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There are a number of potentially harmful effects commonly associated with any amount of water in hydraulic oil, including surface corrosion and accelerated fatigue of metal components. As the water present in hydraulic oil can exist in three distinct states, the specific effects may depend on factors such as water concentration, oil type and operating temperature. Water that is fully dissolved in hydraulic oil is not normally associated with surface corrosion, but high levels of dissolved water can result in accelerated metal fatigue. The presence of water in hydraulic oil can also change the physical characteristics of the oil, resulting in reduced viscosity, or it can even cause components to become stuck if ice crystals form in especially cold working conditions.
Hydraulic oils are a class of substances used to transfer energy in various types of hydraulic machines. In addition to functioning as an energy transfer medium, hydraulic oil can also perform a number of other tasks. These oils are often used to lubricate, transfer heat, and act as a sealing medium. Some hydraulic oils are also specifically designed to be fire or radiation resistant. Hydraulic oil’s ability to perform these tasks is normally reduced by the presence of any water, although the specific effects of water in hydraulic oil depend on several factors.
When water contaminates hydraulic oil, there are three distinct states in which it can exist. Relatively small levels of water can be completely dissolved in large amounts of hydraulic oil, in which case the effects are normally minimal. Surface corrosion does not normally occur due to small amounts of dissolved water, although metal components within the system may experience accelerated fatigue. Studies have shown that reducing dissolved water levels from 400 parts per million (PPM) to 25 PPM can allow some components to last about five times longer.
Each type of hydraulic oil can contain a limited amount of dissolved water. Once this saturation point is reached, the results are either free water or an emulsion. Large amounts of free water in hydraulic oil usually result in a lot of surface corrosion and very high levels often cause component failure. When water in hydraulic oil is mixed into an emulsion, the result is typically a distinct change in the physical characteristics of the oil. This can result in hydraulic oil having a different viscosity or compressibility, which can adversely affect the oil’s ability to transfer energy.