Slewing Bearings

Slewing bearings comprise an inner ring and an outer ring, one of which usually incorporates a gear. Together with attachment holes in both rings, they enable an optimized power transmission with a simple and quick connection between adjacent machine components. The bearing raceways, in conjunction with the rolling elements and cages or spacers, are designed to accommodate loads acting singly or in combination, and in any direction.

Types

What are the classifications of slewing bearings?

Four-point contact ball slewing bearings have high dynamic load capacity.

Crossed cylindrical roller slewing bearings have high static load capacity.

The three-row roller slewing bearing leads to the improvement of the bearing capacity in the height direction of the bearing.

According to different structural types, slewing bearings can be divided into four-point contact ball slewing bearings, double-row angular contact thrust ball slewing bearings, crossed cylindrical roller slewing bearings, crossed tapered roller slewing bearings, and three-row cylindrical roller combined slewing bearings. The types mentioned above of bearings are divided into different structures such as gearless external gear or internal gear according to whether they have teeth and the distribution of gear teeth.

The Features of Slewing Bearing

Slewing bearings generally have to bear several loads, including axial and radial forces and a sizeable overturning moment. The running speed of the slewing bearing is deficient, usually below 10 rpm. In addition, in most cases, the slewing bearing does not rotate continuously but only turns back and forth within a certain angle, equivalent to the so-called “swing bearing.” Therefore, a set of slewing bearings often plays the role of several groups of ordinary rolling bearings.

manufacturing process

In terms of manufacturing process, materials and heat treatment, slewing bearings are very different from rolling bearings.

different structure

Usually, the slewing bearing is equipped with a gear ring for rotary drive and a sealing device for dust prevention.

Installation method of slewing bearing

1. Before installing the slewing bearing, check the mounting surface of the host; the support must have sufficient strength, the connecting surface must be processed, and the character must be free of debris and burrs. If the flatness that needs to be processed cannot be achieved, special plastics with high injection strength can be used as fillers to ensure the accuracy of the installation plane and reduce vibration. The housing of the slewing bearing has a soft hardened band marked “S” on the end face of the sleeve. When installing, the quiet belt position must be placed in a non-loaded or non-repetitive load area (the plug hole is always in the soft belt).
2. When installing the slewing bearing, first determine the radius position, cross-tighten the mounting bolts, and check the bearing rotation. To ensure smooth bearing transmission, gear meshing must be checked before mounting bolts are tightened. When tightening the bolt, there must be sufficient preload, and the preload must be 70% of the yield limit of the bolt material. Mounting bolts must use adjustable flat washers; spring washers are strictly prohibited. After the slewing bearing is installed, start running. After 100 hours of continuous operation, check whether the pre-tightening torque of the mounting bolts meets the requirements. Repeat the above inspection every 500 hours.

A brief introduction to types of slewing bearing

Slewing bearing is one support composition load (axial loads, radial loads, and titling moment) large-scale bearing. Slewing bearing contains mounting holes, an inner ring or outer ring, spacer, isolation holder, grease hole, and seals; therefore, it makes engineer designs compact structure, easy operation, and maintenance convenient.

Crossed Cylindrical Roller Slewing Bearings

The design and application of the crossed cylindrical roller slewing bearings are the same as the four-point contact ball slewing bearings. The difference is that the rolling element is replaced from the ball to the roller, and the contact method between the rolling part and the ring is changed. Point contact becomes line contact. These changes increase load carrying capacity, but wear and friction moment loads also increase.

Double Row Ball Slewing Bearing

The double row ball slewing bearing has two-row steel balls for structure; it could bear axial load, radial load, and tilting moment at the same time. The double row ball slewing bearing ring’s axial and radial size are relatively large and solid, so it is usually used in diameter tower cranes, truck-mounted cranes, etc.

Four-point Contact Ball Slewing Bearing

Four-point contact ball slewing bearing mainly consists of an inner ring, an outer ring, a row of steel balls, and a cage (or spacer). It has a four-point contact ball inner ring, and the outer ring has an integral and split structure. Four-point contact ball slewing bearing can bear axial load, overturning moment, and radial load at the same time. Almost all steel balls will bear the burden under the combined action of the axial load and the tilt moment load.

operation principle

The excavator slewing bearing’s operation principle.

The excavator slewing bearing device comprises a turntable and a slewing bearing. In a slewing mechanism, the outer ring of the slewing bearing is connected to a turntable with high-strength bolts (it divides three stages, forcing the bolts pre-tightening), inner race with teeth and chassis connected by bolts, inner race, and outer race has a rolling body, the rolling body usually divided into ball type and column type, according to different working condition to choose. The vertical load, horizontal load, and overturning moment of the excavator device on the turntable passed to the chassis through the outer, rolling body, and inner race. The housing of the rotary mechanism is fixed on the turntable and messed with the gear ring on the inner race of the slewing bearing through the pinion.

Slewing Bearing Professional Manufacturer

Application field of Slewing Bearing?

Slewing bearings are widely used in large-scale slewing devices of hoisting machinery, mining machinery, construction machinery, port machinery, marine machinery, high-precision radar machinery, and missile launchers. In addition to various engineering machinery, the application range of slewing bearings has gradually expanded; equipment platforms such as port equipment, metallurgical equipment, and drilling platforms have begun to use slewing bearings to replace original bearings on a large scale.

Removal method of slewing bearing

1. Decomposition of the outer ring. Remove the outer ring of the interference fit, set a plurality of outer ring extrusion screws on the circumference of the housing, back-tighten the screws, and remove them at the same time. This screw hole usually covers removable bearings such as blind plugs, tapered roller bearings, etc. Install several cutouts in the shoulder of the housing, disassemble with a backing plate or with a press or lightly tap to disassemble.

2. Remove the cylindrical bore bearing. Pumping with a press is the easiest. At this time, pay attention to the tension on the inner ring. The inner ring of large bearings is decomposed by hydraulic method. Apply hydraulic pressure to the oiler mounted on the shaft to facilitate pulling. Bearings with large widths must be disassembled using both the hydraulic method and the tie rod clamp. The inner ring of NU and NJ cylindrical roller bearings can be decomposed by induction heating. A method of heating the part in a short time to expand the inner ring and then pull it.

3. Disassemble the tapered bore bearing. Remove the relatively small belt retaining bearing, support the inner ring with a block attached to the shaft, turn the nut several times, then use the backing plate to break it down by hammering it. Large bearings are easier to disassemble using hydraulic pressure, which is a method of decomposing the bearing by pressurizing oil onto the oil hole of the tapered bore shaft to expand the inner ring. There is a danger of the bearing falling off suddenly during work, it is best to use the nut as a block.

4. Unloading method of batting. Unloading is one of the simplest and most commonly used decomposition methods. It is a decomposition method that displaces the parts that cooperate with each other by the force of the hammer, so as to separate them from each other and achieve the purpose of decomposition. The structure of mechanical parts is relatively simple, and most of the parts that are strong or unimportant are decomposed in this way. Before disassembly, in order to reduce friction, the joints are often wetted with lubricating oil. Demolition is a simple and easy method of disassembly.

Slewing bearings can be custom designed to meet many of your equipment requirements.

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