I. Core Causes of Hydraulic Systems Pressure Abnormal Volatility
1.Hydraulic Oil Related Issues
Oil Contamination: Metal particles, moisture or oxidation products mixed in hydraulic oil, will increase internal wear and tear of hydraulic pump, decreased volumetric efficiency, resulting in unstable output pressure.
Pollution can also clog the throttle orifices of hydraulic valves,such as safety and proportional valves, causing pressure fluctuations.
Abnormal Oil Viscosity:
Excessively high viscosity (low temperature or oil aging) can increase flow resistance, causing pressure to rise or fluctuate slowly.
Excessively low viscosity (high temperature or oil dilution) can reduce lubrication performance, lead to leakage, and make pressure difficult to maintain.
2.Hydraulic Pump and Actuator Failures
Hydraulic Pump Wear:
Wear of gears, pistons or vanes in the pump results inside unstable displacement and fluctuating output pressure.
The the pump's shaft seal or end cover seal failure, will lead to internal leakage, reduce system pressure.
Executive Body (Hydraulic Cylinder/Motor) Problems:
Hydraulic cylinder seal ring aging or damage will result in high pressure chamber and low pressure chambers communication, preventing pressure accumulation.
Internal leakage or plugging of the hydraulic motor will affect flow output and indirectly cause pressure fluctuations. Hydraulic Valve Failures
Safety valve (s):
Relief valve spring fatigue or jamming, resulting in unstable pressure regulation, pressure often fluctuate near the set value;
Core seal surface wear leads to internal leakage, preventing pressure maintenance.
Proportional Valve/Servo Valve Failures:
Proportional valve coil open circuit or control signal interference leads to misalignment of core position and unstable output flow;
Servo valve feedback sensor failure, to prevent closed loop control pressure, causing oscillations.
Directional Valve Sticking:
Due to oil contamination or insufficient lubrication, the directional valve core jammed, resulting in abnormal fluctuations in hydraulic fluid flow and pressure.
4. Energy storage and Piping Issues
Accumulator Failure:
The failure of Accumulator bladder rupture or nitrogen leakage to absorb pressure pulsations exacerbates stress fluctuations in the system.
Pipeline Design Defects:
Improper pipeline layout (e.g. too many bends, too small diameter) can cause fluid turbulence and increase pressure loss;
Poor pipeline connections or seal failure can lead to leakage and pressure drop.
V. Electrical Control System Interference
Sensor Signal Abnormalities: pressure sensors wiring or calibration errors will lead PLC to receive incorrect signals, resulting in incorrect hydraulic pump output adjustment.
Power Supply Interference: Electromagnetic interference (such as that from frequency converters or welders) can affect proportional valve control signal, causing valve core vibration and pressure fluctuations.
II. Systemic Solutions
1. Hydraulic Oil Management
Periodically replace and filter: Replace hydraulic fluids regularly as required by the equipment specification and filter existing oils with precision filters to remove contaminants.
Viscosity Control: Hydraulic oil is preheated to the appropriate temperature at low temperature (e.g. through heater or circulating pump);
Avoid high temperature environment or prolonged time high load operation, prevent oil viscosity decline.
2.Hydraulic Pump and Actuator Maintenance
Pump Inspection and Replacement: regularly remove hydraulic pump, check wear and tear of gear, piston or vane, replace worn parts;
Replace shaft seals or end cap seals to prevent internal leakage.
Actuator Repair: replace hydraulic cylinder piston seals seal, repair the sealing surface;
Clean the inside of the hydraulic motor and replace worn parts to ensure smooth rotation.
3.Hydraulic Valve Adjustment and replacement
Relief Valve Adjustment:
Wash the core of the relief valve spool, replace the spring, and adjust the pressure to a set value.
Check the spool sealing surface and repair or replace valve body.
Proportional Valve/Servo Valve Calibration:
Calibration of proportional valve coil resistance and control signals using specialized testing equipment;
Replace the servo valve feedback sensor to ensure closed-loop control accuracy.
Directional Valve Cleaning:
Remove the directional valve, clean the core and body, lubricate with hydraulic fluid, then reinstall.
4. Energy accumulator and Piping Optimization
Accumulator Inspection:
Regularly check the bladder integrity of the accumulator and add nitrogen at the specified pressure;
Replace any faulty accumulators to ensure they properly absorb pressure pulsations.
Pipeline improvements:
Optimize the pipeline layout, reduce the number of pipe bends and increase the diameter of key pipe sections.
Tighten pipeline connections and replace aging seals to prevent leaks.
III. Power system anti-jamming measures
Sensor Maintenance:
Check pressure sensor wiring and recalibrate sensor accuracy;
Replace faulty sensors to ensure stable signal transmission. Power Isolation: Installation of filters in proportional valve control to reduce electromagnetic interference; separation of the power supply of hydraulic equipment from high-power equipment (e.g. welders) to avoid voltage fluctuations.
V. Preventive Maintenance Recommendations
Establish a maintenance cycle: check hydraulic fluid levels and temperature daily to record pressure fluctuation range; clean hydraulic valves and filters weekly to check pipeline sealing; Replace hydraulic filters monthly to test accumulator pressure.
Operating procedure training: Train operators to avoid frequently starting hydraulic pumps to reduce pressure shocks; do not adjust hydraulic valve parameters under high pressure to prevent system oscillation.