solenoid valves

Most solenoid valves operate on a digital principle. They therefore

possess two distinct states, which are (1) - when the coil is

activated by an electrical current, and (2) - when the valve is resting

(without electricity). Valve functions are defined from the resting

position.

The direct acting or pilot operated solenoid valves may have two

functions:

Normally closed (NC)

A solenoid valve is normally closed (abbreviated - NC) if there is no

flow across the valve in its resting position (with no current on the

solenoid contacts).

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Please note that in the case of 3-way solenoid valves, port A is

open to port R which, for example, enables the valve’s single-action

cylinder to be exhausted to atmosphere.

Normally open (NO)

A solenoid valve is said to be“normally open” (abbreviated NO)

when it enables fluid to pass in its resting position (with no current

on the solenoid contacts).

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A specific choice of entry ports can change a valve’s function.

However, since balanced-force calculations take rebound effects,

coil effects and the effects of pressure exerted on the seal into

account, the performance of an NC valve fitted in an NO position

would be reduced. In this configuration it would be better to choose

a universal solenoid valve.

Latching or Bi-stable

applications a short electrical impulse enables the solenoid valve

to be opened or closed, and thanks to the residual effects of a

permanent magnet this is sufficient for maintaining the valve in a

particular working position with no electrical energy consumption.

A short impulse of inverted polarity ensures the valve’s return to its

previous position. Electrical power consumption and heating are

almost negligible.