1. 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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