Question 32 DDE01 - Designated Duty Engineer - Unlimited HP

The Correct Answer is B **Explanation for Correct Answer (B):** Option B, "Vertical spacing between the metal discs as determined by the thickness of the cleaner blades," is correct because the strainer described is a common type of edge-type filter or disc-stack strainer (often associated with brands like Cuno or similar designs). In this design, filtration occurs as the lubricating oil passes *radially* (horizontally) inward through the small gaps (slots) between adjacent metal discs. The size of this gap—the vertical spacing—is the critical dimension that determines the largest particle size (degree of filtration) that can pass through the element. This spacing is precisely set by the thickness of the spacer elements, often referred to here as the cleaner blades or spacers. **Explanation for Incorrect Options:** * **A) The dimensions of the triangular oil passages in each disc conveying the strained oil upward:** These passages are designed for collecting and conveying the already-strained (clean) oil out of the element. Their dimensions affect flow rate and pressure drop, but not the particle size exclusion capability (degree of filtration). * **C) The length of the oil sump enclosing the straining element:** The length of the sump (reservoir) primarily dictates the overall volume capacity of the oil system and provides a housing for the strainer. It has no direct relationship to the micron rating or particle exclusion capability of the straining element itself. * **D) The number of discs in the disc-stack making up the straining element:** The number of discs determines the total effective straining surface area. A greater number of discs allows for a higher flow rate or longer operating time before cleaning is required, but it does not change the size of the gap between any two adjacent discs, which is the dimension that sets the filtration degree.