A mechanical, hydraulic governor utilises centrifugal force generated by rotating flyweights to regulate engine speed. The flyweights are mounted on a rotating sleeve whose speed is directly proportional to the engine's speed (often through a gear). As engine speed changes, the centrifugal force acting on the flyweights varies, compressing or expanding a spring. This spring movement acts on a pilot valve, which controls the flow of hydraulic oil to a power piston or servo piston.

• Increased Load (Reduced Speed): When the engine load increases, the engine speed drops. The decrease in centrifugal force allows the spring to push the pilot valve down. This allows pressurised oil to flow under the power piston, forcing it upwards. The upward movement of the power piston increases the fuel supply to the engine, increasing the engine's speed. Simultaneously, the power piston's movement reduces the spring pressure on the pilot valve, causing it to rise and cut off the oil supply, stopping the adjustment.

• Decreased Load (Increased Speed): Conversely, if the load decreases, the engine speed increases. The increased centrifugal force compresses the spring, moving the pilot valve upwards. Oil drains from under the power piston, causing it to move down under spring force, reducing the fuel supply and engine speed. The downward movement of the power piston releases the spring pressure, causing the pilot valve to move down and stop the oil flow.

The conical shape of the spring ensures stability and linearity in the relationship between engine speed and fuel adjustment. A slight "offset" or droop in the speed regulation may exist; this is typically adjustable to minimize but not eliminate the speed variation from the set point.

Causes of Failure:

1. Contaminated or dirty governor oil.
2. Low oil level, allowing air to enter and cause foaming.
3. Play or "lost motion" in engine linkages or fuel pump connections.
4. Insufficient governor output shaft travel to fully adjust fuel delivery.
5. Weak or deteriorated spring.
6. Sticking of the servo piston or pilot valve.
7. Worn governor components.
8. Binding or restriction in linkage movement.
9. Issues with the drive gear.

Actions to Take if Immediate Correction Cannot Be Achieved:

• Shift from Bridge/ECR control to local manoeuvring.
• Reduce the engine load to below 80% MCR.
• Disconnect the governor linkage from the fuel pump and switch to manual or local control.

• In rough seas, where the ship may pitch significantly, the engine may surge as the propeller emerges from the water. To mitigate this, reduce engine speed to ensure stable operation.
• Station a duty engineer at the local manoeuvring stand to monitor the engine closely.
• Record and analyze all parameters, ensuring stable operation.
• Keep the engine room manned at all times and assign additional watchkeepers as necessary during the operation period.

ALTERNATE ANSWER:

Main Engine Governor

(a) Operation of an Electronic Main Engine Governor

An electronic governor for a main engine operates as a speed-setting device rather than a constant-speed governor. Its primary function is to maintain a set speed by regulating fuel injection. The system's main components are:

• A magnetic pickup sensor is installed near the engine's flywheel. It generates a signal proportional to the engine's rotational speed. This signal is the actual speed feedback.
• Speed Control Unit is the "brain" of the system. It continuously compares the actual engine speed (from the sensor) with the commanded speed (set by the operator from the ECR or bridge).
• Actuator: Based on the comparison, the control unit sends a signal to an electro-hydraulic or electro-pneumatic actuator. This actuator is mechanically linked to the fuel racks of the engine's fuel pumps, which it adjusts to control the quantity of fuel injected into each cylinder.

The control unit also incorporates several limiters to prevent engine overload. These include:

• Scavenge air limiter: Prevents excessive fuel injection at low scavenge air pressures.
• Torque limiter: Limits the maximum torque output to protect the engine.
• Load limiter: Prevents the engine from being overloaded beyond its safe operating parameters.

• Pick-up sensor failure
• Control unit malfunction
• Damage to control cables
• Electrical interference due to earth fault
• Loose connections or short circuits in wiring

Action to be taken if the governor fails:

If the governor fails and immediate correction is not possible, the engine must be switched to emergency/local control. This procedure bypasses the electronic governor and allows manual control of the fuel pumps.

Procedure for operating without the governor:

1. The engine speed must first be reduced to below 80% MCR (Maximum Continuous Rating) from the ECR or bridge.
2. The control switch is moved from "Remote" to "Emergency" or "Local."
3. The mechanical link between the governor's actuator and the engine's fuel racks must be disconnected. This is done by quickly moving the governor's impact handwheel to the opposite position.
4. The emergency regulating handwheel is then connected to the fuel racks.
5. The engine speed and load are now controlled manually using the emergency regulating handwheel on the local console. The load is adjusted based on the lever position in the ECR or bridge.

Important Considerations during Emergency Operation:

• The changeover must be performed carefully and quickly to maintain control of the engine.
• Care must be taken to ensure the reversing unit is in the correct position for the desired direction of engine rotation.
• The operator must continuously monitor the engine's parameters as there are no automatic controls or limiters in place during manual operation.