Positive Displacement and Dynamic Air Compressors
By: The Working Man
An air compressor works by increasing the amount of air in a
confined space. This is done by packing the air in, which
increases the pressure on the air and creates force that can
be uses for a variety of purposes.
The oldest type of air compressor is actually a part of your
body: The lung is considered to be an air compressor. For
example, if you take a very deep breath and blow out your
birthday candles you are pressurizing the air that you took
into your lungs previously. This is essentially air under
pressure in a contained space. You use the air that is under
pressure to blow out the candles on your birthday cake.
Manmade air compressors fall into two categories that are
defined by operation: positive displacement and dynamic.
A positive displacement air compressor fills an air chamber
and then empties the air chamber. There are three types of
positive displacement air compressors that are commonly
used, the rotary sliding vane, the rotary screw, and
A dynamic air compressor accelerates and decelerates air
using a rotary device that pushes the air. An example of a
dynamic air compressor is the centrifugal air compressor.
The dynamic air compressor uses the velocity of the air or
the speed of the air to increase the air pressure.
Compressed air can be used in many ways and for many
purposes. It is used to maintain industrial plants, to run
production line manufacturing processes and even to change
the chemical composition of fertilizer.
The air compressor has become a very useful machine to power
tools such as the air-powered staplers, nail guns, sanders,
ratchet wrenches and spray guns. It can also be used to move
debris around via a blower and such air compressors are
usually available for rent or purchase at your local
Air compressors can be grouped or classified by the number
of stages the air compressor has. A two-stage air compressor
is normally used for industrial purposes and for heavy-duty
jobs. Two stage air compressors can store compressed air for
future use and they are more energy efficient, giving you
more compression of air per unit of horsepower.
A two stage also has more life than a single stage air
compressor because it does not generate as much heat thereby
reducing wear on the unit itself. This type of air
compressor gives you a higher level of compression that the
single stage air compressor.
However, the single stage air compressor has the bonus of
being portable, unlike the second stage air compressors.
They are light and are meant to be used for small
applications such as filling a tire with air.
An air compressor can be powered by hand, electricity or
gas. The gas air compressor is usually more cost effective
than the electric or hand run air compressors. But in order
to avoid gas fumes in a small enclosed place you may want to
use the electric air compressors.
The ASME or American Society of Mechanical Engineers rates
air compressors for purchase or as rentals. They assure the
quality of the protective features of the air compressor. In
some states only an ASME certified air compressor can be
sold or rented.
Many air compressors have added safety features, for example
a safety relief valve which will let air escape if the
tank's pressure exceeds the maximum limit. An air compressor
will usually also have a belt guard and an enclosed air
intake filtration system.
Be sure to wear proper personal protection equipment, read
the air compressor's manual and follow all safety
recommendations while operating the air compressor. An air
compressor is a tool that can be very dangerous if not used
properly. When you are done using an air compressor you
should be sure to follow all recommended shutdown procedures
and then unplug the machine.
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