advice for on which diesel welding machine

i need to find a diesel powered welding machine as part of a rapid response kit for the salvage company i work for. this machine must be capable of absorbing alot of abuse and potenially/very likely saltwater air and spray. for the most part we end up renting lincoln "severe duty" 400 amp machines. i hate these things, they're loud, heavy and don't put much out as far as being used as a generator. I love my trailblazer but it seems to be too complicated as far as circuitry and control boards, so i'm leaning toward the bobcat series, but the only thing that bothers me is they have the option of running in AC, this is a problem because one of the primary uses of this machine would be for underwater burning-which, if someone were to switch it to AC, could/probably would kill a diver(and if the switch is there inevitibly a diver will switch it (don't ask, if we weren't idiots we wouldn't be divers)). so my question is does anyone know of a durable machine, that's fairly small(under 1,000 lbs)and doesn't come in AC? or can you get a bobcat in DC only or is it possibe to disable the AC feature? and yes it has to be diesel.

I have an older Miller Big D4 400 amp DC only machine powered by Perkins Diesel. Problem is though this machine makes ac and then runs that through a bridge rectifying the DC. SO if that bridge shorts (it happens) you can have AC at the leads. Maybe a DC gen/welder is available but I suspect there would be no AC aux. functions. Aren't most big welders basically this way with AC first then DC on the machine. Have you considered that problem?

If weight is that critical A Miller Big 20 D's are excellent machines,200 amp/100 percent duty cycle 300 amps tops at about 1,250 lbs. full of fuel.
Miller quit making them six years ago,I sure like mine, bought it new in 1982 and still runs like the day it was made.

JL
How did you get a Perkins? maybe an option ? the Big 4D/400 I used in '81-'82 had a German Deutz(sp)air cooled engine,it also had the Miller air pack which was really nice but the machine was seven foot plus in length.

The Trailblazer 300 amp machines are nice as well Smooth running. And I think you can get them in stainless. I know for sure the larger machines are available in stainless.

I have not seen the electronics fail on one of these machines yet.

Just lock out the control in DC with a padlock. Then if you need to switch polarity just swap leads.

Engine brand is a choice on many of the generators. Kohler and Onan on the smaller and Deutz and Perkins on the larger.

i'm thinking you might be right, locking out the switch might be the easiest. i wanted to go with miller after the one time we had a miller big blue out on a job(rented), we ran it out of fuel a few times because no one could hear it running. never mind the fact that a crooked barge owner stole it..(this was shortly after katrina and you wouldn't believe what you could get away with). anyway i think i'll go with a bobcat or trailblazer and rig up a lock, for a multimillion dollar company this would be the closest they would come to being able to do aluminum fabrication, i may be coming off as rambling, but i'm venting, beauracracy sucks.

in response to your question about ac to dc on an engine machine, apparently yes it has been given thought, but not very much, i've been told by supervisors in the past that using AC machines(transformers) was bad because they could go(?) and fry us, so always use an engine driven machine.
i think the perkins was available sometime in the 70's. i almost bought one from a welder i used to work for, it needed a new radiator, the engine ran fine otherwise, it was a 400 amp machine, i think, there was no longer any factory recognizable writing of any kind left on it, unless miller used to paint all their machines in a raggedy three tone blue, white and red primer in no recognizable sequence.

I worked with divers a couple of years ago and they used an modern inverter welder (DC output only) for under water cutting. They were quite happy with it. They used a diesel generator for power.

now that's a very interesting idea. does anyone know the likelihood of an inverter somehow shorting out and sending AC current?

Not likely. The AC is rectified as soon as it enters the machine. Then converted back to AC at several kHz and through the transformer. and rectified again.

You might look at the pipe-pro 304. It is a 26HP Kubota Diesel driven machine that has a XMT-304 inverter built into it. Has 12000 watts aux power 1 or 3 phase. Nice machine. But spendy though... but it gives you Stick, Mig, Liftarc DC Tig, ect...

http://www.millerwelds.com/products/enginedriven/pipepro_304/

A bit off topic, but the divers I mentioned used a 43500psi(3000 bar) waterjet to cut concrete. An abrasive was added to the jet to aid cutting.
They cut up to 85mm. steel and 900mm. reinforced concrete. It was trailer-mounted.
It's an expensive piece of kit and you need time to set it up properly under water but it is a lot safer than a thermal arc.

sand cutting. we've done alot of that, but never with anything hand held. usually its a tool that mounts on the outside or more commonly fits down a caisson or jacket leg and cuts from the inside out. a funny story, one time there was a major lack of communication somehow and while the 50,000$ sand cutting tool was still in the caisson we cut the caisson with a guillotine saw, that tool is now about 8,000 feet down. apparently the powers that be didn't think the caisson was cut so the ordered a guillotine saw out, the best part was the sand cutter had cut it, they just didn't pull hard enough with the crane. yes, underwater burning is dangerous, a good friend of mine is only alive by some form of a miracle after an explosion we had in december, burning on a barge and a pocket of oxygen formed from improper venting, that was scary to say the least.