PQR & WPS Voltage range qualified question?

By Brandon Ruot Date 12-04-2010 17:38

Hi all, I'm a wet behind the ears CWI in need of some assistance from some of y'all more experienced. :-)

The company I work for just qualified a FCAW procedure on 1" A-36 carbon steel plate using .045 wire in the 3G position with back gouging for ASME Section IX. The Amps recorded on the PQR ranged from 170 to 212, the Volts ranged from 21.5 to 26, and the Wire Feed Speed ranged from 235 to 315 IPM. The welder performing the PQR test completed it in 10 passes (9 front side passes, and 1 back weld after gouging). The Amps and Volts are recorded on the WPS per weld layer, e.g. 1st layer 170-185 Amps, 21.5 Volts, 2nd layer 185-190 Amps, 22.8 Volts, etc. There seems to be some confusion with the welders as to what is actually qualified; i.e. can the welder (after successful qualification) weld his first (or any) pass with 26 Volts, or is he limited to 21.5 Volts for the first layer, 22.8 for the second, etc. as that is what is recorded on the WPS? I guess to put it a little simpler, seeing as 170 to 212 Amps and 21.5 to 26 Volts were recorded on the PQR and WPS, is that the qualified range for any weld pass?

I hope this makes sense, any help would be greatly appreciated. Thanks in advance!

By MBSims

Date 12-04-2010 23:41

Amperage and voltage are not essential variables for welder performance qualification. The welder may weld in the range specified on the WPS, regardless of the actual amperage and voltage used in performance qualification.

By rangerod (**)

Date 12-11-2010 00:01

MBSims

I have a question. Where do the amprerage & voltage range values specified WPS come from. Is it the judgement of the person writing the WPS. the weldor ect...?

By Shane Feder (****)

Date 12-11-2010 04:25

Rangerod,
It is generally good practice to have the best / most experienced welder in the company perform the procedure qualification coupon.
The amps / volts / travel speed etc used in a successful qualification test are then used for the basis of the WPS.
A small +/- is then given to these variables (eg. +/- 10%) to give some flexibility (and to cater for various welders preferences).
The range of these variables is generally taken from a combination of electrode manufacturers recommendations and the knowledge / experience of the person writing the WPS.
Hope that helps,
Regards,
Shane

By 803056

Date 12-16-2010 02:01

That's the beauty of ASME. You can write a WPS that totally useless that is still code compliant. The code doesn't say it has to be usable.

Best regards - Al

By js55

Date 12-16-2010 13:57

Usefullness and uselessness isn't in the writing. Its in the application. Make the WPS as stringent as you like and it can still be useless.
The biggest problem with WPS's being usefull has never been how they are written or qualified and what variables are included or not.
The biggest problem with WPS's is welder understanding and access.
You cannot Code enforce the usefullness of a WPS. ASME understands this. At least the guys I know that sit on Section IX are profoundly aware of this.

By 803056

Date 12-16-2010 15:12

Same mindset: "Weld as required."

Good management always ensures someone lower on the totum pole can take the fall when the poop hits the fan.

I'm just raising a little dust with you on the subject. I don't disagree with you entirely. The application dictates the needs of the welder, after all, as you have said before, the code sets the minimum requirements that have to be met. It is up to the welding engineer to write a WPS that is appropriate to meet production needs.

Al

By MBSims

Date 12-16-2010 15:15

It would typically be up to the person(s) preparing the WPS to determine the appropriate ranges to specify on the WPS when no tolerance is specified. That could be done in many ways, such as welding specimens, experience from similar welds or the manufacturer's recommended ranges. Some codes place a tight tolerance on the amperage and voltage range used in the PQRs. ASME IX does this also for some processes, but not for GTAW or SMAW. However, a tight tolerance does not ensure that sound welds will be made as long as the tolerance is adhered to, or that welding outside the qualified range would produce bad welds. ASME code seems to place more responsibility on the fabricator for determining the appropriate ranges for the work to be performed. In the end, it is the fabricator that must produce welds that meet the code-required nondestructive testing and hydrostatic testing requirements.

By jon20013 (*****)

Date 12-21-2010 04:33

Another point to consider is when impact testing is required by other codes.