Model 716

Displacer Switch, Top Inserted, Two Point

The Delta Controls Model 716 Displacer Switch provides output switching at two field adjustable points based on a varying liquid level. The unit is located on top of the vessel with the primary element extending down into the vessel. The spring supported displacer type level switches are used in sumps, tanks, and vessels where long insertions and switching over wide variations in liquid level are required.

Displacer actuated units are less sensitive to surface wave action than other models which are actuated by floats. Spring opposed displacer type units are suited to difficult services where the fluid contains entrained solids or otherwise would tend to cause hang-ups in float actuated units.

Displacer actuated units are less sensitive to surface wave action than other models which are actuated by floats. Spring opposed displacer type units are suited to difficult services where the fluid contains entrained solids or otherwise would tend to cause hang-ups in float actuated units.

Operation is based on liquid displacement. A displacer, which is more dense than the process liquid is suspended from a spring. The length of the spring is proportional to the amount of weight that it supports; the less the weight, the longer the spring will be. When liquid covers a displacer, an amount of weight equal to the weight of the process liquid displaced, is removed from the spring and supported by the process liquid. The spring length is proportionally increased and the attractor is moved up into the field of the switch station magnet. The magnet is pulled in against the outside of the sealing tube and the output switch is actuated.

Similarly, when the process fluid uncovers the displacer, the displacer liquid weight is transferred back to the spring. The length of the spring is decreased to its original length and the attractor is pulled out of the field of the magnet. The magnet returns to its original position and the output switch deactivates. The two separate displacers are supported by a single spring. As the liquid covers the first displacer, the spring lifts the entire displacer assembly (along with the attractor) upward a precise amount. The second switch station will be operated as the liquid level continues to rise covering the upper displacer. The displacers may be placed on the cable at widely separated points and the switch action will then be produced when the liquid level surface covers a displacer at the separated points.

Units equipped with the optional GLC Ground Level Checker include a mechanical arm that allows the switch to be manually operated. Operating this lever allows the user to manually verify the function of the switch without changing the level in the tank. Pulling the lever caused the lever arm to raise the switch actuator through the switchpoints. Releasing the lever returns the switch to its previous position. The checker lever can be operated via a cable attached to it and routed to ground level.

Model 716D Differential Option is equipped with only a single switch station and is setup for adjustable differential control action. The most common application is turning a pump on and off to control the filling or emptying of tanks and sumps.