Proportional Solenoid Valves
Many industries rely on proportional solenoid valves to accurately regulate
fluid, gas and air flow to and from components in a wide range of applications.
The automotive, automation and aerospace industries use proportional valves
frequently to regulate fluid flow in engines and hydraulically-powered equipment.
Metalworking, material handling, food processing, woodworking, construction
and marine industries use proportional solenoid valves to regulate power, compressed
air and water flow. The precision of proportional solenoid valves and their
capacity for remote activation and hysteresis, or memory, make them an invaluable
component for countless industrial applications where extremely accurate fluid
or gas flow regulation is necessary.
A proportional solenoid valve utilizes the same elements as a regular pneumatic
or hydraulic solenoid valve but with more advanced flow control capabilities.
A solenoid, or electromagnetic coil, is used to trigger the valve flow with
electronic pulses, moving the magnetized coil at appropriate times. In direct-acting
solenoid valves, a plunger is in direct contact with the in-flow opening in
the valve body, or orifice. This plunger opens and closes the orifice through
the movement of the solenoid, permitting or hindering flow. Pilot-operated
solenoid valves work with a diaphragm rather than a plunger, using differential
pressure to control the flow of fluids. In pilot-operated valves there is a
solenoid-operated vent which is opened to allow the pressure to equalize, permitting
fluids or gases to flow through.
Both direct-acting and pilot-operated proportional solenoid valves regulate
flow based on linearity, frequency response and hysteresis. Linearity refers
to the valve's ability to actuate - that is, to switch on and off - in
a way that creates a smooth line of input and output. An example of linear
regulation is that of a car's cruise control feature as opposed to a
typical heat thermostat. The heating thermostat is actuated only after the
temperature in a room has dropped below programmed temperature and switches
off only after room temperature has risen above it; cruise control, on the
other hand, regulates a vehicle's speed more precisely, maintaining a
steady gas input and adjusting minutely to compensate for factors such as wind
and incline. Both demonstrate hysteresis, or path-dependent "memory",
but only cruise control demonstrates true linearity; proportional valves utilize
both traits. Frequency response refers to the valve's capability to respond
to outside frequencies aimed at regulating valve flow. Proportional valves
with high frequency response, linearity and hysteresis control flow accurately
based on repeatability within close tolerances.
Another important feature of proportional solenoid valves is their ability
to increase or decrease output pressure through one or multiple output lines.
Using the laws of fluid pressure, proportional valves can distribute input
forces in such a way as to increase or decrease output pressure. A classic
example of this is the actuating valve found within most paintball guns. Compressed
carbon dioxide cartridges are used to provide force for each shot, but the
proportioning valve allows for the carbon dioxide gas to be released at a higher
pressure in a very specific amount. Other types of proportional valves have
multiple output lines which can be opened, closed and flowed at various pressures.
Computers are often used to monitor proportional solenoid valves in applications
which require precision accuracy.