Greasing the Turntable of Link-Belt Cranes

[MikePhua]

Turntables, or slewing rings, are essential components of cranes like those produced by Link-Belt. They allow the upper structure of the crane to rotate smoothly on the lower base, enabling efficient movement and positioning of the machine. Proper maintenance of the turntable’s lubrication system is critical to the overall performance and longevity of the crane. This article discusses the importance of greasing the turntable, the types of grease used, and how to maintain this crucial component to ensure your Link-Belt crane operates at peak efficiency.
The Role of the Turntable in Link-Belt Cranes
The turntable is the rotating platform of the crane that sits between the upper and lower structures. It is supported by a large bearing system called the slewing ring. The upper portion of the crane, including the boom and cabin, is mounted on the turntable, while the lower portion, consisting of the tracks or wheels, remains stationary. The turntable enables 360-degree rotation of the upper structure, allowing for greater flexibility and precision in lifting and positioning loads.
A well-maintained turntable ensures that the crane can rotate smoothly and safely without unnecessary wear on its components. This, in turn, contributes to better stability, longer service life, and enhanced performance during operations.
The Importance of Proper Greasing
Grease serves as the lubrication that minimizes friction between the moving parts of the turntable and the slewing bearing. Without proper lubrication, friction can increase, leading to excessive wear, overheating, and even failure of the bearing. This could result in costly repairs, reduced crane performance, and downtime.
Proper greasing helps in the following ways:

1. Reduces Wear: Grease reduces the friction between moving parts, minimizing the wear and tear on the turntable and slewing bearing.
   
2. Prevents Rust and Corrosion: It acts as a protective barrier against moisture and contaminants, reducing the risk of rust and corrosion, which can significantly reduce the lifespan of the crane.
   
3. Improves Performance: Lubrication ensures that the turntable moves smoothly, improving the crane’s rotational speed and efficiency, which is especially important for cranes working in high-demand environments.
   
4. Enhances Longevity: Properly greased turntables experience less wear and tear, meaning that the crane will have a longer operational life, reducing the frequency of repairs and replacements.
   

Choosing the Right Grease for Link-Belt Turntables
Not all greases are suitable for turntable lubrication. The type of grease used depends on several factors, such as the operating environment, temperature, and load conditions. For Link-Belt cranes, manufacturers typically recommend a high-quality, heavy-duty grease that can withstand high pressures and resist breakdown under load.
The following are key attributes to consider when selecting grease for turntable lubrication:

1. Load-Carrying Capacity: Turntables experience high stress and weight during operation, so the grease must have good load-carrying capabilities to withstand these pressures without breaking down.
   
2. Water Resistance: Since cranes often operate in harsh outdoor environments, the grease should be resistant to water, preventing rust and corrosion from forming in the turntable bearing.
   
3. High-Temperature Performance: Cranes working in high-temperature environments need grease that remains stable and effective at elevated temperatures without becoming too thin or losing its lubricating properties.
   
4. Anti-Wear Additives: The grease should contain additives that reduce wear and tear on the turntable, particularly when the crane is used in extreme conditions or for long hours.
   
5. NLGI Rating: The NLGI (National Lubricating Grease Institute) rating refers to the consistency or hardness of grease. For turntable applications, an NLGI rating of 2 is commonly used, but this can vary based on the crane model and operational conditions.
   

Common Grease Types for Turntable Lubrication
Link-Belt cranes typically use specialized greases designed for heavy-duty applications. Some of the most commonly used types include:

1. Lithium-Based Grease: Known for its versatility, lithium-based grease is often used in a wide range of applications due to its stability and resistance to water and heat.
   
2. Calcium Sulfonate Grease: This type of grease offers excellent water resistance and anti-corrosion properties, making it ideal for cranes working in wet or harsh environments.
   
3. Polyurea Grease: Polyurea-based grease is known for its high-temperature stability and excellent wear protection, making it suitable for cranes operating in extreme conditions.
   

Best Practices for Greasing Link-Belt Turntables
To maintain a well-lubricated turntable and extend the life of your Link-Belt crane, it’s crucial to follow the recommended greasing procedures. Below are the best practices for greasing the turntable effectively:

1. Follow Manufacturer Guidelines: Always consult the owner’s manual and follow the grease recommendations provided by the manufacturer. Link-Belt often specifies the exact type of grease and the frequency of greasing required for each crane model.
   
2. Clean the Grease Fittings: Before applying fresh grease, it’s essential to clean the grease fittings on the turntable. Dirt and debris can clog the fittings and prevent the grease from flowing properly. Use a clean rag to wipe away any contaminants before lubricating.
   
3. Grease the Turntable Regularly: The frequency of greasing depends on the amount of use and the operating conditions. As a general rule, the turntable should be greased every 50 to 100 hours of operation, or at least once every 200 hours, whichever comes first. In extremely dusty or wet environments, more frequent greasing may be necessary.
   
4. Grease Until Clean Grease Exits: When applying grease, pump grease into the fittings until clean, fresh grease begins to emerge from the seals. This ensures that old, contaminated grease is expelled, and the bearing is adequately lubricated.
   
5. Monitor Grease Leakage: After greasing, check for any leakage around the turntable area. Excessive leakage could indicate an issue with the seals, which may need to be replaced.
   
6. Inspect for Wear: While greasing, inspect the turntable and slewing bearing for any signs of wear, cracks, or damage. Address any issues promptly to avoid larger problems down the road.
   

Signs That the Turntable May Need Attention
Even with regular greasing, there are signs that the turntable may need additional maintenance or repair. These include:

1. Difficulty in Rotation: If the turntable becomes stiff or difficult to rotate, it may indicate a lack of lubrication, contamination of the grease, or wear in the bearing.
   
2. Excessive Noise: Unusual squealing or grinding noises when the crane rotates can be a sign of inadequate lubrication or damaged bearings.
   
3. Overheating: If the turntable becomes excessively hot during operation, it could indicate friction due to insufficient grease or a failing bearing.
   
4. Visible Wear: Any visible damage to the slewing ring or turntable should be addressed immediately to prevent further issues.
   

Conclusion
Maintaining the turntable and its lubrication system is crucial to the performance and longevity of Link-Belt cranes. By following proper greasing procedures, selecting the right grease, and adhering to manufacturer guidelines, crane operators can ensure their machines operate efficiently and avoid costly repairs. Regular maintenance not only enhances the safety and reliability of the equipment but also contributes to the overall productivity of operations.