Grease sensors

i was curious on what people would suggest on a sensor to detect grease in a line,,heres the situation,,

lots of water and grease is being drained from cookers into a seperator,,grease floats to the top,,water stays on the bottom,,drain the water to til hits grease,,then turn off pump,,(dont want to get grease in the city sewers)

so,,since they are serious about not getting grease in the sewers,,it is a manned operation,,meaning ever 2 hrs or so someone has to start the drain process(1.25 hrs),,and watch through illuminated site glass for grease,,then shut down,,

my thinking is it should be automated,,and they dont seem to want to take the chance of draining a whole silo of grease in to the city sewers so keep it manned,,i think it can be done safely so that a maintained system should save money in the long run(man hours spent babysitting the dump process),,

so my first item is to detect when the water is done and grease is starting to flow,,first thing i notice is the sight glass goes almost black when the grease flows where as with the water its fairly transparent,,so i was thinking of an optical sensor,,,maybe two and a back up way of detecting grease,,to ensure its failsafe(as failsafe as it can be for me to sell the idea to my boss,,he comes here so i hope he isnt reading this,,)

does anybody have any suggestions??ive thought about viscosity,,will any prox's do the trick? what yall think?

Fred Raud

I would try to measure conductivity in combination with transparency in different vawelengthes (through-beams in red, green and infrared).
Another suggestion- fill an intermediate tank of known volume, weigh it with a loadcell and judge the contents by density, drain if allowed and repeat the cycle.

Sergei Troizky said:

I would try to measure conductivity in combination with transparency in different vawelengthes (through-beams in red, green and infrared).
Another suggestion- fill an intermediate tank of known volume, weigh it with a loadcell and judge the contents by density, drain if allowed and repeat the cycle.

Click to expand...

Keyence do some very good and reliable RGB colour sensors.

http://www.keyence.co.uk/products/sensors/rgb/rgb.php?id=0d3eae256e31dca09541648323613988

Have a look round here, plenty of good info.

http://www.keyence.co.uk/services/trial.php?done=/products/sensors/rgb/rgb.php

You can also get free sensors for a trial:

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If you can get the color sensors to work, they should do the trick. My guess though is that a simple capacative sensor would work as well-- it would just be looking for a chnage in density. I have found though that unless the sensor is very close (1-2mm range) you can rule them out for small changes like yours.

Maybe a combination of 2 types of sensor would give you that extra safety you are looking for...

Hello!

We have a lot of those sensors for measuring oil in water in Finland. I will check the manufactures and write some more..

The problem of using anything that touches the grease is that once the probes are covered with grease , they will require cleaning before they work again .
When you say grease , are you talking about solidified animal or veg fat , or a lighter cooking oil , as a byproduct of perhaps a fryer ? - what do they do with the stuff that is in the tank , does it have to be manually skimmed , or can it be drained of as a liquid ?

http://www.wavin-labko.fi/en/276
http://www.wavin-labko.fi/en/273/354

here is some information

Place a hollow steel float ball or tube, in the tube so it floats on the water and sinks in the lighter/less dense grease. You can then detect the float ball with a prox switch.

The float could even be just a short peice of brakeline tubing brazed shut at each end. Adjusting the specific gravity of the tube would be a matter of adding weight till it floats on the water but sinks in the grease.

To expand on Mike's post, use a float in the level sight glass, but also a second ball can be used as a physical drain shut off -- if the ball will float between the water and the grease, and you use a tank with a conical bottom, the ball will seat over the drain when the last of the water has been removed, providing a backup method to keep grease out of the drain.

the problem i have with any type of float system,is the water is being pumped out at a pretty high flow,,and ive thought of arrange ments to put sensors or some type of a float in the silos',,but all so far are impractical,,it would have to be something in the 3 inch pipe ,,

the oil comes from cooking ground beef,,ive thought of conductivity,,and thought about the oil being staying on the sensor,,but it would be quickly washed away being after we hit grease,,pump is shut down,,and a valve is opened to run water through to clear the pipes and prevent solidification,,then we blow air through the pipes,,

im going to look into some of the sensors mentioned earlier,,thanks so far for the advice,,

Fred Raud

ps,,elevmike,,how ya been?

I misunderstood. I thought you had a site tube.

So here's what you do:

Get one of these float switches here: http://www.omega.com/ppt/pptsc.asp?ref=LVK40_50&Nav=grek13

It's all stainless construction & hermetically sealed. There's a reed switch in the tube and a magnet in the ball. You can remove the ball and invert it for a NO or NC contact. To invert the ball there's a C-clip retainer on the bottom of the tube.

You adjust the specific gravity of the ball by adding weight to the ball so the ball sinks in the grease and floats on the water. The weight migh be a 1/2" washer placed on top of the ball. If the washer makes it sink in the water just grind some material from the washer till it's the proper weight.

Place the entire unit in the tank at the "low water shutoff" mark. So when the water is high the ball will activate the pump or valve etc. You might need two, (each placed at a different level) to provide some type of differential so the pump isnt constantly starting and stopping.

the problem with that is its not in a tank,,its in a 20 foot high silo,,and our only means of seeing when we are down to pumping grease is through a sight glass in the pipe that leads to the 'pits'

ill include a diagram later to make it a little clearer

Fred Raud

Fred,

Why wouldnt you be able to install the float switchs in the silo? In this manner you would never chance dumping grease, but would always have some water in the bottom of the silo. After the water level is down you could then pump the grease from just above the water level. It would require a little re-configuration but the process would be operator-less and error free.

well,,,,cause it wouldnt let me use one of those nifty color sensors!!!lol,,

i did some more thinking about it after i read your post elevmike,,and a specific gravity float could do it,,but im unsure how it could be mounted,,im going to do some googling on those types of floats right now,,

Fred Raud

Fred, you could just hang it on two sticks of ridgid pipe. (20' silo right?) Actually you would need 4 float switches. (two to start and stop the pump for the water, and two for pumping the grease.) The reason for two each is to provide for a differential between starting and stopping the pump.

On second thought you could use an ultrasonic sensor for detecting the top of the grease. Once the water level is low (water is still sensed by floats), the ultrasonic sensor (Mounted at the very top of the silo) could tell you exactly how much grease is on top of the water.

So it goes like this, when your high water float goes on you turn on the water discharge untill your low water float goes off. After the water is at the low point then you know the level of the bottom of the grease.The discharge for the grease would be mouned just above the "low water" float switch. Now you can discharge the grease till the top of the grease reaches a point just above the grease discharge.

Then you buy the operator a broom, dustpan & Mad Magazine to keep him occupied while the entire process is running all by it's self.