ABSTRACT
Many different types of liquids are being used for hydraulic control and power transmission systems. They may range from water, to mineral oils, to synthetic and organic liquids, to vegetable oils or to molten metals. Water was the first hydraulic pressure medium to be used in the early days. Water is available every where, it is cheap and rather efficient for power transmission. When mineral oil was discovered in the beginning of the 20“ Century it soon became the preferred pressure medium in hydraulic systems, due to its many superior properties.
