The key physical characteristics of hydraulic pump fluids vary depending on the specific type and grade of oil used. However, here are some key physical properties commonly associated with hydraulic fluids: 1. Viscosity: Viscosity refers to the resistance of oil flow and is one of the most critical properties of hydraulic oil. It determines the ability of the oil to lubricate and provide hydraulic power. Hydraulic fluids typically have a specific viscosity range or grade specified by the manufacturer for optimum performance at varying operating temperatures. 2. Density: Density is the mass of oil per unit volume. It is an important attribute for calculating hydraulic system pressure and determining oil volume requirements. Density will vary depending on the specific formulation of the hydraulic fluid. 3. Flash point: The flash point is the lowest temperature at which oil vaporizes and can be ignited in the presence of an ignition source. It is an important safety parameter, indicating the fire performance of the oil. Different hydraulic oils have different flash point specifications based on their composition. 4. Pour point: The pour point is the lowest temperature at which an oil begins to freeze or lose its ability to flow freely. It indicates the oil's ability to perform in low temperature conditions. Hydraulic fluids with lower pour points are suitable for cooler climates or environments. 5. Oxidation stability: Oxidation stability refers to the ability of an oil to resist chemical degradation under the action of heat, oxygen and other factors. This is critical to maintaining the performance of the oil and preventing the formation of sludge or varnish in the hydraulic system. Higher oxidation stability allows for longer oil life and reduced maintenance requirements. 6. Water content: The water content of hydraulic oil should be low to prevent problems such as corrosion, degradation and reduced lubrication. Water content is usually specified in percent or parts per million (ppm) and should be minimized to maintain optimum oil performance. 7. Anti-wear performance: Hydraulic oil usually contains additives to enhance its anti-wear performance. These additives form a protective film on metal surfaces that reduces friction and prevents wear and damage to hydraulic system components. 8. Antifoam: Antifoam is the ability of an oil to resist the formation of foam when stirred or subjected to high pressure. Excessive foam will result in reduced lubrication and affect the efficiency of the hydraulic system. 9. Thermal stability: Thermal stability refers to the ability of an oil to maintain its properties and resist degradation at high temperatures. Hydraulic oils with good thermal stability can withstand high temperatures without significant changes in viscosity or properties. 10. Air release properties: Air release properties indicate the ability of an oil to release entrapped air or foam. Effective air release is critical to the proper operation of hydraulic systems, as trapped air can lead to reduced system efficiency and performance. 11. Anti-emulsification: Anti-emulsification refers to the ability of oil and water to separate. Hydraulic oils with good demulsibility can easily separate from water, preventing the formation of emulsions that affect lubrication and cause system corrosion. 12. Thermal conductivity: Thermal conductivity is the ability of oil to transfer heat. Hydraulic fluids with good thermal conductivity can effectively dissipate the heat generated during system operation, helping to maintain an optimal operating temperature. 13. Corrosion resistance: Hydraulic oil should have good corrosion resistance to protect system components from rust and corrosion. This is especially important when operating in environments with high humidity or exposure to corrosive substances. 14. Filterability: Filterability refers to the difficulty of oil products to remove pollutants through filtration. Oils with good filterability can effectively filter and remove particles, thereby prolonging the service life of hydraulic system components. 15. Acid/Base Number (AN/BN): Acid Number (AN) and Base Number (BN) measure the acidity or alkalinity of an oil, respectively. These properties indicate the oil's ability to neutralize acids or bases that may form during system operation or due to contamination. Maintaining proper AN/BN levels is important to maintain oil performance and prevent component damage. 16. Lubricity: Lubricity is the ability of an oil to reduce friction and wear between moving parts. Hydraulic oil with good lubricity provides effective lubrication to minimize component wear and ensure smooth operation. 17. Stability with seals and elastomers: Hydraulic oil should be compatible with system seals and elastomers to prevent expansion, contraction or degradation. It is critical to use an oil that is compatible with the specific seal and elastomer materials used in hydraulic systems. Understanding these physical properties and selecting a hydraulic fluid that meets the specific requirements of a hydraulic system is critical to achieving optimum performance, service life and reliability. When selecting a hydraulic fluid, it is advisable to consult the hydraulic pump manufacturer's recommendations and follow industry standards.