## The use of hydraulic systems in many industries

### Knowing how hydraulics pumps work

The coming of the Industrial Revolution in the early 1800s created a need for new and greater sources of power to drive the new machines. Industrialists soon realized that hydraulic machinery could solve many of these problems. By 1850 hydraulic pressure were being used topress cotton into bales and to squeeze oil from seeds.

Since those early days, the development of new types of hydraulic equipment has continually increased for many good reasons. Hydraulic machinery can produce tremendous forces with relatively simple equipment. These forces can be safely applied to do many kinds of work in a minimum amount of space. Finally, hydraulic power can be safely applied to do many kinds of wirk in mimimum amount of space. Finally, hydraulic power can be transmittedalong many convenient path and can be bent around corners. This gives it a great advantage over mechanical power which requires gears or link mechanisms for each change in direction. Today hydraulic machinery does thousands of industrial jobs. The automobile jack, the equipment that lowers an airplane's landing gear, the giant presses that produce thousands of tons of force to forge metal - all operate on the hydraulic principle.

The Principle of Hydraulic Pressure

A French mathematician, Blaise Pascal, stated the principle of hydraulic pressure as follows:

"An increase in pressure at any point in a confined liquid produces an equal increase in pressure at every other point in the liquid."

The Complete Hydraulic Machinery Unit

A complete hydraulic machinery unit contains five basic elements. These necessary elements are:

1) The hydraulic liquid. Water has been largely replaced for this purpose by light mineral oils. Such oils have better lubricating qualities for use with high-speed pumps. They have high viscosity for reduced leakage. Oils do not corrode metal parts as water does. Finally, they can operate at much lower temperatures than water without freezing or setting.

2) The pump, or power generating element.

3) The pipes and connections to carry the liquid.

4) The control element, such as valve or a hydraulic accumulator.

5) The motor element, such as a press or a jack that uses the liquid under pressure to do work.

Industrial Types of Hydraulic Machinery

The simplest type of hydraulic machinery is the hydraulic pressure. It has thousands of uses in the industry. The hydraulic press has a cylinder with a large piston which exerts a great force through a small distance. The liquid is supplied by a pump that corresponds to the small piston shown in the diagram. Small pistons in the pump are operating rapidly. They transmit power from a driving engine to the hydraulic liquid. This increased liquid pressure becomes a slow-moving but powerful force at the press. A small hydraulic press is shown on the facing page.

Specially designed hydraulic machinery operates large machine tools and lifting equipment such as cranes. Hydraulic controls lifts and lower the landing gear on airplanes. The mounts that control the movements of big artillery weapons are driven by hydraulic units. Many other types of mobile equipment use hydraulic machinery for power and control. Hydraulic machinery on some buses is responsible for the operation of steering, brakes, throttle, opening and closing doors, windshield wipers, and units that control the automatic transmission. Hydraulic starters are installed in some large diesel truck engines.