Question 23 DDE04 - Designated Duty Engineer - 1000-4000 HP

The Correct Answer is B **Explanation of Option B (Kerosene or diesel fuel):** Kerosene and diesel fuel are refined petroleum distillates chemically very similar to the fuel (marine diesel) already flowing through the system. They are effective, mild, and readily available petroleum-based solvents suitable for dissolving accumulated sludge, varnish, and light contaminants typically found in fuel strainers. Crucially, because they are chemically related to the fuel oil itself, they are compatible with the metallic elements, gaskets, and seals (which are designed to handle petroleum products) of the strainer, minimizing the risk of corrosion, swelling, or damage. Using the fuel oil itself (or a close relative like kerosene) is a standard, safe, and manufacturer-recommended practice for cleaning fuel system components. **Explanation of Incorrect Options:** * **A) Perchloroethylene or trichlorethylene:** These are chlorinated solvents. While excellent degreasers, they are extremely aggressive and highly volatile. Their chemical properties can potentially damage certain synthetic rubber seals and gaskets (like Viton or Nitrile) commonly used in fuel systems, and residual amounts may also be corrosive to metals or incompatible with the diesel fuel when the system is restarted. They are generally avoided for simple maintenance cleaning in diesel fuel systems. * **C) White mineral spirits:** While mineral spirits (a petroleum distillate) are often used as mild general-purpose solvents, they are not typically the primary recommendation for fuel system components in heavy diesel engines. Kerosene or diesel fuel itself is preferred due to their established compatibility profile with the specific fuel being filtered. * **D) Benzene or toluene:** These are highly volatile, aromatic hydrocarbons. They are powerful solvents but are also toxic, carcinogenic (Benzene), and have very high flash points, making them significant safety hazards (fire and health) in a machinery space environment. Furthermore, their powerful nature is unnecessary for cleaning light fuel contaminants, and the high volatility makes them impractical for an open cleaning procedure.