First of all, when the lubrication is bad.
In the diesel lubrication failure system, the connection of the semi-friction state between the journal and the gasket is weakened, that is, the bearing force at the cutting part will lead to the failure of the bearing bush combustion and the frequent axial and radial runout. In addition, the stress changes after the root is removed, which will lead to the fracture between the root of the crankshaft and the crank arm.
Secondly, the bearings do not work very well.
For diesel engines, when the pivot rolls the main bearing, or when the clearance is too large and the main bearing has a different shaft, too large, that is, the frequent crankshaft, flywheel and radial deflection of the diesel itself has a specific weight and an uneven force on the crankshaft, plus the impact of the operation of each cylinder.
In addition, when the connecting rod bearing assembly clearance is too large, or when the alloy falls, the impact load will cause the crankshaft to occur for the first time, leading to an increase in the cause of fracture
Third, looseness of the main bearing cap nut is one of the important causes of early fatigue fracture of the crankshaft, because its crankshaft is lost or loosened in the support or each coaxial bearing hole is offset coaxially.
If the channel after the loose main bearing nut loosens the track axis and the bearing clearance affects the channel, the diesel engine must exceed the tolerance, i.e. the loss of the spindle neck.
If the concentric deviation causes the crankshaft to rotate to the end of the shell hole, then the crankshaft load is different, resulting in the crankshaft fracture accident.
Fourth, the axial disturbance of the crankshaft is too great.
If the clearance in the direction of the crankshaft is too large, the main reason is due to the axial movement of the crankshaft.
A connector thrust bearing, the crankshaft located on the fourth side of the main track, one (also known as a general synthetic flange shingle) as an example, when it reaches 0.5-0.6 mm or more, the directional clearance.
In order to ensure some degree of deflection, the result is that the workload of diesel engines and crank arms with crank counterforces on the receiving end face will be more severe.
Because of stress concentration, the process of crankshaft cracking can be accelerated.
The flywheel is moving.
Fifth, if the flywheel bolts loose, the crankshaft assembly is easy to break at the end, resulting in crankshaft fatigue, dynamic balance, large inertia forces will be lost.
Where there are crankshafts and flywheels through this mating cone (e.g., diesel S195), the flywheel relaxes so that it ACTS as an external surface or the crankshaft breaks and the keyway fits, as the crankshaft affects, the coupling area is less than 75% of the diesel engine.
Sixth, the imbalance of power.
When the maintenance switch to the crankshaft, iron or iron balance does not meet the requirements of imbalance, destroy the original balance, easy to manufacture crankshaft bearing, but the inertia impact force is greater.
Moreover, if the crankshaft is repaired, the bearing causes strong vibration and diesel overload by counteracting the crank radius, so that since the crank arm I will have a large allowable value, the imbalance is an unbalance that exceeds the centrifugal force.
Over a long period of time, the fracture tends to fatigue the crankshaft.
Seventh,The crankshaft is not properly grounded.
Because it is the effect of the crankshaft and connecting rod crank arm shaft neck the bending fatigue strength of fillet between the main journal and the crank arm and the most important factor between starting the crank arm, crankshaft, just ignore the crankshaft crankshaft main journal check, due to grinding, ignore the rounded, rod journal coaxial, parallel to the crank radius, and other repair shoulder axis neck surface roughness, and the included Angle between each crank pin size and shape.
The uncorded journal of the grinding wheel is used to grind improper fillet holes or right-angle fillet corners are not selected correctly. As a result, the crankshaft fillet is prone to stress concentration and strength decline, which is likely to occur cracking.