Question 163Motor Plants - 1st Asst/Chief

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 Chief: After following the prescribed procedures to measure the thrust bearing...

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

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

CIt 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.

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 C. These dimensions indicate that the shaft can move axially 2.3 mm during astern operation, which relates to an excess movement of 1.3 mm, 0.3 mm beyond the maximum worn play. This is the correct interpretation because the maximum recommended axial play for a thrust bearing is typically 2.0 mm, and the measured play of 2.3 mm exceeds this limit, indicating potential issues with the thrust bearing. The other answer choices are incorrect because: A) the loading ratio is not mentioned in the problem; B) the flourishing marks are not a relevant factor in this scenario; and D) the total active thrust area is not a key measurement in determining the condition of the thrust bearing.