Crankshaft fracture
Most of the fractures occur at the transition between the journal and the crank arm. The reasons are as follows: the transition radius is too small; the radius is not processed during heat treatment, resulting in stress concentration at the junction; the radius is processed irregularly, with local cross-section mutations; long-term overload operation, and some users increase the speed at will to increase production, which worsens the stress condition; the material itself has defects, such as sand holes and shrinkage in the casting. In addition, cracks at the oil hole on the crankshaft can also be seen causing fractures.
Fault cause analysis:
1. Poor crankshaft quality
If the crankshaft is not original and of poor quality, the high-speed operation of the excavator may easily cause the crankshaft to break.
2. Improper operation
During the operation of the excavator, if the throttle is too large/too small, fluctuates, or the excavator is operated at high load for a long time, the crankshaft will be damaged by excessive force and impact, causing fracture.
3. Frequent emergency braking
When operating the excavator, if the clutch pedal is often not stepped on, the emergency braking will cause the crankshaft to break.
4. The main bearings are not aligned
When installing the crankshaft, if the center lines of the main bearings on the cylinder block are not aligned, after the excavator is started, it is easy to cause the bearings to burn and the shaft to stick, thereby causing the crankshaft to break.
5. Poor crankshaft lubrication
If the oil pump is severely worn, the oil supply is insufficient, the oil pressure is insufficient, and the engine lubricating oil channel is blocked, the crankshaft and the bearing will be in a state of friction for a long time, causing the crankshaft to break.
6. The gap between the crankshaft parts is too large
If the gap between the crankshaft journal and the bearing is too large, the crankshaft will impact the bearing after the excavator is running, causing the bearing to burn and the crankshaft to be damaged.
7. Loose flywheel
If the flywheel bolts are loose, the crankshaft parts will lose their original balance and shake during the operation of the excavator, which may easily cause the tail end of the crankshaft to break.
8. Unbalanced operation of each cylinder
If one or more cylinders of the excavator are not working, the cylinders are unbalanced, and the weight deviation of the piston connecting rod group is too large, it will also cause the crankshaft to break due to uneven force.
9. Too early oil supply time
If the fuel supply time is too early, the diesel will burn before the piston reaches the dead center, which will cause the crankshaft to be subjected to great impact and load. If the operation is carried out in this way for a long time, the crankshaft will be fatigued and broken.
10. The piston is broken and forced to work
If the power output is reduced and there is an abnormal sound in the cylinder, continue to work. It is likely that the piston is broken, causing the crankshaft to lose balance, deform or break easily.
Tel/Whatsapp:+8613367611012
Email:karen@coolerfreezerunit.com
Post time: Jul-24-2024