ASME B31.3 PWHT Requirement
ASME B31.3 PWHT Requirement
(OP)
My company is welding 18" Schedule 60 carbon steel pipe (nominal pipe wall thickness of 0.750") and per B31.3 Table 331.1.1 this would be exempt from PWHT.
I know that there is tolerance on the pipe wall thickness, if I remember correctly it is ±12.5% of nominal.
My question is that if the pipe is over the nominal thickness is PWHT is required?
Paragraph 331.1.3 state the governing thickness for PWHT is the component measured at the joint, but Table 331.1.1 refers to nominal thickness.
Which should I use to determine the PWHT requirement nominal pipe thickness or actual at the joint?
I know that there is tolerance on the pipe wall thickness, if I remember correctly it is ±12.5% of nominal.
My question is that if the pipe is over the nominal thickness is PWHT is required?
Paragraph 331.1.3 state the governing thickness for PWHT is the component measured at the joint, but Table 331.1.1 refers to nominal thickness.
Which should I use to determine the PWHT requirement nominal pipe thickness or actual at the joint?





RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
Table 330.1.1 clearly calls for Nominal Wall Thickness.
To my opinion, para. 331.1.3 only indicates the place to be referred in order to consider the thickness of the component that is to be welded. It not requires measuring the actual thickness at that place.
RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
You are not grasping what is being said. PWHT is exempt for P1 materials of ALL THICKNESSES. If the nominal thickness is greater than 1" you must preheat to 200 Deg. F to avoid PWHT.
RE: ASME B31.3 PWHT Requirement
Thanks for the reply ..... if thickness is greater than 1" avoiding PWHT due to 95 C preheat is ok per table 331.1.3 as in my previous question but where is the reference that PWHT is exempt for P1 material for all thicknesses?
RE: ASME B31.3 PWHT Requirement
RE: ASME B31.3 PWHT Requirement
a. PWHT is exempted for P-1 materials for thickness up to 25mm?
b. For Pipe to pipe branch connections with R'Pad, the computed thickness as per clause 331.1.3 (referring Fig 328.5.4D) shall be more than 25mm in order to carry out PWHT (as per table 331.1.3)
RE: ASME B31.3 PWHT Requirement
B) Yes. But again, if computed thickness is over 1" you don't have to PWHT. Pre-heat to 200F prior to welding and no PWHT necessary.
RE: ASME B31.3 PWHT Requirement