Troubleshooting MDI Yutani 120 LC Swing Problem: A Comprehensive Guide

[MikePhua]

The MDI Yutani 120 LC is a robust hydraulic excavator, known for its performance and versatility in various construction tasks. However, like many heavy machinery models, it can occasionally experience issues with its swing function. The swing system allows the upper body of the excavator (the superstructure) to rotate independently of the undercarriage, which is essential for various digging and material handling operations. A malfunction in the swing system can lead to operational inefficiency, which may significantly affect productivity. In this article, we will delve into the potential causes, diagnosis, and solutions to a swing problem in the MDI Yutani 120 LC.
Understanding the Swing Function in Excavators
The swing function of an excavator allows it to rotate its upper structure 360 degrees, providing enhanced flexibility for digging and placing materials. This rotation is powered by a swing motor, which is typically hydraulically driven. The swing motor is connected to a swing ring or slewing ring, which provides the rotational axis.
When there is a problem with the swing function, it can manifest in various forms, such as slow or jerky movement, complete lack of rotation, or unusual noises during operation. Diagnosing and addressing these issues promptly is crucial to prevent further damage and reduce downtime.
Symptoms of Swing Issues in the MDI Yutani 120 LC
Common symptoms that indicate a swing problem on the MDI Yutani 120 LC include:

1. Slow or Jerky Swinging: If the upper body of the excavator is rotating slowly or jerking during operation, this could be a sign of issues with the swing motor, hydraulic system, or swing bearings.
   
2. No Swing Movement: Complete lack of swing movement is a more severe problem, which could point to a malfunctioning swing motor, loss of hydraulic pressure, or a failure in the control system.
   
3. Uneven Swing Speed: The machine may rotate at different speeds depending on the direction of the swing, which could indicate a problem with the swing control valve or hydraulic pump.
   
4. Unusual Noises: Grinding or whining noises when swinging can indicate wear in the swing motor, gears, or bearings. This should be addressed immediately to avoid further damage.
   

Diagnosing the Problem
Diagnosing the root cause of the swing problem in an MDI Yutani 120 LC involves checking several key components of the swing system, including the hydraulic system, swing motor, swing ring, and control valves. Here’s a step-by-step approach to diagnosing the issue:
1. Check Hydraulic Fluid Levels
The first step in diagnosing a swing issue is to check the hydraulic fluid. Low or contaminated fluid is a common cause of performance problems in hydraulic systems, including the swing motor.

• Low Fluid Levels: Insufficient hydraulic fluid can lead to poor performance or complete failure of the swing motor, as it may not receive the required pressure.
  
• Contaminated Fluid: Dirty fluid can clog filters, causing flow restrictions and inefficient operation of the swing motor.
  

2. Inspect the Swing Motor
The swing motor is responsible for powering the rotation of the excavator’s upper structure. If the motor is damaged or malfunctioning, it can lead to slow, jerky, or no movement.

• Leaks: Check for hydraulic leaks around the swing motor. If fluid is leaking from the motor, it may not be able to generate the required pressure for rotation.
  
• Motor Damage: Look for signs of overheating, unusual vibrations, or noise, which could indicate internal motor damage.
  

3. Check the Swing Ring and Bearings
The swing ring (or slewing ring) is the component that enables the upper structure to rotate. If it is worn or damaged, it can cause difficulty in rotating the machine.

• Wear and Tear: Inspect the swing ring for signs of wear, pitting, or cracks that could hinder smooth rotation.
  
• Bearings: Worn-out bearings can result in noisy or uneven swinging. Regular lubrication of the swing bearing is crucial to maintaining smooth operation.
  

4. Inspect the Swing Valve and Control System
The swing valve controls the flow of hydraulic fluid to the swing motor. A malfunction in the valve or the control system can lead to erratic or no swing movement.

• Clogged or Faulty Valve: If the valve is clogged or damaged, it may restrict the flow of fluid to the swing motor, causing sluggish or erratic movement.
  
• Sensor or Control Issues: Some excavators have sensors and electronic controls that regulate swing speed and movement. A malfunction in the electronic control system can lead to issues with swing functionality.
  

Common Causes of Swing Problems in MDI Yutani 120 LC
Several potential causes could be at the heart of swing problems in the MDI Yutani 120 LC. These include:
1. Hydraulic Issues
The most common cause of swing problems is hydraulic-related. This can include low fluid levels, air in the hydraulic lines, or a malfunctioning pump. The swing motor depends on consistent hydraulic pressure to operate smoothly, and any deviation from this can result in malfunctioning swing operations.
2. Worn Swing Motor
If the swing motor has been in operation for a long time, it may have become worn out. Over time, the seals and internal components of the motor can deteriorate, leading to reduced efficiency or complete failure.
3. Swing Ring Wear
The swing ring is a critical component that facilitates smooth rotation. If the swing ring has worn down due to extended use, it can cause the upper structure to rotate unevenly or even become completely stuck.
4. Control Valve Malfunctions
Control valves regulate hydraulic fluid flow to the swing motor. If these valves malfunction due to blockages or wear, the flow of fluid can be compromised, leading to erratic swinging or complete failure.
Solutions to Fix Swing Issues
Once the problem has been identified, there are several solutions depending on the specific cause:
1. Top Up or Replace Hydraulic Fluid
If low fluid is the issue, simply topping up or replacing the hydraulic fluid can solve the problem. Be sure to use the recommended fluid type as specified in the machine’s manual.
2. Repair or Replace the Swing Motor
If the swing motor is leaking or damaged, it may need to be repaired or replaced. Depending on the extent of the damage, a simple seal replacement might suffice, or the entire motor may need to be swapped out.
3. Replace or Lubricate the Swing Ring and Bearings
If the swing ring is worn, it may need to be replaced. Additionally, lubricating the swing bearing regularly can prevent wear and ensure smooth movement.
4. Clean or Replace the Swing Valve
If the swing valve is clogged or malfunctioning, it may need to be cleaned or replaced. Regular maintenance of the hydraulic control system can prevent these issues from arising.
Preventive Maintenance Tips
To prevent future swing issues on the MDI Yutani 120 LC, regular maintenance is essential. Here are a few tips to keep the swing system functioning optimally:

1. Regularly Check and Maintain Hydraulic Fluid: Keep the fluid at the proper levels and replace it at the intervals recommended in the manual.
   
2. Inspect the Swing Motor: Periodically inspect the swing motor for leaks or signs of damage.
   
3. Lubricate the Swing Bearing: Ensure that the swing bearing is properly lubricated to prevent wear and maintain smooth rotation.
   
4. Clean and Maintain Hydraulic Valves: Clean the swing valve regularly to prevent clogging and ensure proper hydraulic flow.
   

Conclusion
Swing issues on the MDI Yutani 120 LC excavator can be caused by a variety of factors, including hydraulic problems, wear in the swing motor, issues with the swing ring or bearings, and valve malfunctions. By following a systematic approach to diagnosing and addressing the issue, operators can restore the swing function and minimize downtime. Regular maintenance and attention to the swing system can prevent many of these issues from occurring in the first place, ensuring that the excavator continues to operate efficiently on job sites.