Komatsu PC600-7 Excavator: Comprehensive Repair and Troubleshooting Guide

introduction

Komatsu PC600-7 Main Pump Disassembly and Inspection

First, we conducted a disassembly inspection of the main pump. During the inspection, we found that the plunger, plunger sleeve, distribution plate, and slippers were excessively worn, with large axial clearances. These wear and clearance issues directly impacted the efficiency of the hydraulic system, leading to insufficient pressure. As the core component of the excavator’s hydraulic system, the performance of the hydraulic pump is critical to the overall machine efficiency. Due to severe wear, the hydraulic pump could not provide adequate pressure, causing the actuators to slow down and even crawl. Therefore, these components must be replaced and adjusted to restore the normal operation of the hydraulic pump.

Actuator Inspection

Next, we carried out a detailed inspection of the actuators. No internal leakage, external leakage, or impact phenomena were found during the inspection, indicating that the mechanical parts of the actuators themselves were not problematic. The issue mainly lay in the insufficient hydraulic pressure. The normal operation of the actuators depends on stable and sufficient hydraulic pressure, and the current hydraulic system could not provide the required pressure, which was one of the main reasons for the slow movements and crawling state.

Directional Control Valve Disassembly and Inspection

We then disassembled and inspected the directional control valve. The inspection revealed that the clearance between the spool and the valve body was too large, with an oil leakage rate of 2L/min at a test pressure of 10MPa, far exceeding the standard value. The clearance between the spool and the valve body reached 0.2mm, and there were significant scratches on the pressure control valve spool and seat, with leak rates also exceeding the standard (20mL/min). When the test pressure reached 15MPa, the main relief valve opened prematurely (standard should be at 31.4MPa), causing a significant oil leakage. The performance of the directional control valve is critical to the efficiency and stability of the hydraulic system. The excessive clearance between the spool and the valve body led to substantial oil leakage, severely affecting the stability of the hydraulic system pressure. Therefore, the directional control valve must be repaired and adjusted.

Inspection of Other Components

During the inspection, other components such as the cooling fan motor, fan blades, and hydraulic oil cooler were also thoroughly checked. The results showed that these components were all in good condition, with no abnormalities found. This indicated that the hydraulic system issues were mainly concentrated in the hydraulic pump and directional control valve, with no impact from other components on the hydraulic system’s normal operation.

Repair and Adjustment Process

First, we replaced and ground the main hydraulic pump plunger, plunger sleeve, distribution plate, and slippers, adjusted the axial clearance, and then conducted a machine test. At this point, the pressure had significantly increased, reaching a maximum of 25MPa, but the oil temperature was still too high. After the machine worked for 1 hour, the oil temperature exceeded 100℃, making the machine still unable to operate normally. This indicated that although the replacement and adjustment of the hydraulic pump improved the pressure, there were still other issues in the hydraulic system.

Next, we reground, chrome-plated, and finely ground the directional control valve spool, and matched and ground the main relief valve, unloading relief valve, safety valve, and pressure reducing valve. After reassembling and testing the machine, it resumed normal operation. This indicated that the repair and adjustment of the directional control valve effectively resolved the leakage issues in the hydraulic system, restoring normal pressure and effectively controlling the oil temperature.

Introduction and Inspection Steps of PC600-7 Excavator Slewing Bearing (Part Number: 21M-25-11100)

Introduction:

The slewing bearing is one of the essential components of an excavator, connecting the upper and lower frames and bearing the machine’s rotational movement. The part number for the slewing bearing of the PC600-7 excavator is 21M-25-11100. This slewing bearing has a high load capacity and long service life, maintaining stable performance in harsh working environments. The quality and performance of the slewing bearing directly affect the excavator’s efficiency and safety.

