Basic Components of a Hydraulic System

 Hydraulic systems are power-transmitting assemblies employing pressurized liquid as a fluid
for transmitting energy from an energy-generating source to an energy-using point to
accomplish useful work. Figure shows a simple circuit of a hydraulic system with basic
components.

Basic Components Of Hydraulic System
Basic Components Of Hydraulic System

Functions of the components shown in Fig.  are as follows: 

1. The hydraulic actuator is a device used to convert the fluid power into mechanical
power to do useful work. The actuator may be of the linear type (e.g., hydraulic
cylinder) or rotary type(e.g., hydraulic motor) to provide linear or rotary motion,
respectively. 

2. The hydraulic pump is used to force the fluid from the reservoir to rest of the
hydraulic circuit by converting mechanical energy into hydraulic energy.

 3. Valves are used to control the direction, pressure and flow rate of a fluid flowing
through the circuit.
Motor 1 – Off 2 – Forward 3– Return
3 2
1
Load
Direction
control
valve
Pump
Oil tank
Filter
Actuator
Pressure
regulator 

4. External power supply (motor) is required to drive the pump. 

5. Reservoir is used to hold the hydraulic liquid, usually hydraulic oil. 

6. Piping system carries the hydraulic oil from one place to another. 

7. Filters are used to remove any foreign particles so as keep the fluid system clean and
efficient, as well as avoid damage to the actuator and valves. 

8. Pressure regulator regulates (i.e., maintains) the required level of pressure in the
hydraulic fluid. 

The piping shown in Fig.  is of closed-loop type with fluid transferred from the storage
tank to one side of the piston and returned back from the other side of the piston to the tank.
Fluid is drawn from the tank by a pump that produces fluid flow at the required level of
pressure. If the fluid pressure exceeds the required level, then the excess fluid returns back to
the reservoir and remains there until the pressure acquires the required level.
Cylinder movement is controlled by a three-position change over a control valve.
1. When the piston of the valve is changed to upper position, the pipe pressure line is
connected to port A and thus the load is raised.
2. When the position of the valve is changed to lower position, the pipe pressure line is
connected to port B and thus the load is lowered.
3. When the valve is at center position, it locks the fluid into the cylinder(thereby holding it in
position) and dead-ends the fluid line (causing all the pump output fluid to return to tank via
the pressure relief). 

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