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Slewing Bearing Has Unique Features Because of Its Structure, and Is Used in Cranes, Swing Yarder, etc.
Slewing bearing is affordable, and it functions quickly, installs quickly, and operated excellently as well. It has a wide range of uses because of its features.

Slewing Bearing

A slewing bearing is a ring-shaped bearing that has some unique and extraordinary features. The slewing bearing is also recognized as the “turntable bearing”. In other words, a slewing bearing is itself a rotational accessory that supports loads of various kinds including the axial, the radial, and the moment loads. The oscillations or turning by slewing bearing are usually not very fast but on the contrary, they are very slow. Their area of application is mostly the horizontal platform.

For instance, a swing yarder, crane, or the wind-facing side of the windmill (horizontal axis) are some of the primary usages. Moreover, some other types of horizontal usages also exist; they include the load attachment sides of the forklifts, grapple managements, jigs used in welding turnovers, and many more. When it comes to loading carrying capacities these ordinary-looking elements are proven to be excellent. There are many configurations in which both the radial and the axial bearings are needed to be installed. So to cut short the job slewing bearing is enough.

This will help in reducing the cost many times as compared to traditional roller bearings. Apart from the price reduction, the most important thing is the shortening of work and the time involved in the installation of the complex systems.

Slewing Bearings! What Do They Look Like?

The construction of slewing bearings as per the SKF standard is not very complex. There are two main rings; one is the inner while the other is the outer ring. A gear is present in either of the ring. This gear is not found commonly in many other bearing assemblies. They can be easily attached with the relevant components as there are holes provided in both of the rings. This configuration creates a powerful optimized transmission between the adjacent components of the machine. Moreover, the mounting or installation of the slewing bearings is not a tough job they can be easily set up according to the required conditions. One of the major plus points of slewing bearing is their bearing raceways. When we say the raceways we can isolate them, rather they are connected with other elements like rollers, cages, and the spacers. Their design is a way to cope with the loads occurring in any direction.

construction of slewing bearings
exact selection of slewing bearing

How to Select the Exact Slewing Bearing

The three factors technicality, reliability, and economic demands are responsible for the exact selection of slewing bearing. Therefore we are ready to provide you with the exact solution according to your requirements. The top brands like SKF are distributed by us, so you should not be worried about the quality and durability of the product. Moreover, to select the exact type, and size there are some advanced level calculations and simulations available for your perusal. We are here to guide you at every technical step. By using the state-of-the-art methods of analyzing and optimizing the design we become ahead of our competitors.

Apart from selling the slewing bearings, we exhibit some of the best value-added services to our clients. From the top brands like SKF and many more, we help our clients to get their slewing bearing remanufactured. This process is very helpful in saving costs. Instead of buying the new one, customers can reuse their previous one which is as good as new. But remember the bearing which has almost 30 percent of his life left can be remanufactured. In addition to the cost-saving, this remanufacturing thing helps a lot in extending the usable service life of the bearing. These steps contribute a lot towards the improvement of the slewing bearing quality alongside reducing the cost and making the operations safer.

In the selection of slewing bearings, the following parameters have to be kept in mind.

  • How much accuracy is needed?
  • What is the magnitude and direction of the loads?
  • How much operating temperature is allowed?
  • The amount of vibration permissible
  • What is the desired operating speed?
  • And finally, what type of sealing is required?

Below we will describe these factors in detail as they are very significant concerning slewing bearings.

Accuracy

The slewing bearings have a larger roller contact area than any other bearings. Thus they provide more stiffness as compared to others. This allows the slewing bearing to develop the highest possible running accuracy making them the most accurate of all the bearings. Therefore, they are employed in conditions where a critical level of accuracy is the demanding factor of operation. However, when we talk about four-point slewing bearing they are not as rigid.

Accuracy of Slewing Bearing
Slewing Bearing Extent and Direction of Loads

Extent and Direction of Loads

The next factor that is of significant interest while selecting the bearing is the direction and magnitude of the loads. This parameter is important in determining the size of the slewing bearing. In case some heavier loads are to be incorporated four-point slewing bearings are generally used. Moreover, these four-point slewing bearings have an adaptive tendency and they can vary or adjust themselves according to the varying loads. Furthermore, the bearing size can be exactly determined with the help of pre-devised algorithms. These algorithms are based on analysis obtained from various types of static loads. The load consider in this way is the axial load and the how much magnitude required during the rotation that is tilting movement.

Operating Temperature

Like many other variants of bearings, the slewing bearing is also selected and applied in the practical application based on their temperature ratings. The elements that decide the operational temperature of slewing bearing include the type of seal, the material of spacer, and the kind of grease that is used for lubrication purposes. Generally, the temperature ranges for a typical slewing bearing are from -25 degrees to +70 degrees. The cushion is available from many manufacturers like the giants SKF about alteration in the operating temperature ranges. If the customer wants to operate the bearing outside the given range he has to apply for a modified version of slewing bearing from the manufacturer. The engineering department of the manufacturing unit has the capability of making changes in the operational temperature ranges. The temperature of the whole slewing bearing unit can be modified as well as the temperature of the individual rings can also be altered. For Instance, if the customer wants to make the outer ring’s temperature high and for the inner ring of the slewing bearing low, this can also be done accordingly. But such types of modifications may result in the increased payload of the slewing bearing.

