PC40 MAIN RELEF VALVE

PC40 MAIN RELEF VALVE

2 month ago

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Ningbo Hengnuo Hydraulic Drive Co.,Ltd

 4 year year

Product details

I. Core Functions

The PC40 hydraulic system main relief valve is a critical safety protection device in excavator hydraulic systems, with core functions including:

1. Pressure Regulation & Overflow:

Automatically opens overflow channels when system pressure exceeds the set value, diverting excess oil back to the tank to prevent continuous pressure rise.

2. Pressure Stabilization Control:

Dynamically adjusts overflow volume to maintain system pressure within the set range, ensuring smooth operation of hydraulic actuators (e.g., boom, arm, bucket).

3. Safety Protection:

Prevents system overpressure caused by sudden load changes or operational errors, protecting core components like hydraulic pumps and motors from damage.

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II. Working Principle

The main relief valve adopts apilot-operated structure, consisting of a main valve and a pilot valve. Its operation proceeds in the following stages:

1. Pressure Sensing Phase:

System pressure is transmitted from the main valve inlet to the pilot valve spring chamber. When pressure is below the pilot valve's set value, the pilot valve remains closed, and the main valve spool stays shut under spring force, allowing pressure to rise.

2. Overflow Initiation Phase:

When system pressure reaches the pilot valve's set value, the pilot valve opens, discharging high-pressure oil through its drain port. A pressure differential across the orifice pushes the main valve spool open against spring force, initiating overflow.

3. Pressure Stabilization Phase:

After the main valve opens, system pressure drops with increased overflow. When pressure falls below the pilot valve's set value, the pilot valve closes, and the main valve spool resets under spring force, stopping overflow. Dynamic equilibrium maintains stable pressure.

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III. Technical Specifications (Typical Configuration)

【表格】

Parameter Value Range/Characteristics

Set Pressure 25–35 MPa (adjustable based on model requirements)

Flow Range 50–150 L/min (matches PC40 hydraulic pump flow)

Response Time ≤50 ms (rapid response to pressure surges)

Pressure Drop ≤0.5 MPa (under full-load conditions)

Materials Main spool: High-strength alloy steel; Seals: Fluororubber (FKM)

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IV. Common Faults & Troubleshooting

【表格】

Fault Symptom Possible Causes Solutions

Low System Pressure Low relief valve setting; Pilot valve spring fatigue Readjust pressure; Replace pilot valve spring

Pressure Fluctuations Stuck main spool; Clogged orifice Clean spool and orifice; Replace hydraulic oil filter

Excessive Valve Noise Air in oil; Worn spool Bleed air; Replace spool and seals

Valve Leakage Aged seals; Cracked valve body Replace seals; Weld or replace valve body

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V. Maintenance Recommendations

1. Regular Inspections: Check relief valve pressure settings every 500 hours to ensure compliance with equipment requirements.

2. Oil Management: Use anti-wear hydraulic oil meeting ISO VG46 standards and replace filters every 250 hours.

3. Cleaning: Clean the valve body internally every 1,000 hours to prevent debris from jamming the spool.

4. Operation Norms: Avoid prolonged overload operation to minimize pressure shocks that damage valve components.

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VI. Selection Considerations

1. Pressure Matching: Choose a relief valve with a set pressure range covering the system's maximum operating pressure.

2. Flow Compatibility: Ensure the valve's rated flow exceeds the hydraulic pump's maximum flow to prevent pressure spikes during overflow.

3. Environmental Adaptability: Select high-temperature-resistant seals for hot environments and low-pour-point hydraulic oil for cold climates.

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Ningbo Hengnuo Hydraulic Drive Co.,Ltd

 Audited supplier

4 year

Address: Ningbo, China

Main Product: hydraulic motor, gear box, hydraulic pump, hydraulic valve , hydraulic winch, hydraulic system

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