Level in Transformer tank

[KnicksJets]

We have a 27,900 gallons capacity transformer tank, with two small elliptical conservator tanks on top. The conservator tank has an air bladder inside and is filled with transformer oil (except for the air bladder).
We want to know the exact oil level on the transformer without going to the top of the tank as this is a 345 kv tank and you don't want to be close to the top of the tank.
We thought of thermography, but the image wasn't helpful (it doesn't seperate between the hot oil and tank). We are thinking of taking the pressure reading of the oil from the vent valve at the bottom of the tank. We will then apply l=p/r where l=level, p=pressure reading and r=density of the oil.

What do you think? Do you see any problem with this method? Do you suggest any other way to measure the oil level on the tank (possibly in the eliptical conservator tank)? Is there a better infrared imager available? any other technology?

 

[BigInch]

you might get a level that includes the effects of any hot pressured air in the bladder.

http://virtualpipeline.spaces.msn.com

 

[GregLamberson]

A couple of clarifications - what is the tolerance of your required volume of oil (you said exact, but is that +/- 1 cu ft or .05 cu in) and at what frequency do you need the readings?

I assume as the liquid level builds up in the tank, the air bladdetr above the liquid is compressed to pre-determined pressure. When this pressure is reached, a pressure sensor activates a motor switch which turns off a pump.

If that is a correct assumption, then you can calculate the volume of the bladder based on the pressure on the gauge, you know the tank volume, the difference would be the oil volume.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[KnicksJets]

Thank you for the answers.
There is no pressure gauge in the tank.
I guess my question now is, if there is any way of finding the oil level in the eliptical tank. The tank wall is 1" alumunium. Thermography didn't show a good signature. Any other ideas without going to the top of the tank or even touching it?

 

[BigInch]

ultrasonics

http://virtualpipeline.spaces.msn.com

 

[BigInch]

ultrasonics?

http://virtualpipeline.spaces.msn.com

 

[unclesyd]

Backscatter scanning would be the way to go. We used a hand held device routinely to set/check level controllers.

Here is just on of sevral companies that does this kind of work. There should be someone nearby that has a hand held device that you could have them use. It shouldn't take more than 10 minutes. I don't think there will be any license problem though these instruments are registered due to the radioactive source contained in the hand held instrument.

http://www.towerscan.com/level_measurement.htm

 

[BigInch]

Very nice! I didn't know about that kind of handheld backscatter.

http://virtualpipeline.spaces.msn.com

 

[rzrbk]

Air bladders at the top would indicate that this tank is supposed to be run liquid full with no vapor space, and the bladders would allow for thermal expansion.

Are you looking for an accurate level indication, or an alarm to tell you if the tank is not full?