What Is An Air Compressor?
An air compressor is a machine designed to transform power into potential energy by having the compressed or pressurized air stored in the machine. As the best air compressor for power tools achieves to compress additional air into a storage tank, the pressure increases. Each air compressor has its limit set for pressure. Engineers of air compressors ensure that it will stop adding air and pressure in the storage tank as soon as the limit was met, thus having it stored at that state until the moment to use the compressed air is needed.
The most common compressor one can find in any hardware is the air compressor for tires and/or balloons. Anyone can use it by simply plugging to a power source, turn in on and plug the air fill tube and then your tire or balloon shall be automatically filled with air. The most complicated air compressor however is the one being used in factories or huge plants for gas or liquid conversion for hundreds of applications.
Low-pressure Air Compressors
The low-pressure air compressor can cover tool or machine pressure requirement of up to 150 psi (pressure per square inch). This can suffice the common pneumatic tool requirement found in home workshops.
Medium-pressure Air Compressors (the best air compressors for power tools)
The medium-pressure air compressor can cover tool or machine pressure requirement between 151 psi (pressure per square inch) to 1,000 psi. This can suffice the simultaneous use of several common pneumatic tool requirement found in home workshops.
High-pressure Air Compressors
The high-pressure air compressor can cover tool or machine pressure requirement of above 1,000 psi (pressure per square inch). This can suffice simultaneous use of machines found in larger workshops, factories or plants.
How It Works
Simply put, the air compressor works by reducing the size of the space that contains air to increase air pressure, thus the name compressor come from. Most air compressors have air tank to hold a preset pressure capacity or range of a specific quantity of air. The stored pressured air can then be used according to needs.
Most air compressor models used by woodworkers, mechanics, contractors and home owners for home workshop, basement and garage is the reciprocating compressor which is discussed on Chapter 2. The compressed air is used to induce the air tools. To maintain the pressure of the tank automatically, its motor turns on when the pressure becomes low and turns off when the required or pre-set pressure is met.
The Basic Process
- Air at its atmospheric pressure is vacuumed in the air compressor machine.
- The air then fills the machine and triggers positive displacement or piston to compress the vacuumed air.
- The air is then reduced in size or volume.
- As the air is reduced in size or volume, air pressure increases.
- The reduction of air in size or volume, also known as air compression shall continue until the tank detects its limit.
- The compressed air is now stored and ready for use.
- As soon as the compressed air is used, steps 1-6 shall automatically commence.
If you intend to use air compressor for spray painting, pneumatic sander, pneumatic nail gun, sandblaster and other tools that require oil-free air for your application, choose air compressor types of models that produces oil-free air.
Air compressors that produces oil-free air usually have permanent lubrication on its internal parts that works as air compression takes place. This way, it can produce 100% oil-free air to keep your work from having oil blasts caused by the oil-lubricated internal parts of the oil-lubricated air compressor along the process of compressing the air.
Uses of Air Compressor
Over a hundred years, air compressors are utilized for its known safety, flexibility and convenience of use. It is therefore not a surprise at all to know that air compressors are widely used from a single household to large factories for many reasons.
Now even if you already know which specific compressor you currently need, it is still notably worthy to know whether in which things you can apply the use of these compressors. You may after all use it for other needs in the future!
Below are the common uses of air compressors:
Air compressor is widely used on balloon business. You can inflate a single balloon in few seconds using an ‘electric balloon air pump’ or air compressor pump. Compared to manual balloon pump, it will take you a minute to inflate a single balloon with so much effort and strength in the long run.
Use of electric balloon air pump can allow you to inflate hundreds of balloons in an hour. Not only that, you save your hands and fingers from straining when using pump. You can save a lot of time too!
For Other Inflatable
Yes, you name it! Beach ball, inflatable life buoy, inflatable kayak, inflatable swimming pool, inflatable playground and the list goes on. Air compressor is a breeze on electric air pump used to inflate them all.
For Water Pump
Air compressor is widely used for pressurized water pump or more popularly known as ‘pressure washer’. Compressed air causes the water to be released in a high pressure. Pressure washer is commonly used in cleaning home exterior dirt drenched surfaces such as driveways, patios, decks, exterior walls, fences, outdoor furniture, cars, motorcycles, boat and others.
