Sweet Service vs Sour Service

[innocent1234]

We are in the process of evaluating transferring a sweet service oil emulsion skid to a sour field. The system will operate at ~30 psig and the vessel has a 50 psig MAWP. The vessel is internally coated, so I believe the vessel to be suitable for this application, but what about the piping, isolation valves and psv which was all originally designed for sweet service?

Looking through Mr0175 it does not appear that sulfide cracking would be an issue at these low pressures. Am I correct in stating this or are there other things I should be worried about?

 

[SJones]

Under the applicability tables of all three parts of ISO 15156, your quoted application may be excluded. However, it would be considered prudent to review the expected environmental severity of the new operation against 7.2.1.2 of Part 2 and, for any plate material including items made from plate, review clause 8 and then conclude whether there is a need for any further action. A review of materials and certification for the skid would also be considered prudent just in case there is anything that doesn't like H2S like some elastomeric seals.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/