In every hydraulic system, a tightly confined incompressible fluid medium is used to transmit energy from the power pack to the actuators in the system. The fluid medium is formulated from a base stock and additives. The base stock should possess all the essential characteristics to perform well in a particular class of hydraulic systems. Some examples of the base stock are petroleum oils, high-water-based fluids (HWBF), and synthetic fluids. Blending the base stock with suitable additives can improve fluid’s physical and chemical properties, and make the properties more stable even in the presence of heat, oxygen, and water.
The principal requirements of hydraulic fluid are its proper viscosity, high viscosity index, excellent anti-wear protection, good oxidation stability, adequate corrosion resistance, and superior compatibility with seal materials. In certain applications, the fluid should be environmentally safe.
The basic classes of hydraulic fluids include petroleum fluids and fire-resistant fluids. Many of these fluids and their additives are toxic and hazardous to the environment.
Spills of petroleum-based hydraulic fluids and synthetic fluids are known to contaminate soil, groundwater, river water, and seawater. Such fluids are likely to harm humans, plant life, animals, and marine life. Fluid spills can also kill grasses due to the toxicity of the fluid or the temperature associated with the fluid. They can interfere with the photosynthesis and respiration process of grasses and prevent them from growing. The presence of harmful additives including zinc-based additives in hydraulic fluids can also influence the aquatic toxicity in river water or seawater, in case of contact. The negative effects of aquatic toxicity can range from mortality to impaired reproduction or growth abnormalities in aquatic species.
It is recommended to use environmentally safe hydraulic fluids in place of petroleum-based fluids and harmful synthetic fluids – particularly in applications where fluid leakage could harm the environment. With increasing concern about the environmental impact of hydraulic system leaks and spills, biodegradable fluids are receiving greater attention nowadays.
Author – Fluid Power Educational Series
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