How to Fix Generator Overspeed?

Overspeed in generator refers to a situation in which a generator, typically a synchronous generator connected to a power grid, rotates at a speed higher than its rated or designed speed.

How to Fix Generator Overspeed? To fix generator overspeed, take immediate action by stopping the acceleration pedal, pulling back fuel injection pump rods, and engaging the decompression handle (if applicable). Close the extinguishing device, cut off gas and oil supply, and force engine shutdown by engaging high gear and lifting the clutch pedal. Consult professionals for diagnosis and repairs.

How to Fix Generator Overspeed: A Comprehensive Guide

In this guide, we will delve into the causes of generator overspeed and explore effective solutions to address this problem.

Step 1. Understanding the Fault Phenomenon

Under normal operation, overspeed is characterized by a sudden rise in engine speed, emitting a deafening roar, and the exhaust pipe spewing black or blue smoke. Recognizing these signs is crucial to take prompt action.

Step 2. Causes of Generator Overspeed

Faults of Injection Pump and Speed Regulator

Assembly and repair issues: Impacting the plunger or oil outlet valve seat of the fuel injection pump with excessive tightening torque can cause deformations. Additionally, impurities entering the plunger clearance or improper gasket placement can result in inadequate rotation or sticking of the plunger.

Loosening of fixing screw: A loose fixing screw for the adjusting gear ring of the fuel injection pump plunger can cause loss of control over the injection pump plunger.
Misalignment of adjusting components: When the ball head of the plunger adjusting arm or gear rod adjusting arm fails to enter the adjusting fork groove, the plunger may remain in the position of large oil supply.
Stuck components: If the accelerating pedal pull rod, oil supply adjusting gear rod, or movable parts of the governor are stuck, it can lead to loss of control over the governor’s operation.

Issues with the governor: Excessive lubrication oil, viscosity, or dirt in the governor can prevent the governor’s weight from responding promptly to speed increases, causing control loss. Skewed flying ball seats or wear of the inclined sliding groove can increase sliding resistance.
Weak or broken springs: Injector springs that are too weak or broken can result in low injection pressure and excessive fuel consumption in the cylinders.
Mechanical failures: Breakage of the governor’s flying ball pin shaft can lead to the flying ball detaching, causing overspeed.

Additional Fuel Entering the Combustion Chamber

Engine oil level: An excessively high engine oil level can cause oil to rush into the cylinder and subsequently enter the combustion chamber, leading to overspeed.
Piston ring wear and cylinder clearance: Serious wear of piston rings or excessive clearance in the cylinder wall can allow a significant amount of oil to enter the combustion chamber.
Air door coordination: A large gap between the air door and its catheter coordination can allow oil from the valve distribution chamber to enter the combustion chamber.

Residual gasoline in the air cleaner: After cleaning the air cleaner, if excessive residual gasoline remains, higher concentration gasoline vapor can enter the combustion chamber and cause overspeed.
Supercharger issues: Damage to the oil seal of the supercharger in a diesel engine equipped with one can result in fuel entering the combustion chamber.
Cryogenic starter solenoid valve leakage: Oil leakage from the solenoid valve of the cryogenic starter can introduce excess diesel oil into the combustion chamber.

Horizontal diesel engine incline: A severely inclined horizontal diesel engine can cause oil to flow into the valve chamber and be sucked into the combustion chamber, leading to overspeed.

Step 3. Resolving Generator Overspeed

1. Forced Stoppage

When facing an overspeed situation, taking immediate action is crucial to prevent further damage and potential hazards. Here are the steps to force the diesel engine to stop:

Retrieve the accelerating pedal to the stop position quickly.
Pull back the exposed rods or toothed rods of the fuel injection pump to the stop position.

If equipped, pull the decompression handle to the decompression position to shut down the engine.
Close the extinguishing device or block the intake port of the air filter.
Cut off the gas and oil circuit by closing the fuel tank switch to suffocate the cylinder.

Engage the transmission into high gear, press the brake pedal, and gradually lift the clutch pedal to force the engine to shut down.

2. Post-Overspeed Diagnosis

After the generator set has stopped, a definitive diagnosis is necessary to identify the specific cause of the overspeed. Professionals should conduct the following assessments:

Rapidly raising the acceleration pedal and observing if the engine continues to rise indicates a jammed acceleration pedal rod or arm.

If the acceleration pedal cannot immediately reduce or extinguish the engine speed, it suggests a malfunctioning governor.
Raising the acceleration pedal and witnessing a continuous rise in engine speed signifies a fault in the fuel injection pump.
If the fuel supply system is functioning correctly, it points to additional fuel or oil entering the cylinder.

Conclusion

Generator overspeed is a serious issue that demands swift attention to prevent damage and ensure the safety of personnel.

By understanding the causes of overspeed and implementing the appropriate solutions, generator operators can effectively address this problem.

It is vital to seek professional assistance for maintenance and repairs to ensure the reliable and safe operation of diesel generator sets.