Pneumatic systems are designed to emulate their more powerful hydraulic cousins, although there’s several differences to consider. The largest difference, one that should be apparent to anyone with a modicum of engineering know-how, is the substitution of a gas in place of a fluid. Fortunately, the world is already enshrouded in gas, though we’re likely to call the substance ‘air’ and spend our time breathing it instead of discussing the benefits of the invisible stuff within a machine environment.
Now that we’ve snagged our energy source, we can’t just inject it into a system and hope the gas can power large machinery. The gas has to be pressurized, a task that’s accomplished by adding a compressor, usually an electric or diesel-powered pump, to the input stage of the system. Things are beginning to shape up. The system is charged with pressurized air and connected to tubes, valves and actuators. In other words, the apparatus is assuming an operational outline that identifies with other types of fluid power transmission systems, especially that of a hydraulic-powered device. Of course, should a leak in the system ever happen, there’ll be no messy puddles of hydraulic fluid to clean up, but we’re getting ahead of ourselves when we should be mapping out the principles that determine the functions of a pneumatic system.
Pneumatic engineering principles adhere to the same principles that dominate all forms of fluid power transmission. Certain characteristics are obviously going to differ between a gas and a liquid, with hydraulic oils taking on a denser form, but both systems rely on the fundamental laws that define fluid power, its generation, transmission, and the environment required to establish the system. Firstly, the circuit must be closed to enable the compression of the gas (air), at which point the circuit is regulated by opening and closing valves, actions that cause a subsequent output action such as movement in an actuating mechanism.
Partially meant as a converter of energy, the compressed gas takes finite amounts of mechanical energy at the input stage and converts this power into fluid force. The force is then sent into the circuit and manipulated, a process that typically amplifies the pressure and therefore the output energy within the circuit. Anyone who’s ever seen this system at work has probably jumped a little and been startled as a whoosh of air pressure is triggered by the pneumatic systems operational cycle. The source of that power is often kept out of sight, a scenario that any garage owner is familiar with due to the location of the compressor, reservoir tank and pump in its own little closet. Sticking with this example, the horse power of the motor and the mechanical strength built in to the pump decide how much air can be stored in the pressure vessel, although the thickness and volume of the tank actually make a large contribution to this operational factor. The garage mechanic can then manipulate valves and get air-powered hand tools working without encountering any of the difficulties associated with a comparable electrical tool, which is a major advantage when working in a hazardous environment.
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