The article gives you details about the requirements of hydraulic oils and various choices available to meet these requirements.
The Power Transmission Liquid – Hydraulic Oil
The power transmission in a hydraulic system takes place movement of liquid and this liquid has to take the pressure without breaking or changing its mechanical properties. The requirement such as incompressibility, fire retardant properties, absence of deteriorating effect on other part and cost effective solutions are normally provided by the mineral oil manufacturer.
Mineral blends find extensive use in hydraulic power transmission.
Requirements of Hydraulic Oils
The requirement of oils can vary depending on the end use, but the following are the minimum in each case
1. For quick response and effective controls, the hydraulic fluid has to be non compressible. This means that for all practical purposes, the gases are out of question. Water and mineral oils are the easiest that come to mind when we consider this requirement.
2. The fluid should not react with the materials of hydraulic systems. The metallic components should not get dissolved in the fluid or should form compounds with the fluid. Water generally falls short of this requirement since is causes rust with most common materials of construction like steel cast iron etc. Mineral oils do not cause any problem in this regard as specific blends may be made if required.
3. The power transmission function requires relative movements of parts and therefore the hydraulic oil has to have lubrication properties too. Water is woefully inadequate in this regards. Water cannot provide any lubrication except at very low speeds.
4. Fire resistance is also a welcome property in a hydraulic fluid. Water is best in this regard. In the mineral oils this property has to be developed by blending of various oils and the oil made fire resistant
5. The viscosity of oil also plays an important part in selection of oil for being selected as hydraulic oil. There should leave enough oil on the mating surfaces but at the same time the internal friction should not cause additional power to be consumed. Water fails on this count does not leave the film to lubricate the stationary mating surfaces when they start moving. Highly viscous oil will cause problems in seals as the oil may remain there and possibly of form a cake thereby making the seal inoperative.
6. The operating temperature range of oils should cover the entire of minus 40 Deg C to 70 Deg C without freezing or boiling. Water starts becoming into ice at about 4 Deg C and this creates problem in the hydraulic system.
Therefore water is not suitable as a fluid for hydraulic systems and specially developed mineral oils need to be developed as oils for use in hydraulic systems.
Manufacturers of hydraulic equipment take all these points in to consideration while selecting oil for their hydraulic systems. Therefore do not change the oil without consulting the manufacturer. The manufacturer may suggest alternatives if the recommended oil is not available in market for some reason. Therefore do not make any change to the oil without consulting manufacturer of hydraulic equipment.