CO2 Pipeline Material
RE: High Pressure H2S/ CO2 Pipeline Material
304/316 SS in this sour service conditions??
S.
http://www.corrosionist.com
RE: High Pressure H2S/ CO2 Pipeline Material
RE: High Pressure H2S/ CO2 Pipeline Material
in terms of resistance to SSC, sulphide stress cracking, there is no difference between 304SS and 316 SS for NACE / ISO.
In NACE / ISO 15156 table A.2 of part 3 you can see that the limits are valid for a class of Autenitic Stainless Steel (304 and 316).
S.
http://www.corrosionist.com
RE: High Pressure H2S/ CO2 Pipeline Material
RE: High Pressure H2S/ CO2 Pipeline Material
1.) If you have liquid water present, the use of stainless is recommended. The only caution on this is using an external coating to prevent chloride attack from soils and ground water. This is usually a field applied mastic with careful backfilling of the ditch. You need to consider the fact that at some point, the line will cool down to ambient conditions so it's not enough to assume that the line will run warm all the time. We've used 304, 304L, and 316L depending on the service and client.
2.) If no liquid water, we look at using carbon steel. Typically a select chemistry A333 Gr6 seamless steel line with MTR's, component control, hardness controlled welding, and external yellow jacket coating.
Hope this helps.....
RE: High Pressure H2S/ CO2 Pipeline Material
I think we have had enough discussion on this matter, and I thank all participants for their kind advice in this matter; I would like to close this topic for now. Thanks.
RE: High Pressure H2S/ CO2 Pipeline Material
Should we also consider external corrosion of buried stainless steel pipe? If yes, this link may be useful for you.
www.eur
Note :
-No. 1.4301 is equivalent to Type 304.
-No. 1.4401 is equivalent to Type 316.