Power Requirements For Your Industrial Engine Powered Air Compressor

So, you’ve decided you are in the market for an air compressor to add to your existing industrial engine or to include as part of a new piece of equipment you are designing.

Maybe you or your customers are tired of having to haul another separate piece of equipment around to job sites, or maybe you’re looking to open up new markets with a product that does it all. In any case, you are going to have to figure out what your needs are so you can start looking for the right piece of equipment.

To get started you need to consider the following:

  • What tools would you like to use?
    • What are their air requirements?
    • What duty cycle will they be used at?
  • How will your air requirements vary depending on the job at hand?
  • Will you be using an air receiver tank and what is the tank volume?
  • Are you willing to wait for the air pressure to build between tool use?
  • What other loads are going to be imposed on the engine?
  • Will these other loads be running concurrently with air compressor use?

How To Determine Your Tools’ Air Requirements

Each air tool should have a published air requirement specification. Often this is included in the owner’s manual or documentation that came with the tool and is typically stated in airflow (CFM – cubic feet per minute) at a specific pressure. Many air tools are designed to operate in the 90-130 psi range which is a requirement that almost all air compressors can meet.

Where it can get a little interesting is when looking at the airflow specification. Commonly this is stated as an “average airflow consumption” but this can be misleading as it assumes you will only be using the tool intermittently.

Some tools will specify both an average and actual consumption. For example, a popular ½” impact gun states a 4.2 CFM average air consumption and 22CFM during actual use. A quick calculation shows us that this particular tool manufacturer has assumed that this tool will typically only be used an average of 20% of the time.

The amount of time a tool is used is referred to as duty cycle and, in the small air tool industry, it’s commonly based on a cycle time of a minute. Therefore, a 25% duty cycle would refer to using a tool for 15 seconds out of a minute.

For larger or specialized tools, the duty cycle may be quite different. A pneumatic angle grinder or sander might consume 18 CFM under load and be used continuously for five minutes and then put aside for an hour. While this works out to only an 8% duty cycle, because of the longer on time it would require a larger compressor or larger air receiver tank (more on this later) than the impact gun mentioned above.

If possible, find out the actual air requirements for everything you want to power with compressed air and apply the duty cycle that you will actually use each for. It will make the selection of your compressed air system more accurate.

How To Figure Out Everyday Air Needs

Once you have an idea what the air requirements are for each tool and piece of equipment, you need to determine how these air needs might overlap during a typical day. This is an important factor to consider as it has a major impact on the size and type of the compressor and requirements of an air receiver tank.

For example, if the compressor system is part of a mechanic’s service truck, it might only be used to power one tool at a time at a duty cycle of 10-30% in a time span of a minute or two a few times per hour. Contrast this with a compressor system used for the application of spray foam insulation where there are multiple operators each with a spray guns operating at a duty cycle of 60-90% in a time span of an hour.

Do You Need An Air Receiver Tank?

The next important thing to consider is the use and size of an air receiver tank. A receiver tank stores compressed air and acts as a buffer between compressor output and surges in air demand due to heavy tool use.

An appropriately sized tank will allow the compressor to run at its designed duty cycle while still allowing the system to provide a steady supply of air. A larger tank will typically allow a higher intermittent air consumption with a smaller compressor as long as the compressor’s rated duty cycle is not exceeded. In other words, the time to fill the tank from cut-in to cut-out pressure doesn’t overheat the compressor. The duty-cycle and rated maximum run time should be provided by each compressor manufacturer.

Although the rule of thumb of four gallons per HP is sometimes used, it makes many assumptions that may not reflect your particular situation. Instead, use this simple equation to determine the minimum recommended size of your air receiver tank if your demand is occasionally more than the compressor can continuously output. Note this assumes you will not exceed your compressor’s duty cycle when refilling the receiver tank.


