How Do I Choose An Air Compressor?

Determining how you will use your air compressor is a great starting point. Developing the list of tools that will function and those tools' applications is the next vital guiding step. Finally, to get your air supply right, you'll want to arm yourself with the proper knowledge, achieved through extensive research on the tools, output and usage when choosing a compressor.

Guiding this research will be the air consumption specification (measured in litres per minute) or cubic feet per minute together with the operational pressure (measured in bars or pounds per square inch) of the tools planned for use with the compressor. When purchasing a portable air compressor, there are several things you need to look for to ensure you're making the right purchasing decision. These include air pressure and quality, portability (a must), tank size, pressure cycle and duty cycle.

While many are capable of determining these factors themselves, it can be worthwhile getting advice from a professional so that you can be confident in your decision. At Mobile Energy Australia, we specialise in portable air compressors and stock a wide range of machines suitable for domestic and industrial use. Our team thoroughly enjoys offering customers advice; therefore, we've decided to provide a comprehensive guide below on things to look for when buying portable air compressors.

FAQs About Choosing An Air Compressor

To use air tools such as paint guns, impact wrenches, air nailers, and even tyre inflators, you'll need a compressor to run everything. Since it's the heart of any air tool setup, your compressor will need to be capable of meeting the requirements of your tools - which means that you need to buy one that's the right size and is powerful enough to do the job.

Are you going to be carrying out major projects or just an odd job? Primarily automotive maintenance or some home construction? The more involved and varied the tasks you'll need to run air tools, the more likely you will require a larger and more powerful compressor.

Are you going to be sanding and painting? Or running things like wrenches and nailers? Generally speaking, tools that require a constant air supply such as paint guns, sandblasters and grinders will need a compressor with a bigger tank. Also, the more power your tools need to put out, the more airflow your compressor will need to provide them.

If you only intend to work in one place, you can often run hoses of suitable length and keep your compressor in one spot. However, if you intend to work in other locations, be sure to consider the weight and portability of your compressor. Another thing to consider is the noise output of your compressor - the larger and more powerful they are, generally, the louder they are, and the different drive systems will also impact the noise output. Once you have this information in mind, you'll have a good idea of what size of air compressor is best for you.

The amount of airflow an air compressor produces is One of the most important ratings you'll need to consider when choosing your compressor. To find out which air compressor can run which tools, you'll need to know the "LPM" requirements of the tools you'll be using. LPM stands for litres per minute and refers to the air that a compressor can output. Most air tools come with this LPM reading on their packaging to make it easy to match the air tool to the compressor.

Usually, the more powerful your compressor, the larger it will be - so spare a thought as to how you intend to fit it into your workshop or garage. You might be able to stash your compressor away under a workbench, but when it's running, your compressor will need to be free from any interference.

Suitable air compressor tank sizes for the home workshop vary from 5 litres to 50 litres. The tank size determines how long you can run your air tools before the motor in the compressor has to turn back on to compress more air.

Because certain air tools such as grinders and sandblasters require a continuous flow of compressed air, they'll need a larger tank than tools that operate in short bursts, such as nailers and impact wrenches. The fewer times the motor has to cycle on and off, the less heat it will generate, and the less wear it will sustain.

The tank size you choose will be determined by how you intend to use your compressor, and you must choose the size carefully to accommodate all intended uses. For example, tools you want to use for short bursts only require a small tank because the pressurised air won't be used quickly. On the other hand, a larger tank is required for tools that need to be used longer to sustain the amount of airflow. However, keep in mind that a larger tank will affect the ease of portability.

FAD stands for Free air delivery and is essentially another way of referring to the LPM of a compressor - remember that as long as the airflow coming out of your compressor is enough to power all the tools that you intend to run at the appropriate PSI rating to run them, you should have no trouble. A simple equation to figure out if a potential compressor will do the job is to take the highest LPM rating of your current air tools and multiply that by 1.5 to give yourself a little wriggle room.

Choosing The Right Compressor

Buying a quality compressor that's best suited to your needs will save you time and money in the long run, and it's an easy process that requires understanding a few key concepts. This guide will help direct you towards making the best possible purchase.

Selecting the right compressor will mainly depend on four factors:

  • The total air consumption of all the tools you want to power simultaneously with the compressor.
  • The recommended operating pressure of your tools.
  • How you will use your air tools - i.e. will they be run continuously or intermittently.
  • Where you will run the tools - do you need the unit to be portable, and is electricity available on site.

Tool Air Consumption

pexels andrea piacquadio 3822938A compressor needs to supply enough airflow at the right pressure for an air tool to work correctly. So the air tools you want to use will be a primary factor when choosing a compressor. Air tools have a specification for air consumption, normally measured in litres per minute or cubic feet per minute. They also have an operational pressure measured in bars (b) or pounds per square inch. An air saw, for example, may have an air consumption of 170 l/min (6cfm) and require a pressure of 6 bar (90psi) to operate correctly. You will need to consult a tools manual or manufacturer to determine the right air requirements for a particular tool.

Compressor - Free Air Delivery (Fad)

A compressor needs to produce enough air to meet the tool(s) 's air consumption requirements. The volume of air a compressor produces is called the Free Air Delivery (FAD), also measured in litres per minute (or cfm). The FAD relates directly to a tool's air consumption requirement. For example, for an air saw with air consumption of 170 l/min, the compressors FAD rating will need to be at least 170 l/min.

If you intend to operate multiple tools simultaneously, you will need to add up the air consumption values of the tools and use a compressor with a FAD rating that meets the total air demand. For example, to simultaneously run an air saw (170 l/min) and an air ratchet (113 l/min), you will need a compressor with a FAD of at least 283 l/min (170 + 113). 

