Fournier Controls Inc, Petroleum and Chemical 
            tank level sensors
35 years experience
in tank level sensors
Proven Technology for Displacer Alarm Switches
Call us: 321-751-2139

Switch Installation

(Mechanical and Electrical)

Mechanically install displacer switch assembly in a plum vertical position on the top of tank per instructions furnished with unit. The cable and displacer must hang in the free air space above the tank's liquid product. No obstructions are permitted. The PVC displacers are 3 1/2" in diameter. The displacers are secured on the flexable stainless steel cable according to the required switching point/s. See factory instructions for complete details. Electrically connect wiring to proper terminals in displacer switch assembly according to the switching point/s. Wiring is connected through the 3/4" conduit fitting on base of housing. Follow proper electrical codes. See factory instructions for complete details.

Operation - Basic

The displacer switch is installed on the top of a tank with displacers hanging on a cable or beaded chain in the free air space attached to the float rod. The spring in the spring housing is always sightly compressed by the weight of the displacers. The spring rod and armature assembly extend up into the isolation tube out of the magnetic field of the mercury switches with magnets. The mercury switches are in a normally open (NO) or normally closed (NC) position with no alarm. The product level in the tank rises and comes in contact with displacer "B". This displacer sinks in the product but raises the displacer slightly decompressing the spring in the spring housing. This raises the floating rod and armature assembly. The magnet on the armature assembly causes the mercury switch to change position and provides an open circuit or closed circuit. Alarm point "B" is recognized. If the liquid product is removed from the displacer, the displacer again becomes heavier and the switching contacts are reversed.

If the product level in the tank continues to rise and comes in contact with displacer/s "A" the mercury switch "A" changes state and a second level point is recognized.

As liquid product is lowered and the displacers are again permited to hang in the free air space, the switching action is reversed. The switching action is slightly different when product is lowered. This difference is call the switches switching differential.

When installed on a tank with an internal floating pan or other mechanical lifting device the switch acts in a similar manner.

With the addition of an Operation Checker, an operator may manually lift the displacers simulating a rising liquid product to the displacers. Recommended option.

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Fournier Controls Inc. Viera, FL