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304 vs. 316 in CO2 and H2S applications

juanq (Mechanical) (OP)
3 Sep 01 16:56
I'm considering the use of stainless steel (304/316)  in equipment for gas treatment (vessels, heat exchangers and air coolers) due to the presence of CO2 and H2S.
The equipment will be designed in the following pressure/temperature range:
a. 1340 psig/250 F
b. 550 psig/250 F
c. 120 psig/250 F
d. 1350 psig/350 F
Could somebody help me with some guidance in the adequate material selection for this application? (in this case in the material selection for plate, tubes, nozzles)
flames (Materials)
6 Feb 02 20:58
Check some old NACE papers concerning the selection of materials for sour gas treating.  There are at least 4 papers out there on this topic.  

Most gas treating systems use carbon steel for the majority of the system and selectively use stainless for critical locations.  We have had to replace most of our rich piping downstream of our contactors from carbon to 304 to now 316 due to flashing.  Our contactors are carbon with some stainless striplining in the critical zones.  The stills are carbon.  Most gas plants run carbon piping on the lean side.
rusman (Chemical)
9 Feb 02 2:08
Another school of thought...

Why don't you venture the usage of Duplex Stainless Steel (UNS 31803) as this material has high strength than normal Stainless Steel.

rusman
flames (Materials)
12 Feb 02 22:31
I don't have NACE MR0175 so maybe you can correct me but isn't UNS31803 limited to something like 1.5psi partial pressure H2S?  I can't remember off the top of my head.

juang, this is another document that you may have to pay attention to NACE MR0175.



rusman (Chemical)
13 Feb 02 0:10
Folks

NACE MR 0175 latest edition (2001) did explain the safe limit of various duplex stainless steel in cold annealed solution.

For the normal duplex Stainless Steel 22Cr (UNS S31803) the safe limit of H2S partial pressure is limited up to 0.3 psia. If the partial pressure is higher, one must use higher crome and nickel content, eg Incoloy 825 (UNS N08825), Sanicro 28 (aloy 28), Inconel 625 or Hasteloy C-276.

Hope this help

Thanks
stanier (Mechanical)
14 Feb 02 16:15
You may find some data at the NIDI website

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