Duplex Pipe A790 UNS S31803 in High and Low Temp Service
Duplex Pipe A790 UNS S31803 in High and Low Temp Service
(OP)
Our process engineers for some unusual reason requested the piping department to consider increasing and lowering the design temperatures in a couple of duplex piping classes.
These materials are now expected to serve design temperatures of 156 C and -100 C.
Piping Code used is B31.3
Location: Offshore marine environment
Application: High CO2 hydrocarbon gas
First Question
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Duplex pipes are normally limited to a maximum of 100 C if they are uncoated. I understand with the appropriate coating for the temperature range, duplex pipes design/operating can be taken up to 200 C. Is this correct?
Second Question
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The minimum design temperature limit for duplex pipes as per B31.3 is -60 deg C. With impact testing, one can expect the temperatured be lowered a bit, maybe upto -85 C. Has anyone here has the experience of using duplex pipes in such extreme low temperature condition. Will the material be able to withstand the charpy impact testing?
Thanks in advance.
These materials are now expected to serve design temperatures of 156 C and -100 C.
Piping Code used is B31.3
Location: Offshore marine environment
Application: High CO2 hydrocarbon gas
First Question
---------------
Duplex pipes are normally limited to a maximum of 100 C if they are uncoated. I understand with the appropriate coating for the temperature range, duplex pipes design/operating can be taken up to 200 C. Is this correct?
Second Question
---------------
The minimum design temperature limit for duplex pipes as per B31.3 is -60 deg C. With impact testing, one can expect the temperatured be lowered a bit, maybe upto -85 C. Has anyone here has the experience of using duplex pipes in such extreme low temperature condition. Will the material be able to withstand the charpy impact testing?
Thanks in advance.





RE: Duplex Pipe A790 UNS S31803 in High and Low Temp Service
If they are properly protected these alloys will work up to 315C, provided internall corrosion isn't an issue.
You will not be able to go too low in temp. These alloys have a DBT, there is no getting around it.
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Duplex Pipe A790 UNS S31803 in High and Low Temp Service
1) What prior experience have your process engineers in using duplex at higher/lower temps? Have they considered carrying out corrosion testing (with or without coatings) at these temperatures? Are tesile strengths within design limits at 200C?
2) Get a bunch of Charpy tests done at all temperatures from RT down to below the minimum service temp. This will generate a transition curve, showing you where the brittle/ductile transition takes place. Work with potential suppliers on this, as they may have the knowledge you need.
3) If the pipework is supposed to operate at these temps, what about the valves? Will these operate in the same conditions. The lowest temperature we have been asked for charpys on duplex castings is -50C.
Bruv
RE: Duplex Pipe A790 UNS S31803 in High and Low Temp Service
Hope this helps.
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Duplex Pipe A790 UNS S31803 in High and Low Temp Service
W.r.t duplex pipes temperature limitations, yes, I am aware of Shell's piping classes and I did check them earlier.
I may now have to question process engineer's blowdown calcs and see if there are able to control the temperature drop.
Thanks.
RE: Duplex Pipe A790 UNS S31803 in High and Low Temp Service
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Duplex Pipe A790 UNS S31803 in High and Low Temp Service
1.1 ASME B31.3, Table A-1
; 600 deg.F
1.2 ASME Sec.VIII, Div.1 and Sec.II, Part D, Table 1A
; 600 deg.F
2. Minimum Temperature Limitation of 2205 DSS
2.1 ASME B31.3,
[Table 323.2.2]
; Impact test for welds and HAZ is required when MDMT is colder than -20 deg.F.
[Table A-1]
; -60 deg.F
2.2 ASME Sec.VIII, Div.1, UHA-51(d)(3)
Impact test @ the MDMT is required for the DSS which is thicker than 3/8" when MDMT is colder than -20 deg.F.
---> If you do the impact test for 2205 DSS, you may be able to get the DBTT,-40 to -60 deg.F.
Hope this helps,
Thomas Eun
RE: Duplex Pipe A790 UNS S31803 in High and Low Temp Service