Failure of SS 316 Piping in Spent Caustic Application
Failure of SS 316 Piping in Spent Caustic Application
(OP)
We are using SS316 piping for spent caustic lines. Facing frequent failure of piping. I understand SS316 is a good material for this serivce.
However, due to frequent failure, i have proposed to replace piping with PVC. Any comment on thic change or any other suggestion for a better material for this application ?
Thanks
However, due to frequent failure, i have proposed to replace piping with PVC. Any comment on thic change or any other suggestion for a better material for this application ?
Thanks





RE: Failure of SS 316 Piping in Spent Caustic Application
If you don't understand why the pipe is failing, then replacing a material (that's good for the service) with another material may not solve the problem.
Patricia Lougheed
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RE: Failure of SS 316 Piping in Spent Caustic Application
Mark Hutton
RE: Failure of SS 316 Piping in Spent Caustic Application
Nickel base alloys are more resistant to cracking and may be required at higher temperatures and/orcaustic concentrations.
“Stainless steels such as austenitic types 304 (S30400) and 316 (S31600) seem even less reliable than carbon steel for caustic service. The application limits for the austenitic SS are 50% caustic and 70°C to 90°C. The 300 series of SS also suffer caustic cracking at temperatures above 100°C.The cracking susceptibility of either 304 or 316 SS is the same and sensitization does not seem to play a role. Problems rarely occur when the NaOH concentration is limited to 10-20%.
The best metallic material overall to handle caustic solutions at all concentration and temperatures is Ni-200 (N02200). Ni-200 can be used even in molten anhydrous NaOH at temperatures as high as 538°C (1000°F).”
If I were you I wouldl use a carbon steel tank for spent caustic services with the requirements bellow.
Cracking can be effectively prevented by means of a stress-relieving heat treatment (e.g. PWHT). A heat treatment at 1150°F (621°C) is considered an effective stress relieving heat treatment for carbon steel. The same requirement applies to repair welds and to internal and external attachment welds.
luismarques
RE: Failure of SS 316 Piping in Spent Caustic Application
Are you really planning to use PVC ? What size line and what temperatures?
RE: Failure of SS 316 Piping in Spent Caustic Application
OSHA, NFPA and ASME contain cautions about the use of FRP/plastic pipe and plant accidents.
For some fun beachside reading, visit www.csb.gov and read the report about the methanol tank explosion and the death that occured because of plastic piping components.
http://w
Plastic/FRP pipe is useful only to very modest operating temperatures. Hope that yours are not too high....
My opinion only
-MJC
RE: Failure of SS 316 Piping in Spent Caustic Application
Without composition info, pH & temperature of the 'spent caustic,' it's impossible to give a definite answer.
RE: Failure of SS 316 Piping in Spent Caustic Application
where are you?
Mark Hutton