Normally Open/Normally Closed Valve: Which statement is true about normally open valves?

• A. They are designed to allow liquid or gas to flow through in usual circumstances
• B. They block flow until activated
• C. They are not used as safety devices
• D. They require electricity to open

Answer: (A)

Normally open valves are designed so that, when no electrical signal is applied, the valve is in the open position and flow is allowed. That means liquid or gas can pass under usual, unpowered conditions. When the actuator is energized, the valve typically moves to a closed state to stop the flow (though some designs may operate differently, the common behavior is open by default). This is why the statement that describes flow being allowed in normal circumstances is the true one. The idea that they block flow until activated describes normally closed valves, and the notion that electricity is required to open is incorrect because they are open without power. While a normally open valve can be used in safety-related applications in some systems, that usage isn’t inherent to all normally open valves.