Detailed Inspection Steps for Komatsu PC600-7 Excavator Slewing Bearing

Ensuring the optimal performance and longevity of your Komatsu PC600-7 excavator requires a thorough and systematic inspection of its key components, including the slewing bearing. Here are the expanded and detailed steps for inspecting this critical part of your machinery:

Visual Inspection:

1. Examine the Surface:

• Begin by conducting a meticulous visual inspection of the slewing bearing’s exterior. Look for any visible signs of wear, such as scratches, gouges, or dull spots on the bearing surface.
• Check for cracks or fractures in the bearing structure. Even minor cracks can propagate over time, leading to significant mechanical failures.
• Assess any deformation that might be present. Deformation can indicate excessive loads or improper installation, both of which can compromise the bearing’s integrity.

1. Inspect the Seals:

• Closely inspect the seals for any damage. Look for tears, punctures, or material degradation, which are indicative of aging or exposure to harsh operating conditions.
• Ensure the seals are properly seated and not displaced. Dislodged seals can lead to contamination and subsequent bearing failure.

Lubrication Inspection:

1. Assess Grease Condition:

• Check the lubrication status by examining the grease condition. The grease should be clean and free from contamination. Discolored or dirty grease can indicate the presence of contaminants or degradation.
• Verify the amount of grease present. Insufficient lubrication can lead to increased friction and wear, while over-lubrication can cause overheating and seal damage.

1. Apply Grease as Needed:

• Add grease to the slewing bearing using the manufacturer-recommended type and quantity. Ensure the grease is evenly distributed around the bearing to maintain optimal lubrication.
• Utilize a grease gun to inject grease into the lubrication points, and rotate the bearing to ensure the grease is spread uniformly.

Clearance Inspection:

1. Measure Radial and Axial Clearances:

• Use precise measuring tools, such as dial indicators or calipers, to check the radial and axial clearances of the slewing bearing. Compare these measurements against the manufacturer’s specifications to ensure they are within acceptable limits.
• Document the clearance values for future reference and trend analysis. This data can help in predicting potential wear and scheduling maintenance activities.

1. Adjust or Replace if Necessary:

• If the measured clearances exceed the recommended range, consider adjusting the bearing preload or replacing the bearing if adjustment is not feasible.
• Conduct a detailed analysis to determine the cause of excessive clearance, such as wear, improper installation, or material fatigue, and address these issues to prevent recurrence.

Rotational Inspection:

1. Test for Smooth Rotation:

• Manually rotate the slewing bearing or use appropriate tools to check for smooth, unhindered movement. The bearing should rotate freely without any noticeable resistance or roughness.
• Listen for any abnormal noises, such as grinding, clicking, or squeaking, which can indicate internal damage or contamination.

1. Investigate Abnormalities:

• If you detect any sticking or unusual noise during rotation, perform a more detailed inspection of the internal structure. Disassemble the bearing if necessary to examine the rolling elements, raceways, and cages.
• Look for signs of scoring, pitting, or flaking on the bearing surfaces, and replace any damaged components to restore smooth operation.

Load Inspection:

1. Evaluate Performance Under Load:

• Monitor the slewing bearing’s performance during the excavator’s operation under normal working conditions. Observe the bearing’s behavior while the machine is performing typical tasks to ensure it can handle the operational loads.
• Pay attention to any abnormal vibrations or noises that arise under load. These can be signs of misalignment, imbalance, or internal damage.

1. Ensure Stability:

• Verify that the slewing bearing maintains stability and does not exhibit excessive play or movement under load. Excessive movement can lead to inaccurate positioning and increased wear.
• Conduct load tests periodically to ensure the bearing’s performance remains consistent over time and address any issues promptly to avoid operational disruptions.

Conclusion

By meticulously following the expanded inspection steps outlined above, you can gain a comprehensive understanding of the slewing bearing’s condition. This proactive approach allows you to identify and resolve potential issues before they escalate, ensuring the Komatsu PC600-7 excavator operates smoothly and efficiently. Regular inspections and maintenance of key components such as the main pump, actuators, directional control valve, and slewing bearing are essential for preventing hydraulic system failures and maintaining the excavator’s reliability and performance.

In summary, through detailed inspections and timely repairs, we successfully addressed the hydraulic system failures of the Komatsu PC600-7 excavator. This thorough approach restored the machine to its optimal operating condition, ensuring it can continue to perform its critical tasks effectively and reliably.