Slewing Bearing
four-point ball slewing bearing

Vibration

Some applications undergo severe vibration. So the normal slewing bearings are not suitable for such conditions. Therefore, the enhanced version of slewing bearing which is the four-point slewing bearing is used to work efficiently even in the larger vibrations. Apart from four-point ball slewing bearing, cylindrical roller slewing bearings are also good to do the needful. Therefore before selecting the slewing bearing for vibrational operational areas it is better to go through the vendor’s catalog for better guidance and reference.

Speed of Operation

Another decisive factor in the choice of slewing bearings is the speed involved in the operations. The slewing bearings which are four-point contacts are considered the best ones when it comes to delivering high speed. They are faster than their cousin cylindrical roller slewing bearings since they generate very less friction in the operation. As a result, four-point contact slewing bearings are considered compatible slewing bearings with higher speeds. Their typical speed is around 4 m/s which is also known as their tangential speed. On the other hand, crossed cylindrical roller slewing bearings are not very fast they are just limited to around 1.5 m/s. for some shorter periods they can even catch up to 2 m/s as well.

four-point contact slewing bearings
Sealing of Slewing Bearing

Sealing

Apart from many other parameters, proper sealing is important for the enhancement of the operation of the slewing bearing. Mostly the seals that are incorporated in slewing bearings are used to provide optimum protection against many environmental degradation and contamination. The other prime feature of a good quality seal is the retention of lubrication. However, the seals that operate under normal conditions have a longer service life. As most the slewing seals are meant to deliver the performance in ordinary to mild operating conditions. For instance, water, vacuum, and other containments if left for prolonged periods may damage the seals. Therefore in case of work in extreme conditions, some additional seals are to be provided alongside normal ones for better protection against the environmental effects.

Kinds of Slewing Bearing

There are primarily three types of slewing bearing which are further classified as,

  • The tooth type slewing bearing
  • External type slewing bearing
  • Internal Type slewing bearing

The above types are according to the type of teeth of slewing bearing. There are some other classifications as well that are following the type of structure which are as under. And these types are most widely used in the industry.

Single row contact ball slewing bearing
These types of slewing ball bearings are most commonly used. The steel ball in the bearing assembly is separated with the help of a single isolating block. In a single row contact ball slewing bearing the inner and outer rings are joined as a part. Moreover, the plugging holes are used in loading the steel balls in single-row contact ball slewing bearings. The rolling path is the main concern here, which comes to contact at four different points. The three different types of forces can be applied at the point of axial contact, radial, and tipping forces. For applications that require small to medium-sized loads this slewing bearing is considered the most common and preferred type.
Double-row four-point contact ball slewing bearing
There is no difference between the single and double-row slewing bearings except that there are two rows of steel balls. The size of these steel balls is quite the same. Here also the inner and outer rings are joined together. The steels balls are also loaded with the help of plugging holes. It is designed to accommodate the heavy-duty radial structural size.
Three-row roller bearing
These are also designed to cope with the needs of heavy loads. Primarily there are three rings, upper and lower rings. The loads are distributed in the horizontal direction. The axial force and tipping movement can be applied in both directions. To accommodate the radial force, vertically arranged rollers serve the purpose.
Cylindrical Cross roller
It has only one row of rolling steel balls. However, similar axes rollers are perpendicularly arranged. The inner and outer rings are not integrated instead they have separate raceways. In addition, the portion of raceways is undeviating. These are suitable for axial loads as half of the raceways are built to bear upward force while the other half exhibits a downward force.
Double Exclusion Ball Type
There are two rows on both inner and outer rings hence double rows of rolling balls on each ring. Moreover, the rows for lubrication and seals are also doubled, making this bearing a complex from all others.
Light weigh series
The structure of this bearing is almost the same as the ordinary bearing. They are widely used in food factories, filling machines, environmental protection devices, and some other field equipment.
Slewing Bearing

Application of Slewing bearings

Application of Slewing bearings
Application of Slewing bearings

These bearings are widely used in the following sectors.

  • Wind turbines
  • Excavators
  • Rails
  • Marine pods
  • Tidal turbines
  • Medical equipment
  • Stacker reclaimers
  • Water treatment and bottle filling systems

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Slewing bearings

What Is the Purpose of Slewing Ring in a Crane?

They act as a joint between the undercarriage and the upper structure of the machine. The benefit of these bearings is they can create a flexible 360-degree turning of the cranes.

What Is Meant by Slewing Gear?

It is a gearbox that is designed to hold some radial and axial loads. In addition, they also accommodate the torque for smooth rotation. The rotation can be performed on multiple as well as the single axis.

How Slewing Ring Is Measured?

Firstly, place the slewing ring in a vertical orientation. Just measure any three points along the circumference that is 120 degrees apart then take their average value. This is the most precise way of measurement as other measurements may result in faulty readings.

What Is Meant by Slew Ring Connection?

The inner and outer rings are present in the slew ring bearing. One of the rings is supposed to have gear. Moreover, attachment holes are provided in both of the rings. This whole assembly is responsible to deliver the optimized power transmission. In addition, the connection is simple and easier.

What Type of Grease Is Mostly Used in Slewing Bearing?

Mostly the common type of grease used is shell-based No.2 Lithium Grease. Similarly, the greases are different and can be selected according to the lower or higher temperatures. For this purpose bearing lubrication guidelines from a specific vender are helpful.

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