Pipe float valve

Please provide alittle more data.

1.Under steady state operation how quickly does the water level drop?

2.How close do you need the water level to be controlled?

3.How many gallons of water does your tank hold (minimum-maximum)?

I have worked with alot of water level R&D projects your problem will be easy to solve.

Miketheboilerguy@aol.com

1. The liquid (not water) drains at about 500cc per minute. The liquid is not viscous.

2. I need the liquid to be +/- 0.5" in the middle of a tank that is 5" tall x4" deep x23" wide. Basically, the level does not need to be exact. For the most part I just need to make sure that the liquid does not fill the tank completely or get drained completely.

3. I think that the tank can hold up to 2.5 gallons when completely full.

The gas in the tank is a gaseous form of the fluid. Operating pressure is about 1-6PSI.

We need to use viton or EPDM if we use o-rings anywhere. No teflon, oil, rubber, Buna, PVC, nylon.

Thanks

The idea of putting the sensor in a separate transparent tube is good, it may however be a good idea to separate the contents of tank from the tube by placing a diaphragm at the entry point and use coloured water in the tube. A simple adjustable probe could be used as a switch. Two or more probes placed at different heights will actually improve the reliability.

Excessive variations in the measuring tube must be dampened.

A mercury tilt switch (or similar) attached to a small float may also do.

Another method might be to regulate the height by weight.

If the float system works (except for the bouncing about in the moving liquid) then there is a fairly simple solution to your problem :-

You place a piece of plastic tube (suitable for the liquid concerned) in the tank, open at the top (which must be well above the normal full mark) and closed at the bottom, except for a few small holes to allow the level to change with the fluid in the tank. Start with one small hole, in the side of the tube at the bottom. If the float fluid level does not follow the tank's level fast enough, add a further small hole 180° away from the first. Do not make the original hole larger!!! Any further small holes need to be at 90° to the first two and so on. Keeping the holes small means that you control the rate at which the fluid flows in and out of the tube completely....

Select a tube that is several times wider than your float by the way.

If the liquid is as fluid as you say, I believe that you will find a certain number of holes (maybe only one, depending on the maximum speeds of draining/filling and the viscocity of the fluid concerned)that allows the level of the float in the tube to follow the tank's level, but without the violent movements you describe....

Thius should allow you to use the equipment that you have already without further costs.....

Andy,

Thank for your response. I need to add another piece of information -- the drainage of the tank is not steady at 500cc. It can vary significantly from time to time, though at steady state it will be about 500cc. We tried installing a ball valve in the inlet of the tank and found that eventually the system rose to a level that was too high or drained down to a level that was too low.

We will need a dynamic adjusting system, I believe.

Lex

Hi Micronaut

If you add specs as size of tank and how you force the fluid into it and the pressure we will give you a fine fix.

Just for speculation let me use and example as follow:

1. Assume a vertical tank.
2. Add a 1 1/2 or 2 inch schedule pipe of compatible material (clear if you like) with the same orientation as (parallel to) the existing tank connected to the top and bottom of the primary tank. Done correctly the (clear) pipe will have the same fluid level as the primary tank.
3. Put a float switch with SST or compatible plastic stem and float inside the pipe, through an end cap.
4. The electrical switch will turn the fill valve on and off.

Except for visual assurance the float switches that have a cylindrical float on a central tube would fit your existing tank. They are available with approximately 1" diameter floats and work in a straight line, up and down. You would need to drill and tap a fairly large (2" NPT) entrance in your main tank for a switch.

Tom,

This is interesting as this is similar to the clear pipe solution I was presenting previously... Are the floats you are refering to 1" total width or connect to a 1" pipe? The hieght of my tank is 4" and the liquid is being delivered to the tank via gravity feed -- no pumps at the .5" mark from the bottom of the tank. There is another pipe that is transporting gas that is created by the vaporization of the liquid in the tank to an external source that converts the gas back into liquid, draining it back into the tank.

The problem I am having is not with one tank, really, it is with 2 tanks, vertically stacked. The bottom one tends to fill with liquid faster than the top one. This is why I need a float valve -- to prevent the imbalance of the fluid within the tanks over a period of time.

