Hydraulic fluid is a type of fluid used in hydraulic systems. It is the medium used to transfer energy in hydraulic systems. While transmitting hydraulic energy is the primary function of the fluid, it also has other functions including lubrication, sealing, and heat transfer and removing contamination.
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Hydraulic systems produce a lot of heat. Without proper mechanism in place to dissipate this heat, overheating can easily occur. Overheating, in turn, could cause damage of components including valves, seals. The heat is produced as the fluid molecules run against the metal surfaces. The fluid goes through a cooler to maintain a temperature range as it moves back to the reservoir. Similarly, it transfers heat from the heating tank to the system during cold starts.
Common hydraulic fluids are mineral oil or water based. Some major systems that use hydraulic fluids include hydraulic brakes, transmission and power steering systems. For the hydraulic fluid to work effectively, it should be incompressible.
Benefits of Hydraulic Fluid
Hydraulic fluid sweeps solid particle and water from sensitive parts. Filters and similar component trap this contaminant ensuring that only clean hydraulic fluid is returned to the circuit. These contaminants may, however, cause damage to the valves.
Hydraulic fluid is considered as a fluid that requires sealing from components of the hydraulic systems. However, it is surprising to note that hydraulic fluid seals some component of the hydraulic system such as valves, motors and pumps. For instance, a spool valve has a seal at each need to prevent fluid from escaping into the atmosphere. Hydraulic fluid surface tension and shearing resistance aid in sealing. Fluid Viscosity and viscosity index are essential to this critical function of sealing. Viscosity index is the change in viscosity over temperature change
Most hydraulic components require lubrication to prevent wear from friction. It provides lubrication for moving parts such as valve late and slippers. Without these lubricating features, the hydraulic system would have a short life span.
Most hydraulic systems use mineral or synthetic oil. When choosing an ideal hydraulic the major properties that are considered include viscosity index, pour point, viscosity, ambient temperature and operating temperature. A system that operates in low ambient temperature will use a hydraulic fluid that has low pour point and viscosity.
Some chemical additives help to improve the performance of hydraulic fluid. Oxidation and rust inhibitors reduce contaminants production. Similarly, antiwear additive boosts the lubricating feature of the hydraulic fluid.
Most hydraulic fluids have common features discussed above save for water-based fluids.
Symptoms of bad hydraulic fluids
- Poor engine performance
- Abnormal noise in the hydraulic system
- High fluid temperature – This cause by anything that increases heat load or reduces the hydraulic system capacity to dissipate heat effectively
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