Sketch and describe a total flooding CO₂ system for machinery spaces, state which valve to operate first and why, and state the periodic maintenance required?

flowchart TD
    A[CO₂ Cylinder Bank] -->|CO₂| B[Cylinder Head Valve]
    B --> C{Bursting Disc 177-193 bar}
    C -->|CO₂| D[Non-Return Valve]
    D --> E[Sector Valve]
    E --> F[Distribution Chest]
    F --> G[Quick-Opening Valve]
    G --> H[Nozzle]
    I[Pilot Cylinder x2] -->|Pilot Gas| J[Release Box]
    J -->|Pilot| E
    K[Control Panel] -->|Electrical| J
    K -->|Interlock| E

• System components: CO₂ storage cylinders (BS ISO 3500:2005), cylinder head valve with bursting disc (177–193 bar), non-return valves, sector valve, distribution chest, pilot cylinders, nozzles
• CO₂ quantity: Sufficient for largest protected space per SOLAS II-2/10 and FSS Code Chapter 5
• First valve: Sector (stop) valve between storage and manifold to isolate system and engage control cabinet interlock
• Maintenance – cylinders: Inspect/test per MGN 374 and BS EN 1968-2002, retest before twice interval, check bursting discs and discharge valves
• Maintenance – piping/valves: Test non-return valves, operate quick-opening valves, check sector valve and interlock, inspect for leaks/corrosion
• Maintenance – controls: Test pilot cylinders, release box, alarms, electrical interlocks
• Records: Log all maintenance in PMS per ISM Code section 10
• ETO checks: Verify electrical components, interlocks, alarms, manual overrides, record tests