Question 44 1AE01 - First Assistant Engineer

The Correct Answer is A **Why Option A is Correct:** Option A, "Cotton waste packed in perforated metal containers or cylindrical cartridges," describes a type of **full-flow** or **bypass depth filter**. Filters utilizing cotton waste, cellulose, or similar fibrous media are generally classified as mechanical or physical filters. They are designed to remove solid contaminants (dirt, metal particles, carbon) primarily through mechanical entrapment, without significantly altering the chemical composition of the oil. Modern high-detergent additive oils rely on these detergent additives to hold microscopic soot and contaminants in suspension. Filters that are purely mechanical (like cotton waste depth filters) effectively remove the large solid particles while allowing the detergent additives and the suspended contaminants (which are often too fine for mechanical removal) to pass through, preserving the oil's additive package and its ability to keep the engine clean. **Why Other Options Are Incorrect:** * **B) Cylindrical elements containing Fuller's earth combined with cellulose:** Fuller’s earth (or activated clay/bentonite) is a highly effective **adsorbent** material. While excellent for removing moisture, oxidation products, and certain polar compounds, it is known to aggressively strip performance additives (like detergents, dispersants, and corrosion inhibitors) from the oil. Its use is unacceptable for modern, high-detergent additive oils as it quickly renders the lubricant ineffective. * **C) Chemically treated paper and waste in cartridges:** While modern pleated paper elements are common and acceptable (usually referred to as synthetic or cellulose media), the term "chemically treated" often implies treatment intended to enhance adsorption, similar to Fuller's earth, or a specialized media designed for specific chemical removal. If the "chemical treatment" targets polar compounds, it risks removing vital detergent and dispersant additives, making it generally unsuitable for standard high-detergent oils unless specifically certified by the OEM. * **D) Foamed polyurethane of the impingement type supported on perforated metal rings:** Foamed polyurethane media is often used in air filters or preliminary strainers due to its low density and large pore size. While it provides low restriction, it generally lacks the necessary efficiency (Beta ratio) to be effective for fine filtration required for modern engine lube oils, especially in removing critical contaminants like abrasive wear particles or large soot clusters. It is not a standard, acceptable media for high-performance lube oil filtration.