As a continuous conveying machine for vertical lifting materials, Z type bucket elevator has the advantages of large conveying capacity, high lifting height, stable and reliable operation and long service life. The working principle is that the bucket is lifted to the top with the conveyor belt after receiving the material at the bottom feeding port, flips down after bypassing the transmission drum at the top, and then Z type bucket elevator pours the granular material into the discharging port. Based on the daily operation of Z type bucket elevator, the following reasons are found out through discussion and analysis for the looseness and fracture of the fastening bolt of the bucket.
1.After the granulator cleaned the bed, the load of Z type bucket elevator increased, which will cause the central axis of the driven drum of Z type bucket elevator to move down. If there is urea caking at the bottom of Z type bucket elevator, it will collide with the bucket, resulting in additional shear stress on the bucket fastening bolt.
2.The impact between the bucket and the housing causes the belt deviation of Z type bucket elevator, which will make the bucket to swing. If the amplitude is larger, the bucket will collide with the discharge port of the receiving port, or even the shell of the bucket elevator, resulting in additional shear stress on the bucket fastening bolt. The main reason for belt deviation is that the driven roller is not parallel to the active roller.The other is that the uneven feeding results in uneven belt stress and deviation. The gap between the bucket and the discharging port is too small, which may lead to the collision between the bucket and the housing.But the clearance is too big, which can cause the leakage quantity to increase, therefore must choose a reasonable clearance range.
3.At the bottom of the Z type bucket elevator, the accumulated materials will gradually agglomerate in a high temperature environment for a long time, which not only increases the scraper resistance of the bucket, but also causes the bucket fastening bolts to become loose and break when the bucket is scraped for a long period of operation.
4.Improper design and selection of fastening bolt is the direct cause of bolt fracture.
In view of the reasons for the fracture of the bucket fastening bolt identified by the above analysis, the corresponding countermeasures were taken according to the actual situation on site.

1.The collision between the bucket and the housing is mainly caused by the belt deviation of Z type bucket elevator, so the collision between the bucket and the housing can be avoided by dealing with the belt deviation fault. In view of the belt deviation fault of Z type bucket elevator, it is necessary to clean and lubricate the balance slide of driven drum regularly to ensure that the balance slide is free of jam. Then, screw adjusting device is added to both ends of the driven roller to adjust the parallelism of the driven roller and the active roller. At the same time, the feeding port should be reformed to weld baffles on both sides of the feeding port to ensure uniform feeding of bucket. Finally, the device elevation at both ends of the axis of the driven drum is indicated to visually check the parallelism between the driven drum and the active drum. Adjusting the gap between the bucket and the discharging port within a reasonable range to prevent the bucket from colliding with the discharging port during the operation of Z type bucket elevator.
2.The fastening bolt of the bucket is transformed into a one-head bolt. The structural type of the one-head bolt head ensures that the bolt head has sufficient cross-sectional area, and the strength of the bolt will not be insufficient due to the insufficient cross-sectional area.
3.Two measures were taken to prevent nut loosening. The first measure is to change from single nut fastening to double nut fastening, that is, to add a locking back cap of the same specification material, the two locking nuts produce axial force between the nuts after applying the preload, so that the friction between the locking nut teeth and the piston rod thread teeth increases to prevent the nuts from loosening. The second measure is to change the original nut gasket from plain gasket to butterfly gasket to improve the fastening reliability.
Through the targeted measures, the effect of Z type bucket elevator bucket fastening bolt to reduce the looseness and fracture fault is obvious. It is also proved that the analysis and judgment of the fracture cause of fixed bolt is correct, and the hidden trouble of Z type bucket elevator operation is eliminated through targeted measures to make it run smoothly, and the equipment maintenance cost can be reduced.