According to 46 CFR Part 61, what is the maximum allowable permitted wear on a stern tube bushing for a vessel that has its propelling machinery located amidships, with a water lubricated stern tube bearing carrying a 12 inch diameter shaft ?
• 46 CFR Part 61 – especially the tables/paragraphs on stern tube bearing clearances • How shaft diameter is used to determine allowable wear or clearance • Difference between oil-lubricated and water-lubricated stern tube bearings in the regulations
• Identify exactly where in 46 CFR Part 61 stern tube bushing wear or clearance limits are listed and see if it’s given as a fraction of shaft diameter or a fixed value for this size range. • Ask yourself: for a 12-inch shaft, does the regulation specify a single number, or a range (e.g., up to a certain diameter = one value, above that = another)? • Compare the answer choices to what you’d get by applying the regulatory formula or table entry to a 12-inch shaft and see which one matches.
• Confirm you are reading the section for water-lubricated (not oil-lubricated) stern tube bearings. • Verify that the rule applies to vessels with machinery amidships, not aft – some limits differ by machinery location. • Double-check any formula or table value you use for a 12 inch diameter shaft and convert it carefully into inches/fractions that match the answer choices.
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