Model 711D

SKU: 711D

Float Switch, Top Inserted, Two Point, Wide Separation

Operation: A float is carried up and down by variations in liquid level or interface position.

Uses: Provide high and / or low level alarm, pump control, etc.

Insertion: Up to 10 feet below the flange face

Switch Action: From 1 to 4 points of alarm and/or differential; up to 60″ differential available with Type 711

Specific Gravity: From 0.35 to 2.40 SGU

Temperature: From –150 to 750°F (-100 to +400° C)

Pressure: From –15 to 1200 PSIG (-1 to +80 BAR)

Process Connection: 1″ to 4″ NPT threaded; 1″ to 12″ flanged, up to 900# rating; ASA, DIN or JIS equivalents


Model 711D Product Diagram - Delta Controls Corporation

The Delta Controls Model 711D provides switching action at field selectable liquid level elevations. The switch station is isolated from the process liquid by the barrier tube. The output of the control consists of on/off with variable width differential switching action as the liquid level varies. One switch station is operated. Station actuation occurs as the attractor is lifted in front of the switching station magnet; the station remains activated until the float contacts the lower setpoint collar and pulls the attractor out of the field of the magnet. The barrier tube isolates the switch stations from the process liquid.


The Delta Controls Model 711 should be mounted on top of the process vessel containing the liquid level to be controlled. It should be located with the rod and float down in the vessel so that the desired switching points are located between the upper and lower maximum collar positions on the stroke rod. Use the collar screws to position the setpoint collars to the desired liquid level switching points.

Setpoint Collar Adjustment

The setpoint collars are locked in place by a socket head setscrew. The collars may be repositioned as required to achieve switching action at various fluid elevations. Do not position the upper collar so high that the collar strikes the guide. No additional float or stoke rod movement can occur after the fluid level lifts the collar up against the lower guide.

Sliding Float

The spring supports the weight of the attractor/stroke rod assembly, in the middle of its stroke, which is the neutral position. The position of the spring collar is adjusted so that the stroke rod is positioned in the center of its travel when the float is floating on the liquid surface, is being supported by the liquid level, and is not in contact with either setpoint collar.

Sliding Float

The float has a hollow tube through its centerline. The tube is generously larger than the stroke rod which passes through this tube and acts to maintain the floats horizontal position. The float is normally supported by the liquid level and moves up and down on the stroke rod as the liquid level varies. An "upper" and a "lower" setpoint collar are positioned on the stroke rod. The float pushes against one of the collars when the fluid level rises (or falls) to one of the setpoint collar elevations.

Adjustable Differential Action

The attractor is free to slide on the stroke rod. 0.75" of space is adjusted between the top of the attractor and its upper positioning collar. The attractor is carried up into the field of the station magnet when the float pushes the upper setpoint collar up. The switch station magnet is then pulled in against the barrier tube and the attractor is "captured" and supported by the station magnet. The station remains actuated until the float reaches the lower setpoint collar and pushes it down. The upper attractor positioning collar moves down against the attractor and pulls it out of the field of the switch station magnet. The attractor then falls down against its lower setpoint collar and the switching station deactuates. In summary, after being actuated by the float pushing against the upper setpoint collar, the switch station remains actuated until the float pushes against the lower setpoint collar.

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