Shabbar Hussain Aus S.S do not require - generally - PWHT. S.S materials in annealed condition mostly will be at supplied with HRC 16-18. HRC -22 (MAX) is the outer limit or may be the material is work hardened. NACE MR 0175 considers H2S concentration, temperature effect partly to suggest this HRC 22 max in case the material S.S as received in annealed but fabricated and work hardened to likely HRc 22. For wet H2S service - in sweet crude - there should be no problem with HRc 22. For wet H2S sercie - in sour crude - you have to be careful as concentraton of H2S may vary from crude batch to batch receipt. With temp increase or with H2S concentration, any aus S.S would be affected due to SSC. Aus S.S grades 304/316 / 321/ 347 will all perform to the same degree of SSC susceptiblity in sour H2S service.There will be no significant advantage or disadvantage with any of these grades for SSC with high H2S concentration. In fact, all will show failure rates with SSC depending on the concentration of H2S and temp. With higher HRc > 22, be sure that you are using sweet crude which with slight hardness increase to HRc 24 or so may not get affected. With higher HRC > 22 in S.S 347 in sour service you have to be doubly careful to ensure that H2S concentration and temp and aeration and agitiation effect are all considered from SSC points of view. If you wish to be sure of reducing the hardness and bring down to < HRc 22 , PWHT consists of two ways - either do S.R at 850+ deg cent and then quickly air cool. or do mill anneal at 980+ and quickly air cool. This should take care of the internal stresses already developed due to high hardness in S.S 347. Trust this helps you. Best wishes C.V.Srinivasan Tech Dir Nishi Engineers Pvt Ltd India July 13 E-mail: nishi@vsnl.com/nishi@hathway.com >Dear Sir, > >It is an acceptable practice that the Austenetic Stainless >steels are not subjected for the PWHT but when referred to >the MR-175 code it says that the Austenitic SS are >acceptable at a hardness of 22 HRC maximum in the annealed >condition in the wet H2S service. > What would be the requirement of the PWHT when the >hardness measured on the SS-347 weld shows hardness more >than 22 HRC and the service is wet H2S. > >Your immedaite responce would be very much appreciated. > >Regards, >Shabbar Hussain