Level Meas with foam over liquid?

[FixerMan]

What would be the best method to measure the level in a tank which is:
Acid, strong, various types, varying density, etc.
Foaming present on top
Particulate/solids collecting at bottom

I am thinking Radar or Pressure, am I on the right track?

 

[StormPt]

yep!!

 

[ilan7]

Differential pressure was always the best choice for me.
Radars were expensive and could not stand heat and pressure. Now adays it was changed so it must be good choice.
What about the old Bubler? When every thing eals failed - I'm going back to this system.

 

[xnuke]

On the topic of bubblers...

A bubbler will not work correctly if the liquid is varying in density, as FixerMan indicated at the start of this thread. Bubblers rely on density to be constant in order to eliminate it as a factor from the equation relating fluid height to pressure. You could use a two bubbler system, with the tip of each bubbler at different heights, to eliminate the density effects (if the tank is well-mixed so stratification does not occur). The differential pressure between the two bubblers will be proportional to level. Just remember to keep the bubbler tips out of any sediment collecting at the bottom of the tank and keep both tips covered by liquid at all times. Also, the height difference between the bubbler tips must be large enough to achieve a measurable pressure difference.

xnuke

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[glennpan]

Fixerman,

Your application is a complex one. I would not recommend a pressure based system because of the changing densities.

How large is your tank? Radar sounds like it would be the most bulletproof approach (not that any level technology is completely bulletproof).

If price is an issue, and you can prevent a unit from seeing foam by mounting it in a standpipe, an ultrasonic unit will work. But you have to keep it away from the foam.

Glenn

 

[FixerMan]

The tank is 25 ft diameter.
I found some info on Radar (Vega)that indicates that foam depth over a few inches could be a problem even for radar.
The mixing is done with pumps which cause the foaming.
If a standpipe would work, then why wouldn't a simple site glass? Maybe vent the top of the tube to atmos. rather than to the top of the tank to keep foam from getting in that way.

 

[FixerMan]

I am counting out Pressure due to changing densities.
Has anyone used the Resistance tape sensor from Consilium?

http://www.consiliumus.com

It looks like it would work with a Stillpipe to keep the foam and velocity off of it.

Thanks for all the help so far.

 

[Fritzfrederix]

Fixerman,

I would definitely go for RADAR, please don't try ultrasonic it will not work because you are using aggitators which are producing foam.
Pressure transmitters can't be used because of the density variation.
I've compared several Radar measurements including VEGA. And I have to admit Vega together with miltronics were rejected. The only two which were capable of measuring the product (high viscose additive which crystaliesed) were SAAB (now Rosemount / Saab) and Endress & Hauser.
If you got a lot of foam then I would suggest to use a Stillpipe. The best support and advice I received of the people of E&H. They even defined the diëlectric const.

Good luck

 

[209larry]

FixerMan,

K-tek has new level sensor wire rope radar type which they claim that foam, dirt,etc have no effect on measurement. The rope can be cut on site to suit requirement. The rope can be of stainless steel and other exotic metals.


209larry