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PWHT

PWHT

(OP)
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 ?

RE: PWHT

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

RE: PWHT

(OP)
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?

RE: PWHT

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

RE: PWHT

Agree with david.

Refer to table 132.2

RE: PWHT

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

RE: PWHT

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 ?

RE: PWHT

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

RE: PWHT

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

RE: PWHT

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.

RE: PWHT

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

RE: PWHT

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

RE: PWHT

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.

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