The fracture of crankshaft usually starts from the smallest crack, and most of the fracture parts are at the connecting part between the head cylinder or the end cylinder connecting rod journal fillet and the crank arm. In the process of operation, the crack expands gradually and breaks suddenly when it reaches a certain degree. The brown part is often found on the fracture surface, which is obviously an old crack. If the broken surface is shiny, it means that it is suddenly broken. This article will summarize three reasons for the fracture of excavator crankshaft besides the reasons mentioned in the previous article.
1. the oil supply time is too early or the oil quantity of each cylinder is uneven
If the fuel supply time of the fuel injection pump is too early, the piston will burn before it reaches the top dead center. It will cause the diesel engine to knock and make the crankshaft subject to the impact of alternating stress. If the oil supply of each cylinder is uneven, the stress on each journal of the crankshaft will be uneven due to the inconsistent oil supply of each cylinder, resulting in premature cracks.
2. poor crankshaft lubrication
If the oil pump is seriously worn, the lubricating oil passage is dirty and the flow 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 major accidents such as burning the Bush, holding the shaft and breaking the crankshaft.
3. crankshaft fracture caused by improper operation
If the oil valve is too large or too small, braking frequently or overloaded for a long time during operation, the crankshaft will be damaged by excessive torque or impact load. In addition, the crankshaft is also easy to break when the diesel engine has accidents such as runaway, cylinder tamping and top valve.
