Reading guide
The mechanical failure of diesel engine during operation may cause damage to the base parts, or even mechanical accident. Before the failure of the diesel engine, some abnormal signs will appear in the speed, sound, exhaust, water temperature, oil pressure and other aspects, that is, the fault omen feature. Therefore, operators should make accurate judgments quickly based on the characteristics of omens, and judge the acceptance measures to avoid accidents.
1 "runaway" fault
Precursory characteristics
The rotating speed suddenly rises and becomes faster and faster. It is not controlled by the throttle. The sound is abnormal and harsh. A large amount of blue smoke or black smoke is emitted from the exhaust pipe.
"Runaway" belongs to overspeed and idling. It will not happen when working under load. It is only possible when the load suddenly disappears or reduces at the beginning of starting or working. It is mainly caused by the governor system failure, which makes the oil supply out of control or excessive oil in the oil pan. In case of "runaway" omen, if emergency measures are not taken immediately, major accidents such as cylinder tamping and shaft breaking will eventually occur.
Disposal measures
The purpose of flameout is mainly achieved by cutting off oil or gas.
The emergency measures that can be taken are: first, turn off the throttle to curb the oil supply, and step on the brake; The second is to block the intake pipe and cut off the entry of air; Third, quickly loosen the high-pressure oil pipe to stop oil supply; Fourth, the vehicle diesel engine can use high-level heavy load (braking) during running, so that the engine stalls due to insufficient air torsion.
2 cylinder sticking fault
Precursory characteristics
The speed drops, the operation is weak, the sound is boring, the water temperature is too high, and the indication of the water temperature gauge is over 100 ℃. At this time, sprinkle some water on the parts, which will evaporate rapidly. The main reason is the serious water shortage and the failure of the water cooling system. If the engine is shut down immediately, cylinder sticking may occur.
Disposal measures
Idle for a period of time or turn off the engine and crank the crankshaft for auxiliary cooling to reduce the water temperature to about 40 ℃, and then slowly add cooling water. Be careful not to add cooling water immediately, otherwise the parts will be deformed or cracked due to the sudden rapid drop of local temperature.
3 tamping cylinder failure
Precursory characteristics
There is a "clatter" sound at the crankcase, which is like the sound of a small hammer tapping the hard floor, commonly known as "cylinder knocking". The oil pressure drops and becomes more obvious when accelerating rapidly. The cylinder tamping is a destructive mechanical fault, which is mainly caused by the loosening of connecting rod bolts or the stretching and necking of bolts, and the excessive fitting clearance of connecting rod shaft, resulting in the loosening or breaking of bolts. If there is a knocking sound, but the oil pressure is normal, it is not a sign of tamping the cylinder. It should be considered from the aspect of adjusting the oil supply advance angle.
Disposal measures
Stop the machine immediately for maintenance and replace with new parts.
4 Bush burning fault
Precursory characteristics
The sound is dull, as if the load suddenly increases, the speed drops, the oil pressure drops, and the exhaust emits black smoke. Bush burning will cause the bearing bush and journal to lock up and flameout, mainly due to the damage of the lubricating oil film on the surface of the bearing bush, the direct contact between the bearing bush and the metal on the surface of the journal, the rapid rise of the friction temperature and the occurrence of cementation.
Disposal measures
Stop the machine immediately, remove the cover, check the connecting rod and bearing bush, find out the cause, and repair and replace.
5 broken shaft fault
Precursory characteristics
There is a boring knocking sound in the crankcase. When the accelerator is increased, the knocking sound becomes louder. When the engine is idling, the parts shake seriously and the exhaust emits black smoke. The shaft fracture is caused by mechanical fatigue at the shoulder of the crankshaft journal, and there is a gradual process from crack to fracture. During recessive fission, the precursory characteristics are not obvious. With the expansion of the crack, the precursory characteristics become more and more obvious, resulting in the shaft failure and flameout.
If the throttle shudders or knocks at the same frequency, it may be at the critical point of shaft failure. At this time, remove the cover for inspection, and push the flywheel by hand. If the axial clearance is large and the pushing is not hard, it indicates that the crankshaft has been broken.
Disposal measures
In case of any omen, stop the machine immediately for inspection, and replace the crankshaft in time in case of any crack.
