Question 24 QMED01 - Junior Engineer

The Correct Answer is A. ### Why Option A is Correct Option A ("by stop-check valves installed in the bilge suction manifolds") describes a standard, regulatory-required safety feature on ships, particularly in the engine room. * **Function of Stop-Check Valves:** A stop-check valve combines the functions of a stop valve (manual opening and closing) and a non-return or check valve (automatic prevention of backflow). * **Preventing Flooding:** In the context of bilge systems, these valves are installed where the bilge suction lines connect to the pump suction manifold. If the pump is taking suction from a low-level compartment (like the engine room bilge) and then switches to discharge overboard (or if the ship is holed above the waterline), there is a significant risk that seawater could flow backward through the pump and flood the engine room bilges. The **check (non-return) function** of the stop-check valve automatically prevents this backflow, ensuring that water pumped out cannot accidentally re-enter the compartment it just drained, nor can high-pressure seawater enter the system. The **stop function** allows the flow to be manually isolated. ### Why Other Options Are Incorrect **B) by installing a swing check before each bilge valve** * This configuration is redundant or incorrect. Bilge systems use manifolds (a centralized arrangement of pipes and valves). The primary non-return function must be located at the suction manifold (as described in A) to prevent backflow into the entire bilge area from the common discharge line. Furthermore, relying only on a swing check valve (which is purely automatic) is insufficient, as manual isolation (the "stop" function) is also required for maintenance and safety. **C) by installing eductors in all bilge rose boxes** * Eductors (or jet pumps) use the Venturi effect to move fluids and are often used as alternative bilge pumping methods (especially for emergency drainage or handling dirty fluids). However, installing them in bilge rose boxes (the strainers at the end of the suction line) only relates to how fluid is moved out; it provides no mechanical barrier or check valve function to prevent flooding or backflow when the system is shut down or discharging overboard. **D) by using a positive displacement reciprocating bilge pump** * The type of pump (positive displacement reciprocating vs. centrifugal) relates to the efficiency and characteristics of fluid transfer (e.g., handling solids, high head pressure). While a positive displacement pump inherently prevents significant backflow while it is operating, it does not provide the required guaranteed isolation and non-return capability when the pump is stopped, or when the system is subjected to high external pressure (such as when the ship is listing or holed). The required safety barrier must be a dedicated valve mechanism (A), not just the passive characteristic of the pump type.