maintaining liquid level in 500 gallon tank. 1

[ivoryhorseman]

Hi guys,

Could some body help me out with a smart way to maintain fluid level in 500Gallon capacity tank. the fluid will be bled out contimously for various purposes, so the system needs to replenish the the fuel level and ensure the fuel level never reduces.


I was thinking about using a sensor arrangement ,i.e a pressure tansducer attached to the bottom of the tank will give the a value of pressure when the tank is completely filled. this pressure value wil be the reference value. when there is a decrease in pressure, the sensor needs to operate a gate valve to let fuel into the tank and once the pressure has reached the reference value, it needs to shut down the flow my itself.


Can anyone suggest a easier and more reliable technique, cost is a factor.


Cheers.

 

[Latexman]

Is this a totally new design or does all or some of the system exist now? If something exists, a sketch, drawing, P&ID of the existing system would help, especially with the cost part.

Good luck,
Latexman

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[LittleInch]

A really basic system is to install a pump able to supply the total max load and then build a big return pipe at the level you want which returns the excess flow (when flow out isn't max) back to the source tank or supply. This return pipe needs to be sized for max flow in case all the outlets are closed. Veery basic, not efficient, but works and needs no control equipment.

Assuming you can't do that then what you describe is a baisc level control system. Many levle gueages now run on pressure, translating pressure at the bottom of a tank into level using the SG of hte fluid. A simple PLC controller then monitors the level and adjusts an output sisgnal to positiion a control valve, not normally an on/off valve like a gate valve, to maintina the pressure. This is pretty easy, but does need 24V and a bit of wiring.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

Level float attached to pump on and off switch. Look in toilet tank.

Independent events are seldomly independent.

 

[LittleInch]

My toilet doesn't have a power switch in it!

This guy is talking about fuel - he won't use an EXD switch = BOOM. As usual nowhere near enough info to make a decent fist of it (is it pumped flow?, is it gravity?, is there power,.....)

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[chicopee]

But you can have the toilet float mechanism connected to an listed electrical switch which in turn can turn on and off a filling valve.

 

[LittleInch]

Forget the electric switch, just plumb in a ball cock. The op doesn't say anything about turning a pump on and off just opening a valve.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

Simplest solution is always best. Look for it.

Independent events are seldomly independent.

 

[ivoryhorseman]

Little Inch,
to provide you with some more information:

The application is used for a jet pump performance test. We have a jet pump placed in a pressurisd tank which is provided with a motive flow. The motive flow is provided from a different tank. since it is a performance test we use different temperatures and pressure for the fluid which is supplied, also the tank needs to be pressurized for various performance conditions. the tank which the jet pump is sitting on is the one which needs the fuel level to be maintained.

the fluid used for the test is Jet-A

Also,

"translating pressure at the bottom of a tank into level using the SG of the fluid" frm ur previous post. Instead of this, can we use use a twin pressure tannsducer arrangerement in the pressurised tank and maintain the height of the fuel using the formulae h=(P2-P1)/(density * gravity). once a reference value of h is obtained , programme a PLC to maintain the height of fuel using a valve arrangement. does this setup bring any joy to you.

 

[Latexman]

"the tank which the jet pump is sitting on (on or in?) is the one which needs the fuel level to be maintained."

Good luck,
Latexman

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[LittleInch]

After reading this about 5 times I think I finally understand you, but not fully sure. Look at the attached to see if I've got your description right and then next time you post, please include a diagream lke this.... It took me all of 5 minutes.

In this instance what you really need is a differential pressure transmitter (DPT) with one end open above the max liquid level and one end at the base of the tank. Then with the SG programmed in, the transmitter will give you liquid level regardless of the pressure in the tank (P tank) as this presusre will act on both ot the DPT, essentially as you note with P1 and P2, just this is in one transmitter.

What you do with that level signal is then plug it into a PLC which has a PID loop in it which oututs a position of a variable control valve. To translate that position signal into actual valve posiiton you need some sort of motive power, commonly air via a E/P convertor and an air driven position switch. Very common in the petrochem industry. Or the PLC can open / close a solenoid valve, but variable control valves are much smoother... you can get electric control valves as well.

did I guess it right?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[marty007]

I agree with LittleInch, but you'll have to be careful about how you run the lines. The way it's drawn in his sketch opens you up to the possibility of condensation in the vent-space line giving you bad readings.

I've plumbed a level control arrangement like this in the past, but added heat tracing to the vent-space line to ensure no liquid build-up could occur. That was a different fluid, and may not be an option for you depending on flammability limits etc...

 

[LittleInch]

I didn't draw it out fully - you would need a drain on the top line before the DPT to drain off any condensation, but as there is no flow, this is normally quite small. Trace heating inst lines would also prevent it.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Latexman]

Let's wait on the OP to confirm, or post his sketch before we analyze it. My mental image was not close to LI's sketch.

Good luck,
Latexman

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[darai]

Could some body help me out with a smart way to maintain fluid level in 500Gallon capacity tank. the fluid will be bled out contimously for various purposes, so the system needs to replenish the the fuel level and ensure the fuel level never reduces.

how will you know to replenish the fuel if the level never reduces?

 

[msquared48]

My toilet tank does not have a "power switch", but does have a mechanical on-off valve that operates depending on the level of the float. The same mechanism is used on farms to keep livestock watering pens filled from evaporation and use. It's been around for many years.

Mike McCann
MMC Engineering