Should It Close or Stay Open During a Power Failure? — Safety Guidelines for Selecting Normally Closed vs. Normally Open Solenoid Valves
Release time:
2025-09-09
When the power is lost, the valve core closes by the spring force, and when powered on, the electromagnetic force overcomes the spring and opens.
NC（Normally Closed）
When the power is lost, the valve core closes by the spring force, and when powered on, the electromagnetic force overcomes the spring and opens.
Typical uses: fire sprinkler, boiler water replenishment, gas cut-off - flow must be stopped when power is cut off to ensure safety.
NO（Normally Open）
When the power is lost, the valve core opens by the spring force, and when powered on, the electromagnetic force overcomes the spring and closes.
Typical use: Cooling water bypass, unloading circuit - it is necessary to maintain circulation even when power is cut off to prevent high temperature alarm of the unit.
Choosing the wrong code can result in either "power outage leads to interruption" or "power outage leads to overflow", which is opposite to the process safety logic. Therefore, the sample lists the two states separately, allowing users to select based on system safety functions rather than selecting models based on caliber pressure.
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