Oils and other operating liquids, used as lubricants and coolants in various industrial equipment, are prone to degrade under the influence of elevated temperatures, pressures or flow. The functionality of oils depends on viscosity, oxidation stability and purity, lubrication capabilities, corrosion and emulsification. The difference of hydraulic oils from other oils is the relatively higher viscosity of the oil for high pressure hydraulic actuators. High viscosity makes operation of equipment unsafe or impossible. On the other hand, to ensure efficient operation of the systems, oil viscosity must exceed 20 cSt. Otherwise the pumps will experience increased wear, causing rapid loss of efficiency.
Most contaminants enter the oil during operation of the hydraulic drive. Contamination of the oil leads to formation of stable foam. This foam is the main cause of equipment malfunction. Oxidation products increase the acidity of the oil and increase corrosion of metal parts. Oxidation intensifies in higher temperatures and when free or solved air is present in the oil.
The oil film formed between friction parts of piston pumps creates liquid friction and prevents their direct contact. It also serves to cool the parts during operation. Operation of pumps with contaminated oil disrupts the integrity of the film. Various particles of contamination move with the flow of the oil, enter the space between the moving parts and increase their wear. The wear reduces functionality and efficiency of equipment.
Therefore, the main rule of oil-filled equipment operation is to ensure high degree of oil purity and regular oil control and purification.