What is the characteristic of a pressure valve that is normally closed and senses at the input port?

• A. Normally open, sensing at the input port
• B. Normally closed, sensing at the input port (correct)
• C. Normally closed, sensing at the output
• D. Normally open, sensing at the output

Answer: (B)

A pressure valve that is normally closed stays shut by default and only opens when its sensing pressure overcomes the spring force. Sensing at the input port means the valve monitors the upstream pressure—the pressure at the inlet. When that upstream pressure reaches the set value, the valve opens to allow flow, providing protection or relief as needed. This combination is the correct description because it ensures the valve remains closed until the source pressure reaches the threshold, and it responds to the pressure where the potential issue originates. If it sensed downstream pressure, the valve could react to downstream conditions rather than the actual supply pressure, and if it were normally open, it would be open by default, which contradicts the stated condition.