Suppose a water-lubricated stern tube bearing is being evaluated for wear where the propulsion machinery is located aft. If the tail shaft diameter is 13.5 inches, according to 46 CFR regulations pertaining to periodic tests and inspections as related to machinery and equipment, what would be the maximum clearance diameter permissible before the bearing must be re-bushed?
• 46 CFR requirements for stern tube bearing clearances on water-lubricated bearings • How to calculate maximum allowed clearance based on tail shaft diameter • Relationship between shaft diameter and permissible wear before re-bushing is required
• How do the 46 CFR rules express maximum clearance: as a percentage of shaft diameter, as a fixed value, or in another form? • If the regulation gives a fraction or percentage of the shaft diameter, what is that value and what does it become numerically for a 13.5-inch shaft? • Once you calculate the allowed clearance, which choice is closest to but not less than that calculated limit?
• Look up the exact 46 CFR table or paragraph dealing with water-lubricated stern tube bearing clearances for periodic inspections • Confirm the formula or fraction given in the regulation and apply it explicitly to 13.5 inches (show the multiplication and division steps) • Compare your computed maximum clearance with each option and verify which choice aligns numerically with the regulation-based result
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