MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
(OP)
Hello All,
I am trying to select an appropriate materal for the construction of flanged ball valves to be used under the following operating conditions:
Crude Oil & produced water
150 psig max pressure
0-130F temp range
120,000 - 180,000 ppm chlorides
Nil - 300 ppm H2S (hot spots up to 3000 ppm in areas)
<1% CO2
O2 range <5ppb to well into ppm range
A very authoritative materials engineer has reccomended to the end user that 316/CF8M is acceptable for the above conditions excepting that the temprature must stay below 75F. NACE MR0175, however places a constraint on using 316SS in environments with greater than 5000 ppm -Cl. I am confused as to wether or not 316SS is really an acceptable material for this environment,and I am looking for some clarification as to why it is or isnt acceptable.
The alternate reccomendation by the materials engineer was super duplex at tempratures below 175F. I believe it is clear that the super duplex will work, however it is going to be very expensive as compared to the 316.
I am also thinking that a superaustentitic grade of stainless would work. Particularly CN3MN, although I am not sure if it will be more or less expensive than the Super Duplex (6A material). If its more expensive than there is not really any advantage I can see to using it. If there is anything I am overlooking as to why this material might not be suitable, I would appreciate input here too.
Thanks in advance!
-VRF
I am trying to select an appropriate materal for the construction of flanged ball valves to be used under the following operating conditions:
Crude Oil & produced water
150 psig max pressure
0-130F temp range
120,000 - 180,000 ppm chlorides
Nil - 300 ppm H2S (hot spots up to 3000 ppm in areas)
<1% CO2
O2 range <5ppb to well into ppm range
A very authoritative materials engineer has reccomended to the end user that 316/CF8M is acceptable for the above conditions excepting that the temprature must stay below 75F. NACE MR0175, however places a constraint on using 316SS in environments with greater than 5000 ppm -Cl. I am confused as to wether or not 316SS is really an acceptable material for this environment,and I am looking for some clarification as to why it is or isnt acceptable.
The alternate reccomendation by the materials engineer was super duplex at tempratures below 175F. I believe it is clear that the super duplex will work, however it is going to be very expensive as compared to the 316.
I am also thinking that a superaustentitic grade of stainless would work. Particularly CN3MN, although I am not sure if it will be more or less expensive than the Super Duplex (6A material). If its more expensive than there is not really any advantage I can see to using it. If there is anything I am overlooking as to why this material might not be suitable, I would appreciate input here too.
Thanks in advance!
-VRF





RE: MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
If you are certain the temperature will never go above 75F,(like shut in the summer,in the sun) austenitic SS are a reasonable risk. Personally , I would not risk it in the USA.
RE: MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
-VRF
RE: MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
As to the use of ISO 15156-3, you may wish to review Table A.2 again where you will note that, below 60 deg C (140 deg F) and 100 kPa partial pressure H2S, there is no limit on the chloride content of the environment when dealing with sulphide stress cracking/stress corrosion cracking. Get that much oxygen into a system with that much H2S and there is a high likelihood of generating elemental sulphur that will take you into a whole new ball park.
As an aside, please note that ISO 15156 places the onus of materials selection onto the end user, not the valve manufacturer.
As a further aside, 22Cr duplex stainless steel may not have such a price differential as to be unattractive; ask around. Using 22Cr requires that the partial pressure of H2S not exceed 10 kPa.
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
Thank you for your reply!
The piping and storage tanks are all plastic, so there are no major issues there. There is a seperator being employed upstream of the valves, I'm not sure what materials it will be constructed from, but undoubtedly it will be metal.
I am confused about table A.2. Because it is common practice to consider CF8M & 316SS material to be equals, generally speaking, I would assume it is prudent to use the guidelines set out for S31600 in table A.2. That call out indicates that there is a limit on chlorides of 5000 mg/l max. Am I wrong in my thinking?
You bring up the point of Sulfur, and I believe its presence alone would disqualify the CF8M & the CN3MN. 15156 shows "NDS" regarding elemental sulphur for Duplex SS. Do you have any experience with Sulphur causing problems for Duplex?
Yeah that clause in 15156 is a life saver for manufacturers. However, I always do my best to offer only materials that I believe will be acceptable for the intended application. I wouldnt sell them a carbon steel valves in this scenario, and then expect it to be "not my problem" whenever it fails. :)
Regarding the 22Cr or 25Cr, I should have specified that we will be quoting 6A Super Duplex with a PREN greater than 40. Based on that I think it will be acceptable.
Best Regards,
VRF
RE: MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
If you are following ISO 15156-3 (sorry, but to me it is ISO and not NACE) then there is only a restriction on chloride content if the designated equipment temperature exceeds 60 deg C with a chloride content of greater than 50 mg/l, i.e. the first two rows of the table There is then also further restrictions on liquid pH.
Elemental sulphur will cause problems for nickel alloys, let alone duplex!
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
Just so I am clear, are you saying that the restrictive parameters set forth in A.2 for S31600 & S31603 are set to be retracted at some point in the future, leaving, esentially, lines 1 & 2 as a stand alone mandate for Austenitic grades, with the exception of the special restrictions for Nitronic 50(S20910)?
Best Regards,
VRF
RE: MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
Thank you for clarifying that point, and thank you for your other input as well.
Best Regards,
-VRF
RE: MATERIALS SELECTION FOR VALVES IN -Cl & O2 ENVIRONMENT
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04