PWHT per B31.3

[Harshu03]

Reference to Table 331.1.1, only PWHT parameters (soaking time, soaking temperature) where provided based on applicable thickness selected by designer.
However, Table 331.1.3 provides exemption to mandatory PWHT requirements provided preheat of 95 deg cel maintained during welding when nominal welding thickness exceeds 25mm.

Based on above does it mean that PWHT is not applicable where weld thickness is less than 25mm.

 

[david339933]

That is correct for P1 material. Nominal material thickness.

 

[Harshu03]

Does it mean if thickness is less than 25mm then PWHT is not required for P1 materials if preheat temp is 95deg. C.
I read in other threads exactly opposite of this. there it was said by someone if thickness is more than 25mm PWHT is not required if preheat temp is 95deg. C. this caused confusion to me.

 

[david339933]

It means...if thickness is less than 1" no preheat necessary...no pwht necessary. If thickness is greater than 1" you must either preheat to 200F (95C) or PWHT.

In other words...if your thickness is greater than 1" and you don't want to PWHT....you MUST preheat to 200F (95C).

 

[David2007]

Hi,
But the temperature for preheating depends on the material as per Table 331.1.1 ASME B31.3

 

[DanTh3Man]

Also note that there can be other, non-code requirements for PWHT. One such example is concerns around mitigating stress corrosion cracking in sour service.