Solenoid valve: How to choose the right solenoid valve
A solenoid valve must suit the specific application. Before choosing a solenoid valve, you should establish the medium, temperature, pressure, flow, thread size, voltage and whether the valve should be normally closed or normally open. Asking the right questions makes it easier to find a solenoid valve that operates reliably.
What application will your solenoid valve be used in?
The choice of solenoid valve depends first and foremost on the application. A solenoid valve is not just a standard component, but part of a specific solution in which the medium, pressure, temperature and operating conditions play a significant role.
You should therefore start by establishing whether the solenoid valve will be used for air, neutral gases, water, diesel or other liquids and gases. Different applications place different demands on the valve’s materials, function and sizing.
Choose a solenoid valve based on the medium and temperature
The medium whose flow the solenoid valve is to open or shut off directly affects the choice of materials. All wetted parts must be able to withstand the specific medium. This includes the valve body, diaphragms, seals and other parts in contact with the liquid or gas.
Temperature is also important. The coil in a solenoid valve normally becomes warm during operation and must be able to withstand both the heat it generates and the temperature of the medium. At the same time, diaphragms and seals must be able to function reliably at the temperature required by the application.
Should the solenoid valve be normally closed or normally open?
When choosing a solenoid valve, you need to decide whether the valve should be normally closed or normally open. A normally closed solenoid valve, also known as NC, is closed when the coil is de-energised and opens when the coil is energised.
A normally open solenoid valve, also known as NO, works in the opposite way. It is open when the coil is de-energised and closes when the coil is energised. Normally closed is the most common choice, but the right solution depends on how the application should function during normal operation and in the event of a power failure.
Pressure, flow and voltage determine the right solenoid valve
The pressure range across the solenoid valve is crucial to the choice. If there is a pressure differential across the valve, an indirectly operated solenoid valve may often be suitable. For larger sizes without a pressure differential, an assisted-lift solenoid valve may be required instead, while directly operated solenoid valves are typically used for smaller sizes.
Flow is important for sizing. A solenoid valve should not be selected solely on the basis of pipe size, as incorrect sizing can cause operating problems. Excessively high flow can wear the valve seat, while excessively low flow can cause problems with diaphragm operation in indirectly operated solenoid valves.
The voltage must also be specified. A solenoid valve can be designed for AC or DC voltage, and the choice can affect the valve’s pressure range. You should therefore always check the datasheet before choosing the voltage.
7 questions to answer before choosing a solenoid valve:
- What voltage will the solenoid valve require?
- What application will the solenoid valve be used in?
- Which medium will the solenoid valve open or shut off the flow of?
- What is the temperature of the medium?
- Should the valve be normally closed or normally open?
- How high or low is the pressure across the valve?
- What flow rate should the solenoid valve be sized for?
- What voltage will the solenoid valve require?
Need to choose a solenoid valve?
Hans Buch can help you clarify the requirements for media, temperature, pressure, flow, voltage and valve type.
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