The shaft of the Roots blower has broken; please help analyze it
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Belt drive, used for fluidizing the ash bin. Motor power is 37 Kw, with air intake at the top and exhaust at the bottom. Flow rate is 750 cubic meters per hour, with a pressure of 98 KPa. Rotation speed 2880. Shaft material: ductile iron
Imported head, has been in use for 5 years. No obvious damage was seen on the rotor, and it turned very smoothly by hand
Ductile iron boasts excellent wear resistance, while the main operating range of crankshafts in large medium-speed diesel engines is not one requiring high torque output; therefore, greater emphasis is placed on wear resistance under high-speed operation, and there is no high demand for impact resistance； Low-speed diesel engines are primarily designed to deliver high torque, which is why steel is used. Is the inner ring of the bearing inside the red circle in the picture damaged?!
It seems that fatigue failure has occurred; it appears that the concentricity between the motor shaft and the fan shaft is poor. Roller bearings have high rigidity but poor self-aligning capability.
What is the tension of the belt? It could be due to 1) metal fatigue, or it might be an issue with excessive torque or lateral forces.
There will be no misalignment; it’s likely that the belt is too tight, causing fatigue damage.
The gearbox is low on oil; the oil has not been changed for a long time. There are signs of overheating on the inner ring of the bearing
I wonder if a broken shaft is directly related to a lack of oil
The synchronizing gear cannot be removed. The rotor is integrated with the shaft; the shaft cannot be replaced separately