Pretightening for turntable bearing bolts

The connection of the turntable bearing depends on fasteners such as bolts, so the quality choice of bolts and the way of loading and unloading will affect the performance of the turntable bearing.Today, let us introduce you about the pre-tightening requirements of the turntable bearing bolts.
The purpose of preloading is to increase the reliability and tightness of the connection so as to prevent gaps or relative slippage between the connected parts after loading.It has been proved by experience that the proper selection of large preload is beneficial to the reliability of the threaded connection and the fatigue strength of the joint。

Turntable bearing

According to the provisions related to the main engine, the bolt tightening mode should ensure a certain pre-tightening force, except for special provisions, the general pre-tightening force is 0.7 times the bolt limit.Allow a little oiling at the threads while tightening.Preload torque or preload.

“Cross-fixation” is a form of mounting and configuration of turntable bearings, in which each turntable bearing is positioned one way on the shaft and in the opposite direction.This combination is mainly used for short axes.All radial disc bearings capable of bearing at least one axial load in one direction are applicable, including deep groove and angular contact ball bearings, tapered roller bearings, and NJ type cylindrical roller bearings. In some cases, preload must be applied when angular contact ball or tapered roller bearings are used.

After radial positioning of the turntable bearing, cross tighten the mounting bolts according to the star, and check the rotation of the bearing.In order to ensure the bearing transmission is stable, the gear side clearance should be checked and adjusted before the mounting bolts are not tightened completely.When tightening bolts, there should be enough preloading force, which should be 70% of the yield limit of bolt material.The mounting bolt shall be equipped with a tempered flat washer and a spring washer is strictly prohibited.

slewing bearing

The axial preloading method can be divided into positioning preloading and constant pressure preloading.In positioning preload, the appropriate preload can be obtained by adjusting the size of bushing or gasket.The starting friction torque can also be measured or controlled to adjust the appropriate pretightening;Also can be directly used to pre-adjust the pretension of a pair of twin rotary bearings, at this time generally do not need to adjust, in short, after the axial pretension of the rotary bearings, its relative position will certainly not change.
Constant pressure preloading is the use of spiral spring, dish spring and so on to get the proper preloading of the rotary bearing method.The rigidity of the preloaded spring is much smaller than the rigidity of the turntable bearing, so the relative position of the fixed-pressure preloaded turntable bearing will change in use, but the preloaded amount will remain roughly the same.
After the initial operation of the rotary bearing for 100 hours, the bolt pre-tightening force shall be checked, and the bolt pre-tightening force shall be checked once every 500 hours after the operation.