Looking for level transmitter can be worked with high viscous oil

[ahmedhelmy87]

Welcome dears,

I am working at alumina refinery plant and I have had an issue in level transmitter of lubrication tank for 3 years.we have two problems with oil in the tank. first one, Oil viscosity is very high. it looks like grease. the second problem, there is too much foam accumulates on the top of oil surface.

Specification:
tank height is 1.4 m, oil specific gravity is 0.97, tank is atmospheric pressure.

Actions:
During commission, pressure transmitters was installed at the bottom of the tank but it wasn't accurate because pressure head is low. it is about 1300mmwater (13KPA) when tank is fully. so we moved to ultrasound level transmitters, but it is also failed because of foam issue, foam reaches at blocking distance below transducer and started to confuse transmitter then reading is gone or flactuated.

we have recently got some recommendations from Emerson to install GWR 5301, we installed and it was ok for only one week then reading started to go down gradually till reading became zero. when i took sensor out for inspection, i found probe was covered by this oil (grease). once i cleaned and reinstalled again, reading was ok for only a week then problem came again.

i am looking for a stable solution that can be worked with this conditions? Any suggestions?

 

[xnuke]

Mount the tank on load cells and infer the level from the weight. Won't be accurate if the density of the liquid changes significantly, however.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[roydm]

I assume you want to find the level of the oil surface not the foam.
This would be similar to a mining float cell where you could easily have a foot of foam, a common way is to use a bubble tube.
For Ultrasonic a stilling well similar in shape to a funnel with small hole opening at the bottom, this allows the foam to break down, the level inside the funnel is same as liquid.

To break down the foam recycle some oil back to a fine spray nozzle, the spray droplets break the foam bubbles.

 

[danw2]

The pressure transmitter you used was not the correct range, it was not sensitive enough (or wasn't re-ranged to a useable range). Depending on vendor, you might have to go to a DP (connecting the high side, leaving the low side open to atmosphere) but a 0.15 bar range is easily readable to a relatively high degree of accuracy. The correct ranged pressure transmitter would work and the error from foam would be negligible.

A bubbler uses pressure transmitter as well to read the head pressure and a bubbler would work, too, given the properly ranged pressure transmitter. But why consume air when you can get a valid accurate direct reading on clean oil with a correctly ranged pressure transmitter?

A stilling well might or might not reduce the foam (there's all types of foam).

Capacitance will coat like GWR coats.

If it were me, I'd get the right ranged pressure transmitter.

 

[JJPD2]

Bro,

It would be better use a non contact level technology, of course not ultrasound, but what about pulsed radar or FMCW, Rosemount have a 5408 loop power transmitter maybe could be work fine, do you know the oil (grease) DK?

If the grease has high viscosity is recommended not stay in touch with the fluid

Considered use non contact radar, even the radar can work with foam presence.

Regards
JP

 

[georgeverghese]

Agree with @danw2, simplest / reliable solution would be a properly selected PT sitting at the bottom of the tank, and 13kpa static head is plenty to work with. If this viscous oil has a tendency to solidify in the impulse line, consider heat tracing the impulse line.

 

[roydm]

You may in fact find the bubble tube works without air, the fact hat it's foaming indicate there is entrained air or gas, gas bubbles rising to the surface.

Have you considered avoiding the foam, it seems like that is formed from the way the oil is handled?

But I agree with DanW2 a DP cell is the most simple, I would suggest a 3" diaphragm seal close coupled to the tank so the diaphragm is flush to the tank wall

 

[silverlily]

diaphragm seal pressure transmitters can work , the chemical seal flange can work for vicious medium. wish this will help you.

Silver automation Instruments

http://www.silverinstruments.com

 

[berkshire]

Would a magnetic level indicator be a better solution? They work by local switching of the magnetic polarity in the wall of the tank, to an external indicator from a magnetic float inside the tank, or sight glass, there are many different models. here are a few:

http://www.magnetrol.com/en/products/atlas-magnetic-level-indicator

B.E.

You are judged not by what you know, but by what you can do.

 

[hacksaw]

The d/p cell approach will work for 1400 mm levels, but if the oil is really grease like, you may need a tank heater.

By the way, what is the oil weight or viscosity rating? and is the tank vented to atmosphere.

 

[Jason.sprigg]

If the oil is very heavy you may need to upsize your process connection and use come heat trace to get things to move at little better for your dp cell to work well.