Skeblco SK235SRLC Boom Down Stick Out Problem and Solutions

[MikePhua]

The Kobelco SK235SRLC is a popular model in the field of hydraulic excavators, widely used for its versatility and robust performance in construction, mining, and digging projects. However, like many pieces of heavy machinery, it is not immune to operational challenges. One common issue that operators of the SK235SRLC face is a problem with the boom down stick-out, which can occur during normal operation. This problem refers to the boom not fully retracting or sticking out excessively when the excavator’s boom is lowered. Understanding the root causes and addressing the issue is critical for maintaining the machine’s performance and safety. This article delves into the causes, effects, and solutions related to the boom down stick-out issue in the Kobelco SK235SRLC.
Overview of the Kobelco SK235SRLC Excavator
Kobelco, a leading Japanese manufacturer of construction machinery, has a long history of producing high-quality excavators. The SK235SRLC model is one of its mid-size hydraulic excavators, commonly used in earthmoving, grading, trenching, and demolition projects. This excavator is well-known for its fuel efficiency, powerful hydraulics, and user-friendly controls, making it a popular choice for a wide range of construction tasks.

• Engine Power: Approximately 160 horsepower
  
• Operating Weight: Around 24,500 kg (54,013 lbs)
  
• Digging Depth: 6.7 meters (22 feet)
  
• Maximum Reach: 9.6 meters (31.5 feet)
  

These specifications make the SK235SRLC a solid choice for tasks requiring a balance between power and maneuverability. However, like any heavy machinery, the excavator can encounter issues that require attention to maintain its high operational standards.
What is Boom Down Stick-Out?
Boom down stick-out refers to a condition where the excavator's boom, when lowered, sticks out further than expected. This can be an issue for operators as it can affect the excavator's ability to dig with precision or maneuver in confined spaces. The term "stick-out" refers to the excess length of the boom or stick (arm) when the hydraulic system is supposed to bring the boom into a retracted or stored position.
This issue can manifest in several ways:

• The boom does not fully retract to its designated resting position.
  
• The boom extends beyond the normal range when it is lowered, affecting digging angles and efficiency.
  
• The machine might experience jerky or incomplete movement during boom operations.
  

Common Causes of Boom Down Stick-Out in Kobelco SK235SRLC
Several factors can lead to boom down stick-out in an excavator like the Kobelco SK235SRLC. It is essential to identify the underlying issue to perform proper diagnostics and repairs. The most common causes include:

1. Hydraulic Pressure Imbalance
   Hydraulic excavators rely on pressurized fluid to operate the boom and other components. If the hydraulic pressure is imbalanced or if there is a malfunction in the hydraulic control valve, the boom may not retract or lower correctly. The fluid pressure must be correctly regulated to ensure smooth operation.
   • Cause: Worn hydraulic pumps, faulty valves, or pressure relief valves malfunctioning.
     
   • Symptoms: Unusual movement, slow boom response, or excessive boom stick-out.
     
2. Cylinder Seal Failure
   The boom’s hydraulic cylinders contain seals that prevent hydraulic fluid from leaking. If these seals wear out or become damaged, the hydraulic pressure in the cylinder can be compromised, causing the boom to fail to retract fully.
   • Cause: Worn or damaged seals in the boom's hydraulic cylinders.
     
   • Symptoms: Leaking hydraulic fluid around the cylinders and incomplete boom retraction.
     
3. Boom Cylinder Wear
   Over time, hydraulic cylinders can experience internal wear, leading to reduced functionality. This wear can occur from excessive use or lack of proper maintenance. A worn-out cylinder may not extend or retract properly, leading to the boom sticking out when it should be retracted.
   • Cause: Excessive wear in the boom cylinder or piston.
     
   • Symptoms: Sluggish boom movements and the inability to fully retract the boom.
     
4. Improper Hydraulic Fluid Levels
   Hydraulic systems in excavators like the Kobelco SK235SRLC rely on the proper fluid levels to function correctly. Low hydraulic fluid levels can cause erratic movement and the inability to fully retract the boom.
   • Cause: Leaks in the hydraulic system, improper fluid replenishment.
     
   • Symptoms: Reduced boom speed, unresponsive controls, and potential overheating.
     
5. Control Valve Malfunction
   The control valve regulates the flow of hydraulic fluid to different components of the excavator, including the boom. A malfunction in the control valve can prevent the boom from properly extending or retracting, causing issues such as the boom sticking out when it is lowered.
   • Cause: Faulty or malfunctioning control valves.
     
   • Symptoms: Unstable or inconsistent boom movements.
     

Diagnosing and Fixing the Boom Down Stick-Out Issue
To address boom down stick-out issues, a detailed inspection and diagnosis of the hydraulic system and related components is necessary. Operators and technicians should follow these steps:

1. Check Hydraulic Fluid Levels and Quality
   Ensure that the hydraulic fluid is at the proper level and that the fluid is free from contaminants. Dirty or low-quality hydraulic fluid can affect the system's performance. Replace the fluid and filters if necessary.
   
2. Inspect the Hydraulic Cylinders
   Examine the hydraulic cylinders for signs of leaks or damage. Check the seals around the cylinder for wear and replace them if they are damaged. If the cylinder is severely worn, a full replacement may be required.
   
3. Test the Control Valve
   Verify that the hydraulic control valve is functioning correctly. A faulty control valve can lead to improper movement of the boom. If the control valve is malfunctioning, it should be repaired or replaced.
   
4. Check for Hydraulic Pressure Imbalances
   Using a hydraulic pressure gauge, check the pressure settings of the hydraulic system. Ensure that the pressure is within the manufacturer’s recommended range. If the pressure is too high or too low, the issue could stem from a faulty pump or pressure relief valve.
   
5. Look for Signs of Structural Damage
   Inspect the boom and stick for any signs of physical damage or misalignment. A bent boom or stick can lead to incorrect boom movements. If structural damage is found, the damaged part may need to be repaired or replaced.
   

Preventive Measures and Maintenance Tips
To prevent boom down stick-out issues and ensure the longevity of the Kobelco SK235SRLC's hydraulic system, operators should perform regular maintenance and inspections:

1. Regular Fluid Checks
   Ensure that the hydraulic fluid levels are always maintained within the recommended range. Clean fluid helps to reduce wear and tear on the hydraulic components.
   
2. Periodic Seal Replacement
   The seals in the hydraulic cylinders should be checked regularly and replaced as necessary. This prevents leaks and ensures consistent pressure in the system.
   
3. Routine System Inspections
   Schedule regular inspections of the hydraulic system, control valves, and cylinders to catch any potential issues early before they develop into more serious problems.
   
4. Proper Operation and Handling
   Operators should avoid using the excavator for excessive lifting or overloading, which can lead to hydraulic strain. Proper operation techniques can significantly reduce the wear and tear on the machine.
   

Conclusion
The boom down stick-out problem in the Kobelco SK235SRLC is a hydraulic issue that can significantly impact the machine's performance if left unaddressed. Understanding the potential causes of this problem, including hydraulic pressure imbalances, cylinder seal failure, and control valve malfunctions, is key to diagnosing and resolving the issue. Regular maintenance, proper fluid checks, and timely repairs are essential in keeping the machine in peak working condition. By staying proactive with maintenance and addressing issues promptly, operators can extend the lifespan of their Kobelco SK235SRLC excavator and avoid costly downtime.