HYDRAULIC INTRODUCTION

HYDRAULICS DEFINITION

Hydraulics ( which stems from the Greek word “Hydor” = water ) is, from the scientific view point, the science of liquids at rest and in motion (i.e. hydrostatics and Hydrodynamics). When reference is made in the mechanical engineering, automotive, and aircraft industries to hydraulic. Then one is speaking of the practical application of this branch of physics in the areas of power transmission and closed and open loop control techniques.

In contrast to hydrodynamics converters, turbo clutches and coupling etc, in which the kinetic energy of accelerated fluids is utilized to transmit power, one refers to hydrostatic system when considering the remainder of hydraulics as a whole. Although the laws of hydrodynamics apply here equally as well in connection with motion, flow resistance and the effects upon pressure of changes in the cross-sectional area of a restriction.

COMPARISON OF SYSTEM

Hydraulics stands side by side with mechanics, electrics, electronics, and pneumatics as a mean of transmitting power and as medium for use in open and closed loop controls. In some cases these system are indirect competition with each other. On the other hand, they complement each other in some respects and are often combined. For instance, it is quite normal to apply hydraulics for the energy flow in a system whereas, on the other hand, the signal flow is taken care of electrically.

The correct decision regarding the application of a particular system ( or combination of system ) presupposes a thorough knowledge of the characteristic involved, as well as of the advantages and disadvantages. The following table contain a comparison of the above named systems taking into account a number of different criteria. Considering examples of application, for which all the marginal conditions are defined, a firm decision can usually be reached. In border line cases, cost, operating reliability, service, know-how, and other criteria which are impossible to allow for in overall comparison, are in the facts which finally lead to a decision.