PWHT

[Arkaprava Ghosh]

As per ASME B31.1 2014 edition, where is the thickness specified above which PWHT is mandatory for P1 material. In the older versions, 19mm was mandatory. In the 2014 version if I do not meet the exempt requirements , is PWHT compulsory for all P1 material ?

 

[DSB123]

If you are not exempt then yes it would deem it is required by logic!!!

 

[Arkaprava Ghosh]

Suppose for 20mm thickness weld, I am not preheating the joint as it is not required by Table 134.1.1 and ny carbon content is 0.18%. IS PWHT mandatory in that case for 20mm thickness weld?

 

[david339933]

You are exempt. Preheat (200F) must be applied at thicknesses over 1".

 

[DVWE]

Agree with david.

Refer to table 132.2

 

[metengr]

B31.1 piping committee removed PWHT requirements for P-No 1 material provided preheat is applied for material over 1" thickness.

 

[DekDee]

B31.3 followed suit with similar requirements but note 4 of Table 331.1.3 lists no exemptions if PWHT required by the designer or if listed on the WPS.
Is that requirement noted in B31.1 as well ?

 

[metengr]

Hi DekDee
No, per the 2016 edition of ASME B31.1, Table 132.2 and Notes.

...The mandatory preheat has been
applied Specified carbon content of the base
materials ≤0.15% Multiple layer welds are used when the
nominal material thickness >3⁄16 in.
(5 mm)
See Note (6)
(6) Single layer or single pass welds may be exempted from PWHT, provided the WPS has been qualified using single pass welds with ±10% heat input and that all other conditions for exemption are met

 

[DekDee]

Thanks metengr,
Is the OP's carbon content of 0.18% not greater than the allowed 0.15% noted ?

 

[weldstan]

The "Specified" carbon content would apply to the base material SA Specification chemistry requirements and not to the actual heat analysis chemistry. This reflects a major amendment to the original PWHT relaxation.

 

[Arkaprava Ghosh]

Weldstan,
I thought "specified" is supposed to be actual. The Sa requirements should be treated as minimum and maximum.

 

[DekDee]

What is your material and it may be easier to explain ?

 

[metengr]

Again, read the Code which includes me, for 2016 Edition of B31.1, the 0.15%C is based on below

132.3.2 The postweld heat treatment exemptions
of Table 132.2 may be based on the actual chemical composition
as determined by a ladle or product analysis
in accordance with the material specification in lieu of
the specified or maximum specified chemical composition
limits.

For carbon steel P-No 1 in Table 132.2

A preheat of 200°F (95°C) is applied
prior to welding on any nominal material
thickness >1 in. (25 mm)
Multiple layer welds are used when the
nominal material thickness >3⁄16 in.
(5 mm)
See Note (6)

Apparently, when I copied the information it was for P-No 5A and not P-No 1.
My error, so there is no 0.15%C limit for P-No 1 BM.
The above would apply for P-No 5A for information.