Hi,

Which is the suitable sensor type to detect the level of hot edible oil in 15 meters height tank..?
Can I use ultrasonic or radar type...?

 

How hot?

 

Ultrasonic will probably not work reliably because of the presence of volatile vapor in the tank. The oil is hot, so there will be vapor. Radar is possible. It depends on the dielectric constant of the oil. If it is too low, it will be transparent to the radar beam. I would try both types of non-contacting radar if it were me...FMCW and pulse. You also may need to compensate for temperature if you are attempting an inventory management system.

Best,
Walt

Walt Boyes
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Control and ControlGlobal.com
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Is there a pressure tap at, or near the bottom of the tank to install a pressure transducer for level measurement?

Temperature concerns can be addressed by adjusting the length of tubing between the sensor and the pressure tap to allow for cooling of the liquid.

 

I agree that ultrasonic would not be a good choice with hot vapours present. Radar could be OK. Other possibilities are hydrostatic pressure measurement and capacitance/RF admittance type probes. If there’s a handy flanged nozzle near the tank bottom (say 2" or larger) an extended diaphragm gauge pressure transmitter could be installed with the diaphragm flush with the inner surface of the tank wall - this would avoid problems with the oil solidifying in impulse lines but can be a maintenance hassle, as the tank needs to be drained to remove/replace the transmitter. Also, density/temperature correction might be needed if you require a fairly exact measurement, rather than just an approximate (+/-5%) level A capacitance/admittance 'rope' type probe from the tank top might also be suitable but as David says "how hot?" matters. Ian.

 

Why not put a valve between the tank and pressure transmitter? Then you can replace it with the tank full (except initial installation).

 

> Why not put a valve between the tank and pressure transmitter? Then you can replace it with the tank full (except initial installation). <

My thinking in suggesting a flush-mount diaphragm transmitter was that this edible oil may be stored hot because it solidifies or 'gels' at ambient temps. If this were the case, it could well do so in the impulse line from the tapping point on the tank (with or without isolation valve) to the transmitter body. (Yes, the impulse line could be lagged and heated but that's more expense, complication and maintenance). Beside, good quality transmitters rarely fail these days, so the chances of having to drain the tank for transmitter replacement would be low.

All that said, a top-mounted radar or capacitance/admittance probe avoids all these potential problems and gives a 'true' liquid level, rather than one 'implied' by density and/or temperature assumptions (or 'typical values').

Ian

 

The Portable Level Indicator sold by Class Instrumentation should do the trick with no problem.

http://www.classltd.com/liquidlevelindicator.html

 

In such situation , we normally put 3 flush diaphragm type transmitters.

Middle of the tank [ 3 mtrs approx ]
Top of the Tank

Bottom & Middle transmitter can be used for density measurement & can be used for Level correction for Bottom & Top transmitter, dp
correction for level.

Size of Diaphragm , normally used for oil Industry
for 15 mtr height is about 4 " , due to viscosity
issue

Regards

Jariwala

 

guided wave radar would do this application. all you need is an open port at the top of the tank to install it in. 15m is quite long, so i would recommend the flexible type. Manufacturers for this type of instrument would include Rosemount, Ohmart-Vega (I recommend those two first), then Magnetrol, Krohne, Siemens, E&H. This is an easy application for Guided Wave Radar. Thru air radar may work fine too - talk to your local sales person that you trust.

 

Why even bother trying to use all these non invasive sensors. All you need to do is use bolt on strain guages. The next time you have the tank empty drill a couple of tiny holes like 1/4" and put one on each leg, you will have to consult with a company that specializes in things like this such as Kistler-Morse in Spartanburg, SC to know exactly how to bolt them. (I do not work for KM I just have used their products in the past and had great success) Once you get this done, you can either use a load cell indicator or a PLC"s millivolt input module and use whatever amount of channels you need. You will have to average the channels together to get your composite weight when it is full but once you do that then you are off to the races and you don't even have to cut any pipes.