Compressed Air


This page provides a broad range of information about compressed air. The more you understand about what compressed air is and the use of compressed air as an energy source, likely the better you will be at integrating it into your workshop or plant.

There are three commonly available energy sources for manufacturing and industry. They are:

     - Compressed Air (Fluid Power) Energy
     - Hydraulic (Fluid Power) Energy
     - Electrical Energy

Of these three, compressed air is the energy source of choice for doing much of our nation's industrial work. There are good reasons for that.

Compressed air is an energy source that's relatively easy to store, is non-flammable, is very powerful, and can generate high productions speeds in a variety of ways including air cylinders and air actuators. Compressed air is extremely versatile in the numbers of ways it can be used.

Compressed air - car tire

For example, compressed air can provide an air cushion upon which we drive our vehicles. The air inside the tire is "pumped" into the it with a manual bicycle type air compressor, or via the compressed air hose from the air compressor that's located somewhere inside the local tire store or corner garage.

Remember when pumping air into your car tire at the gas station was free? Compressed air still is if you chose to use that hand compressor we all had at one time... the bicycle tire pump. But who wants to do that?

Air Tool

With compressed air you can rough or fine finish the surface of a piece of woodwork, or smooth weldments in steel with an air sander or grinder. Compressed air is used everywhere.

Portable Compressed Air


Compressed air can be carried anywhere with an appropriate pressure vessel - sometimes called an air hog or air pig.

Compressed air helps people breathe underwater with portable SCUBA tanks, in an environment that is foreign and deadly to them.

And as mentioned earlier, compressed air is relatively safe in that it's non-flammable. When you spill compressed air, it doesn't make a mess!

Energy Conversion


Compressed air is able to do work because as you compress air you transform one form of energy into another form of energy which you then store for later use.

This stored energy, in the form of compressed air, is now at imbalance, in that you have an area of high pressure in a compressor tank surrounded by an area of lower pressure; our atmosphere.

Imbalance in Compressed Air


Mother Nature doesn't like imbalance in her systems. If you have a container - an air tank, a receiver, an air-hog or a plant air main filled with compressed air at 150 PSI or so, this bothers her. She wants that air to be back at a nice, comfortable, 14.7 PSI everywhere- that 14.7 PSI being the pressure of the atmosphere at sea level. And she wants high pressure gone right now!

That drive to achieve balance in nature - that is, to get the compressed air from an area of high pressure back to atmospheric pressure, means that when you open the valve on the tank or air line, air will move at almost the speed of sound, rushing from high to low pressure, to get back to normal atmospheric pressure.

By controlling this flow of air, and directing it into tools that in themselves can perform work, then you can extract the work energy from the compressed air energy as it decompresses back to atmospheric levels.

Over the years, we have learned how to use this high-to-low pressure flow of air to do work for us via specialty nozzles, air tools, air actuators, air motors, and so on. Compressed air really is a neat way to store and use energy.

Reduce Fire Risk With Compressed Air


If your application involves manufacturing or processing products that are flammable or explosive, compressed air actuators and air operated directional control valves don't create sparks.

Therefore, fire or explosion risk can be reduced to an acceptable level when using compressed air equipment in almost all flammable operations. Compressed air can be used in applications where other energy forms might blow you to kingdom come!

Compressed Air Does Have Some Risk


Compressed air can be, and often is, worked with and on by persons without formal training. If that person isn't skilled in using compressed air, it could result in injury or death to them or their colleagues, or cause damaged equipment. Be very careful! Compressed air can be dangerous.

Air Instead Of Hydraulics


If the force you require for your application can be generated by an air compressor using appropriately air valves and actuators, then you would pick compressed air as your energy source over hydraulics simply because compressed air components, from the compressor through to tools, are less expensive.

Using hydraulic energy is more expensive in generation of energy to do work, and in the cost of the components to use hydraulic force. If you don't need the immense pressures and force that hydraulics can give you, it doesn't make sense to pay for that capability. Use compressed air, instead.

And, when you get a hydraulic leak, that's quite a visible phenomenon. A hydraulic oil leak generates issues with regards to safety as well, as high pressure oil spraying from a small orifice can hurt someone. Whether a high pressure leak or just a drip, hydraulic oil in the wrong place does create more than just a mess, but a significant slip hazard as well.

There's also an increasing concern about the potential for environmental damage from hydraulic oil leaking onto and into where it's not supposed to be.

A compressed air leak, albeit costly in wasted energy to compress that air in the first place, usually doesn't create these same hazards.

Electricity As An Energy Source?


Electricity use is often complex to employ, requiring a skill set many folks don't have. Also, electricity can be quite dangerous.

An electrician told me once that you might get killed by being well grounded and touching a 120 Volt AC power source. That same electrician said if you touch a 240 volt source, there's no more might about it, you will die. Electrical work should be performed by a licensed electrician, and if you haven't one on staff, that can get costly, which may be an issue for some businesses.

On the up side, in the urban world, electricity is ubiquitous - found almost everywhere.

Many industrial operations use a great deal of electricity in their operations, often in a control capacity or smaller manufacturing processes. However, electricity cannot economically generate the force that's available from compressed air or hydraulic power. It compares poorly in both size of components and the strength of the force generated.

Ironically, it's electricity that most often drives the industrial air compressor and the hydraulic power pack. But it is the compressed air from that compressor that provide the heavy lifting work in the typical manufacturing plant. And it's the hydraulic system that provides huge amounts of force when that force is what's called for.

Compressed Air First


Electricity has its place in the industrial world, as does hydraulic energy.

Regardless, for my money, if compressed air can generate the force I need versus other energy sources, for the reasons outlined here, compressed air is the energy source that I would pick first.

Here's some more general information that may interest you.

Pascal's Law

When force is applied to a fluid in a closed vessel, it is transmitted equally in all directions.

Force is applied to the inside of the compressor tank with the compressor driving air into it, and that air pressure inside is pushing equally against the entire inside of the tank.

When a downstream air valve opens, since air is pushing equally in all areas, it will instantly blast out of the tank through the now open line, to pressurize the downstream air mains, racing towards atmosphere and what nature calls balance; where air pressure is at the same level.

The compressed air wants to maintain pressure equally so it flows from high pressure to low until pressure is equalized.

Bernoulli's Law

When the height and temperature are constant, if the pressure in a fluid is reduced the flow will accelerate, and if you increase the pressure, the flow will slow.

Boyle's Law

P1V1=P2V2

Essentially, if you keep the temperature constant and you halve the volume of a vessel, you will double the pressure of the fluid inside it. Or, doubling the volume of the vessel will halve the pressure inside.

Did you know that...

"every 10 psig increase of pressure in a plant system requires about 5% more power to produce."
Source: Kaeser Compressors

Got a questin about compressed air? Just ask!