Like inflating balloons, mattresses and other soft inflatable, air compressor is also used on inflating automobile tires. This has become a stable tool to inflate tires especially for tubeless type tires.
For Pneumatic Tools
Pneumatic tools nowadays are commonly used in workshops. They are air powered tools induced by compressed air equipped by air compressor. The most common pneumatic tools are pneumatic drill, pneumatic sander, pneumatic nail gun, sandblaster, paint sprayer, airbrush, pneumatic saw and many more.
Air compressor is used as well in oxygen tanks and even on centralized oxygen system in clinics and hospitals. Air pressure is required to compress air in tanks and to quickly deliver air (for centralized system) seamlessly.
For Industrial Machines and Power Plants
Air compressor has many applications for industrial machine and power plant utilization. It can be a requirement concerning force, gas, liquid and many more.
TYPES OF COMPRESSORS
Choosing the right type of compressor is as important as its function for your workshop. A certain job may not be done just because you have chosen the wrong type of the compressor. Without knowing the types, you may either choose air compressor that cannot do the job well or the one that is overkill for a small job.
The reciprocating air compressor is also known as ‘positive displacement’ or ‘piston’ compressor. It uses piston(s) in a reciprocating or back and forth manner inside a cylinder, operated by crankshaft which helps produce gases at high pressure.
The intake and exhaust are conduced by the two sets of valves. As the machine intakes a subsequent volume of air, the pistons of reciprocating air compressor reduces the said air volume. Lessened air volume is then converted to a higher pressure.
The reciprocating air compressor is widely used in the following:
- Cleaning dust
- Gas pipelines
- Small paint jobs
- Hand tools
- Chemical plants
- Natural gas processing plants
- Refrigeration plants
- Oil refineries
- Blowing of plastic PET bottles
Single-stage Reciprocating Compressor
The single-stage compressor is commercially available as type of reciprocating air compressor. It uses only one side of the piston (or one piston) to compress air. The reciprocating piston pulls the air into a cylinder which is being compressed by the single piston. The compressed air is then stored in a tank which will become the pressurized air when used. It is used in general for pressures within 70 psig to 100 psig.
It is made available to offer wide range of pressure and capacity such as air-cooled lubricated, air-cooled non-lubricated, water-cooled lubricated and water-cooled non-lubricated configurations.
Two-stage Reciprocating Compressor
The two-stage compressor is commercially available as type of reciprocating air compressor. It uses two pistons to compress air. Like the single-stage compressor, the one side of the piston (or one piston) compress the air. The reciprocating piston also pulls the air into a cylinder which is being compressed by the single piston. But the other piston (or the second, usually smaller piston) compress the compressed air to a higher pressure. Then the dual compressed air is then stored in a tank which will become the pressurized air when used. It is used in general for higher pressure requirements ranging from 100 psig to 250 psig.
Like the single-stage compressor, the two-stage compressor is also made available to offer wide range of pressure and capacity such as air-cooled lubricated, air-cooled non-lubricated, water-cooled lubricated and water-cooled non-lubricated configurations.
- Suitable for high pressures
- Comparatively economical
- Uncomplicated maintenance
- Very loud when operating
- Hot oil content (air piping)
- High outlet temperature (compressed air)
Centrifugal compressor is also known as ‘radial compressor’ for its radial design. It is a type of dynamic compressor which works at a constant pressure and dependency on inlet temperature changes and other external factors. This type of air compressor has become popular due to its capacity to produce high pressure discharge created by its dynamic displacement.
One of the key parts of a centrifugal compressor is the rotating impeller, also known as a sucking force producing rotor. Said rotating impeller has radial blades which pushes the air drawn from its center by centrifugal force. This causes a radial movement of the air which is then transformed into pressure by converting the produced kinetic energy by going through volute and diffuser.
It can be used within a wide range of application pressure requirements as it can be adjusted or controlled, thanks to its multi-stage feature. This becomes possible because of the continuous air flow through the compressor.
