Question 18 UFIV02 - Assistant Engineer - UFIV

The Correct Answer is C ### Why Option C (Kerosene or diesel fuel) is Correct: The fuel strainer elements are designed to filter fuel, typically diesel fuel. When cleaning these metallic elements, the preferred solvent is one that is chemically compatible with the materials (metal, gaskets, etc.) and effective at dissolving the residues (fuel gums, light oils) without leaving harmful residue itself. **Kerosene and diesel fuel** are chemically identical to or closely related to the fuel being filtered. They are petroleum-based solvents with low volatility, excellent lubricating properties, and high flash points (making them safer to handle than highly volatile solvents). They dissolve the accumulated sludge and residues effectively, and any remaining fuel solvent residue in the filter element is simply compatible with the engine's main fuel supply. ### Why the Other Options are Incorrect: * **A) White mineral spirits:** While mineral spirits are a petroleum-based solvent and could potentially clean the element, they are generally less effective at dissolving heavy diesel residues than kerosene or diesel fuel itself. Furthermore, mineral spirits sometimes contain additives or higher levels of less volatile components that are not ideal to introduce into the high-pressure fuel system of a diesel engine. Standard practice favors using the fuel itself (diesel) or a closely related product (kerosene). * **B) Benzene or toluene:** These are aromatic hydrocarbons that are highly effective solvents but are extremely volatile, have very low flash points (making them highly flammable and dangerous for general shop use), and are significant health hazards (carcinogens and severe respiratory irritants). They would not be recommended by an engine manufacturer for routine cleaning on a vessel due to safety concerns. * **D) Perchlorethylene or trichlorethylene:** These are chlorinated solvents. While excellent degreasers, they are highly toxic, environmentally restricted, and have serious negative effects on many rubber compounds and seal materials (potentially damaging gaskets within the strainer assembly). They are not standardly recommended for cleaning fuel system components where material compatibility and safety are paramount.