State the causes of scavenge fire in a two-stroke engine, how to reduce the risk, the action if one occurs, and describe a fixed CO₂ installation for extinguishing it?

flowchart TD
    A[Oily deposits in scavenge belt] -->|Hot blow-by gas| B[Ignition]
    B --> C[Scavenge fire]
    C --> D[Rising scavenge temperature]
    D --> E[Slow/stop engine]
    D --> F[Cut fuel to unit]
    D --> G[Smother space]
    G --> H[Use CO₂ or dry powder]

• Causes: oily carbonaceous deposits in scavenge belt, hot gases blowing past piston rings (blow-by)
• Reduction: regular draining and cleaning of scavenge spaces, clear drain lines, correct cylinder-oil feed, maintain piston rings and liners, monitor scavenge temperatures
• Action on fire: raise alarm, inform watchkeeper and Chief Engineer, slow/stop engine, cut fuel to affected unit, isolate scavenge space, apply extinguishing agent
• CO₂: displaces oxygen, less effective in turbulent scavenge air belt
• Dry powder: smothers and interrupts combustion chain, preferred for scavenge fires
• Fixed CO₂ installation: storage cylinders, distribution piping with nozzles into scavenge space, remote release controls
• EOW duties: monitor scavenge temperatures and oil feed, ensure cleaning/drainage per PMS, initiate emergency procedure on detection, operate fixed system only when authorized, record incident