In our modern world, we use air compressors to power a huge range of machinery, processes and tools. The most obvious examples lie in construction, with tools like nail guns and welding kits. However, compressed air is more ubiquitous than you might imagine — it is also the driving force behind many diverse industries and has shaped the modern world to an unexpected degree.
The most common image that comes to mind is the squat, pot-bellied little red tank that sits alongside those doing construction work, but air compressors also have a broad range of sizes. These compressors perform the same basic function regardless of size, and they are responsible for most of our greatest construction feats in the last century.
In this article, we will discuss what an air compressor is, what it does and how it is engineered to perform its job. Additionally, we’ll take a look at the different parts and components of an air compressor that add up to the whole product. You’ll gain an idea of what ownership of an industrial air compressor looks like and what maintenance may be required on it over time. We’ll end with some examples of different air compressors and what you should look for when purchasing one.
What Is an Air Compressor?
An air compressor takes air from the surrounding atmosphere and, unsurprisingly, compresses it. It does so using a motor and a series of parts. This air collects in the storage tank where it waits for tools to use it. In some cases, an air compressor provides air that does work directly, such as blowing metal shavings off a workstation or filling a tire. But more typically, it will drive a hammer or perform some other mechanical work, which changes its role to that of a power source.
Thinking of an air compressor as a source of power is useful in understanding its popularity in mechanical applications. As an example, consider an automated arm in a car factory that is used to punch holes in sheet metal. The arm itself is operated electrically, but the hole-puncher at its end needs to employ a great deal of torque in a short period of time.
Whereas it might require a cumbersome motor to perform this function via electricity, compressed air can provide tremendous power with very few parts. A hose of compressed gas simply travels through the arm to the punching device, where it delivers the power to drive the hammer downward as needed.
Compressed air was, at one point, a candidate for powering our infrastructure — picture powerlines full of compressed gas instead of electric cables — but the idea failed to catch on. Regardless, compressed air was of undeniable use in many mechanical applications. Its ability to cleanly transfer energy to different tools made it valuable to construction and factory work. In fact, many argue that compressed air is the key driver of the modern, automated factory assembly line. It is still the most elegant form of power available for performing high-impact operations that need to reload quickly.
It is critical to lay a foundation for understanding air compressors by first understanding how they work. Luckily, air compressors’ design is mercifully simple. Before we dive into the applications and industries air compressors are used in, let’s take a look at how they operate.
How Do Piston Air Compressor Motors Work?
Air compressors operate under the same basic mechanical principles as most other engines, but they are not as complex. A compressor’s motor has a streamlined and effective design. Some models utilize impellors to increase air pressure, but the most common air compressor model uses a reciprocating piston. This piston makes use of the fact that if a constant mass of air is squeezed into a smaller volume, its pressure will naturally increase. The reciprocating piston is a perfect tool for this job, as it is continually creating alternating high- and low-pressure environments within its chamber.
The rest of the motor is reminiscent of the internal combustion engine. There are cylinders, a crankshaft and a piston, which is linked to the crankshaft via a connecting rod. The crankshaft delivers power to the rest of the motor, and it is powered by either electricity or gasoline. The cylinder is where the mechanics of the air compression system begin to reveal themselves — on the top of it lies a valve head, which has both air intake and outlet valves. These are simple discs of metal that allow air in and out of the cylinder.
As the piston moves downward, this creates low pressure in the chamber above it. In response, air naturally flows in through the intake valve and fills the chamber, creating standard atmospheric pressure above the piston as it comes to a stop at the bottom of its cycle.
When the piston reverses its direction, this process reverses. The pocket of air at atmospheric pressure suddenly grows hotter and denser, increasing its pressure and pressing the intake valve firmly sealed. The outlet valve, which opens under the increasing pressure from the rising piston, then lets the air escape into the holding tank.
How Do Rotary Screw Air Compressors Work?
The most elegant form of air compressor is the rotary screw compressor. Instead of using pistons, this model uses a set of large, helical screws with interlocking threads to move air downward into a high-pressure holding tank. As the pockets of air are forced downward, the pressure in the holding tank increases.
