Welding Tips and Tricks

Hi Guys

Just recently got our small business a second hand tig (murex transtig 255).

Being one of the old trusty, can't go wrong and never need repaired murex models, and this being our second one after our first has lasted years and years, I thought we could not go wrong.
However, after one day of use and running absolutely fine with no problems, the water cooler had been switched off (I know!) by one of our employees. The torch promptly overheated and melted almost everything close to the torch and the power cable a good 3 meters down from the torch. - A right mess!

Next best and obvious step was to get a new torch, so with the noisy water cooler not being too popular in the workshop we ordered a new air cooled torch to fit the 255 (wp-26). Which is the same setup on our other tig which is a lot quieter and with the Amps we use, air cooled torches are fine. Needless to say, the new torch did not solve what we expected to be a quick solution. The argon, once the welder is switched on would free flow straight out the torch immediately, also, no matter what setting we choose or frequency we cannot get the torch to ark and without the welder being prompted remotely by the torch itself, argon or no argon, will or no will, hope or no hope!

Obviously worrying the overheating had caused further damage to the welder itself we tried some other tests:

We have disconnected the torch completely, turned the welder on and the argon would still directly free flow out the gas outlet. I know that this should not happen.

Checked every fuse. All fine.

Checked all wires and connections. Again all fine (we'll seem to be).

Before I go down the painful expensive route of taking the welder to be repaired, is there any suggestions out there for a easy fix of a common problem or safety mechanism activated to cause the above after a water cooled torch has overheated?

Your help would be much appreciated,

Thanks in advance,

Josh
Black Forge

So, what's your arc control. A pedal? Thumbwheel? A simple paddle switch? Is it HF-start?

Or is this a lift-arc machine?

If the noise of the cooler bothers people, you must weld in a library!

If it's a lift-arc machine, you may have internal damage. If you have a remote for it (switch, pedal, whatever..) I'd at least trace that circuit before sending the machine for service.

Welcome to the forum, BTW!

Steve S

Hi Steve, - and thanks for the reply.

As I say, its a newly arrived, big old school Murex 255 tig with a water cooling pump and torch fitted, very similar to our other, air cooled Murex 352tig welder which we've had for lots of years. (and of course go on working forever).
Its a 3 phase machine which apparently can be used on single phase if you've got a heavy duty supply, - it came with a 4 pin 3 phase plug (which only had 3 massive wires inside?) and we used it on 3 phase.
Two big copper coiled transformers inside and not an inverter to be seen!
Amps were set on the dial on the welder.
Torch button activated
High Frequency start
No pedal connected
Dunno what a 'Lift Arc' is but it sounds too techno for this old girl.

We'd only had it for a day but were looking forward to years of maintenance free indestructibility, (as proven by our collection of other Murex kit in the workshop),

So - afer lots of impressive testing, the waterpump gets disconnected, (with a plan to put a manual switch in-line for an occassional cooling of the torch if felt necessary), - honestly, really, the watercooling pump noise was unacceptable next to the bench.
Later in the day, a third party comes along, wants to try out the new welder and uses the torch on higher amps.
Torch overheats within a few minutes and melt down down of torch and entire length of torch lead results.
So we immediately replace torch and lead with new, non watercooled version = guaranteed fix. yes?

Nope, - nothing, - welder fan still working but no arc from torch, no clicking of solenoids when pressing torch button or any other obvious life from inspecting circuit boards with basic circuit tester, - plus constant gas freeflow from torch as soon as the welder is switched on.

We've taken all the sides off to examine the insides for any visual signs of damage, - but nothing obvious.
Fuses all ok, including circuit board fuse, pop-out circuit breaker ok. Nothing burnt looking. etc.

A basic glowing 'wand' type circuit tester shows power to and beyond the transformers then to the circuitry but then nothing. (but maybe the voltage here is too low for a basic tester?)

So where to go next?

Confusingly (and maybe a red herring?) - this machine, came to us wired up with a 32 amp 3 phase, 4 pin plug, - but inside the plug were only 3 (huge!) wires as opposed to the usual 4 ?? - i.e. one earth and two lives. - Could this have resulted in the loss of a phase and a completely dead arcing circuit? - but leave the fan working? (there are the usual 4 wires feeding the wall socket which its plugged into).

Any ideas chaps? - all suggestions gratefully appreciated.

Cheers for now.

Josh

My TIG welder is a Single Phase 575, but we plug it into our 600v 3 phase with only 3 wires in a 4 pole plug. cause we also use the extension cord to power our buffing machine, shear and dust extractor. its only grabbing a single phase from the 3 phase and using it like single phase 575. its pretty normal for where i am. Yours might have been that way, because it is not a true 3 phase.

It was not unusual on older machines to run 440 volt from 2phases on moderate size machines - it was done when the current draw would be around 30amps or over on single phase 240volt as this made plugs & extension cables unwieldy on portable machines - nowadays they tend to be either 240volt single phase or true 3phase.

As to what's happened to the machine I would start with a simple test - get a meter & test the old torch between the power cable & the 2 small switch leads - if where the cable suffered meltdown the insulation broke down & there is now continuity between them I hate to say it but there is every chance that welding current & HF traveled from one to the other - the switch leads are usually quite low voltage direct to the control board & will not tolerate this - there is a good chance it's done some damage to the control board - it's likely you can still get a replacement but it's not likely to be cheap - sorry.
I'm not saying this is the case - but I have seen it happen both to Tig sets & migs with torch assembly damage - hard to be definitive without seeing it.

Back to the water cooler; just get longer hoses and cables and move the cooler away from the whiners.

Thanks so far lads (especially Noddy).
I'll get onto the meter testing with fingers crossed when back down there tomorrow, - and let you know in due course.
Cheers
Josh