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Plan 32 seal piping material

Plan 32 seal piping material

Plan 32 seal piping material

(OP)
Hi Experts,

Pumping liquid has chloride concentration in a minimum of 1000 ppm and some have 22000 ppm with an operating temp. of >66C.
Pumps have seal Plan 32 with seal tubing material specified as 316SS. Given the properties of the pumping liquid, there is a potential for chloride stress corrosion cracking to the 316SS tubing and fitting. Hence, it was changed to duplex 2205 as recommended by the material engineer. Reason is per the below:

Per API 610 para. 6.5.2.1, lines for injection of external fluid like the Plan 32 were classified as auxiliary process fluid piping which per the next paragraph 6.5.2.4, there is caution on using stainless steel like 316SS if chlorides present in the pumping liquid in a concentration above 10 ppm.

Pump and seal vendor is reluctant to provide the higher MOC for seal tubing and asking for verification of discrepancy since pump material is S-6 and seal tubing of Duplex? They believe the pumped liquid with lots of chloride will not go into the seal tubing. Vendor have requested for the external seal flush fluid characteristics if it's compatible with 316SS seal tubing line so they could provide one. Unfortunately at this point, we don't have yet the details from the client.

My understanding is regardless of the external flushing fluid details, the high chloride concentration of the pumping liquid dictates the recommended duplex. Per API 682, piping system for contacting wet seals(i.e Plan 32) shall be designed self-venting to allow removal of possible trapped gases out of this pumped liquid with chloride concentration due to continuous pumping operation? If Plan 32 flushing lines are not to be taken into consideration when pumping liquid has higher chloride concentration, then what is the intent of API why it was included as auxiliary process-fluid piping?

I hope I have covered all on the above. Thanks in advance for your help and advice.

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