PWHT of dss clad vessel

[ypal]

50 mm CS vessel cladded with 3 mm thick DSS is required to be PWHT as per ASME Sec VIII Div1. Pl advise if any damage to DSS is possible during PWHT

Ypal

[hermes]

Hi, Ypal:
I don´t have experience with DSS Cladding, but I did a few projects with SS cladding on CS.
The problem is that each PWHT you do on the plate formed/welded, you are going to have a loss of properties from the cladding, because the dilution of C from CS into the SS structure.
To make it not so long, you should be very carefully when specify a PWHT in cladded CS plates.
When possible, you should have to do just one PWHT – a final PWHT - at the end of your fabrication process. During the fabrication process, any finished weld need to be heat treated in a final PWHT, should be postheated by a postweld hydrogen bakeout procedure (usually 2h at 250-300 Deg.Cent, then slowly cooled in still air) as stated in the WPS.
Hope it will help you. Regards.

[hermes]

Hi, Ypal:
I don´t have experience with DSS Cladding, but I did a few projects with SS cladding on CS.
The problem is that each PWHT you do on the plate formed/welded, you are going to have a loss of properties from the cladding, because the dilution of C from CS into the SS structure.
To make it not so long, you should be very carefully when specify a PWHT in cladded CS plates.
When possible, you should have to do just one PWHT – a final PWHT - at the end of your fabrication process. During the fabrication process, any finished weld need to be heat treated in a final PWHT, should be postheated by a postweld hydrogen bakeout procedure (usually 2h at 250-300 Deg.Cent, then slowly cooled in still air) as stated in the WPS.
Hope it will help you. Regards.

[duazo2009]

Hi, Ypal:
I don´t have experience with DSS Cladding, but I did a few projects with SS cladding on CS.
The problem is that each PWHT you do on the plate formed/welded, you are going to have a loss of properties from the cladding, because the dilution of C from CS into the SS structure.
To make it not so long, you should be very carefully when specify a PWHT in cladded CS plates.
When possible, you should have to do just one PWHT – a final PWHT - at the end of your fabrication process. During the fabrication process, any finished weld need to be heat treated in a final PWHT, should be postheated by a postweld hydrogen bakeout procedure (usually 2h at 250-300 Deg.Cent, then slowly cooled in still air) as stated in the WPS.
Hope it will help you. Regards.

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duazo2009