V=required minimum receiver tank volume ( US gallons)
Pmax = Compressor cut-out pressure (PSI)
Pmin = Compressor cut-in pressure (PSI)
CFMtools = Max total air consumption possible at one time (CFM)
CFMcompressor = continuous output of the compressor (CFM)
T = Length of time high air consumption will be in demand (minutes)

This equation can be used to find a balance between compressor output and tank size that best suits your needs, for example if you occasionally require 45 CFM at a minimum pressure of 90 psi for one minute out of every 10 minutes, you could meet this need with a compressor that can output 45 CFM and not require a receiver tank at all, or you could use a compressor that outputs only 10 CFM coupled with a 100-gallon tank with a cut-out pressure of 130 PSI.

Properly sizing a receiver tank and air distribution system is beyond the scope of this article, but you can learn more in our How To Size An Air Receiver Tank blog.

How To Determine Your Power Requirements

Now you have an idea what your air consumption needs are and have decided on a compressor size and receiver tank. The next step is to determine the power requirements of running the compressor, commonly specified as CFM per HP.

An important factor in determining a compressor’s CFM/HP ratio is its thermal efficiency. This is fundamentally a measure of how efficient the compressor can turn the engine power into compressed air. There are many factors that influence the isothermal efficiency of an air compressor; compressor type (i.e. piston vs rotary screw or multiple vs single stage compression), discharge pressure, cooling method, etc.

Each compressor manufacturer should be able to supply a CFM/HP curve at different pressures but if not the following table shows how actual output can vary with pressure and isothermal efficiency.
If this information is not available, we can approximate a typical compressor’s performance using the following table at about 3-4 CFM per HP:


Now that you have a ballpark power requirement for compressor operation, you need to add in the other loads to arrive at a total load demand on the engine.

Engine manufacturers will commonly specify a gross and net rated power. Gross power refers to the engine power without any loads (i.e. no water pump, alternator, oil pump, or cooling fan), a situation that you will typically never experience. The Net power rating is the one to use but you may still need to factor in the power required to run the cooling fan and alternator.

You will want to work with your engine supplier to determine what has been accounted for in the net power rating specification.

Torque Curves Under Operating Conditions

Once you have some engines to consider, you can look at comparing the torque curves under the operating conditions you will be running at.

A typical industrial engine has a hill-shaped curve with a peak somewhere is the upper-middle rpm range while a compressor’s drive torque curve at a particular operating pressure can be almost flat or slightly U shaped.

These curves should be plotted to compare the engine’s ability to drive the compressor (and any other concurrent loads) at different operating RPMs. You are going to want to source an engine that can provide the torque you require with some reserve as a safety margin for situations where the engine is not able to produce rated power. A basic graph showing this comparison is shown below.


Some factors that may reduce the available power include: low-quality fuel, extreme high or low ambient temperatures, high altitude, turbo or charge air cooler not working properly, clogged air filter, exhaust restrictions, or simply an engine that is worn out or in need of servicing.

Your engine supplier should be able to provide you with conversion tables to help calculate some of these effects which can lower the engine’s torque by 30 % or more.

Similar factors also apply to the compressor drive torque and should be discussed with your compressor manufacturer to ensure that, even under the worst-case scenario, there is still enough torque available to meet the demand of the compressor.

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There are many factors to consider when sourcing an appropriate engine to power your compressor. Hopefully, this article has helped prepare you to be able to better discuss your options with your chosen engine and compressor supplier.

Park Industries “RAPTOR” Quarry Drill Exceeds Expectations with help from VMAC Hydraulic Drive Air Compressor

Working in stone quarries can present some of the most challenging environmental conditions on the planet for both man and machine. Extreme heat in the summer, followed by extreme cold in the winter, along with large amounts of dust when it’s dry and excessive mud when it’s raining or snowing; each create a unique set of adverse conditions. Continue reading “Park Industries “RAPTOR” Quarry Drill Exceeds Expectations with help from VMAC Hydraulic Drive Air Compressor”

6 Reasons OEMs Choose VMAC Air Compressors & Air Ends

Vancer Rail ExcavatorVMAC air compressor systems are known globally for their performance and reliability, so it’s little surprise that many successful OEMs choose our air ends and air compressor systems for their custom applications. VMAC air ends can be found around the world in railway systems, heavy duty equipment, stock service vehicles, and countless industrial applications.

