Solenoid Valve

Solenoid valves use an electromagnetic coil to a attract a moving core that links to a diaphragm or piston that effects the opening and closing of the valve. Two way valves are on/off valves for fluid isolation and in the de-energised state can be normally closed(NC) or normally open (NO). Two way valves often only work with one flow direction and this is clearly marked although bidirectional 2 way valves can be supplied when necessary.

Three way valves are used to divert the flow from one path to another or select a flow source from two inlets. Often used to pilot spring return actuators, three way valves offer the same NC and NO functions as two way valves but can also be universal (U) in that the design is possible to be piped for any function and the valve is not directionally biassed.

Five way valves divert 2 flow streams and can be considered as a pair of 3/2 valves sharing a common inlet port and operation. Five way valves often employ two solenoid coils making them bistable and requiring separate coil activation to change state. 

Three and five way valves are often described as directional control valves.

Types of Solenoid Valve

Normally Closed Solenoid Valve

With normally closed solenoid valves, the valve is closed when de-energised and the media (liquid, gas) cannot flow through it. When the coil is energised, however, it creates an electromagnetic field that pushes a plunger upwards against a spring. This allows the media to flow through the valve freely. 

Normally Open Solenoid Valve

On the other hand, with a normally open solenoid valve, the valve is open when de-energised and media can freely flow through it. When the coil is energised, the electromagnetic field that is created forces the plunger downwards against a spring. This closes the valve and prevents media from flowing through it. Normally open solenoid valves are ideal in situations where the valve is open for a long duration, as it's use is more energy efficient. 

Uses of Solenoid Valves

Solenoid valves are versatile and can be used to distribute media, mix media, shut off media or release media. Solenoid valves can be pneumatic or hydraulic, depending on the industrial use of the valve and its unique requirements. Solenoid valves can also be found in the home, to control the flow of water in and out of household appliances such as washing machines and dishwashers. 

Benefits of Solenoid Valves

Solenoid valves have a number of benefits, depending on their unique use case. A handful are as follows:

• Automatic operation
• The ability to switch open/closed almost instantaneously 
• Highly reliable
• Energy efficient compared to a direct acting valve, in similar circumstances