bulk material flow measurement


Thread Starter


I am interested in measuring the mass flow in a pneumatic conveying line. Since space is limited invasive methods such as belt weighing etc. is problematic. I am considering a Corriolis type sensor that basically measures torque of a rotating wheel on which the material is dropped. However, this gadget will not tolerate being flushed with the conveying air according to the manufacturer. The second option is gamma ray absorption but if I understand correctly this will only give the density of air/powder mixture?
Any ideas out there?

This is an incredibly difficult measurement. Last I looked, gamma nuclear gauges didn't work well, because of the very low ratio of solids to air... the density change per unit quantity is very low. The Coriolis type sensor is designed for gravity conveyed, not pneumatically conveyed material. Breaking the line and inserting a weighfeeder is the only method I have 100% confidence in.

I'd be interested in hearing other views.

Walt Boyes

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As Walt said... it's a tough one.

You might have a look at triboelectric devices. I have not seen them work well but some people claim good experience with them. The manufactureres may be able to give you some advice depending on the moisture content of the air, solids characteristics and loading. They operate by having an electrode inserted into the
stream and measuring the total charge transfer. There are two transfer mechanisms in play. One is triboelectric. I forget what the other is. Be careful of interference. That electrode is a good aerial. In theory, it should be possible to do some pulse shaping on a signal like that and use a multichannel analyser as used in nuclear instrumenttion to quantify size distribution as well as total particle throughput. I don't know whether anyone has tried that.

Even in liquids there is interaction between particles and electrodes. Slurry particles superimpose pulses on the electrodes of magnetic flowmeters.

Vince Dooley