Solenoid valves are used to control the flow of fluids (gases and liquids). These valves act by opening or closing orifices through which these fluids flow. There are two basic operations of solenoid valves: the normally open solenoid valve (NO) and the normally closed (NC) versions. These valves are produced by different manufacturers, but their basic operations are the same. The operation of the valve is one of the considerations to make while choosing a solenoid valve.
In the NO operation, energizing (passing electric current through) the coil closes the solenoid valve. When the current is cut off (what is known as de-energizing), the valve opens. This valve operation is normally preferred for non-explosive and non-corrosive fluids such as air, light oil and water.
The Normally Open valve operation is useful in situations where it is necessary to keep the fluids flowing at all times. A good example is the cooling tower of an industrial system that should always be on to avoid overheating. In that case, the solenoid is only energized (to close the valve) when there is a real need to close it, for example, during scheduled maintenance or repairs.
The operation of the valve is just one of the considerations to make while choosing a solenoid valve. Everything that influences the operation of the solenoid valve should be considered. For example, the viscosity of the fluid, the size of the orifice as well as the temperature of the medium should be considered.
Another consideration to make is the compatibility of the fluid and the material of the valve. The good news is that most valve materials are compatible with different fluids such as oil, air, water, steam and even corrosive fluids. Nonetheless, this fact must still be confirmed before choosing a valve. Finally, the pressure rating of the valve, which is directly related to the size of the orifice, must also be considered.
Pairing the correct Normally Open Solenoid Valve to your project shouldn’t be to difficult if you have all of the information available that we discussed. These types of valves are less common and might be harder to find when your looking around. Make sure to always buy your valves from a reputable distributor that can offer support in the event your valve gives you any trouble.