ER. SUNIL PANCHAL

UNIT 8 HYDRAULIC SYSTEM

HYDRAULIC ACCUMULATOR

 Hydraulic accumulator is a device used for storing the pressure

energy of the liquid. The capacity of the Hydraulic accumulator is the

maximum amount of pressure energy which it can store for the

various applications. It is a device used for storing the pressure energy

of the liquid. Its action is just similar to storage battery. The energy

stored can be supplied at any time when required either suddenly or

intermittently.

                                

                             Fig. Hydraulic accumulator

It consists of a vertical cylinder which is fixed in position. It is

provided with inlet and outlet value. A ram is fitted which carries

heavy weight which slides up and down. At the beginning the ram is

at the lower most position. When high pressure is supplied by the

pump it lifts the ram and high pressure is stored in the pump. When

ER. SUNIL PANCHAL

UNIT 8 HYDRAULIC SYSTEM

hydraulic system requires large amount of pressure energy it can be

taken from accumulator the ram moves down.

DIFFERENTIAL ACCUMULATOR

        

             Fig. Differential hydraulic accumulator

FLUID COUPLING

Hydraulic coupling is a device which is employed for transmission of

power from one shaft to another through a liquid medium.

 

 

ER. SUNIL PANCHAL

UNIT 8 HYDRAULIC SYSTEM

                         

              Fig. Typical Hydrauling coupling

A) Construction:

It consists of two rotating elements:

1. Pump impeller-It is attached to driving shaft of the prime mover

which may be I.C. engine, a steam engine or an electric motor.

2. Turbine runner— It is attached to driven shaft.

B) Working

As soon as the prime mover starts rotating, the pump impeller also

starts rotating and throws the oil outward. The oil then enters the

turbine runner and exerts a force on the runner blades. The magnitude

of the torque increases with an increase in the speed of the driving

shaft and eventually when this torque overcomes the inertia force, the

turbine runner and driven shaft begins to rotate.The speed of the

driven shaft is always less than the speed of driving shaft. The

difference is measured by ‘slip’.

ER. SUNIL PANCHAL

UNIT 8 HYDRAULIC SYSTEM

                       S (Slip) = 

a) Speed of driving pump

b) Speed of driven turbine

Efficiency is defined as the ratio of power output to input power

                   h 

HYDRAULIC RAM 

Hydraulic ram is a device or pump which raises water without any

external power for its operation. When large quantity of water is

available at a small height, a small quantity of water can be raised to a

greater height with the help of hydraulic ram. It works on the

principle of water hammer.

                     

Fig. Hydraulic ram

ER. SUNIL PANCHAL

UNIT 8 HYDRAULIC SYSTEM

Working

When the inlet valve fitted to the supply pipe is opened, water starts

flowing from the supply tank to the chamber, which has two valves   

and . The valve,   is waste valve and  is called delivery valve. As

the water is coming into the chamber from supply tank, the level of

water rises in the chamber and waste valve   starts moving upward

and ultimately it closes. This sudden closure of waste valve   creates

high pressure inside the chamber. The increased high pressure lifts the

valve , a part of water enters the air vessel and compresses the air

inside the air vessel. The compressed air exerts force on the water in

the air vessel and a small quantity of water is raised to greater height.

TORQUE CONVERTOR

This device is used to transmit increased or decreased torque of an

automobile engine shaft to the propeller shaft (driven shaft).

                   

ER. SUNIL PANCHAL

UNIT 8 HYDRAULIC SYSTEM

The construction is similar to coupling.

It consists of driving member fixed on driving shaft, driven member

fixed on driven shaft and a stationary member known as stator fixed

to the frame. In addition there is a transmission oil pump which keeps

the convertor full of oil under pressure which is necessary to keep the

convertor full of oil when rotating. It has a series of fixed guide vanes

between pump impeller and turbine runner. The oil exerts a torque on

these vanes as it flows from pump to turbine.

HYDRAULIC INTENSIFIER

 Hydraulic intensifier is used to increase the liquid pressure above that

available from a pump. The task is accomplished by utilizing the

energy of a large quantity of liquid at low pressure. It is located

between the pump and the application (pump, crane etc).

Working 

The configuration of hydraulic intensifier is shown in figure. It

consists of a fixed ram surrounded by a sliding cylinder, which

contains high pressure water or oil. The sliding cylinder   is

encased in a fixed cylinder and fixed cylinder   which contains low

pressure liquid supplied from the main supply.

Valves   and   gives low pressure water or oil and valve   is for

discharge and through valve 

ER. SUNIL PANCHAL

UNIT 8 HYDRAULIC SYSTEM

To understand at start assume that the sliding cylinder is at bottom

most position and cylinder (fixed) is full of low pressure water or oil.

Then the valves   and   are closed and valve   is opened, so the

low pressure water or oil from supply through valve   is admitted

into the sliding cylinder This permits the low pressure water or oil

from the fixed cylinder to be discharged through the discharge

valve 

Now when the sliding cylinder reaches its top most position, the

inside of the sliding cylinder is full of low pressure or oil water. The

valves   and   closes and valves   and are opened. The low

pressure water or oil through the valve   enters at the top of sliding

cylinder which forces the sliding cylinder downwards and produces

high pressure water or oil in the sliding cylinder. The cycle is repeated

again and again.

                          

                                   Fig. Hydraulic intensifier