Discuss principle of hydraulic power system and law associated with it. Explain the operation of a simple hydraulic system using double acting cylinder with block diagram.

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The controlled movement of part or a controlled application of force is a common requirement in the industries. These operations are performed mainly by using electrical machines or diesel, petrol and steam engines as a prime mover. These prime movers can provide various movement to the objects by using some mechanical attachments like screw jack,lever,rack and pinion etc. However these are not the only prime movers.

The enclosed fluids (liquid and gases) can also be used as prime movers to provide controlled motion and force to the objects or substance. The specially designed enclosed fluid system can provide both linear as well as rotary motion. The high magnitude controlled force can also be applied by using these systems. This kind of enclosed fluid based systems using pressurized liquids as transmission media are called as hydraulic system.

The hydraulic system works on the principle of Pascal's law which says that the pressure in an enclosed fluid is uniform in all directions. The force given by fluid is given by the multiplication of pressure and area of cross section. As the pressure is same in all the direction the smaller piston feels a smaller force and a large piston feels a large force. Therefore a large force can be generated with smaller force input by using hydraulic systems.



  1. -Reservoir
  2. -Pump
  3. -Prime mover
  4. -Valves
  5. -Actuator
  6. -Piping
 The motor (M) drive the hydraulic pump (P) so that the fluid pumped from the tank at the required pressure. The fluid circulated into the system should be clean to reduce the wear of the pump cylinder ; hence a filter is used immediate to the storage tank. Since the pump delivers constant volume of fluid for each revolution of the shaft, the fluid pressure rise indefinitely until a pipe or pump itself fails to avoid this, some kind of pressure regulator is used to spill out the excess fluid back to the tank.

Cylinder movement is controlled by a 3- position changeover control valve. One side of the valve is connected to a pressurized fluid line and the fluid retrieval line, the other side of the valve is connected to port A & B of the cylinder.

Since the hydraulic circuit is a closed one the liquid transferred from the storage tank to one side of the piston and the fluid at the other side of the piston is retrieved back to the tank.




                           



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