This type of compressor is more complex than a piston compressor. The tolerances that must be achieved to make the interlocking threads airtight require extremely precise machining. As a result, these compressors tend to be more expensive. The tradeoff, however, is a quieter compressor that provides a continuous output of air at full power.
Its design makes the rotary compressor useful for tools like jackhammers, as well as other equipment that needs a higher continuous output of air.
How Do Air Compressor Tanks Work?
As the reciprocating piston or rotary screws continue compressing air within the cylinder, this air escapes through the outlet valve and enters the holding tank. Note that if the holding tank is unpressurized, the compressed air will quickly disperse to fill it — no great amount of pressure is necessary for it to do so. With each subsequent cycle of the piston or rotary screws, more pressurized air is forced into the tank.
It’s when the pressure within the tank increases to a high level that the effectiveness of the machine becomes truly evident. At this point, the air within the holding tank is under pressure and ready for any opportunity to escape. The tightness of the rotary screws’ threads ensures that air continues to move into the tank and not out of it. The pressure within the threads is still sufficient to move air, even as the tank’s pressure increases dramatically.
Tanks are preset to hold a certain amount of pressure before shutting off. This setting gives the motor a chance to cool down and ensures that the tank is never over-pressurized — although, if the pressure switch fails for some reason, there is an emergency escape valve built in so that the tank will not rupture. Additionally, there is typically an unloader valve that relieves the tank of its pressure after the compressor is switched off.
The main pressure switch is typically set to a limit of around 125 psi for many air compressors. However, tools often do not require this much pressure. A pressure regulator, located on the hose itself, allows users to dial in the pressure to accommodate whatever tools they are using. Two gauges, one before the regulator and one after it, monitor the air pressure in the tank and the air pressure going to the tool.
How Are Air Compressors Rated for Power?
As with motors, air compressors typically display a horsepower rating, which refers to the power of the motor itself. In reality, it’s not the most useful metric — much more useful is knowing how many cubic feet per minute, or cfm, an air compressor can deliver into its tank at a certain pressure.
Atmospheric pressure plays a large role in how fast air can enter a tank. Atmospheric pressure affects how much force is applied to the tank and how much air is available to compress, so manufacturers agreed to used standardized atmospheric pressure criteria as a common base of reference. Manufacturers calculate their cfm rates at 68 degrees Fahrenheit, with 36 percent humidity and air pressure at sea level. They refer to this rating as standard cubic feet per minute, or sfcm.
Another rating is the pounds per square inch, or psi, that an air compressor can sustain in its tank. This measure indicates what tools the machine can power. Additionally, a rating called displacement cubic feet per minute is used that is the result of the motor’s rotations per minute and the displacement of the cylinder multiplied together. Displacement cubic feet per minute is a useful measurement for finding out a motor’s efficiency.
Air Compressor Parts
Air compressors are, as we have seen, relatively simple devices. Let’s take a look at the main components you will be dealing with in using them:
- Holding tanks: The holding tank stores pressurized air. The more air you use — namely, the bigger and more numerous your tools — the larger tank you’ll need to supply the needed air. The size of the tank is important, but it must be chosen in conjunction with a motor of sufficient power and rate of cubic feet per minute. Holding tanks are specially engineered to safely contain high pressures without risk of rupture or explosion.
- Air filters: The air that enters the motor to be compressed must be free of particulates, and the air filter is what performs this task. If enough dust, dirt or debris enter the system, it can clog up the valves and wear out the rotor screws. You will need to replace air filters regularly to ensure the longevity of your air compressor.
- Belts: As with most engines, a belt transfers energy between different moving parts. In doing so, it undertakes various forces, from strain to flexing to tension. Belts will periodically need to be tightened and/or replaced.
- Check valves: These valves keep air in the tank when it is full. If your tank loses pressure, there’s a chance your check valve needs to be replaced. These valves can lose their effectiveness due to debris or moisture from the tank, which can cause them to rust and corrode. Check valves often connect to a bleeder tube, which carries air to the unloader valve. If you feel air coming out of the base of the unloader valve, it could be because of your check valve.
