The rated speed of the main propulsion...

Question 1 / 2066636eef28f7522a1c52017e

Question 1 of 2066636eef28f7522a1c52017e

The rated speed of the main propulsion diesel engines on your oil platform supply vessel is 900 rpm. The installed centrifugal overspeed trip device similar to the one shown in the illustration is designed to shut down the engine at 110% of rated speed. Upon testing the overspeed trip device, you determine that the actual shutdown occurs at 1080 rpm. Which of the following would account for this? Illustration MO-0101

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🔍 Key Concepts

• Centrifugal overspeed trip operation: flyweights vs spring force • Relationship between spring compression and the RPM at which the trip occurs • Difference between designed trip speed (110% of 900 rpm) and actual trip speed (1080 rpm)

💭 Think About

• Is the actual trip speed higher or lower than the designed 110% speed, and what does that tell you about the total spring force holding the trip mechanism in? • If the compression spring is made stronger (more compressed) versus weaker (less compressed or broken), would the weights need a higher or lower RPM to move outward enough to trip? • How would a loose jam nut affect the setting of the adjusting nut over time—could it move so the spring gets tighter, looser, or either depending on vibration direction?

✅ Before You Answer

• Calculate 110% of the rated 900 rpm and compare it to 1080 rpm to decide whether the trip is occurring early or late. • Match early vs late trip to the effect of more vs less spring compression on centrifugal devices. • Rule out choices that would clearly make the trip happen at a lower RPM, not a higher one.

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Question 1 of 20

The jam nut (item #14) was not properly tightened against the adjusting nut (items #13) when the overspeed trip was last set.

The compression spring (item #12) was excessively compressed when the overspeed trip was last set.

The compression spring (item #12) was insufficiently compressed when the overspeed trip was last set.

The compression spring (item #12) has broken since the last time the overspeed trip was last set.

Question 1 / 2066636eef28f7522a1c52017e

Question 1 of 2066636eef28f7522a1c52017e

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Question 1 of 20

66636eef28f7522a1c52017e

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🔍 Key Concepts

💭 Think About

✅ Before You Answer

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