Welding Equipment Calibration 1

[tc7]

I recently inherited some new work, that being to write and coordinate qualification of weld procedures. And I have two basic question that I hope to get your advice on:
1. On some of the old standard forms for our procedures, there is a block for "Calibration Procedure" which has typically been left blank. My question is, do the welding machine power supplies or transformers require calibration by Code (any) or is it standard shop practice to do so? Or is it never done (which appears to be our case)?
2. Should a weld procedure be qualified for the specific machine owned by the shop? In other words if we own Lincoln and Hobart TIG machines, is there a requirement to do qualify the procedure twice (once with each machine)?

By the way, we do Mil Std NAVY) and AWS welding.

Thanks in advance.
TC

 

[gtaw]

Calibration of the welding machine is not required by many welding standards. That is a general statement that will be shot down in flames by the next person that responds to your inquiry.

There are welding codes, such as AWS D1.5 Bridge Welding Code, that do require the calibration of the meters, i.e., typically voltage and amperage.

Many fabricators have their machine's meters calibrated as part of their quality control system and to provide a level of assurance the machines are in good operating condition.

Many welding standards and codes do require the welders to follow written welding procedure specifications that list the acceptable ranges for arc voltage, amperage, travel speed, etc. It is reasonable to assume that welding with a machine that is "way" out of calibration is not going to produce the optimum condition necessary to produce acceptable welds or within the parameters listed in the WPS.

Another issue is that most military work requires compliance with standards other than the welding standard. Usually there are quality control standards that require the calibration of all measuring tool and meters used to monitor or control processes such as welding, heat treating, etc.

You do not have to qualify the WPS for each power supply. However, you can run into trouble with some of the new inverter pulsing GMAW power supplies that used "canned" programs to control welding variables such as pulse frequency, duration, peak amperage, background amperage, and the slope of the power supply, etc. The slope of the power supply in some cases switches between constant current and constant potential when switching to a different program. Each model power supply can have welding parameters that are entirely incompatible with a machine made by another manufacturer or a different model made by the same manufacturer. The meters provided on the machine only tell a part of the story, so a WPS qualified using a programmed machine made by Lincoln will not work with a programmed machine made by ESAB.

Codes and standards set the minimum requirements. It is up to the manufacturer to make sure the minimum requirements are met and in some cases has to go above and beyond what is required by the customer’s imposed standards to assure acceptable product is produced.


Best regards - Al

 

[tc7]

Hello GTAW-
I wasn't sure my question was a legitimate one, but your very extensive answer tells me it was worth asking. Actually you have given me more to think about then I realized before. The meters will certainly go on the cal schedule.

Thankyou very much.
Tom

 

[gtaw]

That's probably a good decision even if not specifically required by your welding standard.

Best regards - Al

 

[SJones]

ISO 17662

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[tc7]

Thanks Steve,
That sounds like a good one for me to look at. I wish I had access to it.
tc

 

[GregLamberson]

gtaw

Slightly off subject, but in response to your statement - "You do not have to qualify the WPS for each power supply". One exception, under API 1104 if you change from AC to DC or DC+ to DC- it is considered an essential variable.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[deanc]

If I came to audit you,and you handed me a WPS,how would I know you were in compiance if your machines are not calibrated?

 

[gtaw]

As I said in my original post, I was speaking in general terms. The fabricator has to understand the specific requirements of the fabrication standard they are working to. Not all require calibration. Not all, ASME Section IX for instance, requires the voltage and amperage to be recorded on the PQR unless impact toughness is a requirement.

Many manual SMAW and GTAW machines have no meters of any type and the same is true with some semi-automatic GMAW machine. Calibration in those instances is meaningless to either the welder or welding engineer. The is nothing to calibrate.

I do record all the welding parameters, code required or not, to eliminate the need to requalify the WPS every time a new job that references and different welding standard comes into the shop.

I calibrate my hand meters and use them to verify the proper operation of the meters on the welding machines. Again, as I said, it is a means to make sure the welding machines are in good operating order and the welder is working within the parameters permitted by the WPS.

Best regards - Al

 

[gtaw]

As for your audits, I would expect you to bring your own calibrated meters. Why would you trust mine to be correct?

Many welding standards published for military work state that the inspector can request a qualified welder to weld a test coupon, succesful results, i.e., bend tests or radiograph, is satisfactory evidence the machine is in proper working order. Again, no calibration of existing or none existant meters is necessary.

Best regards - Al

 

[deanc]

Well...lets see. Do you have an ISO cert? Yes...do you have a calibration program? Yes....do you calibrate measuring equipment for process and material control and verification? Yes...don't think calibrated gauges or clamp-on meters for the weld machines would be a stretch.

As you said above...need for PQRs. Use your gauges....of course,if your calibration program was not up to snuff it woould be an NCR and a Audit Finding.

Reason to charge you again for another visit.

But I guess if one was building horse trailers or wash tubs,you would not see me anyway.

 

[gtaw]

In the grand scheme of things, relatively few fabricators are ISO registered. It isn't required for the majority of work performed in the US.

It is a great trade barrier and keeps many small companies from quoting work where ISO registration is imposed. Why would Europe ever get rid of it? I do appreciate the concept of complete documentation of the manufacturing operation. It allows a manufacturer to manufacture poor quality product in a consistent manner. It also puts a lot of pencil pushers to work.

Just kidding. You haven't said anything I would disagree with, but as I point out, there's a lot of welding equipment manufactured without meters of any sort. Meters, calibrated or not, aren't a guarantee a quality weld will be made with the manual welding process.

There are welding processes that are dependent on meters as a way of monitoring the welding process. Typically, semiautomatic, mechanized, and automatic welding processes would fit into that category. That being the case, I would urge the company to calibrate the meters irrespective of the welding standard's requirements.

I would expect anyone charged with auditing a welding operation to be familiar with the welding standard being used; the requirements of the welding standard, the welding process, and the companies approved QC/QA system. The audit should be based on the requirements, not personal opinions. If calibration of the meters is not a requirement, the auditor should not impose their personal will on the manufacturer. If the auditor is convinced that calibrated meters is going to mean the difference between success and failure, he/she should have the requirement included in the next project specification, purchase order, or welding standard. I don't share the concept that the auditor is god, free to impose his/her personal will on the victim.





Best regards - Al

 

[deanc]

I am just poking at you gtaw/Al.

Really don't disagree with you for the most part. I apporoach an audit as merely verifing one is following their own program.

Perhaps I should come for a visit?

 

[gtaw]

No, no, not that! Pull my fingernails out by their roots, but please not an audit!

I crossed my fingers and hoped you had a sense of humor "deanc". I'm glad to see you didn't take offence at my warped sense of humor.

Audits are always good for business. Its one means of determining if the company is working together or just paying lip service to the QC/QA system. All too often it’s the latter.

Happy holidays!

Best regards - Al