Cutting underwater with a plasma

[duraflap]

Has anyone any experience cutting underwater with plasma?
Hoping to learn
Dennis

[Torchhead]

Can't be down with conventional plasma torches. You can cut ON Water (with water touching the back of the metal) and it cuts down dramatically on plasma smoke and dust and gives better cuts on stainless (reduced edge discoloration) and less warping on thin material. See the threads on constant level water tanks.

[nzben]

This guy here has a torchmate and cuts underwater don't think he does anything special http://www.l2manufacturing.com/cnc_plasma.html#

[kirkln]

Just fire the torch before submerging is my guess

[jimcolt]

Almost any plasma torch will fire and cut underwater...the question is...how long will the torch last! All of Hypertherm's industrial grade torches use high frequency start, which means there are no moving parts in the torch...and no low voltage switching power inside the torch assembly. These torches are designed for underwater cutting if it is desired.

Most entry level air plasma torches, including all of Hypetherms Powermax torches...use a moving electrode inside the torch that creates a short circuit spark that ionizes the air and starts the arc. If these torches are used constantly in water it is possible that the moving parts inside the torch can become damaged or gunked up from the dirty water...rendering them inoperable. There is also a low voltage cap on safety switch mounted inside the torch mounting tube....this switch is not waterproof...and it likely will fail after repeated soakings. Other manufacturers including Thermal Dynamics, Miller and Lincoln use similar technology in their torches.

Check with the manufacturer for compatibility with underwater cutting! If you are cutting with the water level below the top surface of the plate...you can likely use any torch.

Jim Colt (Hypertherm)

[duraflap]

Thank you all for yor feed back.
I have a new Hypertherm 1000 and made my choice of machine because of the fine cut consumables and the great support here on this site. I'm thinking that I made a good choice.
I'm hoping that I'm able to cut 14 ga #8 Stainless Steel finish with this torch with less dross and blueing than some of the other torches I've used in the past. It appears that under water cutting holds some good possibility for great results.
I've yet to buy a cnc to put under this torch and after looking for some time now think so far the best cnc company (great support which is as important as the machine) and their cnc machine I've found is from Plasmaroute.com . Steve there has given me some remarkable help in solving my questions and has run some serious testing in my behalf. He definatly knows what he is doing with plasma.
Now, hopefully I will get a bit more info from others that have cut this #8 SS and hopfully more a little help with the insights that experience yields.
Still looking for the answers
Dennis

[DSL PWR]

This guy here has a torchmate and cuts underwater don't think he does anything special http://www.l2manufacturing.com/cnc_plasma.html#

If you look at the pic on the front page a little closer you will see the water just covers the plate. The air is blowing the water away from the torch, and isn't cutting under water.

[nzben]

If you look at the picture on the right hand side of the page at the top it looks to me like it's underwater.

The other thing I was wondering is if you're cutting thin sheet at fast rates like over 1000ipm, will the warping still be an issue?

[jimcolt]

Warping is usually eliminated with underwater cutting.

[Tig]

Dennis,
check out Esabs Air Curtain (water muffler) P/N 22018
Go to the ESAB web site and Plug: F-15-189-B into the search window to retrieve the article.
This device mounts onto the business end of the torch and produces a curtain of air. Quote from article.

"The device mounts onto the torch and produces a curtain of air. This allows the plasma arc to operate in a relatively dry zone, even though the torch has been submerged to reduce noise, fume, and are radiation".

I think somthing similar could be rigged up for a Hypertherm torch, but you will need a fairly big compressor as it requires : 80 psi @ 1200cfh
(5.5 bar @ 34 m3h) of clean, dry & oil-free shop air. The air flow could be triggered before the torch is submerged the torch head would never even get wet.
Just a thought,
Tig

[DSL PWR]

Dennis,
check out Esabs Air Curtain (water muffler) P/N 22018
Go to the ESAB web site and Plug: F-15-189-B into the search window to retrieve the article.
This device mounts onto the business end of the torch and produces a curtain of air. Quote from article.
I think somthing similar could be rigged up for a Hypertherm torch, but you will need a fairly big compressor as it requires : 80 psi @ 1200cfh
(5.5 bar @ 34 m3h) of clean, dry & oil-free shop air. The air flow could be triggered before the torch is submerged the torch head would never even get wet.
Just a thought,
Tig

That's 20 cfm! The air comp for that would cost as much as most people have in their tables.

[jimcolt]

The Esab air curtain is designed for Esab's large industrial torches....the PT19xl, the PT600 and the PT15xl style torches. It performs a similar function to Hypertherm's air injected water muffler that was patented back in the 1980's for underwater cutting with a 340 Amp oxygen plasma...the Hypertherm HT400 and HT4001 systems.

I am not aware of any of these devices that have been made to work with smaller air plasma systems....although the thought of using one is interesting. The biggest concern with most air plasma torches is that they have internal moving parts, and small microswitches internal to the torch that could be affected by water.

Jim Colt