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BigJohnT
11-20-2012, 09:34 AM
Anyone used a water tank with a plasma table or edm that uses air to pump the fluid up to the water table?

Do you need to regulate the air pressure?

Do I need a shut off valve for the water or will so much pressure only raise so much fluid?

Any operating hints are welcome.

I've scored a 40 gallon water heater that does not leak and I've made a dip tube for the element hole and pressure tested it to 20 psig and no leaks. I assume I'll need an air inlet valve and an exhaust valve to allow the water to drain back into the tank.

Thanks
John

Jaakko Fagerlund
11-20-2012, 11:46 AM
Regulate the pressure, you only need 0.1 bar to raise water about 1 meter high (10 meters per bar or per 100 KPa).

I would put a shutoff valve on the water line, that way you just shut it off and the water stays in the table. When you let the pressure go from your tank and open the valve, the water flows back to the storage tank.

BigJohnT
11-20-2012, 01:06 PM
Thanks I'll add a regulator. Wow that is only like 1 1/2 pounds of pressure.

Thanks
John

Jaakko Fagerlund
11-20-2012, 03:32 PM
Yeah, most people are surprised of that fact. You can use higher pressure to get more flow, but just test it first with low pressure and if it seems slow, try using double the pressure and so on. But I'd not stress the storage tank unnecessarily with higher pressures

jkilroy
11-20-2012, 04:52 PM
You are going to use an overflow type system right? Where there is an overflow drain in the table that keeps the water level at a preset point? Why use an air pump? Seems inefficient at best, when an elcheapo bilge pump will take care of it easily.

Plain ol Bill
11-20-2012, 06:18 PM
I used my plasma water table for about six hours today so I do know how they work . I use full line pressure to force the water into the table. It takes about 65 seconds to fill to the top of the slats. Keep an eye on it while filling to prevent messes.

oddball racing
11-20-2012, 06:28 PM
Can someone explain to the uninformed, this process of using a water table please?
Does plasma go through water or stop at water. Is the piece submerged or on the surface, Etc, Etc.
What is the purpose cooling cleaner cuts more efficient?

See?, I'm uninformed.:confused:

BigJohnT
11-20-2012, 07:26 PM
Bill, I just used a Schrader valve today and an air chuck and put air in till it flowed good. Worked like a champ. The tank is rated for 100psig or so and I doubt I had over 15 psig on it... I need to level my water table now and make some legs for the tank.

Oddball, the water catches the dust and if your table is so that the water will come to the top of the slats it helps keep thin material cool.

I'm Stoked!
John

kf2qd
11-20-2012, 07:30 PM
A water table uses air to displace the water. The depth of the water is not enough that pressure can be used to control the height of the water. It reqires a large volumn of air. Generally the easiest way to get a large volumn is to supply it at high pressure and let it expand.

The advantages of cutting with the workpiece submerged is that the material does not warp from the heat. Submerged (2-3" of water over the material) also means that there is no flash from the plasma arc.

For lower power plasma the water is brought to the bottom surface of the workpiece. This cools the material and reduces warping (think 16 ga or 11 ga sheet)

In both cases the water also catches the slag and smoke and makes the shop environment a bit cleaner.

It is also possible to oxy/fuel cut under water. Did it completely by accident. Was setting up a new water table and the air lines to the table had a bit of crud. Had to clean the valves after the first "flood". Wound up putting some restictor plates in the lines so there was enough back pressure to make the valves work properly.ator was cutting some parts with oxy/fuel and just left the machine running to the end of the cut. Parts came out just fine. Not a normal practice...

digger_doug
11-21-2012, 08:11 AM
Not a normal practice...

It is a normal practice using oxy/fuel gas.

I did it many times.

When I used to program a large gantry burn machine, and the part was under
1/4" thick and plasma was not used, we would routinely run the water above the plate,
and increase the pre-heat flames to compensate.

ironmonger
11-21-2012, 08:41 AM
If you are going to fabricate the storage tank why not connect the table and the tank with a 3" or 4" hose and use an air cylinder to raise and lower the tank
A 2 inch or larger air cylinder will lift the tank at shop air pressures.
you only need to raise the tank a 18" or so to empty it, your mileage may vary...
This would be immensely faster than the air pressure transfer.
You could use a mechanical method of raising and lowering the tank as well, like a ball screw or a winch system.

paul

BigJohnT
11-21-2012, 09:34 AM
Far too much work and cost to do something like that and that would not be able to fit under the table.

John

macona
11-21-2012, 04:56 PM
If you are going to fabricate the storage tank why not connect the table and the tank with a 3" or 4" hose and use an air cylinder to raise and lower the tank
A 2 inch or larger air cylinder will lift the tank at shop air pressures.
you only need to raise the tank a 18" or so to empty it, your mileage may vary...
This would be immensely faster than the air pressure transfer.
You could use a mechanical method of raising and lowering the tank as well, like a ball screw or a winch system.

paul

Over complicated. Water tables fill really fast. Most of the time people have a 100 gal air tank right next to the table connected by a big 3 way ball valve. One side to the tank, middle to the table, and the other is exhaust. Move lever one way to fill, middle to hold, and the other way to lower.

One issue is you can get hydrogen building up in the tank in the table if you cut aluminum.

BigJohnT
11-21-2012, 05:49 PM
Thanks, I don't cut aluminum. After adding a slightly larger hose from the tank to the table it works like a charm... no more 5 gallon fuel cans full of water to lift.

Thanks
John

BigJohnT
11-21-2012, 05:59 PM
Here is a photo of the almost completed but working water tank.

http://gnipsel.com/shop/plasma/images/plasma-13.jpg

John

Plain ol Bill
11-21-2012, 06:20 PM
Most folks using compressed air plasma units cut with the water below plate level anywhere from 1/4" to 3". Hypertherm does not reccomend submerged cutting with air units (doesn't mean you can't do it). Water tables really help with distortion caused by heat. I cut over 2500 linear inches on a 16 ga. plate yesterday with no visible distortion. LOVE water tables - the inside of my shop is not black!

BigJohnT
11-21-2012, 06:38 PM
the inside of my shop is not black!

That's the main reason I built the water table after learning how nice one is.

John