Hydraulic Devices and types

Hydraulic Devices

There are many types of hydraulic devices in which force and energy are transmitted through an incompressible fluid, oil etc. These devices based on the principles of hydro-static and hydro-kinetics.

Classification of Hydraulic Devices

a) Hydraulic lift

b) Hydraulic jack

c) Hydraulic accumulator

d) Hydraulic crane

e) Hydraulic ram

f) Hydraulic intensifier

Hydraulic lift (Direct acting and Suspended type)

The hydraulic lift is a device used to lift or bring down passengers and loads from one floor to another in multi-storeyed buildings.

CLASSIFICATION OF HYDRAULIC LIFT

Direct Acting Hydraulic Lift

CONSTRUCTION DETAILS: Components of direct acting hydraulic lift:

• Fixed cylinder: It is fixed with the wall of the floor, where the sliding ram reciprocate when we apply the pressure.

• Cage: It is fitted on the top of the sliding ram where the load is placed (i.e. lifted load).

• Sliding ram: It is fitted in the fixed cylinder which is reciprocate (upward or downward direction) when we applied the pressure (i.e. reaches the floor wise.)

Diagram

WORKING OF DIRECT ACTING HYDRAULIC LIFT:

When fluid under pressure is forced into the cylinder, the ram gets a push upward. The platform carries loads or passengers and moves between the guides. At required height, it can be made to stay in level with each floor so that the good or passengers can be transferred.

In direct acting hydraulic lift, stroke of the ram is equal to the lift of the cage.

SUSPENDED HYDRAULIC LIFT

CONSTRUCTION DETAILS:

Cage: It is fitted on the top of the sliding ram where the load is placed (i.e. lifted load).

Wire rope: It connects the cage to pulley.

Sliding ram: It is fitted in the fixed cylinder which is reciprocate (upward or downward direction) when we applied the pressure (i.e. reaches the floor wise)

Pulleys: pulleys are connected to the sliding ram and fixed cylinder; where one pulley is fixed and other pulley is movable.

Hydraulic jigger: It consists of a moving ram which slides inside a fixed hydraulic cylinder.

Fixed cylinder-: It is fixed with the wall of the floor, where the sliding ram reciprocate when we apply the pressure.

WORKING OF SUSPENDED HYDRAULIC LIFT

When fluid under pressure is forced into the cylinder, the ram gets reciprocate to the movable pulleys. With the help of arrangement of hydraulic jigger; pulley can rotates; with the help of wire rope the cage is maintain there pressure force with there floor. At required height, it can be made to stay in level with each floor so that the good or passengers can be transferred.

Working period of the lift is ratio of the height of lift to the velocity of lift.

Idle period of lift is the difference of the total time for one operation and the working period of the lift.

HYDRAULIC JACK or HYDRAULIC PRESS

The hydraulic jack is a device used for lifting heavy loads by the application of much smaller force. It is based on Pascal’s law, which states that intensity of pressure is transmitted equally in all directions through a mass of fluid at rest.

WORKING PRINCIPLE: The working principle of a hydraulic jack may be explained with the help of Fig. 23. Consider a ram and plunger, operating in two cylinders of different diameters, which are interconnected at the bottom, through a chamber, which is filled with some liquid.

 

Fig. Hydraulic jack Fig. Plunger

Let

W= Weight to be lifted,

F = Force applied on the plunger,

A = Area of ram, and

a = Area of plunger.

Pressure intensity produced by the force F, p = F/Area of plunger = F/a

As per Pascal’s law, the above intensity p will be equally transmitted in all directions.

Therefore, The pressure intensity on ram = p = F/a = W/A or W= F(A/a)

Above Equation indicates that by applying a small force F on the plunger, a large force W may be developed by the ram.

Mechanical advantage of press = A/a

If the force in the plunger is applied by a lever which has a mechanical advantage (L/l) then total mechanical advantage of machine = (L/l)(A/a)

The ratio (L/l) is known as leverage of press.

Hydraulic jack may be employed for the following jobs:

• Metal press work (to press sheet metal to any required shape).
• Drawing and pushing rods.
• Bending and straightening any metal piece .
• Packing press.