Excavator Engine Crankshaft Fracture Problem

 The fracture of the crankshaft usually starts from the smallest crack, and most of the cracks occur in the connection part with the crank arm at the fillet of the connecting rod journal of the head cylinder or the end cylinder. During the operation, the crack gradually expands and suddenly breaks when it reaches a certain level. The brown part is often found on the broken surface, which is an old crack, and the shiny and shiny tissue is the trace that developed to the sudden breakage later. LandTopMall is a store that integrates various engine parts such as excavators and diesel engines. There are many high-quality parts in our store. For instance, crankshafts fit for Yanmar 4tnv94l engine were the best-selling.

 

 

Engine Crankshaft Fracture Problem

1. The rounded corners at both ends of the crankshaft journal are too small

When grinding the crankshaft, the grinder failed to correctly control the axial fillet of the crankshaft. In addition to the rough surface processing, the fillet radius was too small, so a large stress concentration occurred at the fillet when the crankshaft was working, and the crankshaft was shortened. fatigue life.

 

2. The offset of crankshaft main journal axis

The axis of the crankshaft main journal is offset, which destroys the dynamic balance of the crankshaft assembly. When the diesel engine runs at high speed, a strong inertial force is generated, which leads to the fracture of the crankshaft.

 

3. The cold competition of the crankshaft is too large

The crankshaft will be greatly bent after long-term use, especially after the accident of burning tiles or pounding the cylinder, and should be removed and corrected by cold pressing. Due to the plastic deformation of the metal inside the crankshaft during calibration, large additional stress will be generated, thereby reducing the strength of the crankshaft. If the cold competition is too large, the crankshaft may be damaged or cracked, and this crankshaft will break soon after installation.

 

4. The flywheel is loose

If the flywheel bolt is loose, the crankshaft assembly will lose its original dynamic balance, and the diesel engine will vibrate after running, and at the same time generate a large inertial force, resulting in fatigue of the crankshaft and easy breakage at the rear end.

 

 

5. The crankshaft itself is of poor quality

Buying crankshafts should not be greedy for cheap and must be purchased from regular channels. It should also be checked carefully before installation, and if there is any problem, it should be replaced or returned in time. In addition, when the engine is overhauled, the crankshaft should be subjected to magnetic flaw detection or oil-immersed percussion inspection. If there are radial or axial cracks extending to the shoulder fillet on the surface of the journal, the crankshaft cannot be reused. LandTopMall is a leading crankshafts supplier, our crankshafts are provided by an experienced manufacturing company from Global Sources. Currently the best-selling crankshaft in LandTopMall, it is not only suitable for Yanmar 4tnv94l engine but also suitable for Komatsu 4d94le engine.

 

6. The main bush is different from the shaft

When the crankshaft is assembled, if the center lines of the main bushes on the cylinder block are not on the same axis, the accident of burning the bushes and holding the axles will easily occur after the diesel engine works, and the crankshaft will also break under the strong action of alternating stress.

 

7. Excessive crankshaft assembly clearance

If the clearance between the crankshaft journal and the bearing bush is too large, the crankshaft will impact the bearing bush after the diesel engine runs, but the alloy falls off and the bush is burned to hold the shaft, and the crankshaft is also easily damaged.

 

8. The oil supply time is too early or the oil volume of each cylinder is uneven

If the fuel injection pump supplies fuel too early, the piston will burn before reaching the top dead center, which will cause the diesel engine to knock, and the crankshaft will be impacted by alternating stress. If the amount of oil supplied to each cylinder is not uniform, the crankshaft journals will be unevenly stressed due to the inconsistency of the explosion cases of each cylinder, resulting in premature fatigue and cracks.

 

9. Poor crankshaft lubrication

If the oil pump is seriously worn, the lubricating oil channel is dirty and the circulation is not smooth, the oil supply will be insufficient and the oil pressure will drop, resulting in the failure to form a normal lubricating oil film between the crankshaft and the bearing bush, resulting in dry friction and causing the burning bush to hold the shaft. , broken crankshaft, and other major accidents

 

10. Crankshaft fracture caused by improper operation

If the accelerator is too large or too small, frequent braking, or overloaded operation for a long time, the crankshaft will be damaged by excessive torque or shock load. In addition, when accidents such as speeding, ramming, and top valve occur in the diesel engine, the crankshaft is also prone to breakage.

For replacement engine parts, please call: (+852) 63548665 to contact our parts experts for more information and prices on crankshafts.