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.
Magnetrol float level controls use a simple float and magnetic coupling action.
As the float rises or falls with liquid level, it moves a magnetic sleeve into or out of the field of a switch actuating magnet, causing switch operation. A non-magnetic barrier tube effectively isolates the switch mechanisms from the controlled liquid.
Float type level controls are available for top mounting, side mounting and external cage applications. A wide range of dry contact, hermetically sealed and pneumatic switch mechanisms are available. The process temperature and pressure maximums for floats are +1000° F and 3750 psig with specific gravities as low as 0.32. Single, dual and three switch models are available. Standard models are also available for interface control (float rides on the interface between two liquids).