How to choose between normally closed and normally open direct-acting solenoid valves

The so-called normally closed type means that when the power is lost, the solenoid valve is in a closed state, the air source is also in a cut-off state, and the corresponding valve is also in a closed state. When the power is turned on, the solenoid valve opens and the air source is connected. , thus driving the valve to open;

The so-called normally open type, when the power is lost, the solenoid valve is in the open state, and the air source is also connected. The valve is in the open state, and when the power is turned on, the solenoid valve is closed, the air source is cut off, and the valve is also closed. Normally, the solenoid valve is normally closed, but there are also working conditions that require the normally open type, such as the torch system, which requires the solenoid valve to be in the open state for a long time.