Preheat mentainance

[tekari123]

Dear All,

I am working in a power plant construction project. The WPS says preheat maintainance at 150 degree C for one hour for A 213 T22 joints. But contractor is saying that as per ASME section IX preheat mentainance is not an essential variable. Shall We insists for preheat maintanance as given in WPS...?

Thanks in advance.
Alok

 

[weldstan]

For tubes ASME I governs and preheat maintenance is not required. I'm not sure what the WPS means since PWHT is not required and preheat maintenance is used to assure freedom from hydrogen induced cracking prior to PWHT. They may change the preheat maintenance requirement on the WPS at will.

 

[metengr]

weldstan is correct, ASME Section I provides minimum recommended preheat but not preheat maintenance because PWHT is not required for material thickness 5/8" (16mm) or less at the weld. Use good engineering practice to enforce preheat for tube welds.

 

[gtaw]

ASME code sections assumes the contractor is technically competent. Maybe this is a case where the contractor believes the job is done once the moisture is driven out of the base metal. I suppose the contractor's welders figure that once the moisture is driven out it is just fine to go to lunch and resume welding when lunch is over.

I would venture to say the contractor doesn't understand the real reasons for preheat. Scary!



Best regards - Al

 

[GenB]

Then You need a new WPS. Am is right but assuming going to lunch in the middle of a weld and return an hour later then the preheat apply again. Preheat maintenance is assured with the wps you already have so as long as you are welding the preheat is maintained at plus required by wps.then the existing wps is also correct. Keep welding, no stops, no breaks. Or change the wps... Genblr

 

[pandithan]

fOR LESSER THICK OF T22, PREHEAT MAINTANANCE/POST HEATING NOT REQUIRE,BUT PREHEAT IS MUST TO AVOID PWHT FOR LESS THAN 16MM THICK OR 13MM FILLET WELD