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Up Topic Welding Industry / Inspection & Qualification / D1.3 PreQualified WPS GTAW welding variables
- - By SeeJeepGo (*) Date 02-28-2019 15:46
I spent some time searching for info and only found a few relevant posts so I hoped to get some clarification. While expanding our GTAW WPS' to include thinner gauge HSS tubing I went into D1.3 to use Clause3 PreQualified. I've done this before for GMAWs and all is good. I quickly realized I was now unsure about what values to use for my initial WPS. I witnessed a welder do some samples for me and I saw how much fluctuation there was with both Voltage and Amperage used. Especially with the start and stop but also mid weld to help w puddle control on a vertical its not uncommon to manually pulse the pedal. And the 10% range is not much, ie, with a median of 80 and you can only go from 72-88 ? that's nothing for GTAW. In my test I saw anywhere from a 120 peak to get the puddle fluid, then drop to 60ish and rise to 75 80 for welding and back to 50s to end. and that was just a 1" weld! 

the volts also ranged from 11.5 to 12.8 which isnt crazy, but I always wondered why they were listed as required on a GTAW WPS. not like you can see that when welding, nor can you really use it as an adjustment. It's not an essential variable for GTAW in clause 4 but it IS listed as req for Clause3?

Am I correct in saying that a Clause 3 Prequalified WPS is not held to the 10% +/- restriction of Table 4.2 ?

Can I include a more real-world range on my WPS? actually can i even include a range at all? All 3.1 says is "A written WPS that includes a recorded value for each of the variable requirements as shown in table 3.1"

On a similar issue I have an AWS SWPS for GTAW on thicker steel that says "AMPERES Groove and Fillet" as the column header and then shows 60/130 on the line for 3/32 tungsten and 90/180 for 1/8"  Is that a range? 60-130 or 60 for groove and 130 for fillet ??? kinda not clear.
Parent - - By Lawrence (*****) Date 03-06-2019 12:52 Edited 03-06-2019 12:55
Hi Jeep

Your questions are just too good I guess.   They should be placed in the "hot potato" section of the forum :)

Table 5.1 needs some help.   And help it will get.    It has become an agenda item for the D1.3 committee meeting in April.   So that's how good your question is.

While I'm on the D1.3 committee,   I cannot speak for it.    With that understanding I'll tell you what I would probably do when making a prequalified WPS <my opinion>.    Every D1.3 WPS I've ever made was qualified because of paint or galvanizing, so this just never came up for me and I've only been a user for a few years.

The essential variable ranges provided in the Qualification Clause (6 in 2018 revision & 4 in the 2008 revision) make enough sense to use on your prequalified WPS's.  For GMAW, FCAW or SAW, The manufacturers recommended ranges would be the starting point for the mean value for WFS/Current, and voltage.   

GTAW is a little more tricky.   Table 6.2 does not speak to voltage for GTAW as an essential variable requiring a range but Table 5.1 has that little "x"    Common sense says that voltage on a CC process is not that critical unless it's an automated process that uses voltage to control the tungsten or Z axis height.. For manual it's pretty much negligible.    You could put a reasonable value or put NA in the box and I doubt any auditor will have heartburn with it...   The WPS is supposed to serve the welder and this value just does not serve the welder.      As far as current goes..  Maybe take the highest value you are going to need and use that at the top, subtract the appropriate percentage from table 6.2 for the range for your WPS.   The current swing in production from the foot pedal is just the nature of the process; meaning how the arc is getting to where it should be.  Not a problem.

I think the information should be there in the Prequalification clause to guide users who are making prequalified WPS's.  Jumping to another clause to get the range without being directed to do so can lead to beefs with auditors, inspectors and confusion by users.  It's logical to do it since there is no other guidance, but I think there should be at least some link to make the clause a bit more easy to use. 

I'm not going to speak at all to the SWPS, except one piece of advice....  If your engineer accepts it... Fire away..   The D1.3 acceptance criteria is generous enough that you will likely be ok so long as you keep an eye on your production operations...  

The advice is this:   MOST SWPS ranges are so wide that without an expert user, or additional supporting data sheets, an operator can take a high parameter value from one variable and a low value from another variable and make a cocktail for disaster...    SWPS demand some expert knowledge to be usable, and the problem is that experts are rarely the people that buy them.  (present company excepted)
Parent - By SeeJeepGo (*) Date 03-26-2019 15:51
Thanks for the insight Lawrence and good luck on that committee. I just received my 2018 version of D1.3 but hopefully future enhancements are in the pipeline. oh wait, pipeline? that's a different code.... humm.:lol:
Up Topic Welding Industry / Inspection & Qualification / D1.3 PreQualified WPS GTAW welding variables

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