Compressed Air Makes Pneumatic Dampers Move
It's not the damper in pneumatic dampers that's pneumatic, it's the actuator. The actuator moves the damper, the actual piece that allows or blocks air flow, into open or closed positions, and derives its energy from pneumatics.
Pneumatics is a branch of physics that deals with the mechanical properties of air and other gases. Pneumatic damper actuators compress gas and convert that energy into the motion that opens and closes dampers. The motion can be linear or rotary.
Automated pneumatic dampers are common in systems such as those used for heating, ventilating and air-conditioning (HVAC). Automated alternatives include electric dampers and hydraulic dampers, which closely resemble their pneumatic cousins but use fluid instead of gas.
Without the automated systems, dampers would have to be closed by hand, an endeavor that would range from laborious to impossible.
Industries including metals and mining, power generation, petroleum and water and wastewater treatment require dampers with actuators, but they're most noticeable to the average person in residential and commercial HVAC systems.
They're found in the boxes that mix fresh air with the air that comes through vents, in central fan systems, variable air volume (VAV) systems and fire, smoke and exhaust dampers.
A simple item such as a pneumatic car jack demonstrates the power of pneumatics. The pneumatic cylinder multiplies the amount of force applied to the jack handle enough that an average person can lift a car that weighs more than a ton.
A pneumatic actuator is connected to a solenoid valve and generally consists of a cylinder, a piston and valves or ports. The piston usually, but not always, is covered by a diaphragm or seal that keeps air/gas in the upper part of the cylinder, allowing pressure to force the diaphragm down, thus moving the piston below. The piston in turn moves the valve stem, which connects with the parts inside the actuator and moves the damper. Larger pistons produce greater output pressure.
The advantages that pneumatic damper actuators have over electric ones are several. Their design is simple, making them easy to understand and operate. Pneumatic systems generally require little maintenance and last longer, and because they use air that compresses, the equipment is less susceptible to shock.
Pneumatic damper actuators are generally the safest, and because compressed air can be stored, dampers can still operate even if power is lost. They also usually are far less expensive to buy and install than are electric damper actuators.
The main advantage that electrical actuators offer is precision. They can position a damper more accurately, but the systems are more expensive and require more expertise to operate.
The motions that the damper actuators create are easy to understand. The configurations are linear or rotary. A rotary actuator simply works on a motion that isn't in a straight line, while a linear actuator takes a movement that isn't straight and converts it into one that is.
In any form, damper actuators spare people a lot of hard work, and the espoused merits of pneumatic systems are more than hot air.
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