Basic Principles Of Hydraulics

Basic Principles Of Hydraulics
Page content


Earlier, weights were lifted using pulleys, levers, block and tackles, etc. Movements for a ship’s rudder or steering a vehicle where achieved by mechanical linkages like cams, levers, couplings, and gears which made the system complicated. These manual or mechanical methods of operation had several limitations. They also involved huge man power and long working hours for a particular job. As the population and technology increased exponentially, the demand for quicker and easier to operate equipment increased. To cater to this need, hydraulic machines were introduced.

Basic Hydraulic Principles


A simple hydraulic system consists of hydraulic fluid, pistons or rams, cylinders, accumulator or oil reservoir, a complete working mechanism, and safety devices. These systems are capable of remotely controlling a wide variety of equipment by transmitting force, carried by the hydraulic fluid, in a confined medium. Modern developments in hydraulics have involved many fields in engineering and transportation. These systems transfer high forces rapidly and accurately even in small pipes of light weight, small size, any shape, and over a long distance. These systems play a vital role from small car’s steering to super sonic aircraft’s maneuvering devices. More powerful and accurate systems are also used in maneuvering huge ships.

Pascal’s Law:

pascals law

Pascal’s Law, framed by Blaise Pascal, states that “Pressure applied to any part of a confined fluid transmits to every other part with no loss. The pressure acts with equal force on all equal areas of the confining walls and perpendicular to the walls.” This is the basic principle for any hydraulic system.

Hydraulic Pressure & Force:

Pressure can be defined as “the force acting on unit area, applied in a direction perpendicular to the surface of the object”.

Pressure = Force/ Area.

So, hydraulic pressure can be stated as the force exerted by a fluid on unit area, anywhere on the surface within the container.

A Simple Hydraulic System:

hydraulic pressure

A closed toothpaste tube can be considered as an example for a simple hydraulic system. The toothpaste can be considered as a hydraulic fluid working inside the system which is confined. Four or five holes are made on the tube. By keeping the cap of the toothpaste tube closed, apply pressure at a particular point on the tube. This makes the toothpaste to come out from all the holes evenly. This is a simple example to understand Pascal’s law. Thus force applied at a particular point on a fluid in closed system, transfers equal force on all other parts of the system. Further, the force acts perpendicular to the walls of the confined area.

Other example is the hydraulic brakes used in automobiles. The driver applies force at the break pedal (one particular point on fluid in closed system), thus transmitting this force onto the hydraulic fluid under the piston (break pedal), transfers equal force to all other brake shoes, thus stopping the vehicle.

steering gear

There are several other areas where hydraulics are applied. They are:

1. Automobile garage

2. Petrol pumps

3. Measuring weights of heavy-lift trucks

4. Hydraulic cranes

5. Automobile steering gears

6. Automobile brake, (disc brakes)

7. Ship’s steering gear

8. Robotics

9. Aircraft’s rudder and other maneuvering systems

10. Industries and power plants

11. Servo machanisms and control systems etc.

pascal’s law

hydraulic brakes

hydraulic lifts–air craft carrier

Also, this same principle is used in hydraulic lifts and other machineries. In the next article we will discuss how hydraulic presses are used in industries.

Image Credits: