Identifying and Replacing Swing Bearings on the ZX85US-3: A Comprehensive Guide

[MikePhua]

The swing bearing, also known as the slew ring, is an integral component of any hydraulic excavator, including the ZX85US-3, that allows the upper structure of the machine to rotate independently of the undercarriage. This bearing plays a critical role in the machine’s operation, particularly when rotating the cab for digging, material handling, or operating attachments. Over time, these bearings can wear out or become damaged, leading to performance issues. In this article, we will explore how to identify, inspect, and replace the swing bearing on a ZX85US-3 and the importance of maintaining this component.
What Is a Swing Bearing?
A swing bearing is a large, ring-shaped bearing that connects the upper and lower portions of an excavator. It allows the upper structure, which includes the cab and arm, to rotate smoothly and accurately relative to the chassis.
Swing bearings typically consist of:

• Outer and Inner Rings: The large circular rings that hold the bearing’s rolling elements.
  
• Rolling Elements: Typically, these are spherical rollers or ball bearings inside the bearing, which help facilitate smooth rotation.
  
• Seals: These are designed to prevent contaminants like dirt, dust, and water from entering the bearing, which can lead to corrosion or premature wear.
  

The swing bearing is subjected to high mechanical stress during operation, especially when the excavator rotates frequently or works with heavy loads. It is essential to maintain the swing bearing in good condition to prevent costly repairs or machine downtime.
Identifying Issues with the Swing Bearing
There are several signs that may indicate problems with the swing bearing on your ZX85US-3. Recognizing these issues early can help prevent further damage to the excavator and improve its overall lifespan.
Common Symptoms of a Faulty Swing Bearing

1. Excessive Play or Looseness: Over time, wear and tear can cause the swing bearing to loosen, leading to excessive play between the upper structure and the undercarriage. This can result in a sloppy or imprecise rotation, affecting the machine’s accuracy and control.
   
2. Strange Noises: Grinding, squealing, or clicking noises coming from the swing bearing area while rotating the cab can be a sign of damage. These noises often occur when the rolling elements inside the bearing are worn or when debris is lodged in the bearing.
   
3. Jerky Rotation: If the excavator's upper structure moves in a jerky or uneven manner, it can indicate that the swing bearing is either damaged or worn out. This can make operations like grading or digging more difficult, as the machine lacks the fluid motion necessary for precise control.
   
4. Uneven Wear or Damage: If you notice that one side of the machine is leaning or the upper structure isn’t rotating evenly, the swing bearing may have internal damage or issues with alignment.
   

How to Inspect the Swing Bearing
A visual and mechanical inspection is necessary to identify if the swing bearing needs to be replaced. Here are the steps for inspecting the ZX85US-3’s swing bearing:

1. Visual Inspection:
   • Look for visible cracks or deformation around the bearing’s rings.
     
   • Check for any signs of rust or corrosion, which could indicate water or debris has entered the bearing.
     
   • Inspect the seals for wear and tear.
     
2. Listen for Abnormal Sounds:
   • Rotate the upper structure while listening for unusual sounds like grinding, clicking, or scraping.
     
   • These noises can suggest damaged rolling elements or lack of proper lubrication.
     
3. Measure Play and Movement:
   • Check for excessive play by moving the upper structure back and forth. Any noticeable wobbling or unsteady rotation indicates the bearing might be worn out.
     
   • If possible, use a micrometer to measure the clearance between the inner and outer rings of the bearing.
     
4. Lubrication Check:
   • Inspect the lubrication points on the swing bearing. If lubrication is insufficient or the grease is contaminated, this can lead to faster wear and damage.
     
5. Structural Alignment:
   • Check the alignment of the upper structure in relation to the undercarriage. Misalignment can indicate issues with the swing bearing or other components like the swing motor.
     

Replacing the Swing Bearing on the ZX85US-3
If you’ve determined that the swing bearing on your ZX85US-3 is indeed faulty and needs replacement, here’s a step-by-step guide to the process. Replacing a swing bearing is a significant job that requires careful planning and proper tools.
Steps to Replace the Swing Bearing

1. Preparation:
   • Park the Excavator: Ensure the machine is on a flat, stable surface. Engage the parking brake and disconnect the battery to avoid any electrical hazards.
     
   • Lift the Upper Structure: Use a crane or a lifting device to raise the upper structure of the machine so that you can access the swing bearing easily.
     
   • Remove the Old Bearing: Before removing the swing bearing, you must disassemble the surrounding components, including the swing motor and hydraulic lines. Remove any bolts securing the bearing.
     
2. Clean and Inspect:
   • Once the bearing is removed, clean the housing to remove any debris, dirt, or old grease. Inspect the surrounding components, including the swing motor and mounts, for any damage.
     
3. Install the New Bearing:
   • Carefully position the new swing bearing in place. Ensure the alignment is perfect before securing it with bolts. The bearing must be tightly fitted into place without any gaps or misalignment.
     
   • Lubricate the bearing with the appropriate grease or oil as specified in the manufacturer’s manual.
     
4. Reassemble and Test:
   • Reassemble the swing motor, hydraulic lines, and any other components that were removed during the bearing replacement.
     
   • Test the new swing bearing by operating the machine. Check for smooth rotation and listen for any abnormal noises. Ensure there is no excessive play or looseness.
     
5. Lubrication and Maintenance:
   • Regularly check the swing bearing for proper lubrication. Proper lubrication is essential for extending the life of the bearing and preventing premature wear.
     

Tips for Preventing Swing Bearing Issues
Maintaining your swing bearing is key to extending the life of your ZX85US-3 and avoiding costly repairs. Here are some helpful tips:

• Routine Inspections: Regularly inspect the swing bearing for wear and tear, especially after long hours of operation.
  
• Lubrication: Ensure that the swing bearing is always properly lubricated. Use the correct grease and check the lubrication levels frequently.
  
• Avoid Overloading: Avoid excessive stress on the swing bearing by not overloading the machine or pushing it beyond its capabilities.
  
• Protect from Contaminants: Ensure that seals are intact and functioning correctly to prevent dirt, water, and other debris from entering the bearing.
  

Conclusion
The swing bearing on the ZX85US-3 is a critical component that ensures smooth rotation and optimal performance. By regularly inspecting the bearing for wear, lubricating it properly, and addressing any issues promptly, you can keep your excavator in top working condition. When replacement is necessary, following the correct procedures will ensure that the new bearing performs as expected, extending the life of your machine and enhancing its performance. Regular maintenance, proper lubrication, and vigilance against wear and tear are essential for maximizing the lifespan of your ZX85US-3 and minimizing downtime.