First, you can use the table below to quickly understand hydraulic fluid selection recommendations for different operating conditions:
Operating Conditions Recommended Hydraulic Fluid Type Common Viscosity Grades (ISO VG) Key Considerations
Medium-High Pressure (7-14 MPa), Normal Temperature (Below 50°C) L-HM Anti-Wear Hydraulic Fluid 32, 46, 68 Anti-wear and oxidation resistance
High Pressure (>14 MPa), High Temperature (80-100°C) High-Pressure Anti-Wear Hydraulic Fluid (Ashless is preferred) 46, 68, 100 High-Temperature Stability, Anti-Wear, and Oxidation Resistance
For Severely Cold Regions or Large Temperature Fluctuations L-HV Low-Temperature Anti-Wear Hydraulic Fluid 32, 46 High Viscosity Index, Low Pour Point, and Good Low-Temperature Fluidity
For High Temperatures and Flame-Resistant Environments L-HFC Water-Ethylene Glycol Flame-Resistant Hydraulic Fluid 46, 68 Fire Safety
Precision Systems Containing Copper/Silver Components Ashless Anti-Wear Hydraulic Fluid 32, 46, 68 Non-corrosive to copper and silver
🧰 Key Performance Indicators of Hydraulic Fluid
When selecting hydraulic fluid, it's important to consider the following key performance indicators, as they directly impact the stable operation of the actuator:
• Viscosity and Viscosity-Temperature Characteristics (VI): Viscosity is one of the most important properties of hydraulic fluid. Excessively low viscosity can lead to severe leakage and high power consumption; excessively high viscosity can result in increased friction, wear, and reduced system sensitivity. Viscosity-temperature characteristics refer to the degree to which viscosity changes with temperature. Fluids with a high viscosity index (VI) maintain more stable viscosity with temperature fluctuations, which is particularly important for hydraulic systems subject to large temperature fluctuations.
• Lubricity and Anti-Wear Properties: Hydraulic fluids must provide excellent lubrication for components such as pumps, cylinders, and valves to reduce wear. Anti-wear properties are particularly important for high-pressure systems.
• Oxidation Stability: This refers to the hydraulic fluid's ability to resist oxidative deterioration. Oxidation can produce harmful substances such as gums and asphalt. The higher the operating temperature, the faster the oxidation rate. Therefore, fluids with good oxidation stability are recommended for high-temperature operating conditions.
• Anti-foaming and air release properties: Air in the hydraulic system can cause foaming, leading to unstable pressure, sluggish operation, and even shock and vibration. Good anti-foaming and air release properties are crucial.
• Cleanliness and filterability: Moisture and mechanical impurities in the oil can cause component corrosion, block oil lines and valve orifices, and affect system operation. Maintaining good filtration and cleanliness can effectively reduce system failures.
• Rust and corrosion resistance: Prevents corrosion of metal components by moisture and air.
🔧 Practical steps for selecting hydraulic fluid
1. Determine the hydraulic pump type and operating requirements: The hydraulic pump is the most viscosity-sensitive component. Refer to the equipment manufacturer's manual for recommended hydraulic fluid grades and viscosities.
2. Determine the viscosity grade:
◦ Refer to the table above and select based on the primary operating and ambient temperatures.
◦ Generally speaking, higher viscosities (such as ISO VG 68 or 100) are used for high-pressure, high-temperature systems, while lower viscosities (such as ISO VG 32 or 46) are used for low-pressure, low-temperature systems.
◦ Vane pumps generally require a viscosity of at least 10 mm²/s, plunger pumps require greater than 8 mm²/s, and gear pumps require even higher, around 20 mm²/s.
3. Consider the operating environment and special requirements:
◦ In extremely cold conditions or where there are large temperature differences between outdoor and indoor temperatures: Use L-HV or L-HS low-freezing-point hydraulic fluids.
◦ In high temperatures or where there is a risk of open flames (such as near smelting equipment): Use flame-retardant hydraulic fluids such as L-HFC water-glycol or HFDR phosphate esters.
◦ For systems containing copper or silver components: Always use an ashless (zinc content less than 0.03%) anti-wear hydraulic fluid to avoid electrochemical reactions with silver components and corrosion.
4. Verify compatibility: Ensure the selected hydraulic fluid is compatible with the seals, coatings, and piping materials within the system.
🛡️ Usage and Maintenance Recommendations
• Strictly manage oils:
◦ Avoid mixing hydraulic fluids of different brands and models to prevent additive reactions and performance degradation.
◦ Filter the oil before refueling to ensure it is clean.
• Control oil temperature: The oil temperature should be kept below 70°C. Excessively high oil temperatures will accelerate oil oxidation and deterioration. Install a cooling device if necessary.
• Regular oil monitoring and changes:
◦ Regularly check the oil's color, viscosity, acidity, and cleanliness.
◦ Implement "oil changes based on quality" and replace the oil immediately if the oil quality indicators exceed the specified values.
• Prevent contamination: Keep the oil tank sealed to prevent the intrusion of dust and moisture. Clean or replace the filter element regularly.
💎 In short, the key to selecting hydraulic fluid for industrial electric hydraulic actuators lies in matching the operating conditions, paying attention to viscosity, and meeting specific requirements. The most reliable approach is to prioritize the equipment manufacturer's specified oil recommendations. When operating conditions change or when a replacement is needed, combine the above principles when selecting a suitable oil and closely monitor the system's operating status.
I hope this information helps you make an informed choice. If you can provide the actuator's specific operating pressure, ambient temperature, or manufacturer model, I may be able to provide more specific recommendations.
