Model 740D

SKU: 740D

Float Switch, Side Inserted, Two Point, Optional Differential

One On/Off Adjustable Differential Control Point

Operation: A pivoted float rides on the liquid level or interface position. Two switch actions occur as the elevation varies.

Uses: Two point alarm or on-off pump control

Specific Gravity: 0.4 to 2.4

Temperature: -50 to 750°F (-47 to +400° C)

Pressure: -15 to 750 PSIG (-1 to +50 BAR)

Process Connection: 3″ NPT threaded, 3″ to 12″ flanged, up to 600# rating, ASA, DIN, JIS


Model 740D Product Diagram - Delta Controls Corporation


The Delta Controls Model 740D provides switch action at two points as the liquid level varies. The unit is located on the side of the vessel with the float extending into the vessel. The float rides on the surface of the liquid and is carried up and down as the liquid level varies. The attractor is coupled to the float by the linkage and also moves up and down as the level varies. The attractor is located inside of the barrier tube and contacts the process fluid. The switching station is located on the outside of the barrier tube and is isolated from the process fluid. The station contains a magnet whose magnetic lines of force penetrate the nonmagnetic barrier, and are magnetically attracted to magnetic materials such as the attractor. The magnet is pulled in against the tube as the attractor moves up into its field. The magnet is connected to an output switch which actuates as the magnet is pulled in against the barrier tube.

The switch station actuates as the float moves downward and lifts the attractor into the magnetic field of the station. The magnet is pulled in against the barrier tube, the output switch actuates and the attractor is "captured" and held up by the magnet. The switch station will continue to be actuated until the float rises high enough to lower the top collar to the attractor and then to pull it out of the field. The attractor then falls to the lower collar by gravity. The amount of differential is controlled by moving the top collar up and down. The wider the spacing between the top collar and the attractor; the greater will be the switching differential. The longer the float rod, the greater the switching differential referenced to the change in liquid level elevation.


The Delta Controls Model 740D should be mounted on the side of the vessel at the point where switching is to occur. The float rod must be long enough so that the float extends past the nozzle end and inside the vessel. A baffle or stilling tube is required if the fluid is agitated or has severe surface turbulence.

The process connection must be large enough to allow insertion of the float into the vessel. The switch housing must be positioned vertically up. The sealing tube may be unscrewed to expose the attractor for adjustment, cleaning, maintenance, etc.

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