Air Pressure & Quality

A compressor also needs to deliver air at a tool operational pressure. For example, if a tool requires 12 bar (174psi) to operate, you need a compressor that can pressurise air to 12 bar. On the other hand, if a tool needs only 6 bar (90psi), a pressure regulator fitted to the compressor will allow you to adjust the air supply to lower pressure.

  • Note: Excessively high pressure can damage tools not built to handle it.

Being an air compressor, one of the most important things to look for when purchasing is the air pressure and quality. To serve its purpose, an air compressor must deliver a volume of air to tools at the right pressure.

For example, if a tool requires 174psi to operate, your compressor must be able to deliver air at 174psi. In the same way, if a tool only needs 80psi, you can adjust a higher psi tool to supply a lower pressure. Therefore, always purchase your air compressor to power the highest-pressure tool you have.

Air Quality

Compressors can produce an air of varying quality. Dust, moisture and oil particles can all be present in the airflow unless filtered out. If your tools or application requires "clean" air, consider a compressor with particle and moisture filters installed. Oil-less pumps are also available, negating the risk of oil entering the airflow. On the other hand, air quality refers to the cleanliness of the air your compressor is producing. As compressors can produce an air of varying quality, dust, moisture and oil particles can all be present in the airflow if the compressor doesn't have good air quality. Therefore, it's a good idea to choose a compressor that has particle and moisture filters installed, lessening the risk of contaminated air.

Tool Usage

The third factor to consider when buying a compressor is how you intend to use your tools. The volume of air a tool may require will be affected by how you use that tool. For example, an air saw that's run in continuous long bursts will require a greater volume of air to operate efficiently over that period than if it is run in intermittent short bursts.

Pressure Cycle

Most compressors force air into a storage tank, increasing the pressure until it reaches an upper-pressure limit at which the compressor shuts off. When the compressed air is being used by a tool, the pressure decreases until the tank reaches its lower pressure limit; at that point, the compressor turns on to re-pressurise the tank. This is the compressor pressure cycle. Compressing air produces heat which can damage the compressor if it's not managed. When the compressor turns off (after reaching maximum tank pressure), it has time to cool down while the air in the tank is being consumed.

When a tool consumes the stored air quickly, the time for cool-down is reduced because the unit needs to turn on to re-pressurise. The compressor can overheat and become damaged if not enough time is dedicated to the cool-down phase.

Duty Cycle

The ratio between the pressurisation and cool-down phases is called the Duty Cycle. Ideally, to maximise a compressor's operational life, its duty cycle over any given timeframe should be no more than 60% of the time turned on, and 40% turned off (cooling down). If you think you'll be continuously using high air consumption tools, consider a compressor with a higher FAD rating and a larger storage tank to reduce the risk of wearing out or overheating the unit.

Where Do You Want To Use The Compressor?

Where you need to operate your tools & compressor is the fourth major point to consider when buying a compressor.

Portability

Do you need your compressor to be portable? If you want to move your unit around easily, then your compressor will be limited in size, power and volume of air that it can produce.

Electric Vs Petrol Engine

A petrol compressor is best suited for outdoor applications where electrical power isn't available. Never use one in an enclosed environment. However, a compressor with an electric motor will be cheaper to buy and operate and require less maintenance. If you choose an electric compressor, ensure you have adequate power to operate it. Your compressor may require 10amp, 15amp or even 3 phase electricity.

Tank Size

The size of the tank you require will most likely be determined by how you will use your compressor and the tools attached to it. For example, a tool used intermittently in short bursts should only require a small tank as the air volume will not be used quickly. But if your compressor needs to sustain long usage periods, a larger tank is recommended. Keep in mind that a larger tank will affect portability.

Site Location

Ensure the location you wish to place the compressor is large enough to fit the unit and has adequate ventilation so it won't overheat.

Large Workshop Systems

Suppose you plan to install a large air system with more than five workstations or require air for an industrial application. In that case, you may require a screw compressor and a specialised airline and filtration configuration, so consult with a Total Tools staff member, and they will provide the expert advice you require to build the right system for your needs.

Other Things You Should Know

  • anthony fomin stw2kypoujk unsplashThe tank stores air; it doesn't generate it. A bigger tank doesn't mean more air, and it means a longer cycle time.
  • Too much pressure for your application wastes energy and can damage tools.
  • If you have three-phase power, buy a three-phase compressor, they are more efficient and reliable.
  • Extension leads reduce power to the motor, so use a longer air hose instead when possible.
  • If you need a long lead, consider a petrol compressor instead.
  • Overheating is a major factor in compressor failure; ensure your unit has adequate ventilation and access for maintenance.
  • Divide the FAD by 28.3 to convert to CFM.

Using An Air Compressor

Once you've chosen the right air compressor, remember these few simple tips for easy use and maintenance. 

  • Try to avoid extension leads. If you have to extend your compressors reach, it's recommended to use a longer air hose.
  • Please avoid using the air tool while the pump operates to ensure the compressor stays within its recommended duty cycle. Wait until the pump has stopped before continuing work.

Conclusion

To find out which tools match which air compressor, you'll need to know the LPM requirements of the tool you'll be using. LPM is the litres per minute of compressed air needed to run the air tool effectively. All Blackridge air tools come with this LPM reading on their packaging to make it easy to match the air tool to the compressor. Air tools are some of the most useful tools in any home workshop. They provide better power to weight ratios, run cooler and are cheaper to purchase than their electrical counterparts. Two hundred forty volt air compressors work by compressing air using an electric motor to pressure around one hundred and fifteen pounds per square inch. When you use your air tool, the compressed air is released and shoots out of the tank to power the tool. Once the pressure in that tank is lowered, the pump automatically begins re-pressurising the tank. You may also find that you can save money by using a compressor and air tools rather than buying the equivalent electrical option.

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