Question 31 QMED01 - Junior Engineer

The Correct Answer is A. **Why option A ("pump suction line") is correct:** A coarse screen wire mesh strainer (often called a sump strainer or suction strainer) is placed in the pump suction line, typically submerged in the oil sump or reservoir. Its primary function is to provide basic, preliminary filtration to protect the positive displacement oil pump itself. The coarse mesh is designed to catch large debris, rags, metal chips, or foreign objects before they can enter and damage the precision components of the pump (gears, rotors, etc.). Because it is upstream of the pump, the strainer must have a large surface area and coarse mesh to prevent restricting the oil flow, which would cause pump cavitation and lubrication failure. **Why the other options are incorrect:** * **B) filter bypass return line:** The filter bypass line is used to route oil around the main filter element if it becomes clogged. This line might be equipped with a pressure relief valve, but it typically does not contain a dedicated coarse screen. Furthermore, oil passing through this line is destined directly for the bearings/system and needs fine filtration, not coarse screening. * **C) pump discharge line:** The pump discharge line is under high pressure. This location is where the fine-tolerance main lubricating oil filters (full-flow filters) are located. Placing a coarse screen here would be redundant and inefficient, as the oil must still pass through the much finer main filters immediately afterward, and the high pressure could damage a simple mesh strainer. * **D) gravity tank inlet line:** While some complex, very large diesel systems might use a gravity settling tank, the oil entering such a tank would either be clean makeup oil or return oil from the engine. Return oil would already have passed the main filters and the sump strainer. Gravity settling is a method for separating water and sludge, not a primary location for mechanical coarse straining.