12v solenoid valves are typically used for simple ON/OFF control of gas or liquid media. A basic brass 2/2 way solenoid valve (2 port 2 position) valve when fitted into a pipework system will control the flow of media flow or no flow. In the case of a normally closed (fail-safe closed) solenoid valve when 12 volts is applied the solenoid valve opens allowing flow. When the 12 volts are removed from the solenoid valve then the valve will automatically close and prevent flow along the pipe. For a normally open solenoid valve then the opposite is true, i.e. the solenoid valve fail-safe position is open and when power (12vDC) is applied the solenoid valve will power close. 12 Volt solenoid valves are typically found in excavator applications.