1. Sources of Contaminants
(1) Contaminants in new oil. Although hydraulic oil is refined and processed under relatively clean conditions, it can become contaminated during transportation and storage through pipes, drums, and storage tanks, resulting in the introduction of dust, sand, rust, moisture, and other liquids into the oil.
(2) Contaminants Residual in Components and Systems. During the manufacturing, assembly, and cleaning of hydraulic components and systems, some contaminants may remain due to incomplete cleaning procedures.
(3) External Contaminants. During the operation of hydraulic components and machinery, contaminants such as dust, sand, and moisture may enter the system from the outside due to imperfect tank seals, damaged component seals, or compromised protective devices.
(4) Contaminants generated within the hydraulic system. During operation, the hydraulic system itself generates solid particulate contaminants, including metal particles or rubber powder resulting from the wear and corrosion of hydraulic components, as well as contaminants produced by the oxidation of the hydraulic fluid.
2. Hazards of Hydraulic Oil Contamination
(1) Contaminants often cause throttle valves and pressure-damping orifices to become intermittently blocked or unblocked, or even jam the valve spool, leading to fluctuating operating pressure and speed in the hydraulic system and affecting its normal
operation.
(2) Contaminants accelerate the wear of hydraulic pumps, motors, and valve assemblies, leading to increased internal leakage.
(3) Moisture mixed into the hydraulic oil corrodes metal and accelerates the aging and degradation of the oil.
(4) Air mixed into the hydraulic oil can cause noise, vibration, crawling, cavitation, and shock, thereby degrading the hydraulic system's performance.
3. Maintenance of Hydraulic Oil
1. Preventing Oil Contamination
In the various pumps and valve components used in motor graders, the clearance between moving parts and the working surfaces are relatively small. Additionally, hydraulic components contain numerous orifices and slotted control valve openings. If contaminants enter the oil, blockages may occur, potentially scratching mating surfaces, increasing leakage, or even causing valve spools to seize, resulting in component failure. Therefore, maintaining oil cleanliness is critical to hydraulic system maintenance.
Hydraulic fluid must undergo rigorous filtration. When filling the hydraulic reservoir, use a filter with a mesh rating of 120 or higher.
(2) Regularly check the fluid's cleanliness and replace it periodically based on operating conditions. During replacement, drain approximately 40 liters of fluid from the hydraulic system as much as possible. Using an external circulation method is generally more practical. The procedure involves first draining the used oil from the reservoir and radiator, then refilling with new oil. Disconnect the return line leading to the reservoir, start the engine, and allow the used oil to drain completely through the return line. It is particularly important to monitor the oil level in the reservoir during this process to ensure it remains at a safe level. When replacing the oil, the filter element should also be replaced.
(3) Do not disassemble hydraulic components lightly. If disassembly is necessary, clean the parts with kerosene or diesel and store them in a clean area to prevent contaminants from entering during reassembly.
2. Preventing Air Ingestion
Air dissolved in the hydraulic fluid will escape from the oil when pressure is low, creating bubbles and causing cavitation.
3. Preventing Water Ingestion
Implement measures such as filtration and oil-water separation to prevent water from entering the hydraulic fluid and causing emulsification.
4. Preventing Excessive Oil Temperature
The optimal operating temperature range for grader hydraulic oil is generally between 60 and 80°C. Excessively high oil temperatures can cause a decrease in oil viscosity, reduced volumetric efficiency of the oil pump, a thinner lubricating film, increased mechanical wear, and the aging and deterioration of seals, leading to a loss of sealing performance.
5. Regularly inspect the hydraulic system
Regularly check the pressure at each monitoring point in the grader's hydraulic system to prevent the system from operating under abnormal pressure for extended periods. This helps reduce wear on the hydraulic system and ensures its proper functioning.185HP Motor Grader
