When at the buffet of level indicators, Mix-n-Match as you please.

I recently went on a sales call to a coffee manufacturer (grinder).  They receive whole raw beans, roast them, grind them and then package them.  The process involves a lot of hoppers and bins.

The customer was looking for a very simple method for low and high level indication on hoppers containing whole beans.  The whole beans come from the cooler on various conveyors and then up a bucket elevator.  The elevator raises the beans up and into a hopper where they are held pending the grinding process or packaged as whole beans.  After reviewing the application, a diaphragm type level indicator was recommended for low level indication.  It was recommended that the indicator be mounted approximately 1/2 to 2/3 the distance up the sloped section of the hopper. 

Diaphragm type level indicators are one of the simplest types of bin level indicators.  A diaphragm (usually neoprene) covers an actuator plate that in turn pushes on a micro switch for indication.  A light or relay can be used to indicate when the switch has detected presence or absence of material.  A spring pushes the actuator away from the micro switch when material is not present.  Because whole coffee beans are not that abrasive, the projected life of the diaphragm switch should be good.

A rotary paddle switch was recommended for the high level indicator.  Why a rotary paddle switch?  The customer was not sure where the proper location of a diaphragm switch should be to indicate when the hopper was full.  The rotary paddle switch could be mounted vertically on the top of the hopper and the customer could adjust the height of the paddle via pipe extensions as required to meet the proper height for high level indication .

Could a rotary paddle switch be used for the low level indicator?  Sure.  However, we all believed that having the product slide across a rubber diaphragm would be a "cleaner" installation and operation vs a paddle sticking out into the product.

That's why one type of indicator may not be the best for all applications.  Don't be afraid to Mix-n-Match.

Ross Jamison

Technorati Tags: level sensor level measurement bin level indicator level control solids level indicator diaphragm level switch rotary paddle level indicator