The slewing bearing on the aerial work vehicle

A slewing bearing, also known as a turntable bearing or slewing ring, is a crucial component of an aerial work vehicle. It plays a vital role in providing support for platform rotation and facilitating smooth movement. Here are some key points about slewing bearings in aerial work vehicles:

The Function of Slewing Bearing in Aerial Work Vehicles

The function of a slewing bearing in aerial work vehicles (AWPs) is to provide support for the rotary motion of the platform, allowing operators to easily access different areas and maintain flexibility during operation. Specifically, slewing bearings:

  1. Enable rotation: They allow the aerial work platform to rotate horizontally around a vertical axis, which improves access to various work areas and facilitates navigation around obstacles.

  2. Bear load: Slewing bearings are designed to support both radial and axial loads, enabling smooth and stable rotation even when the aerial platform is exposed to various forces during operation.

  3. Maximize precision: The construction of slewing bearings enables precise control of platform rotation, which is crucial for accurately positioning workers in hard-to-reach areas within a work site.

  4. Enhance safety: By providing a stable and reliable connection between the platform and vehicle, slewing bearings contribute to the overall safety of aerial work vehicles during operation.

Slewing bearings play an essential role in aerial work vehicles by providing support for horizontal rotation, bearing loads, ensuring precise control, and enhancing safety and efficiency during operation.

The Components of Slewing Bearing in Aerial Work Vehicles

The primary components of a slewing bearing are:

  1. Inner ring: The inner ring connects directly to the rotating platform or basket of the aerial work vehicle. It houses the channels and raceways for the rolling elements and can feature external or internal gear teeth when necessary.

  2. Outer ring: The outer ring is typically fixed to the base structure of the vehicle. It provides a stationary support for the inner ring, working in conjunction with the rolling elements to facilitate the smooth rotation of the platform.

  3. Rolling elements: Rolling elements play a critical role in enabling a smooth rotation between the inner and outer rings. The two primary types of rolling elements are ball bearings and roller bearings. Ball bearings provide excellent performance for smaller loads, while roller bearings are used for higher load-carrying capacities and increased stiffness.

  4. Spacers: Spacers are placed between the rolling elements to maintain consistent distances between them, ensuring even distribution of load and preventing contact or collisions between bearings.

  5. Seals: Slewing bearing seals are crucial for protecting the bearing from external contamination, such as dirt, grit, and moisture. They also help retain the internal lubricant, ensuring the bearing remains adequately lubricated. There are various seal designs, with the most common being axial lip seals and labyrinth seals.

  6. Gears: Some slewing bearings incorporate an internal or external gear system that meshes with a pinion gear, providing torque for rotation. Depending on the application, designers may choose between internal or external gear configurations, each with its specific benefits.

  7. Lubrication system: Although not technically part of the bearing itself, lubrication systems are crucial to the proper function of a slewing bearing in aerial work vehicles. Grease should be applied at regular intervals, reducing friction, preventing wear, and minimizing the risk of bearing failure.

The Types of Slewing Bearing in Aerial Work Vehicles

There are two main types of slewing bearings used in aerial work vehicles: ball-slewing bearings and roller-slewing bearings. Both types have different characteristics, offering specific advantages depending on the application and required performance.

1.Ball-Slewing Bearings:

  • Construction: These bearings utilize multiple rows of ball elements accommodated between the inner and outer rings. The balls enable the inner and outer rings to rotate smoothly around one another.

  • Advantages: Ball-slewing bearings are generally more cost-effective and lighter, making them suitable for applications that require lower load-carrying capacities or have weight limitations.

  • Applications: These bearings are used in smaller aerial work platforms, lightweight boom lifts, and smaller vehicle-mounted lifts.

2.Roller-Slewing Bearings:

  • Construction: Roller-slewing bearings consist of cylindrical or tapered roller elements positioned between the inner and outer rings. The rollers provide a contact line with the rings, allowing for higher load capacities and improved stiffness.

  • Advantages: Roller bearings can bear higher radial, axial, and moment loads due to their contact line with the rings. They are generally more robust and have better overall stiffness and resistance to deformation under loads.

  • Applications: Roller-slewing bearings are used in larger aerial work platforms, heavy-duty boom lifts, and large vehicle-mounted lifts.

