Additional welding after PWHT

[cmryu]

Dear Engineers

I have a quck question about additional wleding after PWHT
and Hydro test completely.

present situation is as follows.
In a vertical pressure vessel of ID3000mm, shell Thk 17mm
herewith, one of Internal supporter (T10mm x 50mm) was attached with 8mm fillet welding and then, this support was revomed as per client requirement.

In this condition, client ask for additional requirement as follows as per their precess requirement.
- PWHT again
- Hydrotest again.
However, this requirements is not related to ASME requirement, but only for process condition.

 

[Goahead]

As you did not specify the material of the vessel, the filler metal used, nor the service conditions (temperature), and if the removal was done by flame cutting or by grinding it is difficult to say what is the real need for PWHT.

http://www.welding-advisers.com/

 

[doct9960]

cmryu,

Was there additional welding or grinding on the VESSEL SHELL after it has been postweld heat treated & hydrotested?

 

[cmryu]

For the additional information, this vessel material is of A516-70, and Design temp is 160 Deg. C, Process condition is NACE and Sour service for this vessel.
This internal stiffener was attached after PWHT and Hydro Test, and then this stifferner was removed again by Grinding.

 

[metengr]

IF this vessel has already been ASME Code stamped and is in service, I would locally PWHT the base metal heat affected zone from the welded attachment. I would not perform a second hydrotest, there is no benefit to be gained from it.

I would also mandate an NDT (like wet fluorescent MT) of the base metal heat affected zone after local PWHT, in lieu of a hydrotest.

IF this vessel is under construction, and before ASME Code stamping, you will probably need to PWHT the base metal heat affected zone, and perform a second hydrotest to apply the ASME Code stamp.

 

[cmryu]

this vessel is not rewuired ASME code STAMP.
Is it also required Local PWHT and Hydro test again.?

 

[cmryu]

As per UCS56 in ASME, less than 13mm throut length of weld , PWHT is not required, but Client is asking for PWHT and Hydro test again due to precess requirement.
Process requirement is only for NACE and Sour service as we know.

 

[doct9960]

cmryu,

I would do what your client is asking for. By welding on the vessel after PWHT, you have reintroduced residual stresses that might cause in-service cracking of the vessel.

 

[metengr]

I would perform the local PWHT per the clients requirements, but I would not re-hydrotest, if at all possible. Hydrotesting must be performed with extreme caution for components that have been installed for service.