DH220-5 auxiliary valve
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Product details
CAT320 Excavator Swing Priority & Relief Valve Specification
Basic Info
Applicable Models: CAT320C / CAT320D
Alternative Names: Swing buffer valve, swing overload valve
Mounting Position: Top of swing motor, one set each for port A and port B.
Core Functions
1. Swing Overload Relief Protection
- Limits maximum circuit pressure of swing loop, factory preset: 24–26 MPa.
- Absorbs hydraulic shock during swing start and stop to protect swing motor and high-pressure hoses from bursting.
- Dual-side independent protection for clockwise and counter-clockwise rotation respectively.
2. Swing Priority Control
- Supplies priority oil flow to swing circuit under combined working conditions (swing plus boom / arm operation).
- Operates as pressure-controlled sequence valve: pilot signal of swing shifts the valve to restrict flow toward auxiliary actuators and divert most oil to swing motor.
- Improves coordination of multi-action and boosts loading efficiency.
Working Principle & Construction
- Structure: Direct-acting poppet valve assembled with poppet, spring, orifice and adjusting screw, symmetric dual-way layout.
- Relief function: Poppet remains closed below preset pressure for full oil supply to motor; poppet opens to drain excess oil back to tank once overloaded to stabilize circuit pressure.
- Priority function: Full flow feeds swing under single movement; pilot pressure triggers priority spool to cut redundant flow of boom/arm during compound operation.
Key Technical Parameters
- Standard set pressure: 25 MPa; cracking pressure: 24 MPa
- Mount thread: M18×1.5
- Component material: Hardened steel poppet, carbon steel valve body, alloy spring
- Matched swing motor part: 165-9578 for CAT320 series
Common Faults & Symptoms
1. Set pressure below 22 MPa: Weak swing output, slow swing speed, deteriorated performance during combined actions.
2. Set pressure over 28 MPa: Engine lugging, pipeline vibration and abnormal noise on swing stop.
3. Stuck valve core: Residual high pressure after swing halt, rising oil temperature.
4. Internal leakage or damaged seals: Swing drifting, idle pressure drop and shaking movement.
5. Failed priority function: Swing speed drops sharply while arm/boom takes preferential oil flow in compound operation.
Pressure Adjustment
- Clockwise = increase setting pressure; Counter-clockwise = decrease setting pressure.
- Standard factory setting: 25 MPa; normal pilot pressure: 3.5–4.0 MPa.
- Recommended tightening torque of lock nut: 25–30 N·m.
Related Terminology
Swing Relief Valve
Swing Overload Valve
Swing Priority Valve
Swing Motor Integrated Priority & Relief Valve
In the CAT320 excavator, therelief valveand theswing priority valveare two distinct hydraulic components, each playing a crucial role. Here is a detailed introduction to both:
Relief Valve
1. Function: The relief valve is a key safety device in the hydraulic system, primarily used to control the maximum pressure of the system, prevent overload, and protect hydraulic components from damage. When the system pressure exceeds the set value, the relief valve automatically opens, allowing some hydraulic oil to flow back to the tank, thereby reducing the system pressure and ensuring safe system operation.
2. Characteristics:
• Pressure Regulation: The relief valve can adjust the outlet pressure according to system requirements, maintaining stable system pressure.
• Overload Protection: When the system pressure exceeds the set value, the relief valve opens to prevent system damage.
• High-precision Machining: Key components such as the valve spool and valve seat of the relief valve are typically machined with high precision to ensure excellent sealing performance and stable pressure regulation.
3. Application: In the CAT320 excavator, relief valves are widely used in hydraulic circuits for work equipment control, swing systems, and travel systems, ensuring that each system operates within a safe pressure range.
Swing Priority Valve
1. Function: The swing priority valve is a specially designed priority valve that ensures the swing system receives a relatively larger supply of hydraulic oil during compound actions (such as lifting the boom while swinging), thereby improving swing speed and efficiency.
2. Characteristics:
• Priority Oil Supply: During compound actions, the swing priority valve ensures that the swing system receives priority oil supply, enhancing swing performance.
• Compact Structure: The swing priority valve is typically designed to be compact and easy to install in the hydraulic system.
• Wear-resistant and Corrosion-resistant: Considering the harsh working environment of excavators, the components of the swing priority valve may be made of wear-resistant and corrosion-resistant materials to extend their service life.
3. Application: In the CAT320 excavator, the swing priority valve is usually installed in the swing hydraulic circuit, working in conjunction with the main valve, swing motor, and other components to ensure stable operation of the swing system.
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