Analysis of vibration phenomenon of gear reducer

Through the spectrum analysis of the vibration phenomenon of the gear reducer, the foundation crack fault of the gear reducer body can be accurately judged, which can avoid the occurrence of equipment accidents and reduce the blindness of maintenance.

Operating conditions of the unit: the unit is of two-stage reduction, driven by motor, with input shaft speed of 1500r / min, power of 220kw, air volume of 3.15 million m3 / h, blade diameter of φ 9140mm, the maintenance personnel inspected the transmission shaft and blade, found no problems, and then inspected the large and small gears of the reducer through the inspection hole, and found no abnormal phenomena such as broken teeth, pitting corrosion and wear.

After the unit is restarted, the off-line diagnostic instrument is used to collect data in the vertical and horizontal directions of the input shaft bearing of the gear reducer for spectrum analysis and fault diagnosis. It can be seen from the spectrum diagram that in addition to the input shaft power frequency (rotational speed frequency), there are also 2-4 times of the rotational speed spectrum, and the peak value is relatively high, especially in the vertical spectrum diagram. There is no gear meshing frequency and its harmonic components, No sideband is formed and gear failure can be eliminated. The octave and quadruple frequency components are also very high, which indicates that it is not rotor imbalance or unit misalignment fault. The bearing failure can be completely eliminated, because there is no high-frequency failure frequency of the inner and outer rings of the bearing and the rolling elements.

Combined with the above cause analysis, it is preliminarily diagnosed that the unit vibration is caused by the loose foundation of the reducer. The foundation of the reducer is a wooden square truss structure, and the base is welded with angle steel and I-steel. There are three anchors at the bottom of the reducer case connected and fixed with the foundation base, one at the bottom of the input shaft and one on both sides of the output shaft. In order to verify the diagnosis result of the fault cause, the foundation of the reducer was carefully inspected. As a result, three cracks were found at the foundation at the bottom of the input shaft on the reducer housing. It is because the foundation cracks and the connection between the reducer and the base is loose that the vibration of the reducer increases. After the reducer is replaced and reinstalled, the vibration of the unit returns to normal and the operation is in good condition.

There are many reasons for the vibration of gear reducer, and the analysis is complicated. If we only rely on the experience of maintenance personnel, pay attention to the inspection of gears, bearings and units for medium problems, and ignore other details, we will not be able to completely eliminate the fault, but also lead to excessive maintenance and waste of manpower and material resources. Practice has proved that the equipment fault diagnosis should rely on modern equipment fault diagnosis instruments, carry out scientific analysis, accurately judge the fault causes, and formulate reasonable maintenance measures for gear reducer.