In this article, we break down the top 6 reasons that OEMs like Caterpillar, Cummins, Ford Industrial Engines, John Deere, and Lincoln Electric use VMAC air ends as their custom rotary screw air compressor solution.

1. 100% Duty Cycle

VMAC manufactures custom OEM rotary screw air compressors that can operate at 100% duty cycle, which means the supply of air is continuous. No time is wasted waiting for air, which makes VMAC air ends a good fit for certain continuous duty applications. By contrast, reciprocating air compressors are designed for approximately 25% duty cycle and often can’t keep up with the air demand required for OEM applications. If your application needs continuous air, VMAC rotary air ends are a great bet.

Compressed air foam firefighting

2. High CFM Output

Rotary screw air compressors offer a steady supply of air flow, resulting in a higher output of air than reciprocating air compressors can produce. VMAC rotary screw air compressors are powerful, and air end capabilities range from 10-30 CFM, 30-70 CFM, and 70-130 CFM.

3. Super Compact Design

VMAC air compressors are designed to be compact, with the ability to fit into tight spaces. For many OEMs, space is a major challenge, but VMAC’s compact designs conserve space on any platform, and allow for more room to store other tools and equipment.

4. Lightweight, Durable Materials

In addition to being compact, VMAC air ends and air compressors are lightweight. Each system is designed with materials that will reduce weight without compromising on durability. At only 21 to 57 pounds, even our heaviest air end can keep your system’s overall weight as low as possible. Our lightweight designs make VMAC air ends ideal for mobile industrial applications and the benefits include improved productivity, better fuel economy, and simpler mounting.

5. World Class Customer Support

OEMs will be pleased to know that VMAC’s technical support team is available to help by phone, email, and online on the VMAC Knowledgebase. Should any challenges arise, our OEM team is available to help. We also have a talented and experienced support team that will be available to answer your operator’s questions quickly and get them back to work faster.

6. Highly Customizable Systems

VMAC rotary screw air compressor systems can be designed to your exact specifications, allowing for a completely customizable solution. VMAC’s dedicated OEM team will work closely with your engineering and design team to ensure your customized air compressor system is exactly what you need for your industrial engine application.

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VMAC OEM Custom Solutions

VMAC custom air compressor solutions provide OEMs with high performing and reliable rotary screw compressors, designed specifically for your unique application. VMAC air compressors and air ends produce from 10-130 CFM at 100% duty cycle, and the air compressors are compact, lightweight, and customizable. Each system is backed by a superior technical support team.

Learn more about VMAC OEM, including applications, components, and mounting kits. Alternatively, you may contact the OEM team directly; call 1-888-514-6656 or send an online message to get started.

With Ogura’s help, VMAC develops tiny 30CFM air compressor and discovers new market

VMAC UNDERHOOD 30 CFM Air Compressor

Ogura’s new small size/high torque electromagnetic clutch helps VMAC’s aftermarket UNDERHOOD™ LITE air compressor meet performance and cost reduction goals previously unobtainable.

Today’s commercial van manufacturers are changing the game by delivering new Euro style vans to North America. These new platforms boost fuel efficiency and increase cargo space dramatically. Ford’s 3.7 L Transit, Mercedes Benz’s 3.0L Sprinter, and the Ram 3.6L ProMaster are but three of the new entrees causing shakeups in the mobile service industry.

While these vehicles offer state of the art engines, reduced emissions, and roomy vehicle platforms, they have drastically reduced the amount of available under hood space usually allocated for engine driven aftermarket components such as; air compressors, secondary alternators and hydraulic systems.  Generally, mobile service businesses and municipalities buy these vehicles and outfit them with engine driven accessory systems for the many important tasks they do every day.

Continue reading “With Ogura’s help, VMAC develops tiny 30CFM air compressor and discovers new market”

Types of Air Compressors For Your Industrial Engine

You’ve decided that your current application needs compressed air. You’ve figured out how much air you need, how you are going to drive the compressor and what engine you are going to use to power it.  Now it’s time to decide what type of air compressor is best suited for your needs.

