PWHT holding temperature 1

[iwikr]

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

 

[SJones]

For item number 3, refer to 331.2.3 of ASME B31.3. For the other items don't worry yourself by mixing codes: you either have a pressure vessel or you have process piping.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[metengr]

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.

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.

 

[kjb57]

The ASME 8 Div 1 2004 ed. has an errata dated Feb 2005 for the minimum temp for P1 materials - the errata corrects the temperature to 1100F/595C. (The same errata applies to P10B materials)

 

[VeryPicky]

1. There was an error in PWHT temperature of 650°C for P1 materials in the 2004 edition of ASME VIII Div 1 UCS 56. It was communicated and the 2005 Errata was issued. Please don't consider 650°C as a valid value. 2006 version came back to 595°C.
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

 

[iwikr]

Thanks your valuable answers