- Gas turbines
- Natural gas processing
- Natural gas pipeline compressor
- Oil refineries
- Chemical plants
- Air conditioning
- Automotive engines
- Diesel engine supercharger
- Diesel engine turbochargers
- Pneumatic tools
Single-stage Centrifugal Compressor
The single-stage centrifugal compressor is made up of a single rotating impeller, which is placed on the non-driving end of the shaft. It is called ‘overhung impeller arrangement’ for its beam design. It normally has the pressure or vacuum compression ratio of 3:1
Apart from it having only a single rotating impeller, what separates it from the multi-stage centrifugal compressor is that produced air is totally oil free and surge free, which makes it better when it comes to efficiency.
Multi-stage Centrifugal Compressor
The multi-stage centrifugal compressor may consist of two up to ten rotating impellers. It can be arranged and configured in different variations according to the required flow path of an application. The temperature and compression ratio through each and every stage (from stage 1 to stage 10, or up to 10) are presumed to be constant.
Configuration of multi-stage compressor can vary from straight-through configuration, double flow configuration or compound configuration. Like the single-stage centrifugal compressor, the multi-stage centrifugal compressor also has the beam design but the impellers are placed between the radial bearings instead of the non-driving end of the shaft.
- Energy efficient
- Produces higher air flow
- Suitable for a relatively constant demand
- Most effective when running at full capacity
- Produces oil-free air
- Possibility of choke and surge
- Cannot produce higher compression ratio without multiple stages
- Requires unloading for reduced capacity
- Requires clearance monitoring for high rotational speeds
- Requires special bearings for high rotational speeds
- Specialized maintenance, daily and weekly
Rotary Screw Compressor
The rotary screw compressor rise to prominence for its intricate mechanism design using two rotors of helical screws to compress air. Said rotors in helical or spiral screws, namely male and female rotors, inside the machine are strategically placed in a parallel position with a narrow gap and spin in adverse directions without clashing each other.
This design allows air suction between the rotors. And as the rotors continue to rotate, sucked air gets transferred to the pressure side of the machine. The air suction happening from one end to in between the rotors to the pressure side of the machine keeps on going as both rotors keeps on rotating. This process when uninterrupted can go on smoothly and quietly since the rotors are touching each other.
- Other applications that require enormous volume of high air pressure
Oil-injected Rotary Screw Compressor
The oil-injected rotary screw compressor is more popular than the oil-free rotary screw compressor due to its cheaper cost. So how does it work?
While air compression takes place, oil is directly injected into the compressor component that compress the air. Oil is then removed through the oil separator to produce clean compressed air. However, even if oil is removed and stays inside the compressor only about 99% gets to stay and the other 1% usually pass through the oil separator which is called ‘oil carryover’.
The oil carryover can either be helpful or not. Generally it is helpful to the internal components of the compressor to prevent rust overtime. This lessens the need for maintenance and allows the machine to run efficiently. But if you need 100% oil-free air, use of this type of rotary screw compressor is definitely not for you.
Hey, there is no need to worry! The rotary screw compressor still has another type that will perfectly fit your 100% oil-free air requirement and here comes the oil-free rotary screw compressor!
Oil-free Rotary Screw Compressor
The oil-free rotary screw compressor was developed to cater the air compressor requirement of some industries which is 100% oil-free air. Since it has the capacity to produce 100% oil-free air, its components to make it happen has made its price tag higher than the oil-injected rotary screw compressor.
This type of rotary screw compressor is made for the specific and special need of 100% oil-free air for select businesses. It works almost the same like the oil-injected rotary screw compressor but without the use of oil, of course.
There are two stages done in compressing air when using oil-free rotary screw compressor. The first one compresses the air up to mid-level of compression which becomes burning in temperature. It then passes through an intercooler chamber prior to entering the second stage. The cooled air now enters the second stage to have is compressed in the highest level of compression.
Compared to the oil-injected type, the oil-free rotary screw compressor operates a bit noisier. And since it operates without oil, maintenance is vital to prevent it from rusting.