There are 3 styles of air compressor commonly found in mobile industrial applications:

  • Reciprocating, Piston Compressors
  • Rotary Screw Compressors
  • Rotary Vane Compressors

Each of these air compressors have their own particular benefits and challenges, which we will break down in this article.

Reciprocating Compressors  Reciprocating Compressors

Reciprocating compressors are the most common air compressors found in mobile applications, and they are the type most people are familiar with.  There are a wide variety of manufacturers and suppliers worldwide, providing an array of options.


Of the three compressors types, reciprocating air compressors generally have the lowest initial purchase price.  They are suitable for low duty cycle operations.  Unlike many vane and screw compressors, most reciprocating compressors can be serviced or rebuilt in the field with simple hand tools.


Reciprocating compressors are typically the largest and heaviest when compared to compressors of equal CFM.  They have the most moving parts and like the vane compressor, experience increasing amounts of oil carry over.  With the way reciprocating compressors produce air, there is more after treatment required to reduce air temperatures and pulsation before the compressed air reaches your tools and equipment.  An air receiver tank is also required with a reciprocating air compressor and takes up additional space.

Rotary Screw Compressors

Traditionally, rotary screw compressors were found in stationary applications and were not widespread in mobile applications.  However, times have changed as rotary screw compressors become more affordable and their benefits are increasingly recognized across diverse industries. Today, rotary screw air compressors are used in numerous industrial applications and are being manufactured by more companies around the worldRotary Screw Compressors.


Rotary screw compressors are known for long life and high air flow delivery in a relatively compact size. High duty cycle applications are suited for rotary screw compressors as they are designed to run 100% of the time. Generally, a screw compressor does not need an air receiver tank for operation. Compared to the other compressor types, rotary screw air compressors have fewer wearing parts and maintenance usually consists of changing filters and oil.


Rotary screw compressors generally have a higher initial cost when compared to the other compressor types, but last longer as they have fewer wearing parts.
As most screw compressors found in mobile applications are oil-injected, they have an independent lubrication circuit. As a result, the oil used is specific to the compressor and the system may need routine maintenance.

Rotary Vane Compressors  

Rotary Vane CompressorsOf the three common compressor types found in mobile applications, the rotary vane compressor is the least common. There are fewer manufacturers of the vane compressor compared to reciprocating compressors, and service parts can be more challenging to find.


Like the rotary screw compressor, the rotary vane air compressor has fewer moving parts when compared to a reciprocating one. Vane compressors are compact in size when compared to reciprocating and rotary screw compressors when comparing equal CFM compressors. They are designed for continuous duty and deliver a relatively pulsation free air flow to your tools or equipment. The rotary vane compressor generally has a lower initial purchase cost.


As with other wearing compressors, oil carry-over increases the longer it is in service. A complete rebuild is required to prevent this from happening, which is an expensive process. Finding service parts and support can also be a challenge.


When choosing a compressor for your mobile application, there are many factors to consider.  The initial purchase price, ease of and cost of maintenance, size, availability, air flow and longevity are all important for your overall satisfaction with your compressor.  Knowing which compressor meets your needs is an important step in finalizing your industrial compressor system.

Visit our OEM page to find out how VMAC can help you build your custom industrial application!

Total Patcher™ gives the customer more with help from VMAC

Buoyed by a strong economy, much needed road construction is back underway in the United States. Governments at all levels have money again, and public-private partnerships (P3s) are growing. It’s a marked shift from just a few years ago when things were stalled to a near standstill across the country.

Crews are busy and workers are scarce. These are great problems to have. However, it is also time to make hay while the sun shines and every advantage helps.

After skilled labor, the next biggest investment that effects a road construction company’s ability to drive profit is its equipment. Road crews run a lot of equipment. It’s expensive and cumbersome, making innovation in the highly competitive industry an important endeavor.

