Pneumatics is when gas pressure is the liquid used to transmit energy but when liquid such as oil under pressure is used to transmit energy,it is called hydraulics. Gases and liquids under pressure can be used to transmit energy over a long distances. Such systems are called fluid power system.
Simple Hydraulic And Pneumatic Tools Or Devices
Below are some simple hydraulic and pneumatic devices; they are:
Pumps are used to move gases and liquids by applying pressure greater than those of the gases or liquids. The simplest pump is the bicycle pump that moves air through the pump to the bicycle. Another simple pump is the suction pump. It is used for lifting liquids from a low level and it may also be called lift.
A centrifugal pump has a set of moving vanes which receive the fluid(air or water)at a smaller radius.The moving vanes increases the speed of the fluid. At a larger radius,the fluid enters a row of stationary vanes. These reduce the speed of the fluid,so that the fluid pressure rises.The fluid is then discharged at high pressure.
COMPRESSED AIR DEVICES:
When pressure is exerted at one point on a liquid in a vessel,this pressure is transmitted equally to all other points in the vessel.The pressure is the same in all directions and is independent of the cross sectorial area of the vessel containing the liquid.This means that as long as it is the liquid of the same density that is being transmitted,the pressure is the same throughout,in spite of the shape of the vessel in which the liquid is.
The principle of equal transmission of liquid pressure is the principle on which hydraulic devices are based.These devices includes the hydraulic jack,hydraulic press for steel forging,simple garden sprinkler,reaction turbine,water wheel,car brakes and hydraulic hammers for forging red hot steel.
The hydraulic jack is based on the same principle as the double acting pump.The only difference is that the discharge action in the hydraulic jack moves the liquid into a high pressure compartment.The piston is equipped to carry heavy loads such as cars.
A sprinkler consist of one or more water jets which can revolve about the centre as it sprinkles water in a lawn or garden.
A reaction turbine consists of a row of blades on a wheel.By directing a jet of water on the blade such that the velocity is reversed at the outlet,the wheel is forced to rotate as the result of the reaction force produced.The force produced is much greater than if the jet of water merely comes to rest on the blade.
Unlike the windmill which rotates because of air movement,the waterwheel moves because of water movement.When downstream water that is moving fast hits the vanes on the wheel,higher pressure is created in the side hit by the stream of water than on the side that is not hit.This causes the vanes to move in the direction of flow of the stream.Thus in turn makes the wheel to rotate.