Cause of Diesel Generator Overspeed
by Starlight Generator dieselgeneratortech1.
Fault phenomenon of diesel generator overspeed
Under normal operation,
the engine speed suddenly rises, so that the engine speeds up beyond the rated
speed and loses control, and emits a huge roar, the exhaust pipe emits a lot of
black smoke or blue smoke.
2.
Cause of failure
The fundamental cause of
diesel engine overspeed is that diesel engine loses or changes its speed
regulation characteristics. Faults of fuel injection pump and governor, such as
stagnation or looseness of relevant components, will cause excessive oil supply
and loss of normal speed regulation characteristics, while the combustion
chamber entering additional diesel or oil will change the speed regulation
characteristics of diesel engine.
1) Faults of injection
pump and speed regulator
A. When assembling and
repairing, impact the plunger, oil outlet valve seat of fuel injection pump,
too much tightening torque will cause the deformation of plunger sleeve,
impurities entering into the clearance of plunger pair, too thin gasket on the
positioning bolt of plunger sleeve or too long bolt, which will cause the
plunger of fuel injection pump to rotate inadequately or be stuck in the
position of large oil supply;
B. Loosening of fixing
screw for adjusting gear ring of fuel injection pump plunger which causes
injection pump plunger loss control;
C. The ball head of the
plunger adjusting arm or the gear rod adjusting arm of the fuel injection pump
does not enter the adjusting fork groove, so that the plunger is in the
position of large oil supply;
D. Accelerating pedal
pull rod or oil supply adjusting gear rod and the movable part of governor are
stuck, and oil quantity adjusting gear rod and speed adjusting pull rod are out
of joint;
E. The excessive
lubrication oil, too viscous or too dirty in the governor cause the weight of
the governor can not be thrown out in time when the speed rises, which causes
the pull rod or the gear rod to lose control of the governor;
F. Full speed governor
can not be thrown away because of skew of flying ball seat or abrasion of
inclined sliding groove of thrust plate transmission plate, which increases the
sliding resistance of flying ball;
G. The springs of
injectors are too weak or broken, which results in too low injection pressure
and excessive fuel consumption in cylinders;
H. Flying ball Pin Shaft
of governor broken off and flying ball flying off.
The above reasons make
the speed of diesel engine increase, while the "speed characteristic"
of plunger fuel injection pump increases the fuel supply with the increase of
the speed, which leads to the vicious circle between the speed and the fuel
supply, resulting in the occurrence of overspeed accidents.
2) Additional fuel
enters the combustion chamber
A. Engine oil level too
high causes excessive oil to rush into the cylinder then enter the combustion
chamber to burn;
B. Serious wear of
piston rings and excessive clearance of cylinder wall lead to a large amount of
oil entering combustion chamber to burn;
C. Excessive gap between
air door and its catheter coordination is too large, which cases oil for valve
distribution chamber enter into combustion chamber to burn;
D. After cleaned air
cleaner, the excessive residual gasoline makes the higher concentration
gasoline vapor enter the combustion chamber to burn;
E. A diesel engine with
a supercharger enters the combustion chamber to burn because of the damage to
the oil seal of the supercharger;
F. The solenoid valve of
the cryogenic starter leaks oil, which causes excess diesel oil to enter the
combustion chamber to burn;
G. Horizontal diesel
engine inclines seriously, causing oil to flow into the valve chamber and be
sucked into the combustion chamber to burn.
3.
Solution to overspeed fault of diesel generator set
1) Forced stoppage
Once the diesel engine
has overspeed, the following measures should be taken promptly to force the
diesel engine to stop immediately
A. Quickly retrieve the accelerating pedal to the stop position;
B. For fuel injection
pumps with exposed rods or toothed rods, the rods should be quickly pulled back
to the stop position;
C. For diesel engines
equipped with decompression devices, the decompression handle should be quickly
pulled to the decompression position, so that the diesel engine shuts down
because of the uncompressed gas;
D. If a closing device
is installed on the intake pipe, the extinguishing device shall be closed
immediately or the intake port of the air filter shall be blocked quickly with
cloth, and the fuel tank switch shall be closed to cut off the gas and oil
circuit, stop the oil supply and gas supply, and cause the cylinder to be
suffocated and shut down;
E. Put the transmission
into the high gear in time, while trampling the brake pedal to the bottom, and
slowly lift the clutch pedal, so that the engine is forced to extinguish.
2)After the generator
set stop working, to make a definite diagnose
A. If the acceleration
pedal is raised rapidly, the engine will not continue to rise after reaching
the maximum speed, the fault is the acceleration pedal rod or arm is jammed;
B. If the acceleration
pedal is raised rapidly, the engine speed can not be reduced or extinguished
immediately, usually the governor is out of order;
C. If the acceleration
pedal is picked up, the engine speed continues to rise, indicating that the
fuel injection pump has a fault;
D. If the fuel supply
system is good, it means that there is extra fuel or oil entering the cylinder.
All above problems
should be maintained by professional personnel.
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Created on Apr 27th 2019 20:41. Viewed 172 times.