- Drain cocks: The drain cock, otherwise known as a drain valve, is typically located on the underside of an air compressor tank. As compressors fill and empty, it’s normal for moisture to build up inside them. The point of a drain cock is for the user to unscrew it and let the moisture out. Consequently, the valve can become plugged with dust and debris, which means it may need to be replaced. Be sure to use the drain cock’s air release valve to release air pressure before attempting to remove the piece.
- Air line hoses, hose reels and fittings: Air compressor hoses are designed to safely contain and transmit pressurized air over distances to different tools. As they are heavily handled and used over time, they will need to be replaced. Hose reels are spool-like spindles for wrapping and storing hoses when they’re not in use. Fittings must also perform an important function, as they link the hose to the tools and valves without allowing air leakage.
- Air line manifolds: Air line manifolds are optional parts that allow you to hook several different fittings onto your air compressor. They can replace multiple valves and greatly simplify operations.
- Air compressor moisture filters: As may be evident by now, moisture buildup is an issue in air compressors. A moisture filter is put in line between two hoses and removes moisture from the air stream, thereby reducing the risk of rust.
- Pressure switch: This part is one of the most vital components of an air compressor. It turns the compressor on and off when it meets pre-set minimum and maximum psi limits. Note that pressure switches are typically manufactured with a pressure preset, meaning yours should be appropriate for both your air compressor and the tools you wish to power with it. Air compressor pressure switches need to be replaced if the air compressor no longer engages and disengages when it’s supposed it.
- Pumps: The pump is the heart of the air compressor, as it contains the cylinder or cylinders and pumps air into the system. It also contains a fan to help dissipate heat, which serves to cool the air before it reaches the cylinder — this process means more air will enter the chamber, as lower temperature translates to a higher density. These are available in single-stage and two-stage units. Two-stage units pressurize air in two different screw sets, which bring air to successively higher pressures.
- Pressure regulators: Pressure regulators are one of the best ways to protect and optimize pressure to your tools. Regulators allow you to use an air compressor with higher cubic feet per minute than needed for your tools, giving you the capability to adjust it after it exits the tank. These regulators are compatible with both portable and stationary air compressors.
- Air safety relief valves: These safety relief valves are the unsung superheroes of the air compressor world. In the event of a pressure switch failure, they’re the last defense against tank rupture. Ensure that your safety relief valves are functioning properly and have not accumulated rust. Never replace them with plugs.
- Transfer tubes: Transfer tubes move air from one part of the compressor to another. These tubes are typically made from braided steel or nylon, both of which are safer than the copper used to make older tubes. Copper tends to crack under stress from the compressor’s vibrations.
- Pilot unloader valves: These valves are perhaps the most versatile devices on an air compressor. They engage the engine’s idling, remove air from the tank when its pressure reaches a maximum setting and can even make oil usage more efficient by equalizing pressure across the pump and check valve.
As mentioned earlier, air compressors have quietly — or perhaps not so quietly — revolutionized modern manufacturing. Their ability to produce usable, easily transferable energy makes them useful in an increasing number of fields. Here are some of the industries that utilize them most often today:
- Aerospace: The aerospace industry emerged at the beginning of the twentieth century, but the mass manufacturing of commercial, military, research, private and other air and spacecraft really took off closer to World War II. Manufacturing airplanes is one of the most intensive and productive industries worldwide, as it accounts for so much collective output. Air compressors are an indispensable tool for aircraft manufacturing, as they rely on efficient, precise and high-powered tools to assemble their chassis and parts.
- Automotive: Henry Ford initiated the assembly line method in the automotive industry, but it was compressed air that perfected it. The manufacture of cars relies on compressed air for tools such as drills, nut runners, angle wrenches, screwdrivers, pulse tools, air hammers, impactors, cutting tools, ratchets, sanders, scalers and much more. Compressed air is a necessity in every type of automotive business, whether it’s a smaller auto shop or a large-scale manufacturing plant.
- Manufacture of chemicals: Chemical manufacturing has some of the tightest precision tolerances in any industry. This standard is because the ratios of chemicals must be exact to ensure safety, which requires accuracy on microscopic levels. Air compressors have become extremely useful in fermenting and aerating bacteria, assisting oxidation, performing air separation, producing resin beads, transporting materials pneumatically and performing safety protocols.
