The solenoid valve refers to the actuator for flow control. According to the state of the solenoid valve, we can divide solenoid valve into two types include normally open solenoid valve and normally closed solenoid valve. The “open” and “closed” refers to the state of solenoid valve when the solenoid coil is not powered. For some special functions, the self-retaining solenoid valve is a typical type, and it is known as normally open (closed) solenoid valve.
Normally open solenoid valve
Normally open solenoid valve is closed when the solenoid coil is powered, and the normally closed solenoid valve is open when the solenoid coil is off. If the solenoid valve is required long-term opening, the normally open solenoid valve will be the ideal choice. If the solenoid valve is required long-term opening or close, the bistable solenoid valve is more suitable. As for the voltage, AC (380V, 240V, 220V, 24V) and DC (110V, 24V) is applicable for the normally open solenoid valve.
Normally open solenoid valve applies to the actuator that using steam as heat medium and automatically control temperature. normally open solenoid valve can make two-position automatic control and remote control to the steam heater, radiator, dryer and other steaming plants. Normally open solenoid valve has wide applications, including dyeing, textile, printing and dyeing, food, medicine, tobacco, cement product, petrochemical industry, metallurgy and etc.
Normally closed solenoid valve
Normally closed solenoid valve means closed when the solenoid coil is powered, and the solenoid valve is open when the solenoid coil is off. Normally closed solenoid valve apply for international standard voltage include AC 380V, 240v, 220v, 24v or DC 110V, 24V.
Difference between normally open solenoid valve and normally closed solenoid valve
Models
How to distinguish normally open solenoid valve and normally closed solenoid valve on the model? The model usually consist of different letters, they have different meanings.
- K for normally open, while the normally closed type doesn’t need letters.
- ZC stand for the solenoid valve,
- F for explosion proof,
- X for pilot-operated type,
- Numbers generally stand for the size of the valve.
Working principle
- Normally closed solenoid valve: turn on the solenoid coil, the pipeline will be open; turn off the solenoid coil, the pipeline will be closed, we call this process inching.
- Normally open solenoid valve: turn on the solenoid coil, the pipeline will be closed; turn off the solenoid coil, the pipeline will be open, we also call this inching.
How to choose normally open or closed solenoid valve?
In general, we select solenoid valve type according to the continuous working period. Common types include normally open, normally closed and self-retaining type. Specific rules as blows:
- When the solenoid valve has prolonged on state, and the opening time is much longer than the closing time, we choose normally open solenoid valve.
- When the solenoid valve has long-term off state, and the closing time is much longer than the opening time, we should choose normally closed solenoid valve.
- When the solenoid valve requires same time on the opening and closing, we should choose self-retaining type solenoid valve, also called double acting type.
- For some working conditions used for safety protection, such as the furnace flame detecting and other conditions, normally open solenoid valve is not applicable; we should choose long-term electricity type.
- For gas leak alarm device system, we should choose normally open type gas emergency shut-off solenoid valve. After closing, the solenoid valve should be started up manually.
Kaidi is a solenoid manufacturer who has rich experience in providing on-off solenoid, proportional solenoid, explosion-proof solenoid and solenoid coil. We are the regular supplier of Rexroth, Yuken, Vickers, Parker solenoid. Besides, we also supply customization service based on the particular requirements of different clients.