PWHT times at temperatures

[teokal]

Dear all,
maybe a stupid question, but I have to ask... My existing PQR is for P No5A to P No1, thk 40mm and treated at 720 deg Celcius for 2 hours. Can I use this for the same materials and holding temperature for 6 hours? English is not my mother tongue, so para. 407.2 of ASME IX is nnot so clear to me...
Thank you

 

[metengr]

teokal;
If this PQR/WPS were qualified for impact, the answer is no. QW-407.2 applies for impact qualification as a supplementary essential welding variable for the SMAW process. If the weld procedure is not impact qualified, you can PWHT as long as necessary provided you remain within the qualified temperature range.

As a side note, you should review QW-250, which lists the variables for welding by process. This is where variables that are essential must be followed. For impact qualification, Supplementary essential variables are treated like essential welding variables for procedure qualification.

 

[teokal]

metengr,
The PQR is qualified for impact (mandatory for pressure vessels in Europe). In Europe all supplementary essential become essential, due to PED requirements - wherever this is applicable... What confuses me is that 80% of the time at temperature; Means that the PQR specimen should be heat treated at least 80% of the time of the production heat treatment? Or the production heat treatment should be at least 80% of the specimen PWHT? Hope i'm not confusing you...

 

[metengr]

OK.

Means that the PQR specimen should be heat treated at least 80% of the time of the production heat treatment?

Yes, per QW-407.2. The aggregate times for production are cumulative from original PWHT time at temperature to re-PWHT for repairs, if expected in production or specified by the design engineer.

 

[DVWE]

you can PWHT as long as necessary provided you remain within the qualified temperature range.

Within certain limitations, correct?

 

[metengr]

Yes. The limitations will be the base metal thickness limit of the WPS that was qualified with PWHT. Normally, PWHT minimum temperature is listed on the WPS along with a thickness per hour for PWHT soak time.