Slewing Bearing for Marine Crane: A Comprehensive Guide

Slewing Bearing for Marine Crane to enable rotation and maintain stability during operations. These essential components facilitate precise control and movement of the crane's boom, ensuring safe and efficient cargo handling at sea. Slewing bearings are designed to withstand the harsh marine environment and the high stresses encountered during lifting and rotation processes, making them a crucial part of marine crane systems.

Slewing bearings play a critical role in marine cranes, ensuring smooth operation and reliable cargo handling. This article provides an in-depth look at slewing bearings for marine cranes, including their operation, features, installation, specifications, and more.

What is a Marine Crane?

A marine crane is a specialized lifting device used on ships, boats, and offshore platforms to handle cargo, equipment, and other heavy loads. Marine cranes facilitate ship loading and unloading operations, ensuring smooth and efficient ship-to-shore transfers.

What is a Slewing Bearing for Marine Crane?

A slewing bearing for marine cranes is a specialized type of large-diameter bearing designed to accommodate the rotational and axial forces exerted during crane operations in marine environments. Marine cranes are used on ships, offshore platforms, and ports for various lifting and cargo handling tasks. The slewing bearing plays a crucial role in enabling rotation between the crane's fixed structure and its movable components while supporting the load.

Slewing Bearing for Marine Crane

The Materials of Slewing Bearing for Marine Crane

Currently, 42 Cr Mo alloy tempered steel is the preferred choice as the bearing material in many applications. This material meets not only the standard mechanical performance requirements of bearings, but also offers the following additional advantages:

  • Impressive impact resistance: At -20°C, the average impact energy of three V-notch Charpy test specimens should be no less than 42 J. At least one of these specimens should have an impact energy of 27 J or higher, ensuring reliable performance at low temperatures.

  • Optimal hardness: After heat treatment, the hardness of the bearing ring should fall within the range of 260 to 290 HB, providing an ideal balance of toughness and wear resistance.

As for the material of the steel balls, conventional bearing steel is commonly used, which is consistent with general slewing bearing applications. This combination of materials and performance specifications ensures the reliable, durable, and efficient operation of these bearings.

Force characteristics and common bearing structure

Turntable bearings play a critical role in supporting ship cranes and transferring torque. They primarily handle axial forces and tilting torque. To achieve a compact mainframe, the diameter and height of these bearings are significantly smaller compared to conventional products, and they do not require counterweights. The tilting torque can reach up to 18 times the axial force, with the ratio between the two typically ranging between 14.9 and 18. Common bearing structures include double-row ball bearings and three-row cylindrical roller turntable bearings.

Double-row ball bearings offer several notable advantages:

  • High tilting torque capacity: These bearings can withstand substantial tilting moments, making them well-suited for the operational demands of ship cranes.

  • Strength in handling uneven ground: Double-row ball bearings have a robust capacity to resist inconsistencies on the base plate.

  • Error compensation: These bearings can compensate for processing errors in connecting components, reducing the impact of such inaccuracies on overall performance.

  • Compact radial dimensions: Double-row ball bearings have smaller radial dimensions, contributing to a more compact design.

In summary, turntable bearings are crucial for supporting ship cranes and transferring torque. Double-row ball bearings, in particular, offer several advantages, making them a popular choice for demanding crane applications.

How Does the Slewing Bearing for Marine Crane Work?

A slewing bearing typically consists of an inner and outer ring, rolling elements such as balls or rollers, and seals to protect against environmental factors. The inner and outer rings are designed with raceways on which the rolling elements move, ensuring the smooth rotation of the crane. The bearing system is mounted between the crane's base structure and its rotating platform or boom.

  • Rotation: When the crane operator initiates a rotational movement, the rolling elements within the slewing bearing reduce friction between the inner and outer rings, ensuring smooth and controlled pivoting. This rotation allows the crane to maneuver in various directions as needed for lifting and moving loads.

  • Load Support: The slewing bearing is designed to support both axial and radial loads applied during lifting operations. Axial loads are the vertical forces experienced by the crane, while radial loads are the horizontal forces. Thanks to the bearing's load-carrying capability, the crane can handle heavy loads with maximum stability and safety.

