PWHT as per UCS-56 1

[dursosono]

Per UCS-56 for P-No. 1 state for thickness up to 38 mm pwht is not mandatory if preheat applied during welding at min temp. 200 deg F.
I was ordered 38 mm thk used for shell. Since material under tolerance for SA516-70 (refer to SA20) the actual thk is more than 38.0 mm. The min actual thk is 38.4 mm. There are no actual thk under 38.0 mm. Shall I perform pwht for this case?

 

[SnTMan]

Not if you preheat. Code use of the term "thickness" depends greatly on context, but per the tables in UCS-56 it is nominal thickness that is of interest.

Regards,

Mike

 

[metengr]

Yes, you should perform PWHT if the nominal thickness is over 38mm. If you are trying to split hairs and this was my project, I would error on the conservative side. The code rule is 38mm if your nominal thickness is over this value Note 2 (a) forces you into PWHT regardless of preheat.

 

[weldtek]

dursosono,
My opinion is that generally speaking, material is not going to come under the ordered thickness except by that amount allowed by SA 20 which is 0.010". In most cases it will run slightly over the ordered thickness as you have found. Keeping in mind that Code requirements are minimum, Metengr is giving you good advice to err on the side of safety.
However, by Code rules, you are under no obligation to mic each plate for an exact thickness and PWHT because it exceeds the nominal 38 mm (1.5") by 0.4 mm or 0.015".

 

[JoeTank]

My answer may not agree with all of the others, but I think the Code is pretty clear that PWHT is not required for a plate ordered as a 38mm plate. The 38.4 plate that you received has a nominal thickness of 38mm. UCS-56 is based on NOMINAL thickness. If PWHT is not performed you must follow the 200F preheat requirements of UCS-56

Joe Tank