The normally closed type or the normally open type can be chosen according to the duration of the continuous working time.
1. The normally closed solenoid valve is selected when the solenoid valve needs to be closed for a long time, and the closing time is longer than the opening time, and the continuous opening time is not very long.
2. A long time of opening and closing are both needed, thus self-retaining solenoid valves should be chosen.
3. The normally open type solenoid valve is suitable to the conditions where needs to be opened for a long time, and the opening time is longer than the closing time, and the continuous opening time is not very long.
4. The normally open solenoid valve is used in emergency cut-off solenoid valve with manual opening. But, sometimes, the normally open solenoid valve cannot be selected, such as furnace and kiln fire monitoring,
