ASME B31.3: PWHT or not

Date 11-06-2003 04:55

Hi everybody

I’m writing all WPSs for a piping project according to ASME B31.3 for a company. There are “A671 Gr. CC60 Class 22” and “A672 Gr. C60 Class 22” materials in the pipes, which their wall thickness is ½ in. (13mm) maximum.
Both of these pipes are P no. 1 and according to ASME B31.3, PWHT is not required for P no. 1 when wall thickness is less than 19mm.
However, the pipes class is 22 and according to ASTM A671 & A672, class 22 means that they have stress relieved after production.
Now I’m in doubt to do PWHT or not. According to ASME B31.3, PWHT is not needed for these pipes because of their wall thickness; but if the pipes do not be stress relieved after welding; their class will change from class 22.

By pipewelder_1999 (****)

Date 11-06-2003 11:01

I may not be understanding but if your indication of your requirement for PWHT is based upon the material specification requirement, that has no bearing on the PWHT requirements of the welded joints.

If you feel it is necessary because of the "..22" designation which could be confused with P-22 or T-22 materials (P- Number 5A) then understand that the material is P1.

If something else within the applicable codes indicates the requirement for PWHT let us know what it is.

Have a nice day

Gerald Austin
http://www.weldinginspectionsvcs.com/

By George-kh (**)

Date 11-06-2003 16:04

Mr. Gerald Austin
Please let me to make my question a little bit clearer.
A671 Gr.CC60 & A672 Gr.C60 are P no. one according to ASME IX; and if wall thickness of P no. 1 pipes be less than 19mm, PWHT is not needed according to ASME B31.3.
All of our A671 Gr.CC60 & A672 Gr.C60 pipes have less than 19mm wall thickness; therefore PWHT is not needed.
On the other hand, A671 Gr.CC60 & A672 Gr.C60 pipes are longitudinal welded pipes. According to their ASTM specification class 22 means:
1.The longitudinal weld on pipe is 100% radiographed.
2.The pipe is stress relieved after production.
And class 21 means:
1.The longitudinal weld on pipe is 100% radiographed.
2.The pipe is NOT stress relieved after production.
If I don’t do PWHT the class of pipes falls to class 21.
Well, now please tell me that I must consider PWHT in my WPSs or NOT.

By pipewelder_1999 (****)

Date 11-06-2003 16:52

That requirement for PWHT is contained within the material specification. It is not a requirement for code of construction as far as I know.

Gerald Austin

By jon20013 (*****)

Date 11-06-2003 16:59

I second that Gerald. The PWHT requirements would have been met by the material producer and are not a requirement for the constructor. Also, ASME B31.3 like many of the other ASME Codes, has excemptions from PWHT for certain material types, thicknesses and joint designs provided an elevated preheat is applied (normally 200F).

By GRoberts (***)

Date 11-07-2003 03:43

I would agree with pipewelder and jon. The ASTM specification describes how the pipe must be manufactured, it does not have any jurusdiction on how it is used. The construction codes must be complied with at that point if they apply.