welding indoors

Our welders ,working inside tanks used to swear by Airstream welding helmets .This was a recomendation as they swore at everything else.

Technology has moved on since those days but just another way.

Regards Colin

I see no one else has answered about the fan motor.

I suspect small single phase fans are likely to be shaded pole.

Some form of voltage control will also control speed through increased 'slip' at reduced voltages.

You shouldn't use a conventional TRIAC dimmer style control as these result in a small DC offset, which, depending on the motor DC resistance, will cause internal heating. Something like a small variac or tapped transformer would be best.

Haven't used a downdraught station, but would have liked to (the two in the grinding booth at the welding class at Northampton College were both broken for the four terms I spent learning welding).

As a datum on fan power. a 500 cuft/min dust extractor typically has a half horsepower motor. I've just finished modifying the ex-ebay dust extractor that I've got to make it a bit better for welding and cutting oil smoke abatement:-

The original 1/2 horse motor ate its run capacitor and windings when the capacitor's case got chewed through due to a lack of any mounting clips. I replaced it with a 2hp 3ph motor and VFD because I had one... I added a Camfil F9 grade filter after the dust extractor, which should cope with anything down to 0.3 micron.

I tested the setup with three dozen 3.2mm x 400mm 7018 rods and, while there was a visible haze at the worst point, there was no discomfort at all, unlike previous sessions.

For TIG work, if the material is clean (It's TIG, you need clean material!) then the fume levels are insignificant compared with stick or even MIG.

If the heating/cooling bill or introduction of humidity don't get in the way, then a downdraught table with out-door extraction is going to be a perfect solution assuming it's got a variable speed for TIG and stick. It'll for nasty paints as well. If it's recirculating, it might not be so good for spray painting though.

Regards Mark Rand

Forget about the argon angle - it's an inert gas and cannot harm you - unless you try to take it neat for a few minutes...

It's the cost of the argon, not it's toxicity, which is the issue there. Tain't cheap.

Peter Fairbrother

Haven't gotten round to thanking you all for the replies, especially Mark for his extra-comprehensive reply, and I should have.

Thank you all.

I went a bit smaller, but with outside extraction - a six inch duct fan (which is about 18" across, but never mind) does the job ok. I think it's about 150W, but it doesn't have to push air through a filter, and I suspect my working area is considerably smaller than Mark's...

Thanks once again,

Peter Fairbrother