Series B73 and Series 75 Sealed External Caged Liquid Level Switches

Series B73 and Series 75 external cage type level switches are completely self-contained units designed for side mounting to a tank or vessel with threaded, socket weld or flanged pipe connections. These float-actuated controls have proven their reliability in process control for decades.

Operating Principle

The buoyancy force of a process liquid on the float causes the float to ride on the liquid surface. The movement of the float with the liquid level moves an attraction sleeve into the field of the switch magnet, pulling the magnet toward the sleeve and actuating the switch.


Flare pots
Oil refineries
Flash tanks
Knockout drums
Storage tanks
Chemical processing plants
Steam and electric generating stations


Carbon steel or stainless steel welded float chamber
Service pressures up to 2240 psig (154 bar)
Process temperatures up to +1000° F (+538° C)
Specific gravity ratings as low as 0.32
Available switch styles including dry contact, hermetically sealed and pneumatic
Single or multiple switch mechanisms available
Optional high temperature insulation available
Choice of switch mechanism:
Dry contact
Hermetically sealed
Choice of switch mechanism enclosure:
TYPE 4X/7/9 Class I, Div. 1, Groups B, C & D, polymer coated aluminum
NEMA 1, carbon steel for pneumatics
Choice of tank connection:
1", 1 1⁄2" or 2" NPT
1", 1 1⁄2" or 2" flanged side/side
1", 1 1⁄2" or 2" flanged side/bottom
1", 1 1⁄2" or 2" socket welds


Interface calibration
Extreme temperature modifications
Customized installation dimensions
Customized exterior surface preparation and finish
Customized actuation levels
Vent and drain connections


XP=Explosion Proof
IS=Intrinsically Safe
ELV=EMC/Low Voltage


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