Air Bladder Question

[Normsthename]

I currently have a simple 4" deep water table for my plasma cutter, and it works well but the water capacity is too small and gets contaminated very quickly.
So I want to make Version 2

I would like to make a separate air/water tank and use compressed air to force the water upto the table like I have seen others
A few questions :-

1) If I had the water outlet to the water table in the bottom of the air/water tank, and the Compressed air inlet and vent in the top of the air/water tank, what air pressure would I need to move the water upto the table?
I am thinking that if you go above atmospheric pressure (1 Bar) it would move the water???
I want to make the air/water tank from sheet metal, so I need to know the pressures involved.

2) What is the best method to stop the segiment getting into the Air Tank?

I could stick the water pipe 1/2" above the bottom of the tank, but I would like to be able to completely drain the water table.

Thanks in advance

Andy

[Fiero Addiction]

To keep sediment out of the tank, someone suggested to me to put a sump in the table, with a stand pipe in the middle of the sump. That would trap most of the heavy sediment and still allow you to drain the water all the way down. I think if you put it in an area where you do the least amount of cutting, it should also help keep sediment out. I just welded mine in today, will give it a try tomorrow. I have about a 6" diameter sump with 2" drain pipe going to an 80 gallon air tank. I tried to calculate the air pressure required to lift the water, but I couldn't figure it out. I was told it should be regulated to just a few psi.

[Normsthename]

Thanks for the info Fiero Addiction
A sump sounds like a good idea.
My current table has about 12" one end that the machine cannot reach (I have it this long so I can fit standard width 4' sheets onto it)
It also overhangs the machine bed by about 6" so I could add the sump into this area
I am thinking about building a 1° slope into the bottom of the tank, which works out to about a 1" approx. at its highest point.
Hopefully this will allow all the water to drain out.
My current table, when it is drained out leaves 'islands' and puddles of water.
I also want to design the table so that the slats are mounted into a rack so that I can remove sections of slats easily to retreive small parts etc.

I tried to calculate the air pressure required to lift the water, but I couldn't figure it out. I was told it should be regulated to just a few psi.

I will have to look out for a pressure relief valve of some kind....
My air tank will be made from mild steel sheet, so I need to be careful I don't put too much air pressure into it........

I just welded mine in today, will give it a try tomorrow.

Good luck with the water table, I will be very interested to hear how it performs and how much air pressure you need to use it

Thanks

Andy

[jcc3inc]

Sir,

If you have water at a depth of 12", the pressure is .434 PSI; 24" depth ->.868 PSI. We used to make water tables and used a large manually operated ball valve located near the top of the air chamber to release the pressure. Using shop air to raise the watre level is quite straightforward.

Regards,
Jack C.

[chester1957]

It takes less pressure than you would think, at a past employer, when our lead maintenance man put the air to their first 10' x 20' water table, he was hit with a mini tidal wave about 8" deep. Laughed my a** off.

[Normsthename]

Thanks for the input

If you have water at a depth of 12", the pressure is .434 PSI; 24" depth ->.868 PSI. We used to make water tables and used a large manually operated ball valve located near the top of the air chamber to release the pressure. Using shop air to raise the watre level is quite straightforward.

So the pressures involved are very low, what is the best method to regulate shop air down to such low pressures???
My Shop air is set to 100 psi approx.
I suppose that an air pressure relief valve would be a good idea, any ideas what line of business would stock such low pressure valves?

Andy

[chester1957]

As long as your air valve does not leak, you don't worry about pressure, it's volume and how fast you apply it. Applying large volume @ 100psi will fill the table faster than a small volume at 100psi. Don't open too big a valve too fast and your good to go. When the table has the correct water level, you shut the air off to it and the valve hold the pressure, bleed off the air and the table drops.

[Fiero Addiction]

I just filled mine with water today and I've very pleased with the way it works. I would have liked to make the sump deeper, and it should possibly be larger diameter as well, but it seems like it will prevent most of the sediment from going down the hole. The 2" drain pipe is about level with the bottom of the table, and goes down to the bottom of the air tank. I used a 1/2" ball valve for the air inlet, and a 1" ball valve for the air outlet. It takes about 60 seconds to completely drain, and about the same time to fill the 60 x 60 x 4" table. If I'm not careful with the inlet valve I could have water dripping from the ceiling! I was going to regulate the pressure down, but I think I'll make a deflector on top of the drain pipe, sort of like a miniature stove pipe cap. I experimented with a piece of sheet metal setting over it, and I can fill a lot faster without splashing or making waves.

[Normsthename]

Nice job Fiero Addiction!
I am planning on making my sump the full width of my water table (30") and approx. 4" x 3" deep, I will then place the Water Pipe towards the back in the centre of the tank.
Do you think that this will work O.K?

Just looking at your table, is the water level almost level with the box section?
Do you not get water splashing over the edges when cutting near to the edge?
I had to make some water deflectors for my water table approx. 3" high above the water level to stop the water coming over the edges

I think I will adopt your 'miniature stove pipe cap' for my water pipe

Thanks

Andy

[Fiero Addiction]

Andy, it sounds like that full length sump will work great. I wish I had thought of it for mine, but it's too late now.
The top of my slats are about 1/2" below the top edge of the table. I haven't cut over the water yet, but I'm sure I'll need something to keep the water from going over the edge. Ideally it would be easily removeable to make loading the table easier. I purposely designed the table with low sides so it would be easy to load. I don't want to give that up.

Jon

[NEATman]

This may be a bit too crazy sounding, but what it you added a float valve (like a toilet tank) to automatically turn off the air pressure when the water reached the proper level on the table? It could be as sinple as a valve, but if you modified a air pressure regulator to add an arm and a float, it would automatically fill the table and slowly turn itself off when the water was at the proper level. I've seen a few air pressure regulators used to automatically level optics tables and they have been modified with an arm to actuate the diaphragm in the regulator.
http://www.techmfg.com/products/adva...axdamp_lg.html
http://www.techmfg.com/products/advanced/maxdamp.htm

Also, what about throwing in a few old magnets into the sump to help trap some of the magnetic slag? Perhaps a huge old ring magnet from a large subwoofer right around the drain sump? Or alternately, if most of the slag leftover is magnetic, you could put a PVC sink style sump (see pic) with magnets attached to the outside to catch the contaminants as they drain back to the tank, and the trap may catch the non-magnetic ones.

NEATman

[Normsthename]

Neatman
A ring magnet sounds like a good idea
You could fit it below the water level around the water outlet pipe.
It would hopefully trap most of the fine dust
Only problem (for me!) is that I cut Stainless Steel 99% of the time, so I need to come up with another idea

Andy