Question 41 DDE04 - Designated Duty Engineer - 1000-4000 HP

The Correct Answer is D **Explanation for Option D (Correct):** Option D is correct because pneumatic propulsion control systems (like those controlling clutches or reversing gears on towing vessels) rely entirely on compressed air functioning correctly. 1. **Pressure:** Adequate air pressure is necessary to overcome mechanical resistance and reliably actuate the clutch mechanism. Insufficient pressure leads to slow engagement, slipping, or failure to engage/disengage, causing severe damage to the clutch plates or gearbox. 2. **Dryness:** Moisture (water) in the compressed air system is highly damaging. It can lead to corrosion of internal components, freeze in cold weather (blocking lines or valves), wash away critical lubrication, and cause sticky operation or premature failure of valves, cylinders, and seals. 3. **Cleanliness:** Dirty air (containing oil vapor, rust, or particulate matter) causes premature wear on seals and O-rings, clogs small orifices in control valves (relays, timing valves), and gums up the system, leading to erratic or failed operation. Therefore, successful, reliable, and long-lasting operation requires all three factors—pressure, dryness, and cleanliness—to be maintained rigorously. **Explanation for Other Options (Incorrect):** * **A) Whereas the cleanliness of clutch air is critical, the dryness and pressure are clutch air are of secondary concern.** This is incorrect. Both dryness and pressure are paramount. Lack of pressure prevents operation, and lack of dryness destroys components quickly. * **B) Whereas the clutch air pressure is critical, the dryness and cleanliness of the clutch air are of secondary concern.** This is incorrect. While pressure is vital for function, neglecting dryness and cleanliness will inevitably lead to component failure, system malfunction, and loss of control, overriding the benefit of having correct pressure temporarily. * **C) Whereas the dryness of clutch air is critical, the pressure and cleanliness of the clutch air are of secondary concern.** This is incorrect. While dryness is crucial for longevity, insufficient pressure prevents immediate operation, and lack of cleanliness causes immediate fouling and wear. None of the factors can be considered secondary.