PWHT weld overlayed TS

[metaal]

Weld overlayed tubesheet need to be PWHT according to ASME VIII div 2.

- Tubesheet : SA336 F22Cl3 thickness 408 mm weld overlay with Inconel 600 thickness 8 mm.

According to the code : P5A group needs 1250°F and for this case 7h 45 min.

Is this correct since AF551 "determing thickness is total thickness of base material".Will we have problems with Inconel ?

 

[metengr]

No. The PWHT time is based on nominal thickness, which is the thickness of the weld deposit in this application, not the thickness of the base metal.

 

[pve5]

metengr ( Materials)

Per Table AF-402-1, in case of P-Nos 5A, weld overlay is not listed under exemption. Therefore complete tubesheet should be PWHT.

 

[metengr]

Sorry, but I respectively have to disagree. Did you read Paragraph AF-402.3 and understand the term "nominal thickness" as it pertains to Table AF-402.1? See the top of the Table it is nominal thickness not base metal thickness.

 

[pve5]

metengr ( Materials)

As specified before, Table AF-402.1 does not exempt PWHT of weld overlay of any thickness. Therefore since weldoverlay
is integral with base metal tubesheet should be PWHT. However the normal holding time for PWHT would be based upon 8 mm weldoverlay thickness not base metal thickness i.e 1 hour minimum.

 

[metengr]

pve5;
We are saying the same thing. The original poster had asked if the entire thickness of the tubesheet is used for determination of PWHT holding time. Reply is NO.

 

[weldtek]

Paragraph AF-551 & AF-552 may shed more light on this.

 

[SMF1964]

Metengr: Please correct me if I'm wrong, but doesn't the holding time get set to take into account the heat transfer through the thickness of what you are heating and, if so, then using the thickness of the overlay as your "thickness" would not guarantee that the heat affected zone underneath the overlay would reach the desired temperature?

 

[metengr]

SMF1964;
By Code requirements, PWHT holding time is the time at PWHT temperature. The time is based on the nominal thickness of the weld deposit.

Example; hypothetical situation - if the item took 2 hours to reach the spcified PWHT temperature, the holding time for PWHT clock begins and is held to the time required for the nominal thickness of the weld deposit at the specified PWHT per Code requirements.

Does this help?

 

[SMF1964]

Yes. Thanks. Does the code specify where the monitoring thermocouples are placed?

 

[metengr]

SMF1964;
Good question. No, other than to verify the temperature of the weld and surrounding base material has reached the proper PWHT temperature as performed by - a furnace, resistance heating, flame or induction heating methods. PWHT must be performed to a process procedure that details method of heating, verification of weldment temperature and calibration of equipment. The AI or Inspector will review this procedure.