Wheeled type grab excavators often face the issue of slow steering when making sharp turns while driving. This problem is attributed to a decrease in volumetric efficiency and low system pressure in the hydraulic steering system. The main causes of this phenomenon are internal and external hydraulic leaks in the hydraulic system. This article provides methods for inspection and resolution.
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Check Hydraulic Oil Quality and Level: The quality and quantity of hydraulic oil in grab excavators directly impact the steering system's performance. Impurities in the hydraulic oil can damage seals or components, leading to increased internal leakage and, consequently, slow steering. Regularly check and replace hydraulic oil, ensuring it is free from impurities. Maintain the hydraulic oil level according to specifications.
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Inspect External Hydraulic Leaks: External leaks can result from poorly fitted oil pipe joints, faulty seals, or ruptured pipelines. High oil temperature can also contribute to increased leakage. External hydraulic oil leaks lead to significant oil loss, causing a drop in system pressure, unstable movements in the steering cylinder and motor, resulting in delayed and powerless steering.
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Check Steering Cylinder: Wear or damage to the piston and seals inside the steering cylinder can increase internal leakage, causing delayed steering. To inspect, remove the steering cylinder and test it on another excavator with normal steering. If the steering improves after replacement, the issue lies with the cylinder's seals. Disassemble and repair the steering cylinder accordingly.
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Examine for Air in the Hydraulic System: Air entering the hydraulic system can significantly impact efficiency, causing crawling in the steering cylinder and reducing overall hydraulic system efficiency, leading to delayed steering. Check for air entry points such as loose joints, seal issues, low oil levels, or poor-quality hydraulic oil. Identify and eliminate the cause of air entering the system.
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Check Steering Pump for Internal Leakage: Severe internal leakage in the steering pump can also cause delayed steering. Excessive clearances between the pump's rotor, blades, and side plates can lead to internal leakage. To inspect, replace the pump with a new one for comparative testing. If the steering performance improves, it indicates a problem with the steering pump, requiring replacement.
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Inspect Steering Motor: Significant wear on the working surfaces of the steering motor's stator, rotor, or valve can reduce the effective high-pressure oil volume entering the steering cylinder, resulting in delayed steering. If the steering performance is compromised, inspect and repair or replace the steering motor components.
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Check Central Rotary Joint: Excessive wear on the inner cylindrical surface or seals of the central rotary joint can lead to interconnection of the entire oil and gas system, causing sluggish movements in various systems. Check for oil entering the air circuit during steering, indicating severe wear on the central rotary joint. Replace seals and repair the central rotary joint.
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Examine Single-Circuit Flow Control Valve: Low hydraulic pressure due to reduced spring force in the single-circuit flow control valve can result in powerless steering and delayed responses. To address this, remove the nylon plug from the remote control port on the valve base, attach a pressure gauge, and adjust the valve's adjusting screw if the pressure is below 7 MPa.
Conclusion: Regular inspection and maintenance of hydraulic components, along with prompt troubleshooting, are essential to ensure optimal steering performance in grab excavators, avoiding issues like delayed steering during sharp turns.
