One compressor does not work for all machines or project types. The devil is in the variety, which makes air compressors superbly efficient and unreservedly reliable. The knowledge will certainly help you frame better decisions when choosing the right air compressor for the job. These ‘tools that use air’ have been around for a century and have evolved into diverse sizes, applications, and styles. Not only do they save money and time on projects, they are comparatively lighter than battery-powered cordless and standard electric tools.
No matter how different the compressor, as you will read below, they all share a common function. They use a given gas, namely air, and reduce its volume and increase its pressure as tasked to do so.
Rotary Scroll Air Compressors
Compared to the rotary screw, this one has fewer parts to work with. With this compressor type, internal scroll compression progresses when a fixed helical element and an orbiting one interact with one another. The air being drawn into the machine is thus slowly compressed and when this process is repeated over time, you have yourself compressed air that is free of pulsation. Featured in this compressor design is either an oil-less option or splash lubrication.
Rotary Screw Air Compressors
This type enjoys a central chamber in which a pair of mated helical screws have room to work. The chamber’s pressure levels go up (increase) as these dual screws perform standard rotations. The result is a marked reduction in air volume. One disadvantage has been observed, though, namely the generation of heat and friction that in turn demands a full-system cool down; otherwise, efficiency and functionality are sure to be affected. This is where lubrication comes in but you will need to get the compressed air and oil apart before applying said lubrication.
Rocking Piston Air Compressors
Consider the standard piston-based unit. Rocking piston air compressors are a variation of them; a reciprocating compressor, basically. However, there is one difference, namely a reciprocating interaction is responsible for increases in pressure; this process is carried out by a connecting piston and rod. Due to the presence of non-metallic rings in these types of compressors, no splash lubrication is even required. They also boast valves with lower pressure capabilities and are generally smaller.
Centrifugal Air Compressors
Most of the compressors we are detailing work on the principle of positive displacement, except for this variant. Its modus operandi is dynamic compression that causes increases in air pressure by incrementing velocity. Thanks to the presence of an impeller, you can see rotations per minute attaining the 60,000 mark in centrifugal compressors. The first to speed up are air molecules that a diffuser then works on slowing. There are intercoolers integrated into these compressors to help cool off the air. Also, they extract built-up fluid(s) in the process; the last thing you need is moisture compromising the motor, so this is a good thing.
Rotary Sliding Vane Air Compressors
The primary component in this air compressor variant is a motor that, going into detail, is seen to possess blades, a stator, and rotor. With an intake port present at one end and an exhaust port at the other, the simplified design has the stator sitting between the twain. Inside this rests the rotor. When the rotor begins to turn, the volume of air on the side of the intake port sees a gradual increase while the exhaust end shows a gradual decrease.
Moving in an outward fashion, the blades (vanes) hold their positions against the stator’s walls; a result of good rotational acceleration. If you want to reduce or eliminate friction, using lubricants is a good idea. It also helps plug up leaks (prevents them from happening). Just as you learned with rotational screw compressors, even this one needs the oil and air to be separated before lubricant application.
Reciprocating Air Compressors
This is the commonest air compressor type on the market. You can call them either piston or reciprocating air compressors; the terms mean the same thing. In keeping with standards, this variant is no stranger to the positive displacement principle. Air is encouraged to enter the upper portion of the cylinder when the piston makes its move down. The pressure difference between the inner cylinder and atmosphere are at work to compress the air when the piston makes it way up again. Often, you will hear the term ‘single-stage compressors’ in reference to reciprocating compressors.
There is also another sub-type, a cousin of sorts, namely the two-stage compressor. Even these suck in air from the atmosphere but work with dual cylinders instead of one. In phase one, an intermediate pressure is attained via air compression after which surplus heat is removed. The air is then allowed to flow into an adjacent cylinder where it is tweaked to reach a particular compression value.
Belt-Drive Air Compressors
This is one of two compressor types that depend on ‘drive’. Electric and gas variants alike use a belt drive system owing to its superior versatility when it comes to matching power source and compressor load; the ensemble should also be sold at a good price (as low as it can go). For the operator belts to function within the safety guidelines, you need to rely on a protective cover.
Direct Drive Air Compressors
This is the second compressor variant that uses ‘drive’. Because these are small and need very little maintenance, oil-free portable air compressors often come under this design. The power source can be linked to either a direct-coupled compressor or a flange-mounted one. In keeping with its name, these compressors do not need to fill the air tank before delivering compressed air; they go direct.
Splash Lubricated Air Compressors
The type of lubrication used determines this compressor type; there are three sub-types in this regard, the other two are detailed below. A connecting rod dips into an oil bath. The bottom of this rod has an oil dipper. This component serves to ‘splash’ the lubricant onto bearings and other mechanical segments to help reduce friction and over-heating.
Not only is this the commonest option called upon from this category, they show much less wear and tear let alone heat increase as opposed to oil-less compressors. Non-level surfaces can pose a hassle, though. While heavy-duty applications love working with this compressor sub-type, they do demand plenty of maintenance.
Oil-Less Air Compressors
Thanks to bearings that are permanently oiled, these variants need no lubrication whatsoever. Aside from demanding little maintenance, they have also proven to work at low temperatures and have no problem with uneven surfaces. However, they do heat up more than usual and are not recommended for heavy-duty work.
Pressure Lubrication Air Compressors
With an oil pump to supply oil, important compressor segments receive ideal lubrication via crankshafts, piston bearings, and cylinder walls. It does not come cheap, but sure does bring high efficiency to projects.
With all this in mind, you will be better placed to ask important queries pertaining to air compressors and why you need different variants for sundry tasks and project requirements. Compressor reviews will also make more sense, because you know how the machine is being matched to the purpose.