Maintain Preheat

[dcrgm]

We are welding on a reactor that has 1"CS wall with 1/4 ss clad. Does ASME Code require maintain preheat for welding to this vessel ?

 

[metengr]

Yes. You have a temperature range between minimum preheat and maximum interpass temperature.

 

[dcrgm]

Where could I find the required preheat temperature ? Also does this temperature need to be maintained ?

 

[metengr]

If this is a repair to an in-service vessel, the recommended preheat requirements (for P-No 1 material over 1" thickness is a minimum of 175 deg F) would be located in the National Board Inspection Code (NB-23). For ASME Section VIII, Div 1 P-No 1 base materials, preheat requirements are specified for 1.25" thickness or greater. However, this is for new construction and I would strongly recommend for 1" thickness you follow a 200 deg F minimum preheat. This is good engineering practice.

 

[weldtek]

dcrgm,
As always Metengr is giving you good advice. I just wanted to add that in some cases, the WPS may have preheat requirements in excess of those imposed by Code.