- Reduced noise for ear safe operation
- Relatively lower heat compressed air
- Has better energy efficiency than reciprocating compressor
- Can produce huge volume of compressed air
- Highly dependable for extensive use for a longer time
- Pricier than reciprocating compressor
- Prone to form water condensate
- Prone to rusting, needs more frequent maintenance
- Complicated mechanism design
Scroll compressor is highly popular to those who only need a low volume of compressed air. It is also known in many names such as ‘scroll pump’, ‘scroll vacuum pump’ and ‘spiral compressor’. From its alias name ‘spiral’, the scroll compressor is mainly composed of two spiral components.
Its first spiral component (stationary scroll) does not move or static because it is in a fixed position. The second spiral component (orbiting scroll) moves in tiny extraordinary circles inside the first spiral. The second spiral will require about two and a half full turn around the first spiral in order to produce air pressure at the center.
Since it has lesser moving parts compared to reciprocating compressor, together with lesser torque variation, the result is a quiet and smoother operation. It uses air intake filters keep it from developing rust since it operates without oil. This makes this kind of compressor about nearly maintenance free. But these features makes it price tag soar higher than the other types of compressor.
This specific compressor operates in an ultimately quiet manner. If you are looking for a quiet operating compressor, produces oil-free air and with a high volume of compressed air, scroll compressor is not for you. But hey, oil-free rotary screw compressor might be just perfect for you!
- Drinking water treatment
- Laboratories requiring oil-free air
- Computer peripherals
- Process controls
- Home health care
- Optical equipment
- Medical and Hospital
- Pneumatic controls
- Residential HVAC heat pumps
- Residential HVAC air conditionings
- Some automotive air conditioning systems
Single-stage Scroll Compressor
The single-stage scroll compressor operates in one speed. This can provide ample compressed air needed to completely cool or heat a single household.
Two-stage Scroll Compressor
The two-stage scroll compressor operates in two speeds. The two speed capacity allows a lower yet more efficient speed which aids in removing excess humidity caused by the suctioned air. This helps the compressor to save more energy, having it equipped in operating to its full capacity when holding temperatures steady is needed.
- Minimalist mechanism design
- Impressive small and compact exterior design
- Ultimately quiet when operating
- Nearly maintenance free
- Quite expensive
- Very hot compressed air in comparison to other types of compressors
- Low flow and cubic feet per meter (cfpm)/cubic liter per minute (clpm) capacity
- Defective scroll component means a higher chance of changing the whole machine
Things to Consider When Buying the Best Air Compressor For Power Tools
Sometimes, bad choices occurs because of a single detail you have not known or have forgotten or worse, neglected. Remember that most of these things are commonly neglected by many having bought the wrong air compressor as a result. To avoid this problem, read on this Chapter to help yourself solidify your decision on choosing the best air compressor that you actually need.
Avoid buying the wrong one! What Tools or Machines to Use
The first thing to consider on choosing the best air compressor is to identify the specific tools or machine which is/are needed for use of air compressor.
- Which tools or machines shall be often needing air compressor?
- How long shall a particular tool or machine be used on each application?
- Will there be any tools or machines that shall be used at the same time?
- Determine the process of your work. Verify the time interval of using each tool or machine for air compressor.
Answering the above questions shall be beneficial on the next section of this Chapter.
Know What You Need
Knowing what you need when choosing air compressor is not as easy as choosing which matchstick to light when you open the matchbox. Though it can be as easy as which socks to buy for formal event, sports play and casual strolling.
This was said so because choosing air compressor requires details concerning the purpose of its application. So knowing what you really need is a vital process to address. Such information can either make or break the efficiency of your purchase and the productivity of your workshop project(s).
You may have read or heard these words upon searching on how to choose best air compressor:
“It’s not only the pressure, it’s also the capacity.”
Pressure is important but it is easy to address and always one among the top priorities air compressor buyer is likely to ensure. But the most neglected part is considering the capacity of the air compressor model against the actual capacity your work will be requiring.
The common dilemma of a wrong purchase is that the air compressor can provide the right and even more pressure but it declines at the middle of the work because the capacity of the air flow runs short. As a result, you have to keep on pausing on your work as you wait for the compressor to produce more compressed air. Clarified below are the expanded notations on pressure and capacity.