Some details on your solution would be nice. Thanks.

Would something like a toilet tank flow valve work?? I have see some that are vertically activated. It's made out of plastic, not sure its compatible with your fluid or not.

MidniteFighter

1. Consider a stainless steel float switch.

2. What is the specific gravity of the liquid.

3. What kind of feed thru connection are you planning on for an electrical connection?

4. This float switch will require a slosh guard, either the manufacturer can provide one or you can, either way it will cost something to provide.

Al

1. Consider a stainless steel float switch.

I have not found any, which do you recommend?

2. What is the specific gravity of the liquid.

To be honest with you, I am not sure, but the liquid Density is 1400 kg/m3.

3. What kind of feed thru connection are you planning on for an electrical connection?

We are not planning ot have any electrically connection within the tank.

4. This float switch will require a slosh guard, either the manufacturer can provide one or you can, either way it will cost something to provide.

Can I put the float within an external piping?

Thanks

"The best way to maintain the level in a tank is to get rid of the tank."

The whole purpose of a tank is to allow the level to go up and down, otherwise there is no point in having it. What about a two-pipe system: a supply pipe and a return pipe, with the overflow from the tank going down the return pipe, thereby maintaining the tank level at the height of the weir? Such an arrangement might make the tank a lot smaller.

If the liquid is not water, beware the vapours from it: are they flammable and is there a potentially explosive atmosphere above the liquid surface that might be looking for a free source of ignition from any electrically-operated equipment in the area?

Is there a possibility of asphyxiation from the vapours?

Is there a toxicity issue with the fluid?

I agree with you, a two pipe system would be ideal. Unfortunately, this design calls for us to use a tank due to non-electrical hardware within the tank that is required for our purpose.

The fluid is non-toxic and non-flammable.

Acute Lethal Concentration >30,000 ppmv

8 hr Exposure Guideline 75 ppmv

Skin Irritation Negative1

Mutagenicity Negative1

Ecotoxicity (water solubility < 2.5 ppb)

Very low aquatic toxicity

Acute Oral Toxicity LD50 > 2000 mg/kg1 28-day Inhalation NOAEL=1000 ppm

I would consider inventing your own system. Make a small pcb and use a latching relay and on off switch in series with a N/C hall effect, The hall effect sensor and float containing an HS magnet interact as the float passes next to the sensor causing the latching relay to drop out shutting off the pump. Install a pipe fitting running a 3/4 diameter pipe parallel to the tank in the vertical position.

Well, we are considering using a IR sensor directed at the fluid within an external glass bulb and detecting the level from the results of the sensor. 1. I would prefer to not have an electrical circuit and a solenoid valve and 2. This might not be so easy to set up.

How about weight? Is your setup such that it may be weighed, and, if less than a certain weight, allow fluid to be added?

I am open to the concept of continuously weighing fluid within a pipe or external mini-tank... I am not sure how to go about doing this..

If a pipe is supported by hangers or supports from beneath, the weight of fluid inside, which is a function of fluid level, can be measured with load cells.

If you're having trouble with the concept, think of it as measuring the weight of a 100 lb uniform steel beam with 10 evenly spaced balance scales, each with 10 lbs on them. The sum of forces acting to balance add to 100 lb.

Similarly, if you know the weight of pipe per foot, then you can measure the weight of pipe and fluid, subtract the pipe, and you have the weight of fluid. In practice, it's a little more complicated than that because of dynamics, turbulence, etc., but semi-steady-state conditions may tell you what you want to know.

If you use a vertical reference tube outside of the tank then you could easily place floating ball magnets and a reed switch at the high point to turn off the input and a reed switch at the bottom to turn on the input. Instead of floating ball magnets you could use steel floating balls and magnet reed switches that sense the magnet. Of course the reference tube would be non-magnetic, ie glass or copper. Hope this helps from a repairman and not an engineer.

Install a flow Switch to do the work of a float switch. The sensor will be thin metal 1" strips in 2-3 lengths of 1.5", 2.5", 3.5", 6" to select from.

This will work within the tight space giving on/off with the level.

Look up McDonnell & Miller ITT FS4-3 Flow Switch, or go to Ayvaz/ SMC site and they have a similar model.