Dual Stage Switch
T21 units combine the functions of two separate narrow differential level controls in a single, compact, easy-to-install instrument. Two independent switch mechanisms are employed to provide two actuating levels at least 8” apart, at actuating depths of up to 48 inches (1219 mm), for applications such as high and low level alarm operation. Model T21 tandem float switches are available with optional cages to help stabilize the floats under turbulent conditions.
All float operated liquid level controls operate on the basic buoyancy principle which states "the buoyancy force action on an object is equal to the mass of liquid displaced by the object." As a result, floats ride on the liquid surface partially submerged and move the same distance the liquid level moves. Because of this, they are normally used for narrow level differential applications such as high level alarm or low level alarm.
Float diameters of 3" × 5", 4" and 4½" available
Tank connections available in 1" NPT, cast iron, forged, or stainless steel flanges
Choice of switch mechanism: ◦ Dry contact ◦ Hermetically sealed ◦ Pneumatic
Choice of switch enclosure: ◦ NEMA 1 carbon steel for pneumatics ◦ TYPE 4X/7/9 Class I, Div. 1, Groups C & D, polymer coated aluminum ◦ TYPE 4X/7/9 Class I, Div. 1, Group B, polymer coated aluminum
ATEX approved housing
Float guide cage
Tropicalized switch mechanism
Special flange face finishes