Hydraulic systems are a common type of drive system in industrial equipment. Hydraulic systems comprise a wide range of components, such as piping, valves, and seals, hydraulic system maintenance and inspection are crucial; they enable the timely detection of faults and help prevent unnecessary downtime.
Components of a Hydraulic System
A complete hydraulic system consists of five components: power elements, actuators, control elements, auxiliary components, and hydraulic fluid.
Power elements, such as hydraulic pumps, convert the mechanical energy of a prime mover into the pressure energy of the fluid, serving as the power source for the entire system. Actuators, such as hydraulic cylinders and hydraulic motors, drive the load to perform linear reciprocating or rotary motion. Control elements, such as various hydraulic valves, regulate fluid pressure, flow rate, and direction to ensure the actuators operate as intended. Hydraulic fluid serves as the working medium for energy transmission within the system. Auxiliary components—including hydraulic lines, fittings, pressure gauges, temperature gauges, and filters—connect the system, maintain precise temperature and pressure ranges, ensure normal operation, and facilitate real-time monitoring and routine maintenance.
hydraulic system maintenance
Why is hydraulic system maintenance important?
Hydraulic system maintenance is crucial for ensuring safety, preventing unexpected failures, and extending equipment lifespan; it helps avoid serious damage—or even downtime and accidents—caused by minor contamination or leaks.
Ensuring Safety
Precise interaction between hydraulic components is essential for proper system operation. The ingress of even minute particles, moisture, or air can lead to wear, sticking, or hose bursts. High-pressure leaks, seal failures, or loss of pressure control can result in injuries from fluid injection, fires, or uncontrolled mechanical movement; regular hydraulic system maintenance allows potential hazards to be eliminated before they escalate.
Maintaining Stable Operation
Fluid degradation and increased internal leakage can cause sluggish movement, pressure instability, and positioning errors. Maintenance restores system responsiveness and operational stability.
Extending Hydraulic System Service Life
Timely maintenance allows for the early detection of minor issues; preventive maintenance is far less costly than emergency repairs and can significantly reduce unplanned downtime while extending the system’s service life.
Prolonged neglect of hydraulic system maintenance can lead to the following problems:
Fluid Contamination: Particulate impurities from the environment enter the system, and moisture corrodes hydraulic metal fittings, leading to reduced efficiency and leakage.
Seal Aging: Failure to inspect or replace sealing components over time causes aged seals to fail, resulting in external leakage.
Overheating Cycles: Clogged filter elements or improper pressure settings cause heat generation due to fluid relief, accelerating fluid degradation and the hardening of rubber components.
Sudden Shutdown: Critical equipment halts operations due to hydraulic failure, resulting in significant losses in supply and profits.
Hydraulic System Maintenance Points
Routine Inspection and Maintenance
Oil level check:
Regularly check the hydraulic oil level in the reservoir to ensure it remains within the specified range. An excessively low level can cause the system to ingest air, damaging the pump and other components, while an excessively high level may lead to elevated oil temperatures and leakage.
Oil Temperature Monitoring:
Use a thermometer to monitor the hydraulic oil temperature and ensure it does not exceed the system’s recommended maximum operating temperature. High temperatures accelerate oil oxidation and degradation, reduce lubrication performance, and increase the risk of wear and leakage.
Pressure Monitoring:
Check and adjust pressure. Regularly monitor hydraulic pressure to ensure it remains within the normal range, and make adjustments as necessary.
Cleaning and Protection:
Keep the hydraulic system and its surrounding area clean to prevent dust, moisture, and other contaminants from entering the system.
Clean the oil tank and filter elements. Regularly clean the oil tank and replace filter elements to remove impurities and maintain fluid cleanliness.
Regularly clean components such as the radiator to ensure effective heat dissipation.
Oil Leakage Inspection:
Regularly inspect the system’s connection points, seals, and pipelines for oil leaks. If a leak is detected, identify the cause and repair it immediately to prevent fluid loss and system performance degradation.
Oil Leakage Inspection:
Regularly inspect the system’s connection points, seals, and pipelines for oil leaks. If a leak is detected, identify the cause and repair it immediately to prevent fluid loss and system performance degradation.
Inspection and Cleaning of Pipeline Connections:
Check pipeline connections for looseness, wear, or leaks, and clean or repair them promptly. Regularly inspect hydraulic lines for bulges, cracks, or abnormal noises, and adjust or replace them immediately if issues are found.
Routine Maintenance and Replacement
Regularly replace hydraulic oil
Hydraulic oil is essential for system lubrication and thermal stability; regular replacement maintains the oil’s performance.
