The difference between normally open and normally closed solenoid valves

The working principle of the normally open solenoid valve is to energize the coil and connect the air circuit. Once the coil is powered off, the air circuit will be disconnected, which is equivalent to "inching". The principality principle of normally closed solenoid valve is to energize the coil and disconnect the gas circuit. Once the coil is disconnected, the gas circuit will be connected, which is also "inching".

Normally, it is selected according to the duration of continuous operation: normally closed, normally open, or continuously energized. When the high-temperature solenoid valve needs to be opened for a long time, and the duration is longer than the closing time, the normally open type shall be selected. If the opening time is short or the opening and closing time is short, the normally closed type is selected. However, some working conditions used for safety protection, such as furnace and kiln flame monitoring, cannot be normally open, but can be powered on for a long time.

The solenoid valve mainly uses electricity as the energy source. The current drives the solenoid coil to generate electromagnetic force, and then the electromagnetic force controls the valve through the control of the spring magnetic column level gauge. Of course, this spring can be used to control both the closing and opening of the valve. Therefore, according to this feature, we can make the air circuit open when the coil is not energized, which is a normally closed valve, or make the air circuit open when the coil is not energized, which is a normally open valve.

The working principle of the normally open solenoid valve is to energize the coil and connect the air circuit. Once the coil is powered off, the air circuit will be disconnected, which is equivalent to "inching". The principality principle of normally closed solenoid valve is to energize the coil and disconnect the gas circuit. Once the coil is powered off, the gas circuit will be connected through the electric actuator, which is also "inching".

It is usually selected according to the duration of continuous working: normally closed, normally open, or continuously energized; When the solenoid valve needs to be opened for a long time and the duration is longer than the closing time, the normally open type shall be selected. If the opening time is short or the opening and closing time is short, the normally closed type is selected. However, some working conditions used for safety protection, such as furnace and kiln flame monitoring, cannot be normally open, but can be powered on for a long time.