PQR/WPS D1.1 Newbie Questions

By jxsnyder Date 06-30-2019 17:45

I am reviewing a WPS and PQR per AWS D1.1-2015 edition. I'm very green when it comes to reviewing this type of documentation and want to make sure I am thinking correctly.

Section 4.7 states the following:
The manufacturer or Contractor shall prepare a written WPS that specifies all of the applicable essential variables referenced in 4.8. The specific values for these WPS variable shall be obtained from the procedure qualification record (PQR), which shall serve as written confirmation of a successful WPS qualification.

Section 4.8.1 states the following:
Changes beyond the limitations of PQR essential variables for the SMAW, SAW, GMAW, GTAW, and FCAW processes shown in Table 4.5 and Table 4.6 shall require requalification of the WPS.

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The PQR I am reviewing uses A36 base material, GMAW process, single-v CJP, A36 backing material, 0.035 in. ER70S-6 filler, welded in the 1G position, etc. The PQR shows that the weld was performed using six (6) passes with 221-251 amps, 27.8-27.9 volts, 8.5-20.5 in/min travel speed, and gas flow at 45 CFH.

The WPS allows 0.030, 0.035, and 0.045 in. filler. The WPS allows 150-300 amps, 250-550 in/min wire feed speed, 20-35 volts, 6-22 in/min travel speed, and 20-50 CFH gas flow.

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Here's the problems I am seeing with the WPS:
1). Table 4.5(10) states "any increase or decrease" for filler metal. I interpret this as the PQR 0.035 in. diameter filler is all that is allowed.

2). Table 4.5(12) states "> 10% increase or decrease" for amperage. Average amperage from PQR for the six passes is 234.8. This would mean an allowable range of 212-258 amps.

3). Table 4.5(16) states "> 7% increase or decrease" for voltage. Average voltage from PQR for the six passes is 27.9. This would mean an allowable range of 26-29 volts.

4). Table 4.5(18) states "> 25% increase or decrease" for travel speed. Average travel speed from PQR for the six passes is 14.3 in/min. This would mean an allowable range of 11-17 in/min.

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Questions:
A). Am I interpreting the requirements of Table 4.5 correctly?

B). If so, how should the large range of travel speed on the PQR (8.5-20.5 in/min) be addressed?

By 803056

Date 06-30-2019 18:12

Here's the problems I am seeing with the WPS:
1). Table 4.5(10) states "any increase or decrease" for filler metal. I interpret this as the PQR 0.035 in. diameter filler is all that is allowed. Agree

2). Table 4.5(12) states "> 10% increase or decrease" for amperage. Average amperage from PQR for the six passes is 234.8. This would mean an allowable range of 212-258 amps. Where does the table limit the ranges based on average amperage?

3). Table 4.5(16) states "> 7% increase or decrease" for voltage. Average voltage from PQR for the six passes is 27.9. This would mean an allowable range of 26-29 volts. Where does the table say the range is based on average voltage?

4). Table 4.5(18) states "> 25% increase or decrease" for travel speed. Average travel speed from PQR for the six passes is 14.3 in/min. This would mean an allowable range of 11-17 in/min. Where does the table say the range is based on the average travel speed?

Al

By jxsnyder Date 06-30-2019 18:49

Thanks for taking the time to respond. I think I am misinterpreting Table 4.5.

In the PQR they have amperage listed for each of the six passes with values ranging from 221 to 251 amps. I thought I was supposed to be taking the average of this range and applying the +/- 10%. From your response it seems like this is incorrect. Am I supposed to be applying the 10% to both the high and low values?

For example:

251 + 10% = 276 amps
221 - 10% = 199 amps

By 803056

Date 06-30-2019 23:05

That's how many people approach the problem.

I use the statistical analysis tool available in the MS Excel program. I usually use one standard deviation +/- to eliminate the outliers.
When there is only a few beads involved it doesn't make a lot of difference, but when welding thicker plates with either a manual or semiautomatic welding processes it can make a significant difference.

The use of the statistical analysis tool is one of the many subjects covered in the seminar "The Atlas of Welding Procedure Specifications".

Al

By Shane Feder (****)

Date 07-03-2019 11:05

I agree with Al on the subject of "averages".
A lot of people use that formula but IMHO that is not what the code is stipulating.
Hypothetically, you have a PQR with multiple passes with a large range between lowest and highest amps/ volts/travel.
Take the "averages" for those passes and then apply the 10 percent +/-.
There is a possibility that your recorded PQR lowest or highest amps/volts/travel speed may actually not be within the range calculated via "averaging" the measurements.
Regards,
Shane

By 803056