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What are the experience out there for PWHT of tubesheets?

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vesselguy

Petroleum
Joined
Feb 25, 2002
Messages
386
Location
CA
Hi All,

Just want to hear the problems or experiences people have had during and after PWHT of thick tubesheets > 4" thk. I never had experience with PWHT of tubesheets before and just like to hear some experiences to get a heads up.

My situation right now is P9 tubes are all strength welded to the 410S clad 8" thick tube sheet before PWHT. I am concern about wrappage of the tubesheet and possibly delamination of the cladding due to differential expansion across the clad and parent metal boundary.

 
1)Lamellar tearing of the TS/Shell weld due to differntial expansion caused stress.
2)Tube leaks if the tubes thermally expand against a fixed end.
3)Caustic cracking if shellside alkaline water (boilers) is not removed prior to PWHT

Have been personnaly involved with cases of 1 and 2 and have read about #3
 
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