Pre-qualified WPS-use of parameters Table 4.5 AWSD1.1 2

[LKC]

I have FCAW procedures that were written in 1996 as pre-qualified weld procedures using AWS D1.1. Our customer is not approving them because he feels that they do not meet the criteria of Table 4.5 as referenced in para 3.6. Specifically he has problems with the ranges we have listed on our electrical parameters ie. 175-290 amps, 24-29 volts and a travel speed of 15-20. He claims that these ranges fall outside of the 10% or 7% limitations on table 4.5.

Can anyone give me a good fighting argument that would allow us to use these ranges? Or a way to edit our procedures so that they meet the requirements and are also useable?

They were originally established from the filler metal manufacturers recommendations and the customer wants me to pick a number ie. 26 volts and go 24.18-27.82 (7%)because technically I can not round to 24-28, it would be 25-27 all of which I find absurd!!!!

 

[CWIC]

LKC:
I agree with your reviewers statements regarding the allowable ranges for the WPS.

Amperage: The current of 233 would be the average or mean value for your amperage which permits a tolerance of 10% or 23 amps.

Voltage: 26.5 volts would be your average or mean value for arc voltage whcih permits a tolerance of 7% or 1.9 volts.

ATS: Arc travel speed of 17.5 ipm permits a tolerance of 25% or 4.3 ipm.

On the other hand, I agree with your statement regarding the filler metal manufacturers recommended range for the electrode. Many "reviewers" these days believe if the numbers do not match the manf. range verbatim, you are not in compliance. What they don't understand is that these numbers are "RECOMMENDED" values. You may use a range within their recommended range(s). Some of the most ridiculous requirements have been imposed on some of my clients in the last few years and they are nothing more than an opinion by someone who needs help using this code. If specific WPS requirements are specified in the contract documents or in the code, I'll comply, np. But if the reviewer starts to add stipulations which delays the project, increases the cost of issuing welding documents, etc., etc., everyone loses.

While this info may not contribute to your argument, the fix is relatively simple. Revise your WPS to comply with the code.

 

[LKC]

CWIC,
Thanks for the input. I was just trying to figure out a way to not have to revise all of the existing weld procedures. Do you have any recommendations on a good resource for writing weld procedures? I am new to the industry and some of these things look like they are making a very simple process more difficult than it needs to be. We mostly do FCAW.

LKC

 

[CWIC]

Hi LKC:
Welcome to the world of welding. I think you will find it interesting in time. Lot's to learn!

As far as WPS's, you have several options.
1.) Learn to develope WPS's which really is not difficult once the required process-specific variables are established (which the code has done for you.) Each time a WPS is issued or revised, simply use Table 4.5, 4.6 (for impact requirements) or 4.7 for ESW/EGW.

2.) Software is available which helps out with these types of documents, but I have never found them particularly useful. I use my own WPS format which is satisfactory 99% of the time with the exception noted above by certain reviewers.

3.) Most of my clients prefer to hire a consultant to deal with these issues. Hiring a consultant can be very helpful as they can aid in resolving any discrepencies with your documentation. They can also train you to help yourself. Many companies are going the continuing education route as it is advantageous and cost-effective in the long run. This is where the training comes in.

I personally do not feel the essential variables delineated in the code are stated to add to the already "black box" of welding, but help to define process specifics needed to deposit a satisfactory and code compliant weld. As noted previously, in time it will start to make sense.

Good luck with your new profession.

 

[sayee1]

"Amperage: The current of 233 would be the average or mean value for your amperage which permits a tolerance of 10% or 23 amps.

Voltage: 26.5 volts would be your average or mean value for arc voltage whcih permits a tolerance of 7% or 1.9 volts.

ATS: Arc travel speed of 17.5 ipm permits a tolerance of 25% or 4.3 ipm."

I respectfully disagree with the interpretation above. The title of the Table 4.5 is PQR essential variable requiring WPS requalifcations. So my interpretation is that if I have a variation of 10% over the PQR parameters it would require requalifiaction of the procedure. What it then boils down to is what parameter to use as the base from my PQR to calculate the WPS values.... What I mean is I can calculate the average parameter from the PQR for I, V and TS.. I can then impose the +/-10% or +/-7% or +25% on these average PQR parameters to obtain the WPS values. Or I can put the limits directly on the minimum and maximum values of the PQR to obtain the range. The problem with the second method is that the heat input values are then discordant because of the ambiguity of then having to use the max I and V and min TS value from the WPS which would be impossible situation in real life. As CWIC says, some of the most ridiculous requirements have been imposed on some of my clients in the last few years and they are nothing more than an opinion by someone who needs help using this code.

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!

 

[sayee1]

PS: BTW if any of you guys want a simple excel sheet with formulae fed in with all the possible ways of estimating these ranges based on various client interpretations , do give your email and I will forward the excel sheet to you by email.

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!

 

[CWIC]

Hi Sayee:
I respectfully disagree with your second method for determining ranges of a WPS - if I am understanding you correctly.

You cannot put a range or tolerance on a range (for a WPS), e.g.:
A WPS (A) has an average amperage of 250 amps [+/- 25 amps].
Another WPS (B) has a range of 225 amps to 275 amps.

The tolerance for amperage noted in Table 4.5 would NOT apply to the second WPS (B) which denotes a range. (Please note the range specified in WPS (B) complies with Table 4.5.) Applying the 10% tolerance on WPS (B) would give you a total current range of 202 to 302 amps.

When I qualify a WPS by testing, I use an average value and not the upper (UL) and lower (LL) limits used to perform the PQR - 95% of the time. If I observe a majority of the welders are operating at the UL, then I > my average value, or vice versa.

Heat input WPS's are another story. A range of heat inputs may be qualified individually. The Low Heat Input Test (LHIT) and High Heat Input Test (HHIT) that are recommended by FEMA 353 (Part I, Appendix A) are a good example. This means two individual WPS's and PQR's. But the range for the essential variables of the individual WPS complies with Tables 4.5.

The WPS's noted by LKC are prequalified. AWS D1.1:2004, Section 3 "Prequalification of WPS's", subsection 3.6 denotes Table 4.5 as the "...limitations of variables..."

 

[sayee1]

Sorry CWIC is right, missed on the prequalifed part of the posting....

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!

 

[sayee1]

CWIC
What I was saying is say I have a PQR which is run with 200-250A. Then either you can have 225 +/-22.5 =202.5 to 247.5 as the range or have (200-20=)180 to (250+25=)275 as the range on the WPS. I have had clients accepting both the above methodologies,, though I prefer the first method. In addition I use the average parameters on the PQR to calculate the HI and then on that basis come up with the maximum HI to be specified on the WPS. Again, the client specifications have requirements of HI methodology spelt out.

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!

 

[LKC]

Thank you both for the advice and information. I am going to revise my procedures.