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Hello there people. I'm wondering what the advantages are for having the air bladder design incorporated into the water table? How many inches does the water need to raise or lower? Is it worth the added expense? Are there and videos of someone adjusting water levels or draining/cleaning out table?
Thanks, Bamwa
You drain the table to find little parts that fall in and to clean the slag out... I just have a drain hose and four 5 gallon containers that I store it in.... My water table is 36x52x3 and I put a couple of inches of water in when I cut. Works great for a seldom used table.
John
Thanks for your response. So I am to assume that fishing out small parts is the primary reason for the adjustment of water level? Also, how much green stuff do I need to treat a 6' x 12' x 1' table (most likely filled 2" below the top)? How much clearance do most tables use between water level and top of tank?
Pease out y'allz.
Cleaning is my primary reason as I have a shallow water table. Don't know what "green stuff" is... I use sodium nitrite and another chemical I forget what it is. Do a search on sodium nitrite in this forum and you will find the ratios. I purchased mine on flea bay for very little money.
I found in testing using a oil change pan that anything close did fine and could not tell any difference between 2 and 4 inches.... the closer the more splash back you get.
John
It has nothing to do with cleaning/draining the water tank.Originally Posted by bamwa
It's to keep the water level constant and in contact with the material (but not submerged). Plasma cutting with the material sitting (just) on top of the water (grid is submerged) cuts down on warping, slag and (important if you cut stainless) any heat related discoloring. It requires you have a way to accurately control the water level via some form of feedback (float valve ?). If you don't want to pipe in constant water flow, the bladder approach uses air to displace the water and raise/lower the level. keep the water level constant for tanks where the water is below the back of the material has no function whatsoever.
Having a drain in a shallow water tank is sufficient for tanks below the grid ( where the water level does not touch the metal). It needs to be big enough to let the plasma "gravel" pass. Too small and it clogs instantly. A filter does not help. Fishing out small pieces is best done by feel and by hand unless you just have a lot of spare time or need to look busy for the boss. It can take 20 or 30 minutes to drain, clean and refill a tank.
I often think about having a course grid screen under the water that could be raised to find the dropouts you want, but you have to take the bitter with the sweet. It will also catch all of the dropouts you don't want! Most of the designs I cut are what is left on the top. My grid keeps pieces smaller than about 4" square from falling though. In short there is not much in the tank I care about and it gets scooped out once a week with a modified dustpan I made.
Natural evaporation means you normally have to add water (unless you have the bladder system) and left for a few days my 2" deep tray will dry out enough to let me see the drifts of plasma "sand" that accumulates in the bottom
Thanks torchhead, I am into building the air table and was pressed on the reasons why by a buddy helping me with this build. Thanks. As for the water level under the sheet I thought four inches should be enough but read something stating from Hypertherm to allow 6 or 7 inches under the sheet. I would hate to slice through the air box I am about to carefully build.
Thanks, Bamwa
Your buddy was astute in asking the question. You are spending a lot of time and money to build something you will never use. Keeping the water level constant under the cut (with an air gap between) is fruitless. I don't know if you have cut with plasma before, but unless you are running a HD series torch the reach of the flame is tiny. You can't cut through tin foil 1/2" under a cut. You can't penetrate water. The water is there there to stop the sparks under the cut and douse hot smoking pieces of fallout. It don't matter if it's 2" deep or 3 ft deep. The distance between the back of the material and the top of the water is more a function of the air not causing splash back (harmless). The further it is away the less effective it is. Smoke (vaporized metal) is going to drift UP and deposit itself in every crack and part within 50 ft. It's conductive and abrasive. Even with an inch of gap, 70% of the smoke will curl along the bottom of the sheet and move out though any opening or the edges of the sheet. You will be amazed at the volcanic coating of black "dust" all over your shop and tools.
Sorry I may have confused you. I simply meant if the water is touching the bottom of the sheet, is 4" of water deep enough that's all.
I was trying to figure out if most peoples' tables adjust the water level 2" or 3" or 4" or more. that's all. I guess it depends on how far down small parts may fall, and that would be dependent on design of the table. thanks
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