This is the main relief valve specially designed for DOOSAN DH220-5 excavator, installed on the main control valve assembly.
1. Control and limit the maximum hydraulic pressure of the whole system to protect hydraulic pumps, motors and pipelines from overload damage.
2. Automatically release pressure when system pressure exceeds preset value to stabilize hydraulic output.
3. Serve as the pressure benchmark of the entire main hydraulic circuit.
I. Function and Purpose
1. Core Function
The main relief valve is a critical safety device in the excavator’s hydraulic system, designed to limit the maximum system pressure and prevent damage to hydraulic components (e.g., pumps, cylinders, motors) caused by excessive pressure. When the system pressure exceeds the set value, the relief valve automatically opens, redirecting excess hydraulic fluid back to the tank to maintain stable pressure.
2. Pressure Range
• Typical Set Pressure:32–36 MPa(may vary slightly depending on model configuration).
• Adjustment Range: Must strictly adhere to factory specifications. Pressures exceeding 10% of the rated value can significantly shorten the lifespan of seals, hoses, and fittings.
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II. Technical Characteristics
1. Structural Type
• Mostly utilizes apilot-operated relief valve, which offers fast response and minimal pressure fluctuation by using a pilot valve to control the main valve opening.
• Some models may integratecomposite functions(e.g., relief + unloading) to optimize system efficiency.
2. Key Parameters
• Pressure Adjustment Range: Achieved by rotating the adjustment screw (clockwise to increase pressure, counterclockwise to decrease). Recommended adjustment increments: ≤0.5 MPa per step.
• Pressure Stability: Must be verified under varying operating conditions (e.g., digging, lifting, swinging) to ensure fluctuations remain within design limits (typically ±1 MPa).
• Sealing Performance: Must maintain leak-free operation under high pressure to prevent abnormal oil temperature rise or system pressure drops.
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III. Application Scenarios
1. System Protection
• Prevents hydraulic pump damage during high-load operations (e.g., deep digging, hard soil excavation) by limiting pressure surges.
• Avoids pressure spikes caused by low oil temperature (<30°C) or abnormal oil viscosity, protecting components from shock damage.
2. Pressure Regulation
• Adjustments should be performed after the hydraulic oil reaches normal operating temperature (45–55°C) to ensure accurate readings.
• During adjustment, fully extend the actuator (e.g., boom cylinder) to its mechanical stop to allow the system pressure to reach the relief valve’s set value.
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IV. Maintenance and Troubleshooting
1. Common Failures
• Abnormal Pressure: Stuck valve, spring failure, or loose adjustment screw may cause overpressure or underpressure.
• Leakage: Aging seals or worn valve bodies can lead to fluid leaks, requiring immediate replacement of seals or the valve assembly.
• Noise: Frequent valve activation accompanied by abnormal sounds may indicate system overpressure or a stuck valve spool.
2. Maintenance Recommendations
• Regular Inspection: Check pressure settings and sealing every 500 hours; replace seals every 2,000 hours.
• Cleaning: Clean the valve body surface with clean hydraulic oil to prevent contaminants from entering and affecting performance.
• Professional Repair: If adjustment fails or internal damage is detected, contact a qualified technician to replace the valve spool or entire assembly.
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V. Selection and Compatibility
1. Original Parts Preferred
• The DH220-5 main relief valve must match the original factory model (e.g., AV280 1033000026) to ensure compatibility in pressure characteristics and mounting dimensions.
• Aftermarket alternatives require pressure testing and lifespan verification to avoid system failures due to parameter mismatches.
2. Cross-Model Adaptability
• Some universal relief valves may fit other DH220 series models (e.g., DH220-2, DH220-3), but confirm pressure ratings and interface dimensions first.
