I'm looking for feedback on level measurement instrumentation for use with a highly aerated slurry application, with potential lots of froth / bubbling. I'm considering the normal ultrasonic or radar but can anyone give me some independant feedback, rather than the vendor sales patter.

I am concerned that the bubbling / frothing will lead to falsely high readings. Should I be considering guided radar application?

 

Do you have di-electric contants, or can you tell us what the material is?

I don't think Ultrasonic or Radar will work. Guided radar may work, depending on temperatures and di-electric constants of the liquid versus the foam buildup on the guide. I would try the guided radar first. You can always have the vendor guarantee the device for 60-90 days if they say it will work. We've had good luck with Magnetrol Ellipse and some with Endress&Hauser. Stay away from Saab and Emerson.

 

Thanks for the response. I don't have di-electic constants. Its a minerals slurry that also contains resin. There will be a lot of aeration. Its a bit like flotation cells, but just more highly aerated.

 

Try E&H Micropilot Microwave level transmitters.

 

The frothing and wave will usually give false readings with radar. Capacitance will vary with temperature and require reprogramming if buildup forms on the stem.

Depending on the depth, for economic reasons, you could use a continuous 4-20 or float type point level switch supplied with a slosh shield.

Almeg would rather sell you radar but the above may be the best. Check out http://www.almegcontrols.com

Here is a deep well probe to give you a small-scale idea. http://www.almegcontrols.com/Deep_Well_Probe.htm

Thanks
Bob Hogg

 

Depending on how large your vessel is the best level measurement may be level by weight using load cell technology such as from BLH, Gloabl Weighing, Mettler,etc.
They can provide you w/ load cells on the mountings of the tanks and summing junctions w/ the tranmitters you should be all set.
The vibrations and subsequent froth,etc. will not effect the units reading.

 

Steve,

You can use some types of ultrasonic level measurement as long as they have the power and narrow beam angle. If the foam is thick, ultrasonics will not work and you may need a pressure based level transmitter. See http://www.MJK.com for more info.

Bob Langie
MJK North America, Inc.
877-MJK-LINK
Fax: 312-283-5005
P.O. Box 1183
Deerfield IL 60015
www.mjk.com

 

If there is no agitator, I'd look into a stilling well with either a float or guided wave radar.

 

We ran into all of the problems and limitations cited in the various responses trying to get an analog reading in waste water tanks. In the end we opted for the "good old" float. Certainly not analog... but very reliable. A couple of them give us the critical level indications that we "really" need. They are also available in different weights to allow for different liquid specific gravities.

 

Foam is trouble for most of the suggested instruments... have a vendor do a trial... you could also use a good ol' pressure xmtr. It may be your best bet, it won't care about the level of the foam unless it creates sufficient weight etc, but I doubt it. As long as your SG is stable, you should be good to go.

BR,
Roley

 

Hi

I had used Radar type level transmitter for Hydrocarbon oxidation with Air. The height of Reactor was 11 mt & air was sparged from bottom. This application involved lot of foaming extra air hydrocarbon entraintment. This was carried out at 10.0 Kg pressure. We have used Radar type
level transmitter for this for monitoring & control of reactor level.

We had to carry out experiments for 15 days for logical accuracy of control 1%. This was carried out in 1994 & this Radar is still working well in 2004.

We had other options also but opted for better option, keeping in mind 15 days of experiments at the time of procurement of Radar transmitter.

We did get predictable results.

Jari
[email protected]

 

We used both a stilling well and sonic probe works well but needs a water spray to break down the froth buildup in the well... signal has a lot of noise... Use of a ball and float works best.

 

Why don't you try load cells? Non - intrusive. We can advise you of system solution.

 

Which application and industry is this in? Any location or end-user details?

I think contact radar should be tried on foaming applications but with some care.