  • Structure Stability: An essential function of the slewing bearing is to maintain the stability of the crane, even when lifting heavy loads in challenging marine environments. Its design and construction allow for high precision and rigidity, ensuring proper alignment and reducing potential deformations during use.

  • Sealing: Slewing bearings for marine cranes are equipped with seals to protect against the harsh conditions of the marine environment, including saltwater exposure and potential contaminants. The seals help prolong the life of the bearing and its components, resulting in reduced downtime and maintenance costs.

In summary, the slewing bearing is a vital component of marine cranes, enabling smooth rotation and movement while handling loads efficiently and safely. It plays a critical role in maintaining the crane's stability and performance in harsh marine environments.

Characteristics of a Good Slewing Bearing for Marine Crane

A high-quality slewing bearing for marine cranes should possess the following features:

  • Durability and resistance to corrosion, ensuring a long service life in harsh marine environments.

  • High load-bearing capacity, providing reliable support for heavy loads.

  • Low friction and smooth rotation, ensuring accurate and precise crane movement.

  • Easy maintenance and lubrication, minimizing downtime and extending service life.

Installing a Slewing Bearing for Marine Crane

Installation Site

The ship crane primarily consists of a rotating tower, boom, fixed base post welded to the deck, lifting, tilting, and swinging mechanisms, hydraulic power and piping systems, and electrical control systems. A turntable bearing is mounted at the bottom of the crane tower body for the marine crane. The inner ring's lower end is bolted to the fixed base post, which is welded to the ship's deck. The outer ring's upper end is connected to the crane tower via bolts. When the ship crane is in operation, the swinging mechanism drives the swing pinion, which engages with the ring inside the turntable bearing. This engagement facilitates the rotation of the outer ring, enabling the ship crane to swing smoothly and efficiently during operation.

Installation steps:

  • Carefully clean and inspect the mating surfaces before installation.

  • Align the mounting holes and apply the recommended lubrication between the bearing and its mounting surfaces.

  • Secure the bearing to the crane structure using bolts, ensuring they are evenly tightened following the manufacturer's guidelines.

  • Perform a rotation test to verify the smoothness of rotation and confirm proper installation.

Technical Specifications of Slewing Bearing for Marine Crane

Technical specifications for slewing bearings vary based on crane type and capacity. Key specifications may include:

  • Bearing type (ball, roller, or combined)

  • Ring dimensions (inner, outer, and width)

  • Rated load capacity (axial, radial, and moment)

  • Rated rotation speed

Pricing and Availability of Slewing Bearings for Marine Cranes

Pricing can vary based on factors such as bearing size, type, material, and manufacturer. The slewing bearings for marine cranes usually need to be customized. LTZC Bearing is a trusted manufacturer of slewing bearings for marine cranes. Our engineers can provide you with the most suitable solutions and technical support. Please contact us immediately to get a quote.

Safety Guidelines of Slewing Bearings for Marine Cranes

Proper safety measures for slewing bearings include:

  • Regular inspection and maintenance, addressing any signs of wear or damage.

  • Following manufacturer-recommended guidelines for bearing lubrication and torque values during installation and maintenance.

  • Ensuring crane operators receive appropriate training in safe operation and handling.

Factors Affecting the Price of Slewing Bearings for Marine Cranes

The price of slewing bearings for marine cranes may be influenced by:

  • Bearing size and load capacity

  • Material and manufacturing quality

  • The brand and original equipment manufacturer (OEM) requirements

  • Customization or specialized features


Slewing bearings are essential components of marine cranes, ensuring smooth and precise rotation during cargo handling operations. Understanding their function, characteristics, and maintenance requirements is crucial to ensuring long-lasting performance and reliable crane operation.
As a professional slewing bearing manufacturer or supplier, LTZC Bearing can provide you with detailed specifications including size, load capacity, accuracy requirements, and any other specific features required for your application. If you need to get an accurate cost estimate for Slewing Bearings for Marine Cranes, it is recommended to contact us directly.

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