A solenoid valve gets the name due to the presence an inbuilt solenoid along with a plunger which acts as an actuator to operate the valve. The solenoid is unidirectional and can only act to open the valve when an electrical signal makes it active. But when the electrical signal is removed, the solenoid is rendered inactive and the valve is brought back to its original closed position by a spring. These valves are specifically used to allow the flow when and as long as an electrical signal is sent to the valve. Solenoid valves are also available in normally open mode. For these valves the solenoid acts to close the valve upon electrical signal to the valve. These valves can be used for temporarily stopping the flow when and as long as an electrical signal is sent to the valve.
These valves can be operated using either of AC (Alternating Current) or DC (Direct Current) electrical signals.
Following are a few types of solenoid valves
- Core disc type valves
- Flapper Disc type valves
- Floating Diaphragm type valves
- Hung Diaphragm type valves
- Lever type valves
- Piston type valves
- Poppet type valves
- Slide Disc type valves
- Spool type valves
Another way of classifying the solenoid valves is based on number of pipe connections to a valve.
| Type of valve | Schematic | Description |
| 2 way solenoid valves |  |
2 ports - 1 inlet for pressure and 1 outlet for cylinder |
| 3 way solenoid valves |  |
3 ports - 1 inlet for pressure, 1 outlet for cylinder and 1 port for exhaust |
| 4 way solenoid valves |  |
4 ports - 1 for pressure, 2 ports for cylinder and 1 port for exhaust |
| 5 way solenoid valves | 4 ports - 1 for pressure, 2 ports for cylinder and 2 ports for exhaust |