- Electronics: Electronics require clean, compressed air for sterility and effective production. Air compressors are the industry’s preferred tool to clean and remove dust from components. Their use lets companies lower their bottom lines and reduce resource waste in manufacturing their products.
- Food and beverages: The Food and Drug Administration and U.S. Department of Agriculture both impose stringent sanitation requirements on food and drinks. Air compressors are used for shaping food products, as well as for their cans, labels, lids and virtually every other part of their packaging. These machines are valuable because they provide a versatile set of operational capabilities while also maintaining a high level of hygiene control. Bakeries also use compressed air to mix their batters.
- Manufacturing: Most manufacturing is either automated or heavily reliant on human-operated compressed air machinery. Compressed air powers pneumatic tools, impact wrenches, rivet guns, sanders, brad nailers, grease guns, hot melt dispensers, sealers, spray paints, power drill feeds and more. Manufacturing plants also use compressed air to cut through metal with shears, inflate tires, blow dust away and operate a number of high-precision devices.
- Glassmaking: Glass begins with sand, limestone and soda ash, which are stored after being inspected for quality. Then, an air-powered device feeds the matter into a furnace — heated by compressed gas — to form a molten soup. The molten glass then enters an air-powered formation machine, which shaves off the necessary amount of material for whatever item is being made. This material is then stamped into the proper shape using another air-powered machine. To avoid stresses forming cracks in the glass from uneven cooling, the manufacturer reheats and cools these glass items using compressed air. Nearly every part of this manufacturing process relies on air compressors.
- Medical industry: Hospitals need different air systems for different purposes. For example, a hospital may require a medical air supply, a laboratory air supply and a pneumatic air supply. Oil-less air compressors are again used to ensure air quality and a lack of contaminants. Because air compressors provide such reliable pressure output, they are trustworthy for highly important tasks associated with hospitals, where lives are on the line.
- Metals and metallurgy: When something solid needs to be melted and reshaped, it is almost certain that compressed air will provide the heat. Compressed air historically came to replace the bellows, which for millennia provided air to produce hot flames. Many of the same tools used in other manufacturing processes are also used in manufacturing metals, as well as tools like diaphragm pumps, chipping hammers and rammers. Oxygen for welding is also compressed to be stored in tanks.
- Mining: Mining has seen a lot of transformation in the last century. It used to be a somewhat ramshackle operation that frequently destroyed entire landscapes, but new regulations have spurred many improvements. Modern mining equipment not only bores through the earth but also is responsible for cleaning up after itself — and does so using air compressors. Not surprisingly, machinery capable of blasting through solid rock also benefits greatly from the use of compressed air. Some mining tools include refrigerant and desiccant air dryers, centrifugal air compressors, breakers, diaphragm and lubrication pumps, chipping hammers and manual and pneumatic hoists.
- Plastics: Plastics are one of the most important materials in the world today. They shape our appliances, cars, packaging and devices. The birth of modern plastic came in the 1940s with the invention of polyethylene blow molding. A plastic glob is inflated like a balloon to assume the shape of its final form, and compressed air is the only option available to achieve it. With this method, plastic bottles were suddenly mass-producible on a scale that had been unimaginable years before. Compressed air delivers a precise amount of power, making it fine-tunable and perfect for manufacturing plastics.
How to Choose an Air Compressor for Your Business
Kaishan has the air compressor that is right for your business. Choosing the appropriate one depends on what tools you’ll be driving, how rapidly it will need to refill and what capacity you require. Here are some of the key qualities to look for when deciding on an air compressor to buy.
If a piece of machinery has to compress gas and ferry it through different moving parts without losing any of its pressure, you can be certain you’ll notice changes in quality. High-precision engineering ensures that your air compressor will not develop leaks, cracks or other deformities that affect its efficiency.
Leaks can also pose a danger to those working near the compressor, as they lead to ruptures. A low-quality air compressor will cost much more in the long run — a single, small leak in one can cost thousands of dollars per year in energy by itself. Make sure to invest in a machine that will operate for a long time and allow you to get the most out of your investment.
Your compressor should include software and a user interface for tracking analytics and performance. These allow you to stay ahead of any problems that may occur over time, and you’ll be able to optimize production, increase efficiency and address malfunctions.
