A pneumatic system is one that uses a gas, generally compressed air, to transmit power to a mechanical device. When the fluid is a liquid instead of a gas, then it is called a hydraulic system.
Sometimes a pressure pulse is sent, acting as a signal, to mechanically activate another device, for example a switch.
A pneumatic system is made up of a compressor, valves, actuators, and compressed air lines. The system is connected by pipes, hoses or conduits that are part of the pneumatic circuit and that most of the time does not require a return.
The noisy jackhammer that breaks concrete in streets, sidewalks, and buildings is probably the best-known example of a pneumatic system.
Other tools, such as those used to screw and unscrew wheel nuts, are part of a pneumatic system. In this system, the potential energy of the compressed air is converted into torque that tightens or loosens the nuts.
Likewise, the machine with which rubber or tire rubbers are extracted from automotive rims or wheels is another example of a pneumatic system. In this machine there are some pedals, which at the bottom are pneumatic switches that divert the pressure or flow of compressed air from one part of the machine to another, to perform various functions.
Characteristics of a pneumatic system
Every pneumatic system is characterized by having:
- A compressor (usually air).
- Air cylinder or tank.
- A filter system to remove impurities and moisture.
- Valves to regulate pressure and flow.
- Pneumatic switches, which allow or block the passage of compressed air.
- Air or compressed fluid conduits, which can be metal pipes and / or high pressure hoses.
- Actuators, which are the mechanical devices that carry out work. Most actuators consist of a cylinder with a moving piston, but it can also be a turbine, as in the case of the dentist’s drill.
- Manometers are pressure gauges that are placed in various parts of the pneumatic system with the purpose of knowing and controlling the pressures in each of the parts or stages of the system.
Operation of a pneumatic system
To explain the operation of a pneumatic system, the operation of each of its parts and the way in which each part is integrated into the complete system is described below.
In every pneumatic system the compressor is essential, which absorbs air at atmospheric pressure, and by means of a piston compresses it in such a way that its pressure increases several times the atmospheric pressure.
The cylinder or reservoir retains the high pressure air produced by the compressor, where it accumulates at the pressure and volume required according to the needs of the pneumatic system. Another function of the cylinder is to allow the hot air from the compressor to cool, usually to room temperature.
The filter, which is almost always placed at the outlet of the cylinder, retains dust particles and removes moisture from the compressed air that will pass into the ducts. This is necessary to ensure the proper functioning and longevity of the other parts of the system, such as the valves and the actuators themselves.
The functions of the valves can be various: pressure distribution, pressure regulation, pressure switch, flow regulators and shut-off valves.
Valves can be of various types, depending on their function. There are valves that control the pressure, keeping it at a stable level, according to the function of the system.
Other valves function as switches that allow or prevent the passage of pressure to the other parts of the pneumatic circuit.
There are valves that alternately redirect the flow to one or another part of the pneumatic circuit, for example to execute a movement of the actuator in opposite directions, as in the double-acting cylinder and piston system in the opening and closing mechanisms of the doors of buses and vans.
The valves of a pneumatic system can be controlled manually, by servo-pneumatic systems where the energy of the circuit itself is used and by electro-pneumatic systems, in which the valves of the pneumatic system are actuated by electric solenoids.
There are basically two types of circuits:
1- The circuits with return or closed circuit, where the end part connects with the origin of the circuit guaranteeing a continuous flow of air, in this case energy is saved to keep the system pressure stable.
2- Non-return or open-circuit circuits, the latter are more economical in terms of pipes and are suitable when the actuators work more by pressure than by flow. In these cases, as the compressed air does not return, more work is required by the compressor to maintain the working pressure, so this type of circuit is less efficient from the energy point of view.
Examples of pneumatic systems
Examples of pneumatic systems are the following:
-The turbine drills used in dentistry.
-Pneumatic hammers to break concrete on streets and sidewalks.
-The systems for opening and closing doors in trains, buses and vans.
-Tools for tightening and loosening motor vehicle tires.
-The machines that are used to remove and place the tires of automotive tires.
-Screwdrivers and screwdrivers in industrial assembly plants .
-Industrial riveting machines.
-Industrial staplers for upholstery.
-Nail guns for carpentry.
-In industrial robotics, they are used for the movement of articulated arms, grip systems and lifting of parts.
-In the air brake system for trucks, tractors, construction machinery, gandolas, trailers and trains.
-Pneumatic clutch systems for buses and trucks.