Model 750

SKU: 750

Displacer Switch, External Cage, Horizontal

Operation: The weight of a displacer or heavy-duty float is supported by a counterweight and a pivot shaft. Switching occurs as the level (interface) crosses the body centerline.

Specific Gravity: 0.23 to 2.4

Temperature: -200 to 1100°F (-130 to +650° C)

Pressure: –15 to 6000 PSIG (-1 to +410 BAR)

Process Connection: Top/Bottom or other ½”, ¾”, or 1″ NPT or Socket Weld
½” to 2″ flanged, 600#, ANSI
½” to 1″ flanged, 1500#, ANSI
½” to 2″ hubs, 10,000#, Greyloc


The Delta Controls Model 750 Level Alarm provides a switching output when the liquid level passes the centerline of the body. The unit has its primary element in a cage mounted outside the process vessel. The external cage design is utilized to minimize turbulence effects and in order that the level control may be valved off from the process vessel and depressurized for maintenance without disturbing the operation of the process. The output of the Model 750 is a switch action at a single liquid level point; it may be electric or pneumatic, depending upon the switch station utilized.

The primary element is positioned by a pivot shaft. A counterweight is located on the opposite side of the pivot shaft. The element moves up and down as the liquid level varies. This causes a rotary motion of the element/counterweight as they pivot around the shaft. A magnet, embedded in the counterweight, is continuously coupled to the switch station magnet through their respective magnetic fields. The magnetic lines of force pass through the nonmagnetic body web and connect the two magnets. The magnets' poles are in opposition. When the drive magnet is rotated past the centerline of the station magnet; the magnetic repulsive force causes the station magnet to be driven against its stop in the opposite direction. This snap action is positive and fast. There is never an disengaged"neutral" position. The constantly engaged dual magnet design is insensitive to vibration. The station magnet is connected to an output switch which actuates and deactuates as the station magnet is alternately driven against the two stops. The counterweight design allows heavy displacers to be used in demanding applications.


The Delta Controls Model 750 is mounted horizontally in a vertical riser with straight-through piping. To change the liquid level switch point, add or subtract pipe lengths above and below the cage, thereby moving the entire unit up or down to the desired switching elevation. The switching point is halfway up on the horizontal centerline of the cage assembly. This switch point may be slightly higher or lower depending upon the actual specific gravity of the process liquid and the size of the sensing element.

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