Question 64 1AE01 - First Assistant Engineer

The Correct Answer is D **Explanation for Option D (Correct Answer):** Option D, "Line shaft bearing housings are typically split half pedestal type bearing housings," is correct because of the functional requirements and maintenance considerations associated with industrial line shafts: 1. **Split Half Design:** Line shafts often run continuously over long distances, supported by multiple bearings. A split half housing (where the top and bottom halves separate) is essential because it allows for easy installation, inspection, and replacement of the bearing element (such as a plain bearing, ball bearing, or roller bearing) without requiring the disassembly or removal of the entire shaft, pulleys, or couplings from the system. This significantly reduces downtime for maintenance. 2. **Pedestal (Pillow Block) Type:** The pedestal (or pillow block) design mounts the bearing housing onto a flat surface parallel to the shaft's axis (usually the floor, frame, or ceiling truss via hangers). This robust base provides the necessary stability and alignment crucial for supporting the rotational and radial loads exerted by the shaft and attached machinery (like large drive belts and pulleys). **Explanation for Why Other Options are Incorrect:** * **A) Line shaft bearing housings are typically single-piece pedestal type bearing housings.** * This is incorrect primarily because of the "single-piece" designation. Single-piece (solid) housings necessitate sliding the bearing onto the shaft from the end. This is impractical and often impossible in long line shaft systems that have fixed components (pulleys, couplings) already installed along their length. Maintenance would require dismantling the entire drive system. * **B) Line shaft bearing housings are typically single-piece flange type bearing housings.** * This is incorrect for two reasons: 1) The "single-piece" design presents the same maintenance challenges as noted in A. 2) Flange type housings mount perpendicular to the shaft (often bolted to a machine side or wall), whereas line shafts are typically supported from below or hung from above, requiring the pedestal (pillow block) arrangement. * **C) Line shaft bearing housings are typically split half flange type bearing housings.** * While the "split half" design is desirable, the "flange type" designation is generally incorrect for standard line shaft support. Line shafts usually require the robust base support provided by pedestal (pillow block) housings rather than the mounting orientation typical of flange units.