Water Capture Tank?

[FiveORacing]

I've noticed a few tables with a tank mounted under the table to capture water and then either pump or use pressure to refill the table. I've only had my table a few weeks and probably not close to needing to empty it, but what is the advantage to being able to drain and refill the table with the same water? Wouldn't it be just as easy to replace the water every 3, 6, 8 or ? months with clean water? As far as cleaning, my water tray slides out and I could take it outside and pressure wash it.

While we're on the subject how often DO you guys change the water, and do you just vacumn out the sludge? I'd guess my able holds about 40-50 gallons.

[jimcolt]

The tank, also known as a bladder under the water table is often used so you can raise and lower the water quickly using a simple compressed air displacement circuit.

Why drain and refill? It is easier to clean out the debris with no water, and to find the small parts that dropped. There alos may be cases where you want the water higher (closer to the plate) to control the fumes better, or lower to eliminate splashing (better edge quality with no water).

Pneumatic raise lower water tables have been in heavy use in industrial plasma appplications since about 1970. Almost every large industrial plasma that is equipped with a water table has this capability.

Jim Colt Hyperthem

[FiveORacing]

Thanks Jim. Makes a lot of sense. Does the cooling effect of the water affect the edge quality and dross? I'm pretty new at this and I'm getting an edge of dross on the bottom side that requires a little grinding and sanding to get off, even after chipping most of it off. I've been experimenting with T30 parts this week (PM45) and I'm getting better results on 11 and 16 gauge steel. I'm working toward the day when I have very little work to do after cutting.



Also, I've learned a lot from your posts on various sites, and bought a Hypertherm based largely on the customer rep services you provide. Did you get a PM I sent from this site a few weeks ago?

Joe

[ronsii]

While I don't have a water tray set up on my table yet one of the reasons to add one was I was led to believe I would get better cut quality having the steel right on the water or is this true only if the torch and plasma supply has been designed for cutting over water Anyways like the above post by fiveoracing, I also am interested about the cut quality over water as I have not seen any technical information about this. I will still be making a water table sooner or later if for nothing else just to control the dust, but I may change the design I was thinking about if it is not advantageous(for cut quality) to have the water close or touching the workpiece.

Any information I could find on this subject is greatly appreciated, Thanks, Ron



Ps. i am running a TD cutmaster 81 and usually cutting anything from 14ga. to 5/8 inch mild steel

[jimcolt]

If water is in contact with the cut edge expect a rougher edge than you would get if the plate was completely dry. This is caused by the production of a small amount of hydrogen (released from the water) that will pop and push the arc around slightly....similar effect as having rough motion from your machine. Water in contact with the plate also increases the chance of dross on the bottom of the plate as it cools the molten metal quicker.

Water is great for fume control and warpage control....but for cutting steel has never had a good effect on cut quality regardless of whether the torch was designed for water cutting or not. There are some industrial plasma systems that will show an improvement in cut quality on stainless when a non oxidizing cut and shieled gas is used and the stainless is submerged....this does not apply to carbon steel though!

Jim Colt

[ronsii]

Thank you, Jim for the great explanation on the interaction between water and plasma cutting, it clears up a few things I was wondering about now I have a better idea of how to implement the water table to my setup to make it most effective for the types of material I usually cut.

[tm america]

I recently built me a new plasma table with water table.. i noticed better cut quality but alot more dross?i have been running my water about 3/8-1/2 inch below the plate..What distance have you guys noticed works best to lessen dross and still get the benefits of cooling and dust-smoke collection?I also noticed i have to run a slower cut speed with the water table than i did before without it.Any advise would be a great time saver .. I'd hate to go thru the whole test and learning curve all over again