Both types of slewing bearings may feature internal or external gear systems, depending on the drive type and design of the aerial work vehicle. The choice between ball-slewing and roller-slewing bearings depends on the specific application and performance requirements of the aerial work vehicle.

The Lubrication of Slewing Bearing in Aerial Work Vehicles

Adequate lubrication is crucial for the smooth operation, reliability, and longevity of slewing bearings in aerial work vehicles. It helps minimize friction, reduce wear and tear, and prevent corrosion. Here are some important aspects of lubricating slewing bearings in aerial work vehicles:

  1. Lubricant selection: The choice of lubricant for a slewing bearing is essential. High-quality grease with suitable base oil and a consistent viscosity is required. Lithium or lithium-complex greases with EP additives are commonly used for slewing bearings in aerial work vehicles.

  2. Lubrication points: Slewing bearings usually have lubrication holes or fittings distributed around the inner and outer rings. Grease should be uniformly applied to these points, ensuring that the rolling elements, gear teeth (if present), and seals are adequately covered.

  3. Lubrication frequency: The frequency of lubrication depends on factors such as operating conditions, workload, and environmental factors (e.g., temperature, humidity, dust). Generally, it is recommended to lubricate the bearing at regular intervals, possibly every 100 operating hours, or at least annually for aerial work platforms with infrequent use.

  4. Lubrication method: Grease can be applied either manually or through an automated lubrication system. Manual lubrication involves injecting grease using a grease gun, while automated systems involve pre-programmed injection intervals and may offer more consistent application.

  5. Lubricant monitoring: Regularly monitoring the condition of the lubricant is essential, ensuring the grease has not degraded, become contaminated, or lost its effectiveness. If the grease appears darker, contains metal particles, or has lost its consistency, it should be replaced.

  6. Lubrication inspections: As a part of the maintenance routine, check for any leakage at the seals or excessive grease in the work area. Leakage may indicate an issue with the seal, an over-lubrication, or grease degradation.

Maintaining proper lubrication in slewing bearings on aerial work vehicles is vital for their safe and efficient operation. The appropriate choice of lubricant, correct application, and regular monitoring will help prolong the bearing's lifespan and reduce the risk of failure or operational issues.

The Maintenance of Slewing Bearing in Aerial Work Vehicles

Regular maintenance of slewing bearings in aerial work vehicles is crucial for ensuring their safe operation, longevity, and performance. Here are some key maintenance steps to follow:

  1. Visual Inspection: Periodically check the slewing bearing for visible signs of wear, damage, or corrosion. Inspect the seals for any leakage or deformations, and examine gear teeth (if present) for signs of wear or damage.

  2. Lubrication: Adequate lubrication is essential for preventing wear and reducing friction. Ensure proper lubrication by applying high-quality grease to all contact surfaces of the bearing components (inner and outer raceways, and rolling elements). Follow the manufacturer's recommendations for grease type and application intervals.

  3. Clearance Check: Measure and monitor bearing clearance over time to detect any changes which could indicate issues with the bearing's components. Excessive clearance may lead to instability and potential bearing failure.

  4. Bolting and Fastenings: Inspect all bolts and fastenings securing the slewing bearing to the aerial work vehicle. Ensure they are correctly tightened and in good condition.

  5. Functional Test: Routinely perform operational tests of the aerial work vehicle, checking for excessive play, vibrations, or noises during rotation. If any abnormalities are noticed, inspect the slewing bearing carefully, and address any potential issues promptly.

  6. Record Keeping: Maintain a detailed maintenance log, noting inspection dates, performed actions, and any identified issues. This provides valuable information for tracking the condition of the slewing bearing and helps plan future maintenance.

  7. Replacement: Follow the manufacturer's guidelines for the slewing bearing's expected lifespan, and replace it as recommended. If a bearing is found to be damaged or excessively worn during inspection, replace it before resuming operation.

By performing regular maintenance and addressing potential issues quickly, you can extend the life of a slewing bearing and ensure the aerial work vehicle continues to operate safely and efficiently.


In summary, slewing bearings are critical components of aerial work vehicles, enabling smooth and efficient rotation of platforms. Proper maintenance and lubrication of these bearings are essential for the safe and reliable operation of the vehicle.

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