Recommending an air compressor is not an easy task because, as with any other machine, everything depends on the use we want to give it. In addition, it is easy to get lost in the multitude of technologies, specifications, various circumstances… that are of vital importance when choosing air compressor. This article is therefore intended to be affordable, instructive and, above all, useful for those who want to purchase a compressor.
A simple Google or Amazon search returns dozens of different models and brands, all with their pressure bars, voltages, horses and other paraphernalia. But how to choose an air compressor? The best thing we can do is to understand the basic concepts so that each one chooses the machine that best suits him. Here we go.
There are several technologies that allow us to compress the air: the most common are piston compressors and screw compressors, all of them positive displacement compressors. However, screw compressors are used in industrial applications with very serious pneumatic machinery (large air flows). Those who buy and choose these machines are usually experienced and highly trained professionals. They are well aware of the intricacies of compressed air and know how to choose air compressor.
So if you’re reading this article you’re probably looking for a piston compressor –if you’re not, contact us, or leave us a comment👇, we’ll be happy to help you choose an air compressor. Of course, within the category “piston compressors ” there are many types, from the small garage compressor to inflate mattresses and wheels, to compressors for small and medium-sized enterprises, such as mechanical workshops.
Although on compressed air Blog we have already seen how piston compressors work, it is worth remembering: a bicycle pump is the simplest and closest example of piston compressor; the air is inserted into a cylinder and compressed by a piston that, in this case, we move. When the air reaches the desired pressure, a valve opens that releases compressed air into the balloon, tire or whatever we are inflating.
In more technical words: piston compressors contain a certain volume of gas or air and then increase their pressure by reducing this volume with a moving part (hence the “positive displacement compressors”). The piston compressors you want to buy follow the same principle as a bicycle pump, only the movement of the piston is produced by the action of a Biella and a crankshaft.
Specifications, keys to choosing an air compressor
When choosing air compressor we must pay attention to the requirements of the application or the pneumatic tools we are going to use. They are essentially two: working pressure (bars) and liters per second or per minute. Depending on these two factors we will have to choose a more or less powerful compressor.
Compressed air pressure (bar)
If your pneumatic tool, for example, a stapler or an autograph, requires 6 pressure bars to operate, you will have to purchase a compressor that works at least 6 pressure bars. But you can also choose an 8, 10, 11 bar compressor … because thanks to the pressure gauges you can adjust the desired working pressure. In other words, a 4-bar compressor will not be able to operate at 6 bars, but one 8-bar compressor will be able to do so.
Liters per second or per minute, compressed air flow
At this point, things get complicated because many circumstances influence the measurement of airflow. For example, a compressor does not work the same in a warm environment as in a cold one: if we measure the liters per second at 35 degrees we will get a very different figure that if we do it at 20. This leads to certain misleading distortions in the specifications of some compressors.
How is it possible for such a cheap compressor to produce more liters per second than a compressor of a well-known and more expensive brand? Because the specs have been made up, which is not exclusive to the compressed air world. From the lumens of a projector to the chipset of a smartphone, there are always low-cost versions on the market with features that supposedly surpass those of the high end.
To give us some clarity on this airflow is the “FAD”. The fad (Free Air Delivered) is a magnitude, a standard, to measure the amount of air a compressor produces. To speak of FAD, the flow rate must be measured under certain environmental conditions, usually in a laboratory, which ensures that neither temperature nor any other factor distorts the amount of air supplied.
Safety, important for choosing an air compressor
It is important to note the current rules for air compressors. The regulation of pressure equipment and its additional technical instructions (Royal Decree 2060/2008, December 12) establishes that some equipment must be legalized and registered with the Ministry of Industry. Moreover, a large part of the compressors that we can purchase on large surfaces are subject to this standard and must be periodically reviewed by qualified professionals.
The rules apply to almost all air compressors on the market and although very few people at home legalize their compressors, which they have purchased for specific tasks, they should.
The point is that if there is strict regulation it is because air compressors are not toys. It must be understood that they are pressure air tanks after all. Which, in the worst and most unlikely of cases, can explode. It is not necessary to dramatize, just to understand the risks posed by these tools, just as we understand that chainsaws, circular saws, and other similar machines must be handled with respect.
Where does this lead us? Well, it’s good to bet on recognized brands, with a solid track record in the manufacture of pressure equipment, and not just look at the price. What can we expect from a super-cheap air compressor? Certainly not a long service life, no stable working pressure, no promised compressed air flow, no technical service near you, no spare parts, no guarantees of any kind…
So how to choose an air compressor?
To choose air compressor we first need to know which pneumatic tools we are going to use and look at the working pressure and compressed air flow required (in liters per second or per minute, ideally FAD). After that, we only have to investigate which machine is best suited to our needs, but remember:
- That the working pressure of the compressor must be at least the same as the tools we are going to use.
- That compressed air flow can be tricky. FAD, which is a standard magnitude measured under laboratory conditions, is the only 100% reliable figure.
- Which, sometimes, more is more. Bet on recognized brands, with a track record, that use top quality materials, that offer guarantees … beyond a cheap compressor that will last you one or two news, we are talking about safety, which is always the most important thing.