Question 23 3AE01 - Third Assistant Engineer

The Correct Answer is B **Explanation of Correct Option (B):** A diesel engine crankcase ventilation (CCV) system is primarily designed to manage and remove the "blow-by" gases that leak past the piston rings during combustion. These blow-by gases contain unburnt hydrocarbons, oil mist, water vapor, and combustion byproducts, including gases like methane and other combustible vapors. If these gases are allowed to accumulate in the crankcase, they can: 1. Increase pressure, potentially damaging seals. 2. Contaminate the lubricating oil (leading to sludge and corrosion). 3. Create an explosive atmosphere, especially when mixed with the inherent oil mist. Therefore, the main function of the CCV system is to continuously **remove these combustible gases** and vapors from the crankcase, maintaining a slight negative or neutral pressure and preventing dangerous accumulation. **Explanation of Incorrect Options:** * **A) Prevents spark generation:** While maintaining a safe, non-explosive atmosphere is a result of effective ventilation, the CCV system itself does not directly manage or prevent the mechanical or electrical generation of sparks within the crankcase. Spark generation is prevented through proper mechanical design, grounding, and maintenance. * **C) Determines the level of combustible gases:** The CCV system removes the gases; it does not determine, measure, or analyze their concentration. Determining the level of gases requires a separate sensor or monitoring system (gas detector). * **D) Provides inert gas generation in crankcase:** Diesel engine crankcase ventilation systems typically use filtered atmospheric air (or simply draw the gases out into the intake) and do not intentionally generate or inject inert gases (like nitrogen or carbon dioxide) into the crankcase. Inerting is a highly specialized safety measure, usually reserved for large marine engines or specific industrial applications, but it is not the function of a standard CCV system.