Proper Use of Hydraulic Oil

Density

The mass per unit volume of a liquid is called the density of the liquid. Mathematically, it's expressed as ρ = m/V, where V is volume and m is the mass of the liquid with volume V. Density is an important physical parameter of liquids. While density changes with temperature or pressure, these changes are generally small and can be neglected in most applications.

Most hydraulic oils, including tractor supply hydraulic oil, have a density of approximately 900 kg/m³. This consistent density makes tractor supply hydraulic oil suitable for a wide range of hydraulic systems where predictable performance is required.

Compressibility

Compressibility refers to the phenomenon where a liquid's volume decreases under pressure. If hydraulic oil contains air bubbles, its compressibility increases significantly, which can severely affect the performance of the hydraulic system. Therefore, it is crucial to minimize the content of gases and other volatile substances (such as gasoline, kerosene, ethanol, and benzene) in the oil.

High-quality products like tractor supply hydraulic oil undergo rigorous processing to remove contaminants and air bubbles, ensuring minimal compressibility. This is one reason why tractor supply hydraulic oil is trusted in applications where precise control is essential.

Viscosity

When a liquid flows under external force, the cohesive force between liquid molecules resists relative molecular motion, creating an internal friction. This property is known as the viscosity of the liquid. Viscosity is an important physical characteristic of liquids and a key factor in selecting hydraulic oil. Liquid exhibits viscosity only when it is in motion; it does not show viscosity when stationary.

The viscosity of tractor supply hydraulic oil is carefully formulated to provide optimal performance across different operating conditions. The right viscosity ensures proper lubrication and efficient power transmission, which is why tractor supply hydraulic oil is designed to maintain consistent viscosity under varying temperatures and pressures.

Dynamic Viscosity (μ)

In China's legal measurement system and the SI system, the unit of dynamic viscosity μ is Pa·s (Pascal-second) or N·s/m² (Newton-second per square meter). In the CGS system, the unit of μ is dyn·s/cm² (dyne-second per square centimeter), also known as P (Poise). One percent of a P is called cP (centipoise).

The conversion relationship is as follows: 1 Pa·s = 10 P = 1000 cP. Tractor supply hydraulic oil specifications always include detailed viscosity data to help users select the appropriate product for their specific hydraulic systems.

Kinematic Viscosity (ν)

The ratio of dynamic viscosity μ to the density ρ of the liquid is called kinematic viscosity, expressed as ν = μ/ρ. Kinematic viscosity does not have a clear physical meaning but is so named because its unit only includes dimensions of length and time. It is a commonly used physical quantity in engineering practice.

In China's legal measurement system and the SI system, the unit of kinematic viscosity ν is m²/s (square meters per second). In the CGS system, the unit of ν is cm²/s (square centimeters per second), usually called St (Stokes). 1 St (Stokes) = 100 cSt (centistokes). The conversion relationship between the two unit systems is 1 m²/s = 10⁴ St = 10⁶ cSt.

While ν is not strictly a measure of viscosity in a physical sense, it is commonly used in engineering to represent the viscosity of liquids. For example, the grade of hydraulic oil refers to the average value of the kinematic viscosity ν (mm²/s) of the oil at 40°C. For instance, L-AN32 hydraulic oil means that the average kinematic viscosity of this hydraulic oil at 40°C is 32 mm²/s. Tractor supply hydraulic oil is available in various viscosity grades to suit different application requirements.

Relative Viscosity

Relative viscosity, also known as conditional viscosity, is the viscosity of a liquid measured using a specific viscometer under specified conditions. Depending on the measurement conditions, different countries use different units for relative viscosity. For example, China and Germany use Engler viscosity (°E), the United States uses Saybolt Universal Seconds (SSU), and the United Kingdom uses Redwood viscosity (R).

Engler viscosity is measured using an Engler viscometer. It is determined by measuring the time it takes for 200 cm³ of the tested liquid to flow through a 2.8 mm orifice at a specific temperature (t°C) in the container of the Engler viscometer, and comparing it to the time it takes for the same volume of distilled water to flow through the same orifice at 20°C. The ratio of these two times is the Engler viscosity of the liquid at t°C, denoted as °Et.

