Thermal stabilization or stabilization anneal is a "specific process" which is a design basis requirement in Polythionic Acid service environment in refinaries.This form of PWHT is followed to avoid Polythionic SCC(PTSCC) during service. Such requirements needs to be followed for base metal and welds.
Usually no further welding should be done following "Stabilization Anneal". However thermocouple welds (without futher PWHT) could be an exception provided the depth of the HAZ is only restricted to the skin. It may be required to prove the integrity of "Thermocouple Welding Process", following PWHT with your client/ process licensor.
If permitted by client/process licensor, the consumable to be used would be either ER347 or ER-310. The first one (ER 347) would be preferred as the majority of the components are made of S S 321 alloys.
Welding & Metallurgical Specialist
From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of Siva Kumar
Sent: Wednesday, May 30, 2012 6:45 AM
Subject: [MW:14416] Thermal Stabilization
Need clarification regarding Supplementary Requirement of Thermal Stabilization of A213 TP321 tube materials used for heater jobs.
As per the requirements of the Licensor, thermal stabilization was carried out for tube materials used for coils in heater.
After welding with ER347 and E347 filler metals, thermal stabilization was carried out for the weld and HAZ.
I went through the earlier posts that is available in our group. I would like to have clarification regarding the following:
Skin Thermocouples are to be welded with the coils. The material of thermocouple is SS310.
1. What is the consumable that has to be used for welding the thermocouple SS310 with the A231TP321 tube. Joint would be Fillet.
2. Do we need to perform the same Thermal Stabilization for this weld also? If yes what would be the reason?
Thanks and regards,
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