Question 70 OSE01 - Chief Engineer - OSV

The Correct Answer is A **Explanation for A (Correct):** On large marine diesel engines, especially those used in critical service like anchor handling supply vessels, emergency manual shutdown mechanisms are designed for immediate and reliable stoppage, often leveraging the safety systems already in place. The manual shutdown lever, when activated by a remote pull cable (ensuring the operator is safely away from the running engine), typically triggers the engine's **over speed trip mechanism**. This mechanism is designed to cut off fuel supply or block air intake instantly, ensuring rapid shutdown. Using the over speed trip system for emergency manual shutdown is standard practice because it provides the fastest and most reliable method of engine stoppage independent of the main governor control. **Explanation for B (Incorrect):** While the governor controls the fuel linkage, the primary manual emergency shutdown mechanism does not typically use the governor linkage directly, nor is it operated by the emergency trip *reset* lever. The reset lever is used *after* an over speed trip has occurred to prepare the system for restart, not to initiate the shutdown itself. **Explanation for C (Incorrect):** This option correctly identifies that the shutdown uses the over speed trip mechanism, but incorrectly states the mechanism of operation: it is not operated by the over speed trip *reset* lever. As noted above, the reset lever is for restoring the system after a trip, not initiating a manual trip. The operation is via a remote pull cable connected to the trip lever. **Explanation for D (Incorrect):** This option correctly identifies the use of a remote pull cable for operation, but incorrectly states that it uses the **governor fuel control linkage** to accomplish shutdown. While manipulating the governor linkage could slow the engine or stop it, an emergency manual shutdown requires an immediate, positive stop, which is best achieved by triggering the dedicated high-speed trip mechanism (which instantly cuts fuel or air) rather than relying on the slower, modulated control of the governor linkage.