What is used to isolate portions of firemain?

• A. Gate valves
• B. Check valves
• C. Ball valves
• D. Cut out valves

Answer: (D)

Isolating portions of firemain is about shutting off flow to a defined segment while keeping the rest of the line pressurized. Cut-out valves are designed for this exact purpose on a ship’s firemain. When you close a cut-out valve, that specific section is isolated, allowing you to drain, repair, or test it without shutting down the entire firemain system. Gate valves and ball valves can stop flow, but they aren’t placed specifically for isolating a segment of the firemain in normal operations. Check valves prevent backflow and don’t isolate a section. So the device used to isolate portions of firemain is the cut-out valve.