Replace worn or aged seals
Seals are prone to wear and aging; regular inspection and replacement prevent leaks and malfunctions.
Replace filter elements
Regularly inspect and replace filter elements—such as return-line and intake filters—to prevent impurities from entering the system and to protect the pump and other sensitive components from damage.
Implement anti-corrosion measures
Apply anti-corrosion coatings and perform regular cleaning and rust-prevention treatments to prevent corrosion.
Clean the oil tank and pipelines
Regularly clean the interior of the oil tank and the pipelines to remove deposits, moisture, and impurities. Use specialized cleaning agents and ensure thorough rinsing before adding new oil.
Precautions for Hydraulic System Maintenance
Before performing any maintenance, ensure the power supply is disconnected and system pressure is released.
Maintenance personnel should wear protective clothing and use appropriate tools and equipment to prevent personal injury and component damage.
Keep detailed records of all maintenance activities to facilitate future tracking of the system’s operating status and maintenance history.
Common Hydraulic System Faults and Remedies
Fluid Deterioration
Contaminants entering the fluid cause hydraulic oil to deteriorate. Primary sources of contamination include an unclean external environment, incomplete cleaning of the oil tank or hydraulic hoses, use of substandard containers for refilling, and improper oil storage. Deteriorated fluid corrodes components and accelerates wear and tear within the hydraulic system.
Remedial measures:
Replace with new hydraulic oil that meets specifications.
Hydraulic System Overheating
Causes of hydraulic system overheating include excessive oil temperature, poor heat dissipation, malfunction of the system’s unloading circuit, and the ingress of air or moisture into the hydraulic fluid.
Remedial measures:
Design a reservoir of adequate size and install a cooler if necessary. Isolate the system from the external environment when ambient temperatures are high, and strictly maintain the system temperature within the 20–60°C range, ensuring it does not exceed 70°C.
If high-pressure oil is unnecessarily bypassing back to the reservoir through the relief valve for extended periods, modify the design by using a variable-displacement pump or implementing a proper unloading method.
Keep pipelines as short as possible; avoid lines that are excessively long, narrow, or convoluted to ensure smooth fluid flow.
Strengthen seals and securely fasten connections at points prone to leakage—such as the hydraulic pump and its connection interfaces—to prevent heat generation caused by volumetric losses.
If the pressure setting of the pressure-regulating valve is too high, lower the operating pressure to reduce unnecessary energy loss.
Select hydraulic fluid with the appropriate viscosity.
Abnormal Hydraulic System Pressure
Abnormal hydraulic system pressure may be caused by factors such as excessively high or low hydraulic pump output pressure or the failure of internal hydraulic cylinder seals.
Remedial measures:
Check if the hydraulic pump’s output pressure is correctly set; adjust the pump according to actual operational requirements.
Inspect internal hydraulic cylinder seals for wear; replace them if worn.
Check the pressure valves in the hydraulic system to ensure they are functioning correctly.
Abnormal Vibration and Noise
Primary causes of abnormal noise include air intake by the hydraulic pump, pump damage, relief valve malfunction, abnormal pipeline vibration, and imbalance in the rotating parts of the motor and pump.
Remedial measures:
Inspect the internal vanes of the hydraulic pump or motor for damage or wear; replace them if necessary.
Check for debris or foreign objects inside the hydraulic cylinder; clean or replace the cylinder if found.
Clean and inspect the relief valve; repair or replace it promptly if damage is detected.
In cases of mechanical vibration—particularly where oil lines are long and slender or have many elbows—install fixed pipe clamps and ensure the installation alignment between the motor and hydraulic pump is precise (within 0.1 mm).
Hydraulic System Leakage
Causes of hydraulic system leakage include seal material failure (aging or damage), loose connections at fittings, poor sealing due to rough mating surfaces, excessively low fluid viscosity, and damaged hydraulic hoses.
Remedial measures:
Inspect seals throughout the hydraulic system—such as O-rings and gaskets—to ensure they are intact and undamaged.
Check for loose threads at pipe connections and tighten them if necessary.
Inspect the connection points of hydraulic pumps and cylinders to ensure correct installation and adequate sealing.
Check the sealing surfaces of hydraulic pumps and cylinders for scratches or pits; repair or replace them promptly if any are found.
Installing the hydraulic valve manifold close to the actuators can significantly reduce the total length of hydraulic piping and the number of pipe fittings.
Summary
Proper hydraulic system maintenance effectively preserves the condition, enhancing its reliability and service life. It also helps minimize downtime and repair costs associated with system failures.