Hydraulics

Basic Hydraulic Circuit

BASIC CONCEPT OF A HYDRAULIC SYSTEM

Hydraulics is the engineering science of liquid pressure and liquid flow. Hydraulic power transmission systems are concerned with the generation, modulation and control of fluid pressure and flow.

A Hydraulic system consists of:

A Pump, which converts, available electric or mechanical power from the prime mover to hydraulic power at the actuator. A pump moves the liquid in the system.  The intake of the Pump is connected to a liquid source, usually called the Tank or Reservoir. Atmospheric pressure, pressing the liquid in the reservoir, forces the liquid into the pump. When the pump operates, it forces the liquid from the tank into the discharge pipe at a suitable pressure. The flow of the pressurized liquid discharged by the pump is controlled byValves.

Three control functions are used in most of the hydraulic systems to control and regulate the fluid flow.

a)      Control of the liquid pressure.

b)      Control of the liquid flow rate, and

c)      Control of the direction of liquid flow.

The fluid/liquid discharged by the pump in Fluid Power System is directed by valves to a Hydraulic Motor for developing rotary force (torque) and motion or to a Hydraulic Cylinder when linear motion is desired. Both, hydraulic motor and hydraulic cylinder uses pressurized liquid as their energy sources. Hydraulic motors operate in a reverse manner to that of a pump. Actuators convert hydraulic power to usable mechanical power output at the point required.

The Direction Control of the piston in hydraulic cylinder or the direction of rotation of the hydraulic motor depends on, to which end of the cylinder or motor the liquid enters. The Direction Control Valves (DCV) carries out this work of directing the liquid to proper ports of the actuators. As pressurized liquid enters one end, the existing liquid on the other end must be drained. The drained liquid is led back to the reservoir.

Connectors connecting various system components provide power conductors for the fluid under pressure and flow return to tank (reservoir). Fluid storage and conditioning equipment ensure sufficient quality and quantity as well as cooling of the fluid.

Hydraulic system is not a power source. Power source is the prime mover such as Electric motor or as an Engine, which drives the pump.