Viscosity of Blended Oils

Selecting hydraulic oil with the appropriate viscosity is crucial for the working performance of hydraulic systems. Sometimes, when the viscosity of available oils does not meet the requirements, two oils with different viscosities can be mixed for use, which is called a blended oil. The viscosity of blended oil is related to the proportion of the two oils used in the mixture.

When mixing oils, it's important to consult guidelines to ensure compatibility. Tractor supply hydraulic oil often provides recommendations for oil blending when necessary, ensuring that the resulting mixture maintains proper performance characteristics. Many users rely on tractor supply hydraulic oil for its consistent quality when creating custom blends for specific applications.

Relationship Between Viscosity and Temperature

Temperature has a significant impact on the viscosity of oil. As the temperature of the oil increases, its viscosity decreases significantly. Changes in oil viscosity directly affect the performance and leakage of hydraulic systems. Therefore, it is desirable for viscosity to change as little as possible with temperature variations.

Different oils have different viscosity-temperature relationships, known as the viscometric properties of the oil. The viscosity-temperature characteristics of oil can be expressed by the viscosity index (VI). A higher VI value indicates a smaller rate of change in oil viscosity with temperature, meaning better temperature stability. Generally, hydraulic oils require a VI value above 90, while refined hydraulic oils and those with additives can have VI values greater than 100.

Tractor supply hydraulic oil is formulated to have excellent viscosity-temperature characteristics, ensuring stable performance across a wide range of operating temperatures. This is particularly important for outdoor equipment where temperature fluctuations are common, making tractor supply hydraulic oil a reliable choice for such applications.

Relationship Between Viscosity and Pressure

Pressure also has a certain influence on the viscosity of oil. The higher the pressure, the smaller the distance between molecules, resulting in increased viscosity. Different oils have different viscosity-pressure relationships, known as the viscoplastic properties of the oil.

In hydraulic systems where pressure is not excessively high, the effect of pressure on viscosity is relatively small and can generally be ignored. However, when the pressure is high or varies significantly, the influence of pressure on viscosity must be considered. Tractor supply hydraulic oil is engineered to maintain its viscosity characteristics even under high-pressure conditions, ensuring reliable operation in demanding hydraulic systems.

Other Characteristics

Hydraulic oil also has other physical and chemical properties, such as fire resistance, oxidation resistance, corrosion resistance, anti-foaming properties, anti-emulsifying properties, rust resistance, lubricity, thermal conductivity, stability, and compatibility (mainly referring to the property of not corroding or swelling sealing materials, hoses, etc.). These properties significantly impact the working performance of hydraulic systems.

Different types of hydraulic oils have different指标 for these properties, and specific applications can refer to oil product manuals. Tractor supply hydraulic oil undergoes extensive testing to ensure it meets or exceeds industry standards for all these critical properties. The comprehensive performance of tractor supply hydraulic oil makes it suitable for a wide range of industrial and agricultural applications.

Selection of Oil Type

When selecting the type of oil, you can refer to Table 3-2 and consider factors such as whether it is for special use, specific working pressure, operating temperature, and working environment, making a comprehensive assessment. The right oil type ensures optimal performance and longevity of the hydraulic system.

Tractor supply hydraulic oil offers a range of products that cover most of these recommended grades, making it easy to find the right tractor supply hydraulic oil for your specific pump type and operating conditions. Whether you need oil for a vane pump, gear pump, or piston pump, tractor supply hydraulic oil has formulations designed to provide optimal lubrication and performance.

Selecting Viscosity Grade

After determining the type of hydraulic oil, the next step is to select the appropriate viscosity grade. Viscosity significantly affects the stability, reliability, efficiency, temperature rise, and wear of hydraulic systems. When selecting viscosity, attention should be paid to the working conditions of the hydraulic system, as outlined in Table 3-3.

For systems operating under high pressure, higher viscosity oil is generally recommended to ensure adequate lubrication and reduce leakage. Conversely, low-pressure systems can often perform well with lower viscosity oils, which offer less resistance to flow and can improve efficiency.

Tractor supply hydraulic oil is available in a comprehensive range of viscosity grades to meet these varying requirements. The technical specifications for each tractor supply hydraulic oil product clearly indicate the optimal operating conditions, helping users make informed decisions. Whether your system operates under high pressure, high temperature, or requires low-temperature performance, there is a tractor supply hydraulic oil viscosity grade designed to meet your needs.