Pounds per Square Inch (PSI)
Pressure refers to the required amount of force for a specific application. You can check the specific required pressure on each tool or machine for air compressor applications. Pressure also refers to the strength of the air pressure. It is measured according to ‘pounds per square inch’ or PSI and also expressed in bars. Many say to keep this question in mind to easily remember to which pressure in air compressor refers to:
“How strong amount of pressure do I need?”
Which must be answerable by psi or bar measures.
The best practice to answer this question is to check the highest required pressure on the tools or machines needing the air compressor then use it as the median of the pressure capacity you will be requiring for the air compressor.
Cubic Feet per Minute (FCM)
Capacity refers to the capability of the air compressor to perform within a specific span of time. Therefore capacity is the length of time that air compressor can produce compressed air along with the correct air pressure as required by your work.
Capacity also refers to air flow being produced by the air compressor to your tool or machine. It is measure according to ‘cubic feet per minute’ or CFM, ‘cubic meter per minute’, ‘cubic meter per hour’ and/or ‘liters per second’. Many say to keep this question in mind to easily remember to which capacity in air compressor refers to:
“How much air flow do I need?”
Which must be answerable by cfm, cmm, cmh or ls measures.
The best practice to answer this question is to determine air consumption of all your tools and machines. Add them together and that should be the threshold capacity of your air compressor. This is the case to ensure that your air compressor can suffice the demand in the event that all tools and/or machines shall be used for air compressor at the same time.
Horsepower or HP is the amount of power the compressor motor produce.
Then why do I need a higher horsepower?
Simple, a higher horsepower has a higher capability to produce higher air pressure. Well, this applies only to those who need higher air pressure.
Size indeed matters! It is the tank that holds pressurized air for a longer time. Therefore, the larger the tank, it means the higher capacity for air pressure can be held.
Look for a higher tank size if you prefer a higher air pressure output, together with horsepower and air pressure itself.
Type of Power Source
There are three different types of power source to activate the air compressor. When buying air compressor, ensure that the model you have can run on whichever power source you intend to use.
The three types of power source available to activate or run the air compressor are:
- Diesel Air Compressors
- Petrol Air Compressors
- Electric Air Compressors
Though most of the air compressors nowadays are powered through electricity, still there are models that can be powered through diesel and petrol. This is especially made for those who intend to work in places where electricity could be scarce or when electric outlet for plugs are not readily available. And if your situation is just like this, make sure you don’t get the electric powered model.
Diesel Air Compressors
The diesel powered air compressor are generally portable and heavy duty. It can run outdoors even during the unfortunate state of the weather. This powerful and robust air compressor are expensive for initial cost. But since diesel has lower cost, the higher initial cost can be compensated in the long run.
However, diesel powered air compressor tend to emit fumes. It therefore has higher level of toxicity because of the generated fumes while working on air compression. And since it runs in diesel, expect the operation with higher noise. This is not recommended for use in closed environment, while ideal for use in open and large spaces.
- Less expensive operational cost
- Heavy duty
- More powerful
- Expensive initial cost
- Produces higher level of toxicity due to emitted fumes
- Not recommended for indoor or closed space usage
Petrol Air Compressors
The petrol powered air compressor are great alternative for diesel powered air compressor if you cannot stand the noise while operating and when you need a lower torque or power. This lighter air compressor are less expensive for initial cost. But since petrol has higher cost than diesel, you will end up spending more for petrol operating cost in the long run.
Petrol powered air compressors have cleaner emission as it operates to work on air compression. Unlike diesel powered air compressor, the petrol powered air compressor operates more quietly. It can be use in both closed and open spaces.
- Cheaper initial cost
- Cleaner emission than diesel
- Operates a bit quietly
- Can be used in both closed and open spaces
- Higher operational cost
- Lower torque or power than diesel
Electric Air Compressors
The electric powered air compressor is the most popular power source type for air compressors. It is because electricity are readily available to most households and workshops. However it can be not as powerful as the fossil fuel powered air compressors.
Electric powered air compressors have little to no fume emission, thus making it safest for toxicity. It can be portable in shape and size so you can transfer it from one place to another as needed but it limited only to places where electrical sockets are or can be available.
- Cheaper initial cost
- Little to no toxic fume emission
- Operates quietly
- Higher operational cost
- Lower torque or power than fossil fuel powered air compressors
- Limited outdoor usage
Oil-Free Vs. Lubricated
Lubricated air compressors are generally more durable than the oil-free ones.
