What is firemain pressure?

What is firemain pressure?

• A. 60-100 psi
• B. 200-240 psi
• C. 10-20 psi
• D. 120-180 psi

Answer: (D)

Firemain pressure is the pressure produced by the ship’s firemain pumps that pushes water through the main fire-supply piping to attack lines and fixed monitors. It has to be high enough to overcome friction losses in hose lays and any height differences, yet not so high that it risks damaging piping, valves, or nozzles. On most ships, the operating pressure window is about 120 to 180 psi, which covers the typical nominal pressure around 125 psi used for firefighting. That’s why the range of 120–180 psi is the appropriate choice. Pressures much lower wouldn’t provide adequate flow for multiple lines, while much higher pressures can cause equipment stress or water hammer; the extremely low or high options don’t fit practical shipboard firefighting needs.

Firemain pressure is the pressure produced by the ship’s firemain pumps that pushes water through the main fire-supply piping to attack lines and fixed monitors. It has to be high enough to overcome friction losses in hose lays and any height differences, yet not so high that it risks damaging piping, valves, or nozzles. On most ships, the operating pressure window is about 120 to 180 psi, which covers the typical nominal pressure around 125 psi used for firefighting. That’s why the range of 120–180 psi is the appropriate choice. Pressures much lower wouldn’t provide adequate flow for multiple lines, while much higher pressures can cause equipment stress or water hammer; the extremely low or high options don’t fit practical shipboard firefighting needs.