Existing WPS - PQR PWHT holding temperature lower than minimum specified on WPS 1

[timsch]

I'm looking at several of my company's ASME SEC. IX WPS documents for P-4 material, all of which have a PWHT temperature and holding times per ASME SECTION VIII, DIV.1. Several of these WPS's have PQR's that have a different PWHT temperature that is not within the range of that specified in the WPS. In some instances the PQR temperature is below, i.e. 1100F, while the WPS range is 1200-1300F. In others, the PQR temperature is above it, i.e. 1350F for the same WPS range. These procedures have already been approved by our AI.

These procedures are for GTAW and do not cover applications requiring impact testing, so the only essential variable for PWHT is QW-407.1, and QW-407.2 does not apply, so a change in time and temperature do not necessitate a new procedure qualification. Is it left to sound engineering judgement to determine how far outside the PWHT range given on the WPS a PQR PWHT temperature may be?

Thanks.

 

[Mr168]

Interpretation Number : IX-78-102
Question(s) and Reply(ies):

Question (1): What is meant by the term "range" as it appears in the wording for PWHT in QW-407.1?

Reply (1): The Code does not address itself to specifying a postweld heat treatment temperature range. It would be the responsibility of the manufacturer or fabricator to develop a temperature range suitable for the material used and designated in the Welding Procedure Specification. It is hoped that a postweld heat treatment temperature would be selected to fall midway in the range developed.

Question (2): How much may the temperature of PWHT of WPS qualification coupons differ from the PWHT temperature of the vessel?

Reply (2): There is no connection between the PWHT of welded test coupons and the PWHT requirements of a vessel. The values may be similar, but are not required to be so by Code requirements.

ATTENTION

The foregoing interpretation has been further considered and the following corrected interpretation to Question (2) sent to the inquirer.

Corrected Issued: September 25, 1979

Question (2): How much may the temperature of PWHT of WPS qualification coupons differ from the PWHT temperature of the vessel?

Reply (2): The PWHT of the welded test coupons and the PWHT of the vessel must be of the same type of PWHT as designated for the various conditions outlined in QW-407.1

 

[weldstan]

Mr168,
Thanks and a star for the old Interps. While knowing them when they came out, memories do fade.

.

 

[timsch]

Thank you for the interpretations. However, the wording in the correction has me scratching my head. "the same type of PWHT" is not descriptive when the question, and the initial answer, dealt with temperature/values. Given that the 1st answer did indicate that the values referred to were time and/or temperature, why the more vague "same type of PWHT" in the 2nd?

I found another thread where the situation is the same as mine and the 4th response (metengr) stated that:

...when the PWHT temperature is recorded on the PQR and it is below the lower transformation temperature you can specify a range for the WPS. The PWHT temperature range is good from the minimum of the specified range to the lower transformation temperature of the base material.
Review QW-407.1 in Section IX.

This response from metengr makes me think that there is not a problem with the PQR PWHT temperature being different than that on the WPS, but both this response and the correction in the interpretations refer back to QW-407.1. With the P4 material being considered and the temperatures I'm looking at in the PQR's being below the lower transformation temperature, only QW-407.1(a) apply. I don't see information in QW-407.1 that clarifies this question.

 

[weldstan]

Same type of PWHT refers to subcritical, intercritical and an austenitic (annealin/normalizing) PWHT as defined in 407.1.

 

[timsch]

Thank you for the clarification. If I understand correctly then, the time and temperature for the PWHT do not need to be the same for the PQR & WPS as long as the temperatures are both within the same range, i.e. subcritical in my instance.

 

[metengr]

Yes

 

[timsch]

Thank you all once again for your explanations. They are greatly appreciated.