But keep in mind that lubricated air compressors need regular maintenance to keep all its parts running smoothly and avoid getting rust. This process is actually what makes it more durable, the repetitive servicing of its parts. Since they are well maintained, it can withstand both indoor and outdoor spaces even during winter.
The oil-free air compressors however are for those who have little knowledge and time, and just too lazy to do maintenance. The internal parts of an oil-free air compressors are permanently lubricated in a way it won’t get rust and running tough. But the most important part here is that it produces oil-free compressed air output and if that is what your application requires, you definitely have to go for it.
Air compressors tend to heat up especially over longer time frame of use. Though heating up is normal to most machines during operation, it is safer for the people around it if it does not heat up that much. Also, any machine can work better if the heat inside is managed.
Look for air compressor with cooling capacity feature. These are cooling fins wrapped around a copper tube connecting the pump and the tank. This simple feature can make your compressor cooler or have managed heat, avoiding overheating and stopping your operation. Most of all, keeping your air compressor cool helps a lot on adding years on its life span.
Manage your expectation when it comes to noise level of the air compressor as you operate. Do not always expect a quiet air compressor.
Remember that the noise level of a machine is directly related to higher power, capacity and pressure your application requires. So if you application has high requirements, the best air compressor you can get is the one that is electrically powered but note that it will still get noisy but not as noisy as others.
If your application has higher requirements, ensure that you use ear plugs to protect your ear especially if you are going to operate for a longer period of time.
Air Intake Filters
Choose air compressor that has air intake filter that is easy to maintain. It is vital for air intake filters to be regularly cleaned to keep the performance of your air compressor at its peak.
All air compressors have air intake filters but maintenance varies. For a lower cost, look for the one that can be cleaned several times before having it changed. Though sometimes, changeable air intake filters are offered in bulk at a lower cost. Carefully take time to take a look at all options. But if you simply wanted to change it to skip the cleaning process, then look for the one that must be changed instead of being cleaned.
This one’s a no brainer. Always buy items from a trusted manufacturer. Not only that they provide quality products, but you will a piece of mind on warranty concerns. Buying from a trusted manufacturer also means ensuring the safety of the product since trusted manufacturers will always do their best to diligently put together their craft that is safe to everyone to keep up their brand and integrity and to avoid getting lawsuits.
Space and Portability
Determine if you are going to use the air compressor in one place of your workshop or in many places. If you think you are going to use it from one place to another, then you must choose the one that is portable.
But remember, if space is not a problem to you and you do not need the air compressor to be transferred from one place to another, then you might want to get a bigger compressor with a higher capacity – that is only if you are likely to use a higher capacity in the future. Do not forget that overkill choice or air compressor means higher electric bills as well.
Important Features to Look For
The following are the important features you need to look for when buying air compressor. These are mundane aspects of a compressor but can help you on maintenance, storage and use. These are the features that are commonly offered by the manufacturers and sellers but ignored by many.
Ball Valve Drain
This is applicable on air compressors with tanks. All tanks have drains since draining the tank is vital to keep the compressor tank free from rust and pinhole leaks. There are two type of existing drains: (1) drain cock; and (2) ball valve drain.
The drain cock is the screw type which often than not requires pliers to unlock and lock. The most recommended drain is the ball valve drain because it is a lever type and thus only requires few fingers to unlock and lock which makes it easier to use.
Air compressors in general have a single air hose outlet. But there are a number of air compressors which are capable to host dual air hose outlet which allows you to utilize air compressor with two tools or machines at the same time.
Cord wrap allows you to carry and store your air compressor easier and less messy. This feature is the most sought for due to its obvious help at an advantage.
Extras you can get is always a nice to have when you do not have to pay for it yet it offers great ‘value’ as you work on with your tools. Most compressors come with a hose which can be of great use for your workshop and other needs. Some also comes with a set of inflation accessories which might always come in handy for different occasions or situations you may have.
The thing is, these are mostly bundled with compressor models that have lower chance on getting bought or have lower demands. Check if that specific model can suffice your needs, if it can, then having the freebies is a good grab for you!