[weldin mike 27]

Hi everyone,

Time for me to weigh in,

Plasma cutting under water is a automated process, and the water is used to control the fumes. Maybe also controls the distortion but that may be secondary. We used to have a large system at work, that was 2 x "beds" that were, maybe 5 meters x 10 meters, give or take. The cutting head had a plasma and oa cutter. For plasma the water level was brought about 1" over the plate, and for oa it was left level with the underneath of the plate. Nitrogen and comp air were used in varying combinations depending on the material, ie mild, ss or alum.

http://www.youtube.com/watch?v=zN-YujXhHKY

Mick

[Jason_alex]

Dude - if you read about cutting underwater with either gas either I missed the memo or you've been smoking some really good stuff ! the only cutting process typically used underwater is oxy-arc or thermic lanse - I've used both - but trust me it's not neat or done to anything your going to weld ! - maybe I mis-read this post - stainless can be cut with water jet ( well suspended micro abrasive ) very cleanly & can be welded without any clean up - maybe we are talking at cross purposes ?

Sorry my chart I have here is calling for nitrogen plasma and co2 secondary. Above water or Ar/H2 plasma with N2 secondary. This information is in Thermal Dynamics Pak 15XC Merllin book.

I know you can cut SS under water and I can not find the articular right now about minimizing oxidation on the edge cutting under water.

[noddybrian]

Interesting video - I have to admit I'd never heard of submerged plasma - I've seen a water table that kept the underside of plate wet - but the top was dry where the cutting head is & I'd seen true submerged oxy / fuel cutting ( I believe JCB 's main profiling facility used this ) which was done to provide better tolerance by reducing thermal movement & preventing any dross adhering to the cut pieces so that no grinding or other clean up was needed - just proves how little I know - & how tech stuff sneaks up on you ! - never too late to learn things - but I doubt many of us will get to see this cool stuff first hand.

[Jason_alex]

The reason that the industrial plasmas can do this is because they use high frequency and there are no moving parts inside the head (It is not recommend for a normal plasma). Where most of the cutmaster and power max units have starter cartridges and moving parts, the benefit to the industry is that it will not smoke with the exception of a little bubbling and it knocks down the glare under 2 to 4" of water. It knocks down the noise it makes by quite a bit.

OOOO Yea and as always don't cut aluminum this way!!!

Thanks,
Jason