How do solenoid valves work? Here’s the engineering behind solenoid valve operation – the solenoid valve uses an electromagnetic solenoid coil to change the state of a valve from open to closed or closed to open. If the solenoid valve is ‘normally closed’, when the coil is energized, the valve gets lifted open by the electromagnetic force produced by the coil.
This is why a solenoid valve is sometimes known as an electrically-operated valve or a solenoid operated valves. Solenoid valves remove the need for an engineer to intervene manually.
Where would you use a Solenoid Valve or Solenoid Operated Valve?
Within any clean process media application e.g. an application which needs control of gases, clean liquids, light oils. Typically within these process factories the valves are most popularly used as simply on/off valves, this is due to the line only needing flow or no flow!
Solenoid valves are frequently used instead of larger electrical actuated ball valves, which will save the process plant space. The operation of a solenoid valve is also quicker than other valve technologies.
Additional features of a Solenoid Valve
Other solenoid operated valves use a more advanced technology meaning they can be used to proportionally control flow or pressure depending on a varying input signal. This is where another component further downstream needs a specific pressure or flow to maintain the correct working conditions. Most common input signal used would be a 4-20mA loop signal which most factories will have at their disposal usually controlled by a PLC or similar system. What about options for solenoid valve sealing?
How to select the correct Solenoid Valve
For correct and accurate control functioning, solenoid control valves must be configured and selected according to their special purpose. The most important parameters for selecting a solenoid control valve are:
- Kv value (given in cubic meters per hour)
- The application’s pressure range.
The lower the valve’s orifice or the stronger the coil, the higher the pressure the valve can shut-off. On the basis of the calculated Kv value and the pressure range of the planned application, a correspondingly appropriate valve type and its required orifice can be determined.
The difference between Direct-acting solenoid valves and In-direct acting solenoid valves
Direct-acting valves require no differential pressure to remain in their rest state and in the NC version, they will only allow flow once energized. These valves are very robust and can be used in a process line for simple isolation purposes of for safety purposes. The can also be used on the outlet to a tank where sometimes pressure can get very low but the valve needs to remain open.
In-direct acting valves require a pressure differential across the inlet and outlet to allow them to stay in their rest state. For example if a valve was normally open and there was not a large enough pressure differential, the valve could be intermittent and possibly close if inlet pressure dropped too low. These valves should only be used if pressure levels are within the parameters specified in the datasheet and IOM instructions.