The main engines on your harbor tug are equipped with over speed trip devices as shown in the illustration. By what method is the engine shutdown on an over speed condition? Illustration MO-0171
• Study how the trip shaft in the illustration is linked to the injectors on each bank. • Notice whether the overspeed device is acting on the injector racks (fuel control) or on the plunger motion itself. • Look for any sign of an electrical or solenoid component versus a purely mechanical linkage.
• In the tripped position, what exactly moves on the injectors according to the arrows and labels in the figure? Does anything indicate that the plungers stop reciprocating, or that fuel control goes to a no‑fuel setting? • Does the system shown appear to shut off fuel individually at each injector, or by closing a common supply line? How can you tell from the components drawn? • Compare the latched and tripped positions: what change would actually stop fuel delivery while the camshaft and rocker arms still rotate?
• Verify which part in the drawing is labeled as going to the right bank injectors and left bank injectors, and what motion that shaft causes at the injectors. • Confirm whether the illustration shows any solenoid valve or electrical wiring; if it does not, be cautious with answers mentioning solenoids. • Check whether the injector rocker arm still operates in the tripped position; if it does, then the shutdown must come from how fuel is metered, not from stopping all mechanical motion of the plunger.
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