Precautions for using superimposed hydraulic control check valves

The superimposed hydraulic control check valve is a hydraulic component that integrates the function of the hydraulic control check valve in the superimposed valve block. It has the advantages of compact structure, easy installation, and easy integration. It is widely used in hydraulic systems to achieve one-way locking, pressure holding or reverse opening control. The following are detailed instructions for its usage:

1. Installation and connection precautions

Direction Correctness The oil inlet (P), oil outlet (A) and control oil port (K) of the superimposed hydraulic control check valve must be strictly connected according to the mark to avoid functional failure or damage caused by reverse installation.

Example: If the P-slip is mistakenly connected to the oil return circuit, it may cause insufficient control pressure and the valve core cannot be opened.

Cleanliness requires thorough cleaning of the hydraulic system before installation to prevent impurities from entering the valve body and wear the valve core or seal.

Operation recommendation: Use a special cleaning agent to flush the pipeline and blow dry with compressed air.

The superposition sequence must be superimposed and installed in the order of 'bottom plate → directional valve → pressure valve → superimposed hydraulic control check valve → other functional valves' to ensure the reasonable flow path of the hydraulic oil.

Note: Avoid residual metal chips or sealing ring fragments between the valve blocks.

Tighten the fastening torque using a torque wrench to tighten the connection bolts (usually 10-15N·m) according to the manufacturer's specified torque to prevent leakage or deformation of the valve body.

Risk: Insufficient torque may lead to leakage, and excessive torque may damage the thread.

2. Working medium and temperature control

The hydraulic oil selection requires the use of system-compatible hydraulic oil (such as mineral oil, synthetic oil) and meet the viscosity range marked by the valve body (usually 15-460cSt).

Taboo: Avoid mixing hydraulic oils from different brands or models to prevent chemical reactions from failing seals.

Temperature management working temperature must be controlled within the range of -20℃ to +80℃. High temperature will accelerate the aging of seals, and low temperatures may lead to excessive viscosity of hydraulic oil.

Solution: Use high-temperature resistant sealing rings (such as fluoroelastomer) in high-temperature environments, and preheat hydraulic oil before low-temperature environments.

Pollution control The cleanliness of hydraulic oil must reach NAS level 9 or ISO 4406 18/16 standards, and the filter element should be replaced regularly (usually every 500 hours).

Consequence: Exceeding the pollution standard will cause the valve core to stagnate and increase leakage.

3. Match the control pressure and flow rate

Control pressure range The hydraulic pressure (port K) must be higher than the oil inlet pressure (port P) for a certain value (usually 1.5-3MPa) to ensure that the valve core is opened reliably.

Adjustment method: Precisely adjust the control pressure through a pressure reducing valve or proportional valve to avoid pressure fluctuations causing valve core shaking.

Flow adaptability The actual working flow must not exceed the maximum flow rate marked by the valve body (such as 30L/min), otherwise it may cause noise, vibration or valve core wear.

Selection suggestions: Select the valve body with the appropriate diameter according to the system flow rate (such as the diameter of 6mm corresponds to the flow rate ≤20L/min).

Back pressure affects If there is back pressure (such as resistance to the return oil pipeline), a check-way valve or back pressure valve should be added to the control oil circuit to prevent the valve core from being able to close completely.

4. Key points of functional testing and debugging

After the initial test and installation, a low-pressure (≤5MPa) cycle test is performed to check the leakage of each oil port (the allowable leakage is ≤0.5ml/min).

Tools: Use measuring cups and stopwatch to measure leakage.

Pressure holding performance verification After closing the oil inlet, monitor the pressure drop rate of the oil outlet (usually ≤0.5MPa/min) and verify the locking function.

Improvement measures: If the pressure holding is insufficient, the accumulator can be connected in parallel or the high-precision valve core can be replaced.

Reverse Open Test After applying control pressure, check whether the valve core can be fully opened within 0.5 seconds to avoid delays causing system response lag.

Optimization method: shorten the length of the control oil circuit or increase the diameter of the control oil port.

5. Maintenance and troubleshooting

Regularly check the valve body temperature (should be ≤70℃), leakage and noise level every 1,000 working hours.

Abnormal treatment: If the valve body has severe heat, it may be caused by internal leakage, and the seal needs to be removed, inspected, cleaned or replaced.

Common faults and handling faults 1: Causes of valve core stuck: hydraulic oil contamination or valve core wear.

Solution: Clean the valve body and replace the hydraulic oil, or grind the valve core mating surface.

Fault 2: Cause of insufficient control pressure: a pressure reducing valve failure or oil leakage in the control circuit.

Solution: Maintain the pressure reducing valve and tighten the oil control circuit joint.

Fault 3: The reverse direction cannot be turned on Cause: The control pressure is too low or the spring preload is too large.

Solution: Adjust the control pressure or replace the spring with less preload force.

Before discontinuing long-term maintenance, the valve body must be thoroughly cleaned and rust-proof oil must be applied, and stored in a dry and ventilated place to avoid aging of the seal.

6. Safety operation specifications

The pressure limit is strictly prohibited from exceeding the maximum working pressure marked by the valve body (such as 31.5MPa), otherwise it may cause the valve body to burst.

Protection measures: Install an overflow valve in the system as a safety protection.

Electrical control safety If a solenoid valve is used to control the hydraulically controlled check valve, it is necessary to ensure that the solenoid valve power is stable to avoid sudden power outage and accidental closing of the valve core.

Recommendation: Add redundant power supply design or manual emergency operation device.

Personnel training operators must be familiar with the principles of hydraulic system and the functions of superimposed hydraulic control check valves to avoid accidents caused by misoperation.

By strictly following the above precautions, the superimposed hydraulic control check valve can be ensured to operate stably in the hydraulic system, extending service life and reducing failure rate. In actual use, it is necessary to optimize and adjust the specific working conditions and manufacturer's technical manual.