Hydraulic Fluids

Introduction, Function of Hydraulic Fluids, Physical Properties 

Introduction to Hydraulic Fluid

The hydraulic system will not function at all without hydraulic fluid. The system may or may not function, with the wrong kind of hydraulic fluid, depending on the type of hydraulic fluid that is used. If the system does not function with the wrong types of hydraulic fluid, it is doubtful if it will operate for any length of time, or with any degree of accuracy, or without problems.

In this topic will be described the manner in which a hydraulic must perform its properties, and some of its characteristics. This topic also explains some of the effects hydraulic fluid that had on a hydraulic system when it happened contamination, and the effect of oxidation.

Although you may not to select the fluids used in a hydraulic system, you will be responsible for filling the system and maintaining it in the proper working order after it is in operation. During routine inspections it is your responsibility to ensure that the fluid stays at a level that is acceptable to the system. This lesson presents the information that will enable you to detect hydraulic fluid problems before they become critical.

Function of Hydraulic Fluids

Hydraulic fluids are engineered to work well in many fluid power applications. In most plants one hydraulic fluid can be used in several systems. However, when operating difficulties occur in industrial hydraulic systems, the main cause is from either the use of the wrong fluid or the improper condition of the right fluid.

Fig. 2-1. Lubricating a control valve

The main function of hydraulic fluid is to transmit power effectively from one point in the system to another. In order to do this, the fluid must flow readily and be virtually incompressible. Another function of hydraulic fluid is to lubricate the contacting surfaces of the mechanical working parts of the system. Because components such as vanes, gears, pistons, and valve spools are manufactured to very close tolerances, the hydraulic fluid must reduce the friction between contacting surfaces of the components. It does this with a thin film of hydraulic fluid as shown in Fig. 2-1.