Notes on the use of superimposed relief valves

The superimposed relief valve is a component that realizes pressure control of the hydraulic system through superimposed installation. It has the advantages of compact structure, flexible installation and easy maintenance. It is widely used in hydraulic systems such as machine tools, injection molding machines, and engineering machinery. In order to ensure stable performance, extend service life and avoid safety hazards, the following key things should be paid attention to when using:

1. Installation and connection precautions

1. Installation direction and cleaning degree

• Vertical installation: The superimposed relief valve usually needs to be installed vertically (the axis of the valve core is perpendicular to the ground) to avoid abnormal movement of the internal spring due to gravity deviation. If you need to install horizontally, you need to confirm that the product instructions allow it and install an anti-vibration bracket.

• Cleanliness requirements: Before installation, the hydraulic system must be thoroughly cleaned to avoid impurities (such as metal chips, seal debris) entering the valve body, causing the valve core to stagnate or seal failure. It is recommended to use a special cleaning agent to flush the pipeline and install a filter (filtration accuracy ≥10μm).

2. Overlay order and direction

• Superposition sequence: You must strictly superimpose the order of 'pump → reversing valve → relief valve → actuator' to avoid directly installing the relief valve between the pump outlet and the reversing valve, otherwise it may cause pressure impact to damage the valve body.

• Inlet and outlet direction: Confirm the direction of the oil inlet (P) and oil inlet (T) marked on the valve body. It is strictly forbidden to connect in reverse, otherwise the overflow valve will not be able to relieve pressure normally, causing system overheating or component damage.

3. Tightening torque control

• Bolt torque: Use a torque wrench to tighten the superimposed valve block according to the torque specified in the instruction manual (such as the M6 ​​bolt torque is 8-10N·m) to avoid excessive torque causing deformation of the valve body or insufficient torque causing leakage.

• Anti-loosening measures: Apply thread locking glue (such as Loctite 243) to prevent loosening caused by vibration.

2. Key points of parameter setting and debugging

1. Pressure regulation range

• Initial setting: According to system requirements, adjust the pressure of the relief valve to slightly higher than the required pressure for operation (such as the working pressure is 10MPa and the relief valve is set to 12MPa) to avoid frequent overflows and increase energy consumption.

• Sectional adjustment: If the system requires multiple pressures, multiple relief valves can be added (such as the main relief valve sets the highest pressure and the remote pressure regulating valve sets the second pressure), but it is necessary to ensure that the pressure regulating ranges of each valve do not overlap.

2. Pressure regulation stability

• Slow adjustment: Use a special Allen wrench to rotate the pressure regulating screw, the rotation angle does not exceed 1/4 of the turn, and observe the pressure gauge reading to avoid rapid adjustment causing pressure fluctuations or valve core impact.

• Locking device: After the pressure regulation is completed, use the locking nut to fix the pressure regulation screw to prevent vibration from causing pressure drift.

3. Dynamic response test

• No-load test: Start the pump under no-load state of the system and observe whether the overflow valve is stable overflowing under the set pressure without abnormal noise or vibration.

• Load test: Gradually increase the load and check whether the overflow valve can be opened to relieve pressure in time when the pressure exceeds the set value to avoid the continuous increase in the system pressure.

3. Operation and maintenance and fault prevention

1. Regular inspection and replacement

• Seal inspection: Check O-rings, combined seals and other seals every 500 hours, and replace them in time if they are aging or damaged to avoid leakage and insufficient system pressure.

• Spring status monitoring: The spring stiffness of the overflow valve is detected every year. If the spring is fatigued (free length shortened ≥5%), it needs to be replaced, otherwise it will affect the pressure regulation accuracy.

2. Oil management

• Oil cleanliness: Keep the oil cleanliness level not lower than NAS level 9 (or ISO 4406 18/15), and replace the filter element regularly (replace it every 2000 hours).

• Oil temperature control: Avoid excessive oil temperature (>80℃), otherwise it will accelerate oil oxidation and seal aging, resulting in a degradation of the performance of the overflow valve. It is recommended to install a cooler or use high temperature resistant hydraulic oil (such as HM46 wear-resistant hydraulic oil).

3. Troubleshooting and handling

• Possible causes: valve core vibration, oil bubbles, pressure shock.

• Treatment measures: Adjust the pressure regulating screw to eliminate vibration, exhaust gas and check the oil viscosity, and install accumulator at the pump outlet to buffer the impact.

• Possible causes: damage to the seal, cracks in the valve body, loose connecting bolts.

• Treatment measures: Replace the seal, check the valve body integrity and re-tighten the bolts.

• Possible causes: valve core stuck, spring breakage, oil contamination.

• Treatment measures: Clean the valve body and replace the spring, filter or replace the oil.

• Unstable pressure:

• Serious leak:

• Excessive noise: