Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / Technical Discussions / Calibaration of Welding Power Sources
- - By prakashv58 (*) Date 02-10-2003 19:40
Kindly review the following for the LINCOLN electric welding machines, model SAE 400 used with remote control units, as our client is asking to calibrate the current control rheostats on the machine as well as on remote control units, assuming that the scales are graduated to set the required welding current directly.

1) We know that the scales are graduated for current or percentage to set an approximate welding current, their accuracy is subject to certain factors (input voltage, size and length of the welding and remote control cables, etc.) and final welding current can be set by trail & error methods or with an ammeter for applications, where an accurate welding current is required.
- Are you agreeing with our understanding?

2) Is there any kind of calibration possible on the subject machine and current control system, other than confirming that their output is in accordance to the design rating/ NEMA standard - EW1?

Please advise with necessary information/ supporting documents, preferably from the manufacturer for us to clear this long lasting debate.

Your prompt response is highly appreciated.

Thanks & Regards


Parent - - By DGXL (***) Date 02-10-2003 21:57
Is this for maintenance of an ISO registration?

1.) A calibrated amp/volt meter is commonly used for welding equipment parameter verification. THis is used to avoid "calibrating" each power supply.

2.) Manufacturer's or equipment repair companies connect the power supply to a load bank to calibrate the output controls to the output leads and meters. This calibration only offers accurate numbers at the machine and does not compensate for wound cables, bad connections, excessive lead-lengths, etc.

I regularly verify welding parameters for GMAW, FCAW, SAW, SMAW and GTAW. The calibrated meter is placed at various locations of the welding circuit (depending on the process) to monitor the electrical characteristics of the WPS they are supposed to be using.

I deal with the ISO people (and several other entities) on a regular basis and have shown them calibration of some of the elements of any given process achieves nothing. The meter method of montitoring parameters was generally accepted by most. It was only those who did not understand the basics of welding where problems remained and do to this day.
Parent - - By prakashv58 (*) Date 02-11-2003 08:28

We have about 1,500 Welding power sources for SMAW, GTAW, GMAW, FACW & SAW applications. All these machines are being inspected, serviced and tested with load bank on yearly basis to confirm the performance is in accordance to NEMA EW1.

It is not for ISO. Some of our people think that the scale of the current control rheostat is graduated to set the required current directly and asking to calibarte/ certify them.

How can I prove:
- That it is not necessary as long as the machine is serviced and tested
- Accuracy is subject to certain factors (input, cable length, size, etc.)
- Scale is to have an approximate setting, final setting can be done with an ammeter and to ensure that the setting is not moved out.

Please help me
Parent - - By DGXL (***) Date 02-11-2003 17:03
I think whomever is asking for the dial on any welding power supply to match that of the arc voltage, etc. is not being realistic and may be causing your company to spend lot's of $$. (My humble opinion.)

Your "bullets" (most notably the second one) provide some insight. The factors of cable length, size, condition, etc. will affect the output of the machine where the welding is taking place (i.e.: arc voltage).

Wow! 1500 power supplies? Since your company likes to spend that kind of money, tell them I will be available to "calibrate" all 1500 of them.
Parent - - By jwright650 (*****) Date 02-11-2003 21:02
You might need some help, when should I show up for work?
I thought we had a tough time keeping up with our machines, and we don't have any where near 1500.
John Wright
Parent - By prakashv58 (*) Date 02-12-2003 08:09
Hi Guys,
Thanks for your offer for the calibration services. We got a very good In-house team to carry out all required maintenance, testing and "Great calibration" and doing it for the last 20 years.
I seeking some supports to prove that the calibration of current control rheostats on the machine/ remote control is not necessary/ beneficial for anybody.

Parent - - By rpoche (*) Date 02-12-2003 14:36
DG & JW:

While you are on this subject - where are some sources/information on the proper way to measure the output at the arc and what type of equipment is best for this. We use LN25 & LN7's with FCAW.


Parent - By DGXL (***) Date 02-12-2003 23:50
Go back a ways and you'll find several posts on the subject.
1.) Calibrated amp/volt meter can be placed anywhere in the welding circuit to obtain amperage. Amperage is uniform throughout the circuit. I noticed sometimes (depends on the meter and type of welding equipment) it will pick-up the signal from any control cables, so I take the amp reading off the lead to the wire feeder.

2.) Voltage is taken from the contact block on that LN-25 or the LN7's. Open the door and attach your lead (I use an alligator clamp with a test clip on the other end so as not to damge the welders lead with a test prod). This is about as close as you can get to arc voltage without becoming part of the circuit yourself or damaging the whip.

