Model 6761-P-2-SPDT Top Mounted Displacer Switch
The Model 6761 Displacer Switch is designed for mounting at the top
of a tank in order to either open or close a circuit when the liquid in the
tank rises to a level that causes the displacer to move the steel armature
into the magnetic field of the switch assembly which in turn causes the
mercury switch to tilt.
This switch assembly provides two (2) points of level detection. As liquid in the tank rises and comes in contact with the displacers a switching action takes place. This switch is all mechanical, no AC or DC power is required, only the opening or closing of a switch take place as liquid raises the displacers.
The switch assembly can be supplied with a single switch for high or low level alarm service or with two stiches for both high and low level alarm service.
The switches contacts can be normally open (NO) or normally closed (NC). Models with one (1) point of level detection are available. An independent alarm switch not associated with the tank's level measuring devise is always recommended for a tank's overfill protection. This switch is a standard for tank high and high/high alarms or overfill protection.
The mercury switches supplied are SPST, mercury to mercury, momentary make before break. Resistive ratings are:
- 5 amps at 115 V.A.C.
- 2.5 amps at 220 V.A.C.
Standard materials of construction consist of an aluminum flange and housing, stainless steel
isolation tube, stainless steel cable, PVC displacers and stainless steel trim.
The wetted parts of the assembly consist of stainless steel and PVC and as a result offer excellent corrosion resistance and are suitable for may types of petroleum and chemical products.
Other switches can be supplied to satisfy special requirements.
The standard tank mounting connection is a 4" - 125# ASA flat face flange of aluminum construction. The 4" size has been selected so that the 3-1/8" diameter displacer can readily pass through the tank nozzle. Other size connections both flanged and threaded are optionally available where existing vessel connections require other sizes. Other flange materials such as cast iron, carbon steel or stainless steel are also available.
Each switch assembly is carefully adjusted at the factory prior to shipment and the adjustment is based upon the customer providing information that consists of:
- the type of liquid stored
- specific gravity
- operating temperature
- tank pressure
- level actuation point
The level actuation point can be readily adjusted in the field by positioning the displacer on the stainless steel cable. The standard cable length is 10 FT. but longer cable is optionally available if specified.