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dust detection

dust detection

dust detection

(OP)
i need to detect when dust is present in an exhaust stack and was wondering if anyone knows of any probes or sensors that could be used. I have heard of using triboelectric sensors but these are exspensive and seem to be abit ott for what i want. I have tried using a differnetial pressure switch to monitor any change in pressure between clean and dirty side of the filter when we get a ripped filter bag but there wasnt any significant change in pressure so therefore it didnt work, but i am willing to listen to any suggestions.

RE: dust detection

Gooogle up "opacity meters",  They come in sizes for smoke stacks to exhaust pipes for diesel trucks.  Most use a light source that shines through the dust/smoke.

RE: dust detection

A common problem. A great solution is specular reflection,  just like fog horns work, and they need to be accurate.

A light is flashed and if more than X amount of back-scatter is detected by a sensor next to the lamp, then there is fog = run horn.

You can use this same method in a stack.  You set up the light, and a receiver next to it, and then run a permanent purge air into the barrel of the instrument to prevent any contamination of the sensors.

Someone must make this.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: dust detection

There are systems that detect when a standard HVAC filter is dirty and needs changing. These use pressure sensors that measure full-scale pressure difference of only a few inches of mercury. Your exhaust stack system is not quite the same, but when you tried differential pressure, did you try a sensor with a very small full scale range?

RE: dust detection

(OP)
Thanks comokid the filter typically runs at 13millibars obviously this changes between clean and dirty but for the purpose of what i was doing i used a 0 to 15mbar guage and then set the switch to sense if the pressure dropped below 13mbar. There was no cange of pressure shown on this gauge when the bag was split(cut a hole in the bag with a knife) and the switch didnt pick it up either, the switch was a dwyer series 1910 with a dwyer magnehelic gauge. Dont know if you have any ideas why it didnt work but would appreciate any input.

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