A simple and economic solution to plugged chute detection or material over flow indication is the use of a diaphragm switch. This type of configuration has been used in feed, grain and seed processing for years.
How does it work? A housing that contains a microswitch is activated by the depression of a flexible diaphragm. The standard material of construction for the diaphragm is a thin rubber sheet, however, other materials such as very thin stainless steel, fiberglass, and other flexible materials are available per application. When the material contacts the diaphragm, it depresses the microswitch. The microswitch is a dry type contact that can be tied to a light, horn or some other process indicator/control. A spring or counterweight returns the switch to the open position when the material moves away or cleared from the diaphragm.
The unit should be placed where falling material cannot hit it but material that would back up can activate it. Typical applications could be the following:
- On the top of a screw conveyor housing at above the discharge spout.
- In the upper portion of the discharge housing of a belt conveyor, away from the regular flow of material.
- On the top side of a declined chute.
- In a vertical pipe, located in an offset "Y" with a short stub to mount the diaphragm switch. Be sure to allow enough decline in the stub of the "Y" so that material can clear or fall out of the stub. This is best used for very free flowing material.
The material being detected should be very free flowing, not allowing build up to occur on the face of the diaphragm switch. The diaphragm switch can only be used in atmospheric conditions. No air pressure or pneumatic conveying applications.
When looking for a simple and economical over flow indicator or plugged chute detector, please consider a diaphragm switch.
Ross M. Jamison
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