Exam Question

(a) CO2 flooding system or central bank CO2 system is one of the common fixed fire fighting system installed on most of the ships. It releases carbon dioxide (CO2) in bulk quantity to a protected space (such as engine room, cargo hold, purifier room, pump room, etc.) under fire. Smothering action of CO2 extinguishes the fire thereby preventing spreading of fire to other parts of the ship. It consist of several CO2 cylinders located in a separate room, called CO2 room. These bottles contain CO2 in liquid state. When the fire in a protected space goes out of control or in a situation when the fire is not able to extinguish by local fire fighting media, CO2 flooding system comes into picture. CO2 from the bottles directed via common manifold, main valve and distribution pipe lines to nozzles through which it is released to the protected space for fire extinction. Due to safety reasons, the CO2 flooding system is manually released from a release cabinet located outside the protected space.
The CO2 fire extinguishing installation for the cargo holds normally incorporates a smoke sampling system so that fire can be detected in the early stage at the smoke detecting cabinet, which is situated in the wheelhouse. Each cargo compartment is individually connected to the smoke detecting cabinet by a small bore pipe through which a continuous sample of the air in each space is continually drawn by a fan. Part of the sample can be discharged into the wheelhouse to check for the smell of smoke otherwise it vents to atmosphere. Because the ends of pipes in holds could become blocked, an indicator is fitted at the ends in the cabinet to demonstrate air flow. This telltale is usually in the form of a light propeller which is rotated by the air flow. Any smoke issuing from the pipes in the cabinet, is emphasised by the diffused lighting and should be visible, but a photo-cell detector will automatically operate an alarm.
A three-way valve is fitted on each pipeline below the smoke detector cabinet. This is normally set so that the pipe between the dry cargo space and the smoke detecting cabinet is open. When smoke is detected, the valve for the particular space is operated thus isolating the smoke detecting cabinet from the space and opening the pipe to the CO2 cylinder bank, ready for discharge of gas to the cargo space on fire. The system of pipes for smoke detection are also used for fire extinguishing.
(b) answer will be here soon