Continue reading “Total Patcher™ gives the customer more with help from VMAC”

Methods to Power Your Air Compressor with an Industrial Engine

Powering your air compressor by an industrial engine can be done by various means.  Choosing the way you power your compressor should be decided by a number of factors.  Space, existing components and systems, weight and your engine options are all variables to consider.   In this article we talk about the most common found in the market today.

Engine Mounted FEAD Belt Drive

Auxiliary components are commonly mounted directly to the engine and driven from a serpentine or V belt. This is termed “Front End Accessory Drive” (FEAD) and is often used to drive alternators, generators, air conditioning compressors, water pumps, cooling fans etc.  Air compressors can also be driven via FEAD belt off the front of an engine.  This can be in line with the existing belt system or by adding another pulley to the crankshaft and designing another belt system. The driven and driving pulley diameters can be customized to provide the required compressor output at a given engine speed. Belt drives will also provide some damping of potentially damaging torque pulses.  The compressor can be driven via a clutch or fixed pulley depending on whether it is desirable to be able to completely stop the compressor while the engine is running. A custom bracket will likely be needed to mount to the engine to support the compressor and if equipped, the secondary belt system components such as the idler(s) and tensioner.

Frame Mounted Belt Drive

To simplify the design of a bracket to mount the compressor it can be mounted to the base frame instead of directly to the engine.  The belt is still driven off a pulley mounted to the engine’s crankshaft.  Generally, a V belt will be used instead of a serpentine belt as it is better able to handle misalignment and variations in tension due to the changes in positioning between the engine and compressor under operating conditions, especially if the engine is not hard mounted to the frame.

Auxiliary Port Direct Drive

Many industrial diesel engines and some gasoline engines come equipped with an auxiliary PTO port used to power bolt-on accessories.  These ports are usually part of the front or rear engine cover and are driven via the crankshaft/camshaft/fuel pump gear-train.  Auxiliary ports come in various configurations usually conforming to an industry standard.  The connection to the drivetrain is generally either a splined port or direct gear mount.  Over or under drive ratios may also be available via bolt-on adaptors.  Although traditionally small reciprocating compressors are driven by these auxiliary ports there is a growing number of higher volume rotary screw compressor designs taking advantage of this PTO drive method.

Flywheel Direct Drive

A common method of power to an air compressor is to drive it through a coupling directly off of the flywheel.  Commonly used industrial couplings are designed to dampen vibration and torque spikes while often allowing some misalignment between the engine and compressor.  To generate the high RPM required for rotary screw compressor operation a speed increasing gearbox is commonly used.

Flywheel Belt Drive

Much the same as the FEAD drive listed above, a pulley and belt configuration can be connected to the flywheel to power your compressor.  The main advantage to using a belt driven from the flywheel is that there are generally fewer components to work around which typically makes designing the bracket and belt system simpler.

Hydraulic Drive

While not directly mounted to the engine, the use of an engine-driven hydraulic motor to power an air compressor is not uncommon.  If the engine or equipment is using hydraulic power for other functions, adding hydraulic power to run a compressor can be a convenient option. This method is less efficient compared to the direct drive methods discussed above. It may require additional hydraulic cooling capacity and will burn more fuel for a given compressor output. This method does allow more positional flexibility between the engine and compressor which can be helpful if there is limited space on or around the engine.

Electric Drive

Like the hydraulic drive above, using electric power generated by the engine is another way of producing air power.  While the availability of sufficient power to produce large air volumes is unlikely, small electric driven compressors can be used when air flow and duty cycle are very low.


Ultimately choosing a drive method for your compressor comes down to your unique situation, air compressor requirements, and equipment available to you. The choice of how best to drive your air compressor system is best discussed with the members of the application team of your engine distributor and compressor manufacturer.

If you have any questions about this article or anything mobile compressor related, please contact us.

The Top 7 Questions When Adding a Compressor to Your Industrial Engine

When you are looking at considering putting a compressor on a John Deere™, Kubota™, Cummins™, Caterpillar™, Deutz™, Robins-Subaru™, Isuzu™ or a multitude of other industrial engine manufacturers, there are some key questions about your engine and your application that need to be answered before you can determine the best solution.

