PNEUMATIC SYSTEM
Fluid is that deforms continuously
on the application of shear stress, no matter how much small is it. Fluid
comprises both gases and liquid. The technique of using liquid for power
transmission is called as hydraulics, while which uses gases for power
transmission is called Pneumatics. In most hydraulics system mineral oils will
be used, while in most pneumatic system atmospheric air will be used.
PRINCIPLE BEHIND FLUID POWER
The basic principle which governs any fluid system is the Pascal law. The law applies to fluid power transmission. The other laws which will be used in the analysis, design and manufacturing of any fluid system are Boyle's law, Charles's law and Bernoulli theorem.
Air
is an abundant gas mixture with the following composition: Nitrogen approx. 78
vol. %, Oxygen approx. 21 vol. %. It also contains traces of carbon dioxide,
argon, hydrogen, neon, helium, krypton and xenon.
Characteristics of air:
A
characteristic of air is its minimal cohesion, i.e. the forces between the air
molecules are to be disregarded for operating conditions usual in pneumatics.
In common with all gases, air has no particular shape. Its shape changes with
the slightest resistance, i.e. it assumes the shape of its surroundings.
Boyle-Mariette’s Law:
Air can be compressed and it endeavors to expand. The applicable relationship
is given in Boyle-Mariette’s Law. At constant temperature, the volume of a
given mass of gas is inversely proportional to the absolute pressure, i.e. the
product of absolute pressure and volume is constant for a given mass of
gas.
P1. V1 = P2. V2 =
P3. V3= Constant
Pneumatic system is a system that uses
compressed air to transmit and control energy. The reason for using pneumatics,
or any other type of energy transmission on a machine, is to perform work. The
accomplishment of work requires the application of kinetic energy to a
resisting object resulting in the object moving through a distance. In a
pneumatic system, energy is stored in a potential state under the form of
compressed air. Working energy (kinetic energy and pressure) results in a
pneumatic system when the compressed air is allowed to expand. For example, a tank
is charged to 100 PSIA with compressed air. When the valve at the tank outlet
is opened, the air inside the tank expands until the pressure inside the tank
equals the atmospheric pressure. Air expansion takes the form of airflow.
PARTS OF PNEUMATIC SYSTEM
The pneumatic system comprises of following parts:
Pump or Compressor: This gives the motion
to the fluid which is used to perform useful work.
Control Valves: These are used to regulate and control the flow
of the fluid.
Tubes, pipes and Hoses: These carry the fluid
from the pump/compressor to the actuator.
Actuator: The actual work is
performed by the actuators.
Discharge
Tank: The liquid after performing work
will be discharged into a tank in case of liquids /gases or will let into the
atmosphere in case of air.
Seals: These prevent the leakage of fluid
into the atmosphere or surroundings.
Filter, Lubricator
and Regulator Circuit (FRL UNIT): This circuit is used to remove dirt present in the fluid.
They will also lubricate and regulate the flow of fluid.
