Mud Level inside a Thickener

I'm looking for an Instrument of some sort that can show me the Mud Level inside a Thickener. I 'm using a Turbidity Transmitter to give me the clarity of the water but I need more. I'm in the Gold Mining Industry

I worked in mining for a lot of years, most of the thickeners had a float device. A SS ball about 6" diameter sliding on a length of SS tube. A magnet inside the float activated a series of reed switches inside the tube. I think it was in about 5% steps.

The ball is filled with sand or water until it just sinks in water (floats on mud).
If you put a flange mounted transmitter on the bottom cone zeroed on water it will tell you the percentage of mud to water but not the actual level This can be quite useful.

I have also been told (haven't tried it) that a regular ultrasonic transmitter dipped in the water will work. The speed of sound is much higher in water than air.

Hope this helps
Roy

I've used the ultrasonic thingys, from several different manufacturers, and they seem to work okay until there's an upset, or the rag layer rises. The big problem with the ultrasonics (and I think somebody makes one that is optical, or infrared) is that they have to be picked up when the traveling bridge of the clarifier goes around. This is a mechanical device kludge, and
is prone to failure.

I've also used a Sludge Judge(tm) which is a long clear plastic pipe with a cap and a release on one end. This is "calibrated" by having rule lines painted on it. You can buy them or you can make them.

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Walt,

I share your lack of faith in ultrasonics especially if the interface layer is not well defined.

I searched the web without success trying to find the float type I described, they were very reliable but would not of course measure below the upper rake level. I came across a device from Endress&Hauser that winches down a displacer between rake passings. This is an idea I have seen built on site from time to time.

I am not convinced that bed level is that important provided the overflow is clear. I have had some success in getting operators to use the DP cell as a measure of total mud along with underflow density and flocculent ratioed to feed rate.

Roy

Mate,

Would you know who makes the SS ball devices to accurately measure mud levels?

Rgds,
Kaz

Kaz,

Yay, I finally found it!
http://apitechs.net/pitProbe.aspx#gemProbeSensor

This shows a picture of one for oilfield application.

http://www.gemssensors.com/Content.aspx?id=2842

Shows you the 8" SS ball float.

I'm not sure if Gems know that it's used for interface. I suspect the thickener manufacturers just modified the ball by adding a 1/8" NPT plug. Just add water until it sinks.

Good Luck,
Roy

Kaz,
Drop me an e-mail and I will send some thoughts on thickener roy_matson @ yahoo.ca

Roy

You could try the SmartDiver.

I would like to know, what do you want to measure... Level or % turbidity? if you want to level the "column of mud" at the bottom if thickener, a cheap application it is using a pressure transmitter installed on the bottom of thickener with this you will can know in reference with the density what is the column that you have inside of thickener. usually this can of measure it used to add flocculants in function of mud quantity. Other application it is using a ORCA ultrasonic transmitter from HAWK level measurements. this instrument it is specially designed to use in "bi phase solutions" as thickeners. i hope that tips will be helpful for you.

Eduardo

Ball floats are ok for water or when they are topped up in the supernatant liquor of the thickener, but if the liquor density increases in winter, or with the upstream process changes, like extra acid or dissolved metals, then the ball may float right up to the surface of the supernate.

Dirt settling on the ball may make it dishonest. A steep SS cone, with flat bottom and calibration plug, may be more honest. floats won't work in variable liquor SGs.

> Shows you the 8" SS ball float.
>
> I'm not sure if Gems know that it's used for interface. I suspect
> the thickener manufacturers just modified the ball by adding a 1/8"
> NPT plug. Just add water until it sinks.

Regards,
Alister.