Scratch tig issue

[fill&cap]

hi guys
iv been playing around with scratch tig torches over the last week in my spare time ,the problem im having is on stainless steel. the scratch torch is leaving the weld a little grey instead of the usual clean gold/silver finish .
if i use the hf torch (wp26) with 2.4mm tungsten,gas lens with number 8 cup gas flow 7lpm the weld is clean
if i use the scratch start torch (also a wp26) with the same perameters the weld is dirty. iv checked the connections for leaks and there all fine.
could it be the higher volts on the mma mode causing this ? Or has anyone had the same problem.
cheers jay

 

[hotrodder]

Just throwing ideas out... different welder or same kit set to MMA for scratch start? With the former it could be a calibration thing instead of a volt - amp curve thing i.e. is a setting of 40A really 40A
Flow reading at the reg or at the cup with one of those little pea shooters i.e. could the valve on the torch be messing with things/leaking when open?

 

[fill&cap]

hi rodder

its the same machine just swapped to mma .iv not checked the gas from the cup,i just assumed the same pressure from the regulator ,i use the airproducts integra cylinders with the preset regulators...il get my self a peashooter and check the flow rate.
the torch valve is ok iv leak checked that.
if i set the scratch torch up on the hf set up and try it that way ,that would rule out the possiblle voltage differents.
just had a brain wave !!! iv not checked the back cap for leaks,the seal is new but may not be doin g its job .
jay

 

[biffa]

Surelly by putting it in mma mode, theres no function to opperate the gas, most welderds have a scratch mode and a mma mode

 

[Tigman]

My Thermal Arc has a switch for mma and Tig , gas is a valve on torch , turn gas on , scratch and away you go .

Why are you using mma mode to tig weld ? mma is for arc welding !!!

 

[fill&cap]

Because tig mode on my machine is HF tig not scratch.
Cheers jay

 

[hotrodder]

I'm guessing you've got a job coming up where HF isn't allowed and you can't switch off the HF (to get 'lift start' in TIG mode)?

 

[fill&cap]

Lol no it's a bit simpler than that,my viper 2500 tig unit has stopped working so my idea was temporarily use a scratch torch straight from the gen set until I can find someone who repairs viper add on units.
I tested the voltage from mma an tig,there was 20 or so volts difference so I put the scratch torch on to the HF setting,using the foot peddle to strike up .
i was still getting the same problem arghhhhh.
So this leaves a gas problem. ( I always over complicate problems lol)
Jay

 

[Drains]

I was going to mention the voltage difference but you've found that out yourself. You should still be able to run the job on the MMA setting even with the different voltage.

So the problem is the gas and the scratch torch. You'll probably need to take the torch apart and put it back together again, a quick check of components, a check at the regulator. That works for me, mostly. Drawing in air somewhere?