HydraulicFluidPurposeProperties.pptVIP

Hydraulic FluidPurpose Properties(Chapter 3)11-12-02 Lisa Thompson Julia Boyd Linh Vuong Introduction Fluids used in mobile and stationary machinery must be effective in the transmission of power from the source to provide consistent and reliable response, safe operation, and optimum efficiency. Purposes Compressibility Lubrication Sealing Cooling Compressibility Figure 3-2 Ensures responsiveness of actuation or “stiffness” in a hydraulic circuit, even under high pressure. With the dynamics of loads in industrial machinery, slight decompression or compression can occur and affect actuation slightly. Properly maintained hydraulic systems are extremely responsive and reliable. Petroleum-based fluids are virtually incompressible, for example. 0.4% at 1000 psi and up to 1.1% at 3000 psi operating pressure At a constant operating pressure the oil remains compressed at a given value. Lubrication All hydraulic systems have components with moving parts that have the potential to come in contact with each other Components need a lubricant to prevent excess wear and the production of excess heat Some lubrication condition Full-film Boundary Enhanced (Additives) Anti-Wear Full-Film Lubrication This prevent metal to metal contact and the protect metal surfaces The lubrication film flows between the metal parts while keep the metals completely apart This is the best lubrication condition for a hydraulic system Boundary Lubrication When high pressure is needed, the clearances between the moving components should be reduce to limit leakage The lubrication film flows between two metal parts, now the metal parts can touch each other Disadvantages: Excessive wear Severe heat Enhanced Lubrication To enhance boundary lubrication conditions additives are required such as anti-wear (AW) and extreme pressure (EP) Anti-wear additives prevent metal to metal contact Additive is usually a zinc compound Sealing Internal leakage is caused by