Here are some important questions to have answered:

1. What are you using the air for?

This helps to ensure that you are choosing the most appropriate solution for your unique requirements. How many CFM (cubic feet per minute) and at what pressure do you require to run your tools or equipment correctly?

2. What duty-cycle do you require for the compressor to operate?

This refers to how much you are using the compressor in a given time frame. Do you need air continuously for a piece of machinery (100% duty cycle) or infrequently to do small jobs? (say 15 minutes at various intervals over an hour – 25% duty cycle). This is critical information for selecting the type of air compressor solution you should be pursuing. Is it a heavy duty application where a robust solution like a rotary screw air compressor would be best, or is it a light duty application that an inexpensive reciprocating air compressor is going to provide better value? How critical is the air requirement? How much will downtime cost you?

3. What is your engine load?

Do you require air while running another piece of equipment from the same engine? If multiple pieces of equipment are running at the same time, the power being drawn from the engine is greater than if you turn off each component when not being used. How much horsepower are you already using for your equipment and how much will be available to power the compressor? Not only does this information help calculate the power requirements but also acts as a guide to the type and complexity of control system needed. It is important to ask, “what is really required?” instead of, “what would be nice to have?”.

4. What air pressure do you require?

This also helps to determine the power requirements for the compressor. It potentially determines what type of compressor will be required. High pressure applications require specialized compressors. It is important to not over specify your needs as that may increase costs, create less reliable systems and potentially shorten tool and equipment life downstream of the compressor.


5. What environment do you operate in?

This information is really important for you to know in order to correctly specify cooling and filtration requirements. If you work in frigid conditions, you will also need to consider ways of ensuring the compressor will work well in the cold. Extreme heat requires more cooling. Do you work in dusty environments? If so, protecting your compressor from dirt and other debris will improve the longevity of your compressor. Understanding how the engine and equipment behaves while operating is also a requirement. Is it stationary, moving or rocking back and forth?

6. What is your engine and equipment mounted to?

Are you mounting your equipment to a stationary skid or trailer? Is it truck mounted or on an auxiliary piece of equipment attached to the truck? Are you limited by the space around the unit or is there a requirement for the equipment to be within the confines of an enclosure? Oftentimes, compressors must be mounted to an existing piece of equipment that already has a frame and a sheet metal enclosure, without making changes to the existing structure. Vibration also has to be addressed if your equipment operates in a high vibration environment.

7. What engine are you using?

Can you make changes to your engine if needed?There are many options available from the engine manufacturer for each engine and some are extremely important to the mounting of an air compressor. Engine mounts, coolers, water pump options, auxiliary ports, alternator size, front cover, harmonic balancer and pulley are a few things to consider. What is the horsepower of the engine? Is an auxiliary port available, if so, what type is it? How much free space is around the engine? How about the radiator; is there extra cooling capacity available to handle the heat load from the compressor or will you need to either increase its size or add additional cooling capacity?

Along with the engine details, you need to know what speed your engine is running at. What is the typical operating RPM (revolutions per minute)? The minimum and maximum RPM information is also important. If you want a belt driven, clutch actuated compressor solution, you will need to know at what engine RPM the clutch will be engaged. If the speeds are too high, there is a risk of the clutch burning out prematurely; a control system would be required to prevent this from occurring. Compressor safety systems can also be programmed in to prevent occurrences like over temperature conditions.


There is nobody that knows your business, environment and equipment better than you. With your knowledge and answers to these questions, you are well on the way to adding a compressor to your piece of equipment.

Lastly, it is important to find an air compressor provider that will work with you, and provide the support and expertise that you need. A compressor can be purchased from anyone, but are they asking these questions up front, or just trying to sell you a compressor and leaving you high and dry when it doesn’t meet your expectations, or leaves your operator with an expensive breakdown in the field? Do your research to ensure you get the results you require.

If you need help answering these questions, please don’t hesitate to contact us.