Air compressors are an essential tool across industries. From roller coasters to snow machines, air compressors can be used for a plethora of jobs. Not only are they used commercially but are a valuable tool for those budding DIY junkies. Jobs such as spray painting and blowing up tires require one of these machines.
But for those will little experience, how are we meant to make the right decision when purchasing this piece of apparatus? Direct Air has put together a handy guide on air compressors so we can all gain a better understanding of the workings of these and to guide us into making the right purchase the first time.
Air compressors date back to the 19th Century, and Air is considered as the fourth utility after water, gas and electric. They are affordable, durable, and if the initial investment is made, they require minimal repair and maintenance.
Piston Compressors, Scroll Compressors & Rotary Screw Compressors.
Rotary screw air compressor equipped with a CFC. Source: Wikipedia
The two most common categories of compressors are the scroll (piston) and rotary screw (reciprocating).
Scroll compressors are a form of piston compressor. They are easily available and are the most affordable. They work by the piston drawing down and changing the pressure in the cylinder, which in turn forces open the cylinder door through the creation of a vacuum.
Air is drawn in, the piston then travels back upwards, once again changing the air pressure and forces Air out at a higher-pressure point. The name ‘scroll’ is received from the reciprocating pattern it then follows.
These machines can cool down quickly and have high energy efficiency, but they come at a higher initial cost. Rotary screw compressors work in a very similar manner to the piston but the reply of rollers for compression.
Rollers are placed in the central shaft, with one side in constant contact with the wall. These rotate at an extreme speed causing Air to be drawn in and out at a higher pressure.
These have a good power capacity, are easy to maintain, and are lower in cost. They do, however, have limited cooling abilities and require more frequent maintenance checks.
Low Noise Air Compressors
The most important element when choosing any tool is your own safety. Prolonged exposure to high decibels can cause long-term damage to your hearing.
Consider investing in a low noise air compressor to reduce any issues. Typically, these reduce noise to 40dB, which is far below what is considered the safest decibel of 60dB.
This is achieved by an acoustic chamber added to the machine to store noise. Electrically powered air compressors rather than gas-powered are also quieter machines.
Oil-Free and Oil-Based Air Compressors
Like all equipment, your air compressor requires some form of maintenance.
All compressors require lubrication in order for Air to be drawn in effectively and safely. This can be achieved with the use of oil or a non-stick coating, usually Teflon, within the cylinder.
Oil-based tend to be more costly and heavier machines due to extra elements. The obvious oil top-ups can also add to the cost. However, oil-free compressors will eventually become subject to age as these non-stick coatings will wear away over time.
Therefore, oil-free is best suited to small scale jobs within DIY. They are also used in the food and pharmaceutical industry as there is no worry of contamination from oil.
Single and Dual-Phase Air Compressors
Single and dual-phase compressors work in a very similar way.
After Air is drawn into the cylinder, it is then compressed by a single-piston movement. Once compressed, it is then sent to a storage cylinder. This is at a rate of 120 PSI.
The dual-phase has one extra step. The Air is compressed, then sent to another cylinder. Within this second cylinder, the Air is compressed a second time. This is at a rate of 175 PSI.
As these work, in the same way, they can be applied to the same tasks, but as single-phase tends to be smaller and more affordable, they are usually the best choice for home use.
Fixed and Variable Air Compressors
The main difference between these two forms of air compressor is how the machine gets its power. A variable-speed compressor (also known as VSD or VFD), automatically adjusts the speed of the motor in relation to the demand for Air.
This is achieved with a convertor. This converts the power to AC power and then in DC power using diodes. The capacitor then cleans the AC and uses a transistor to convert to DC; these switches control the frequency of the power sent to the machine.
In return, this gives more accuracy over the machine. Less power is used and therefore is the most cost-effective and better for the environment. Fixed-rate air compressors send a contact stream of power to the machine. These are less energy efficient but are easier and cheaper to maintain.