How Does An
       Air Compressor Work

How does an air compressor work? This question was posed recently on the ASK page on this site by a student, and, as I suspect that this question crosses other folks minds from time to time, so I am glad to share my answer with you.

The question - "I am in school and am doing a science project. We need a pneumatic system and I chose the air compressor and I need to have a good explanation of how it works. I don't really need to know all the little things, just basically what happens.

I couldn't find the answer anywhere and we are supposed to look it up on a site. Thanks.

My response - Hi Emily, and thanks for sending in your question.

Did you know that the air you walk around in, and breathe, is already compressed? The pressure generated at sea level by the weight of the air above and it generates about 14.7 PSI of pressure.

PSI stands for pounds per square inch, and is a measure of force pushing against something. In this case, it is the force of the air around us, pushing on everything at 14.7 PSI. You don't feel it as it's always there, and you are used to it.

An air compressor takes in the air that's all around us through an intake hole, usually near thet top of the compressor pump. Using mechanical means (pistons, screws, rotary sliding vanes etc.) the compressor pushes that air into a the receiver or the air tank beside the compressor pump. As air is pushed into the tank, more and more air enters but the size of the tank cannot get bigger. As a result, the increasing volume of air pumping into the compressor tank makes the air pressure inside the tank increase.

There is a pressure switch connected to and which monitors the air pressure inside the tank. When the air pressure inside the tank reaches the high pressure level setting on the switch, the pressure switch shuts the compressor off.

When compressed air from the tank is used to run an air tool, the air pressure inside the tank will start to fall.

When the air pressure in the tank falls to the pressure switch low pressure setting, the switch turns the compressor back on, allowing it to pump more air into the tank again.

This cycle continues as compressed air is being drawn from the compressor tank. The compressor motor starts and stops as the pressure inside the tank changes, and the pump reacts by pumping more air into the comressor tank as needed. When the air pressure inside the tank reaches the high pressure set point the pressure switch shuts the compressor motor off again.

There is lots of information on this site about the different types of compressors, and the problems compressed air generates. Please help yourself to any of that information if it will help.