If you purchase an industrial air compressor, you should be certain that the company you get it from provides timely, helpful technical support to get you back on track in the event of difficulty. They should view themselves as a business partner for as long as you own the compressor, helping you with repairs and maximizing the performance of the device.
High-Quality Compressors From Kaishan
Compressed air generates a higher torque than electricity, offers better safety and creates a system that is highly interchangeable between tools. Here are some of Kaishan’s industrial-grade products to choose from.
KRSP2: Two-Stage High-Efficiency Air Compressor 100–500 HP
This extremely efficient compressor offers a five-year main components warranty and a lifetime air end warranty in place for standard pressures. It includes a wye-delta starter, TEFC Marathon motors and low-sound enclosures, as well as a slow-speed drive air end with triplex bearings. This equipment grants a life expectancy of 300,000 hours.
This single-pass enclosed cooling system has a centrifugal cooling fan for high efficiency and low noise. Note that the KRSP2 has the best specific power in the industry, averaging 15 kW per 100 cfm. It comes with a two-stage 150 HP pump that operates at 890 cfm. Its password-protected touchscreen controller sequences 16 different machines, and it runs maintenance schedules, history and a fault alarm.
KRSP: Single-Stage High-Efficiency Air Compressor 20–500 HP
The KRSP also includes a lifetime air end warranty — which covers standard pressures — as well as a five-year main components warranty. It comes with premium efficiency motors, a low-sound enclosure and a wye-delta starter. This unit has a 150,000-hour life expectancy.
Like the KRSP2, the KRSP has a single-pass enclosed cooling system that has centrifugal cooling fans. It has one of the lowest specific powers available in the industry — as low as 16KW per 100 cfm. This unit includes a password-protected touchscreen controller that sequences 16 machines, maintenance schedules and history.
KRSD: Single-Stage Direct Drive Air Compressor 30–200 HP
This unit uses a direct drive system, which means no gears — but it does so with a reasonable price tag. It includes a five-year air end warranty in place for standard pressures.
TEFC motors, a wye-delta starter and low-sound enclosures are standard. The KRSD also comes standard with modulation and optional VSD. This system is cooled by a single-pass enclosed system with axial cooling fans. It also comes with a password-protected touchscreen controller that sequences 16 machines, a fault alarm, maintenance schedules and history.
KRSB: Single-Stage Belt Drive Air Compressor 10–50 HP
KRSB is a reliable and economical air compressor offering 10 to 50 HP in a single-stage system. It comes with a two-year air end warranty that’s for standard pressures, as well as TEFC motors, a wye-delta starter and low-sound enclosure. Its single-pass enclosed cooling system comes with axial cooling fans.
This compressor’s air end design is both dependable and efficient, and it comes standard with a belt guard and automatic belt tensioning system. It also has a password-protected touchscreen controller that sequences 16 machines, a fault alarm, maintenance schedules and history.
KRST : Single-Stage Belt Drive Tank-Mounted Air Compressor 7.5–20 HP
This 7.5 to 20 HP range, single-stage rotary screw air compressor is compact, reliable and efficient. Its five-year air end warranty covers operation with standard pressures. The compressor is tank-mounted and includes an optional oversized integrated dryer and air filter. It has a digital control panel, a large, slow-running air end, TEFC motors and a direct or wye-delta starter. This compressor is also quiet, with noise levels of 67-68 dB(A). It is cooled with an integrated aftercooler and cooling fan.
Why You Should Choose a Kaishan Compressor
Kaishan compressors have a proven track record of standing above the competition in value, efficiency, reliability and breadth of products available. Our air compressors are world-class and come with the comfort of knowing that technical support is always available. We pride ourselves on providing reliable compressed air while being a market leader in pricing.
We’re an engineering-based company that has large investments in research and development. We have been in business for 60 years and sell our products in 60 different countries. We have vertically integrated production and make all our own enclosures, air ends, tanks, frames, castings and coolers.
See our selection of products, which serve all sizes of operation and fit a range of budgets. Whatever air compressor you choose from us, you can be sure that it will be reliable, efficient and fully supported. We believe in engineering the future, and each one of our air compressors is a testament to this mission.