Hydraulic Press

Hydraulic press multiplies an applied effort using the pressure of a liquid or gas. This allows the lifting of a heavy load by applying little effort

In hydraulic press small force (Effort) applied on the small piston is used to overcome a much greater force (load) on the large piston.
When a small effort (E) is applied downwards on the effort piston of radius (r) the load piston of radius (R) lifts the load (L).

Consider the diagram below: -

MECHANICAL ADVANTAGE OF HYDRAULIC PRESS

By the principle of transmission of pressure in liquid, the pressure on effort piston is equal to the load piston.   

From

 

But                            M.A = Load
                                             Effort

M.A =    Area of Load piston
                         Effort of Effort piston

                         M.A = πR²
                                     πr²      

             M.A = R²
                                     r²

VELOCITY RATIO OF HYDRAULIC PRESS

If friction is neglected the work done by the effort E is equal to the work done on the load (L). So if the effort piston is moved by distance x and the load piston raised up by a corresponding distance Y, it follows:

Work done by the Effort = Work done by the load

           EX= LY

                              So, X = L
                                    Y    E

                               M.A = Load
                                          Effort

                               M.A = X
                                           Y

Velocity ratio = Mechanical advantage                                   

    V.R = M.A        

                             M.A = R²
                                         r²

                  Velocity ratio = R²
                                              r²  

Note: Due to friction, efficiency of the hydraulic press is not 100%

Uses of Hydraulic Press in Daily Life

i)       It lifts heavy loads

ii)     In ginneries to compress a lump of cotton into small bales

iii)   In industries to form car bodies into the required shapes