| Limit Switches
Electrical switches which may be applied to manual or
automated valves to signal that the valve cycle has been
completed. When applied to manual or pneumatically actuated
valves, it is most common to provide two switches in a Nema
Rated Enclosure. Each switch is activated by an adjustable
tripping device driven by the actuator or valve system.
Normally one switch is adjusted to trip in the open position
and one is adjusted to trip in the closed position. Optional
additional switches are available to perform other
functions; i.e., pump start-up or shut-down. All electric
actuators have Open/Close limit switches.
Mechanical Limit Switch
Any limit switch, usually plunger or lever type, which is
mechanically activated by the tripping mechanism making
physical contact with the switch, and are normally used for
remote valve position indication.
Proximity Limit Switch
A solid state switch is electrically tripped without
mechanical contact being made. This type of switch is
generally used to interface with computer or microprocessor
controls.
Solenoid Valve
An electro-magnetically operated valve which enables
electrical control of the air supply to a pneumatic
actuator. Double-acting actuators require a four-way
solenoid, while the spring-return actuators require a
three-way solenoid to achieve the proper supply-exhaust air
flow patterns.
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