CHANGE IN PRE-HEAT

[kany]

Hi all,

There is ongoing welding in our pipe shop. Approx.the ambient temperature is 24 C outside and much more inside the shop. The thickness of the pipe is 32mm. Per ASME SEC IX (Table 303.1.1) the recommended temp is 80 C, but if the ambient temp is below 0 C, recommendations become requirements ( QW-330.1.1). Everything is fine up to that point. My concern is; Min. pre-heat temperature is stated 80C on our WPS, and ASME lets a 55 C decrease in the pre heat temperature without re-qualification (QW 406.1), could you please clearify me if it is acceptable to start the welding in the shop temperature which is around 28-29 C instead of heating it up to 80C ?

Best Regards

Kaan

 

[Duwe6]

It is unacceptable. This is because of how your WPS is written. If you revise that WPS to reflect the Code minimum temp, that would be acceptable.

Your WPS requires the 80°C preheat, not the Code. Fix the WPS, or use the 80°C preheat on the WPS. This revision, if made, will not require a new PQR -- per QW-406.1.

 

[kany]

Thanks for you reply Duwe6,

I checked the PQR which is impact tested , per our pWPS used in PQR, also the preheat temp. is specified 80 C. Can I prepare a new WPS / revise without pre-heat by using this PQR?

 

[weldtek]

kany,

Review the variables per QW 406 in Sec IX for the applicable process. You're probably going to be restricted to a max change of 55 C.

 

[Duwe6]

kany, be sure your new WPS with the lower preheat does not address Impact Testing. You cannot drop the preheat temperature and still maintain the Impact rating.

 

[weldtek]

Duwe6,
Actually you can't decrease preheat > 100F ( 55C ) whether or not impact testing applies. ( Essential variable)

If impact testing applies you can't increase interpass ( or preheat that exceeds interpass temp qualified) > 100 F ( 55 C ).
( Supplementary essential variable)

 

[kany]

I checked & got it. I will prepare a new WPS based upon the same impact tested PQR. As far as I understand, regarding my question, per Sec IX impact testing is not my concern about preheating. The minimum temp will be 25 C( QW-406.1 & 406.4).

Guys, you re really appreciated for your helps.

Cheers