Analysis of mill vibration

Mining mill (hereinafter referred to as "mill") is the core equipment of concentrator and is widely used in various metal mines. The reliability and stability of its work directly determine the benefits of mining enterprises. In actual production, the causes of mill vibration are transmission system failure, generally including out of tolerance of axis concentricity, bearing damage and gear damage, etc; Faults caused by foundation problems generally include insufficient stiffness, cracking and uneven settlement; Faults caused by other problems include loose anchor bolts, equipment structure itself, etc. If the vibration of the mill is not handled in time, the wear of relevant parts will be intensified, and the equipment will be damaged and the enterprise will stop production. Therefore, it is of great practical significance to find out the causes of vibration and eliminate vibration in time to ensure the normal operation of the equipment.

Foundation cracking and uneven settlement are the main causes of mill vibration. Cracking may be the foundation

Caused by quality or vibration, the two interact, resulting in the continuous development of vibration and cracking. Therefore, the construction quality of foundation is very important. Uneven settlement is a geological problem, and the stability of geological structure must be ensured before construction. The foundation design is relatively weak, resulting in insufficient foundation stiffness. The foundation stiffness design must comply with relevant national standards and industrial specifications. If the construction does not meet the requirements, it must be reinforced. Another situation is that the secondary grouting layer is unqualified, not dense or not well solidified.

In a copper mine double drive semi autogenous mill, the vibration of one side pinion bearing has been poor within one year of operation, and then suddenly intensified. After inspection, cracks were found on the pinion foundation. After the whole pinion was removed, it was found that the epoxy resin in the anti-skid rib groove of its base was not solidified.

There are 2 sets in a mine φ 4.8 m × 7 m overflow ball mill. At the end of November 2011, No. 2 mill suddenly vibrated during operation and was forced to shut down. The field staff inspected the large and small tooth surfaces and found that the contact surface had a good finish. Then check the mill cylinder with a level and find that the height difference between the feed end and the discharge end is as high as 0.38 mm / 250 mm. If the length of the centerline of the two main bearings is 11 m, the feed end is 16.72 mm higher than the discharge end. The inspector checked with the connector again, and the results showed that the feed end on the non drive side was 10 mm higher than the discharge end, the feed end on the drive side was 8 mm higher than the discharge end, and the average feed end was 9 mm higher than the discharge end. It can be seen that the height difference between the feed end and discharge end of the mill has been far greater than the required value of 0.5 ~ 1.0 mm. It is preliminarily judged that the vibration of the mill may be caused by uneven settlement of the foundation. In addition, by observing the pinion foundation at the slow drive side, it is found that the secondary grouting layer has been completely damaged, and there are cracks in the foundation under the grouting layer. These cracks aggravate the vibration, and the vibration increases the cracks, resulting in a vicious circle.

In view of the above situation, the solutions are as follows: ① increase the steel plate and pad the main bearing at the discharge end to make the height difference at the inlet and outlet end meet the relevant regulations. Check the contact between the steel plate and the main bearing base and bottom plate as well as the side clearance and contact of the adjusted large and small gears according to the original requirements, which meet the requirements; ② The secondary grouting layer of pinion base needs to be poured again. The cracked foundation under the grouting layer shall be knocked off, and the re poured foundation shall be connected with the original foundation by welding steel ribs. In order to save time and shorten the construction period, non shrinkage grouting material can be used for grouting. Attention shall be paid to the problems caused by different thermal expansion and cold contraction due to different materials; ③ The design unit shall make a foundation reinforcement scheme to ensure that the foundation will not sink, and make settlement observation points at appropriate positions to observe the changes of mill foundation at any time. After the rectification of the above measures, the vibration of the mill has been significantly improved and can operate normally.