With reference to MARPOL Annex I, draw a 15 ppm oily water separator and explain its principles of operation, and state the periodical maintenance and checks to verify effectiveness?

flowchart TD
    A[Bilge water inlet] --> B[Coalescer\nconical plate pack]
    B --> C{Oil globules\ncoalesce & rise}
    C -->|Oil| D[Oil collection dome]
    C -->|Water| E[Clean water outlet]
    D --> F[Test cocks / level probes]
    F --> G[Oil drain valve]
    E --> H[Oil-content monitor\n15 ppm]
    H --> I{> 15 ppm?}
    I -->|Yes| J[3-way valve\nto bilge/holding]
    I -->|No| K[Overboard]

• MARPOL Annex I requirement: 400 GT and above, bilge water ≤ 15 ppm oil
• Components: Bilge water inlet, conical plate pack, oil collection dome, test cocks/level probes, oil drain valve, clean water outlet, oil-content monitor, automatic stopping device (3-way valve), overboard discharge
• Principles: Coalescence via conical plates, gravity separation, controlled oil drainage, monitoring and automatic diversion if > 15 ppm
• Operational limits: Must be filled with clean water before first use, never exceed rated throughput
• Daily checks: Monitor powered, stopping device position, leaks, oil drain valve and sludge tank level
• Weekly maintenance: Test monitor alarm, clean test cocks/probes, drain accumulated oil
• Monthly/quarterly checks: Monitor calibration valid (<5 years), inspect plate pack, verify no bypass
• Annual/survey checks: Functional test of system, Oil Record Book Part I entries, monitor sealed and data storage intact
• Standards: MEPC.107(49) or MEPC.60(33)
• ETO role: Verify calibration/sealing, stopping device operation, maintenance per manual/SMS, record in Oil Record Book Part I, report defects, confirm IOPP validity