Question 15

The Correct Answer is A ### Why Option A ("Bypass filtration.") is correct: The illustration MO-0182 must depict a lubrication system where only a **small portion** (typically 5% to 10%) of the total oil flow from the pump is continuously diverted to a high-efficiency filter (the bypass filter). The rest of the oil goes directly to the engine bearings or through a main full-flow filter (not the bypass unit). The filtered oil then returns directly to the main oil sump, bypassing the primary lubrication circuit entirely. Bypass filters are designed to remove extremely fine particulates and often water, thereby maintaining overall oil cleanliness over long periods, without restricting the necessary high volume flow required by the engine. This configuration is the definition of a bypass filtration system. ### Why the other options are incorrect: * **B) Shunt filtration:** While "shunt" can sometimes be used synonymously or loosely associated with "bypass," shunt filtration typically refers to a system where a filter is placed in parallel across the main oil flow (similar to bypass), but the term is less standardized in lubrication engineering than "bypass" or "full-flow." In standardized marine engineering terminology, the scheme described is precisely **bypass filtration**. * **C) Sump filtration:** This term generally refers to the use of a coarse strainer or screen placed directly in the sump or at the pump inlet to prevent large debris from entering the pump, not a complete, circulating filtration scheme used to maintain oil cleanliness. * **D) Full-flow filtration:** In a full-flow filtration system, **100%** of the oil pumped from the sump must pass through the main filter element before reaching the critical engine bearings and moving parts. The illustrated system, where only a fraction of the oil is diverted and returned to the sump, clearly is not a full-flow system.