If the hycheck valve fails, in which position does it fail and what is the impact on the system?

• A. Closed position; no flow through the system
• B. Open position; continuous flow of firemain seawater proportioner
• C. Open position; no flow through the system
• D. Closed position; continuous flow of firemain seawater proportioner

Answer: (B)

The function being tested is how a hycheck valve can fail and what that does to the system. A hycheck valve is a one-way valve in the firemain proportioning line that should stay closed when there’s no demand, preventing backflow and allowing isolation of the flow path when needed. If it fails in the open position, it will not stop flow; seawater will continue to move through the proportioner regardless of any control signals.

So the valve being stuck open means there’s a continuous flow through the firemain seawater proportioner, even when the system isn’t commanded to deliver it. That loss of isolation can lead to wasted seawater, pressure issues elsewhere in the system, and potential unintended discharge or flooding, since the flow can’t be stopped by that valve.