When I am working in a shop I will be at for a while, I attach a lead for my test equipment that is not in the way of the welder and continued usage will not damage the welders' welder.
Parent - - By CHGuilford (****) Date 02-12-2003 14:46
Most dials or readouts on welding machines are only useful for providing the welders with a visual reference for returning to the settings found to work the best for that person. There are too many variables, as already pointed out, to "calibrate" in any way that will mean anything. When we are qualifying PQRs, we use a calibrated in-line volt/amp meter to record those variables. For the actual production work, if heat input is an essential variable, we use a calibrated clamp-on meter to verify the individual machines after cables are run. Usually, the dial gets a pencil mark to indicate the needed setting (in fact, most dials already have marks the welders put on them). With digital readouts, we note the readout range allowed. Most D1.1 WPSs have a broad enough allowable range that calibration normally isn't needed. In those cases we calibrate mainly for the sake of the uninitiated.
The biggest problem I run into while trying to comply with the 3 month interval calibrations required by D1.5, is keeping the "matched" equipment together. It seems that there is always a welder who has to switch wire feeders and power supplies around because they feel the machines "run better that way". Of course when they do that, our "calibrations" are null and void. Oh wellll!
Have fun,
Parent - - By DGXL (***) Date 02-12-2003 23:39
As noted by CHG and the other posts, a calibrated meter is introduced to the welding circuit. I like the reply noting "...after the cables are run..." This is the most practicable way to monitor electrical parameters.

It's tough when the welders keep playing with the adjusments, or they want the other wire feeder, etc. This requires lot's of extra work for the QC dude (or dudette). Just switching leads can throw the "calibration" off.

Question for CHG:
Do you guys have to match the equipment even if it is not a FCP project?
Parent - - By jwright650 (*****) Date 02-13-2003 13:02
I'm so thankful they don't let the welders pull machines around and swap feeders, etc. here at our plant. That would be awful to try to keep calibrations straight. All our fitting/welding tables(stations) have two FCAW machines and two SMAW machines and nothing is to be switched around except when something is out for service.
John Wright
Parent - - By CHGuilford (****) Date 02-13-2003 17:46
Our welders have been instructed not to switch the equipment around also. Only Maintenance is supposed to do that and they must notify QA/QC to allow for calibration. Everyone claims they don't do that, but each 3 month calibration exercise finds several switched around. I guess the welding fairies are responsible.
Parent - - By jwright650 (*****) Date 02-13-2003 18:02
I hear what you are saying, and know something of what you are up against. Those welding fairies are responsible for alot around here as well.
John Wright
Parent - By rpoche (*) Date 02-13-2003 18:07

I was always told "Nobody" did it and all this time it was the "fairies"

Parent - - By CHGuilford (****) Date 02-13-2003 17:41
We calibrate for compliance with D1.5 Section 4.26 which covers both FCP and non-FCP. We use FCAW for "run-of-the-mill" fabrication and welding, and SAW for heavy stuff or girders.
SAW isn't bad to calibrate since 1000 amp power supplies and sub arc tractors really aren't that portable and the welding parameters are very stable, at least with automatic welding.
Our FCAW equipment is tougher because it is more portable making it easier to switch equipment around. I record machine & wire feeder serial numbers on my cal records but 3 months later I'll find quite a few swapped around.
We don't use much SMAW which is a good thing because our machines only have dials, no meters.
I do realize it is important to be able to control heat input (A, V, and IPM) for many situations. But on a personal note, I really dislike "calibrating" machines used for manual and semi- automatic processes. Especially on a 3 month basis; and knowing that even though we try to use "average" conditions, every welder will run differently. Even if I locked the controls with FCAW, just having different ESO (stickout) will significantly change amperage, even if the ESO is within allowable limits. And forget trying to develop a chart to allow for variances, it hasn't worked so far. I would much rather calibrate machines when the situation warrants it.
To quote the good sense used in other posts, I'll get down off my soapbox now. I hope I answered your question without going too far overboard.
Parent - By DGXL (***) Date 02-13-2003 19:00
The reason for my query was no one on this side (West Coast) has enforced the 4.26 section of the code. Typically a calibrated meter is required to be with the inspector and readings are taken daily as a minimum.

I tried to explain the concept of ESO vs current to an engineer a couple of years ago and he instructed me to: "...make them consistent..." with their stick-out. I explained to him that it is the nature of the process for there to be some variation in the output as the welder changes angles, travel speed, etc. during welding and they all affect the output (or heat input in this case).

The new FEMA welder qualification requirements (when specified) make this an issue as FEMA requires welder qualification to be performed using the "...highest deposition rate to be used in the work." The highest anticipated deposition rate could be performed during the procedure qualification to ascertain impact (toughness) values.

I am trying to stay out of the DOT arena (regardless of the jurisdiction) as there are too many "Fluid Rules" that are imposed by the various proponents inspectors'.

Up Topic Welding Industry / Technical Discussions / Calibaration of Welding Power Sources

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill