PWHT holding temperature
PWHT holding temperature
(OP)
PWHT holding temperature are specified as below:
P No. Applicable Code Temperature(degree C)
------------------------------------------------------------
P No.1 ASME Sect.8-2001 edition Min. 593
P No.1 ASME Sect.8-2004 Min. 650*(changed)
P No.1 ASME B31.3-2004 594~649
---------------------------------------------------
p No.3 ASME Sect.8-2001 edition Min. 593
P No.3 ASME Sect.8-2004 Min. 595
P No.3 ASME B31.3-2004 593~718
-----------------------------------------------------
p No.4 ASME Sect.8-2001 edition Min. 593
P No.4 ASME Sect.8-2004 Min. 650*(changed)
P No.4 ASME B31.3-2004 704~746
--------------------------------------------------
P No.5 ASME Sect.8-2004 Min. 675
P No.5 ASME B31.3-2004 704~760
The lower crtical temperature to start tranforamation of grain structure, which is base for maximum PWHT holding temperature, are sepcified on the ASME Section 1. Table 129.3.2 as follows:
P No.1 725 oC
P No.3 730 oC
P No.4 Gr.1 745 oC
Can anybody answer to the following queries.
1.Min. holding temp.for P No.1 has been changed to 650 from 593 in ASME sect.8-2004 edition and holding temperature for P No.1 is higher than that of P No.3, although low critical temperature for P No.1 is lower than that of P No.3.
Is there any reason for change of min. holding temperature.
2. Max. holding temperature OF 746 oC for P No.4 in the ASME B31.3 is closer to low critical temperature mentioned above. and Max. holding temperature does not mention on the ASME Section 8.
Is there any guidance for max. PWHT holding temperature, when ASME Sectio 8 Code is to be applied.
3. I would like to know permissable PWHT temperature(min and max) for PWHT for dissimiliar welds of P NO. 1(A106 Gr.B) to P NO. 4(A335 P-11) and P NO. 1 to P NO.4 Gr.1(A335 P-22)material,when ASME B 31.3 Code is applied.
Your valuable answer would be highly appreciated.
W.I Ihm
P No. Applicable Code Temperature(degree C)
------------------------------------------------------------
P No.1 ASME Sect.8-2001 edition Min. 593
P No.1 ASME Sect.8-2004 Min. 650*(changed)
P No.1 ASME B31.3-2004 594~649
---------------------------------------------------
p No.3 ASME Sect.8-2001 edition Min. 593
P No.3 ASME Sect.8-2004 Min. 595
P No.3 ASME B31.3-2004 593~718
-----------------------------------------------------
p No.4 ASME Sect.8-2001 edition Min. 593
P No.4 ASME Sect.8-2004 Min. 650*(changed)
P No.4 ASME B31.3-2004 704~746
--------------------------------------------------
P No.5 ASME Sect.8-2004 Min. 675
P No.5 ASME B31.3-2004 704~760
The lower crtical temperature to start tranforamation of grain structure, which is base for maximum PWHT holding temperature, are sepcified on the ASME Section 1. Table 129.3.2 as follows:
P No.1 725 oC
P No.3 730 oC
P No.4 Gr.1 745 oC
Can anybody answer to the following queries.
1.Min. holding temp.for P No.1 has been changed to 650 from 593 in ASME sect.8-2004 edition and holding temperature for P No.1 is higher than that of P No.3, although low critical temperature for P No.1 is lower than that of P No.3.
Is there any reason for change of min. holding temperature.
2. Max. holding temperature OF 746 oC for P No.4 in the ASME B31.3 is closer to low critical temperature mentioned above. and Max. holding temperature does not mention on the ASME Section 8.
Is there any guidance for max. PWHT holding temperature, when ASME Sectio 8 Code is to be applied.
3. I would like to know permissable PWHT temperature(min and max) for PWHT for dissimiliar welds of P NO. 1(A106 Gr.B) to P NO. 4(A335 P-11) and P NO. 1 to P NO.4 Gr.1(A335 P-22)material,when ASME B 31.3 Code is applied.
Your valuable answer would be highly appreciated.
W.I Ihm





RE: PWHT holding temperature
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: PWHT holding temperature
Reply;
The ASME Boiler and Pressure Vessel Code and ASME Piping Codes do not necessarily follow each others guidelines for PWHT. These are independent Codes and Standards bodies that deal with their respective subject areas. PWHT guidelines have been developed over the years based on specific industry experience. Also, PWHT requirements in ASME B&PV Code are minimum requirements with the maximum being below the lower critical transformation temperature.
As SJones mentioned above you need to use the Code that is for your process application. I can say from experience, that the Code committees can and will endorse common technical issues, PWHT and fabrication practices, over time.
RE: PWHT holding temperature
RE: PWHT holding temperature
2. ASME VIII Div 1 does not specify Maximum holding temperature. The guide is
a. furnace control accuracy range
b. recording equipment accuracy range
c. lower transformation temperature
d. tempering temperature (it is recommended that PWHT maximum holding temperature should be at least 50-20°C lower than tempering temperature).
3. Dissimilar welds between P1 and P4 are tricky. The WPS and PQR should be developped where the weld is deposited with carbon steel electrode, the P4 material buttered, HAZ of P4 is PWHT at 704°C and the complete weldment is PWHT at 630-650°C. I am making an assumption that carbon steel weld is acceptable for the join configuration/service in question.
Please note that those temperatures are a requirement for thicknesses: P1 - over 3/4", P4 - over 1/2".
Putting Human Factor Back in Engineering
RE: PWHT holding temperature
Thanks your valuable answers