Question 418Motor Plants - Assistant Engineer

70% to pass

After following the prescribed procedures to measure the thrust bearing clearance shown in the illustration, the distance "F" is determined to be 200 mm, and 'f1' is 2.3 mm. Which of the following statements describes the condition indicated by these dimensions? Illustration MO-0121

Diagram for USCG Motor Plants Assistant: After following the prescribed procedures to measure the thrust bearing...

AThese dimensions indicate the presence of flourishing marks on the thrust shoes; the marks becoming visible as the distance at 'f1' increases.

BIt is possible for the shaft to move axially 2.3 mm during astern operation and relates to an excess movement of 1.3 mm, 0.3 mm beyond the maximum worn play.

CThe loading ratio, or shaft diameter divided by collar surface area is within 2.7:1.

DThe total active thrust area is 202.3 mm, well within the standards set forth by the GSMA (German Society for Machining Accuracy).

AI Explanation

The correct answer is B. These dimensions indicate that the shaft is able to move axially 2.3 mm during astern operation, which is 1.3 mm more than the maximum worn play typically allowed. This excess axial movement of the shaft suggests potential issues with the thrust bearing clearance and requires further inspection or adjustment to bring it within the recommended specifications. The other answer choices are incorrect because: A) Flourishing marks on the thrust shoes are not directly indicated by the given dimensions. C) The loading ratio is not provided, so this statement cannot be verified. D) The total active thrust area of 202.3 mm does not necessarily fall within any specific standards without more context.

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