Basics of Compressors

Single Stage Portable Air Compressor

What is an air compressor?  This may seem like a simple question, but it is the heartbeat for most industries.  So, let’s dive into the requirements, myths, and types of air compressors that are commonly used.  Like the name implies, air compressors are designed to compress air.  Unlike liquids, air is a compressible gas, which means that it can be “squished” into a smaller volume by pressure.  With this stored energy, it can do work for pneumatic systems.

There are two main types of air compressors, positive displacement and dynamic.  The core component of most air compressors is an electric motor that spins a shaft.  Positive displacement uses the energy from the motor and the shaft to change volume in an area, like a piston in a reciprocating air compressor or like rotors in a rotary air compressor.  The dynamic types use the energy from the motor and the shaft to create a velocity with an impeller like centrifugal air compressors.  This velocity converts to a rise in pressure.

How do they work?  Most air compressors are driven by an electric or gas motor.  The motor spins a shaft to push a piston, turn a rotor, or spin a vane.  At the beginning of the air compressor, we have the intake where a low pressure is generated from the displacement to bring in the surrounding ambient air.  Once trapped, Boyle’s law states that when the volume decreases, the pressure increases.  For the dynamic type, the velocity and design will increase the air pressure.  The higher pressure will then move to a tank to be stored for pneumatic energy.  The amount of power required is dependent on the amount of air that needs to be compressed. 

Compressed air is a clean utility that is used in many ways, and it is much safer than electrical or hydraulic systems.  But most people think that compressed air is free, and it is most certainly not.  Because of the expense, compressed air is considered to be a fourth utility in manufacturing plants.  For an electrical motor to reduce a volume of air by compressing it, it takes roughly 1 horsepower (746 watts) of power to compress 4 cubic feet (113L) of air every minute to 125 PSI (8.5 bar).  With almost every manufacturing plant in the world utilizing air compressors much larger than 1 horsepower, the amount of energy needed to compress a large volume of air is extraordinary.

Let’s determine the energy cost to operate an air compressor to make compressed air by Equation 1:

Equation 1:

Cost = hp * 0.746 * hours * rate / (motor efficiency)

where:

Cost – US$

hp – horsepower of motor

0.746 – conversion KW/hp

hours – running time

rate – cost for electricity, US$/KWh

motor efficiency – average for an electric motor is 95%.

As an example, a manufacturing plant operates a 100 HP air compressor in their facility.  The cycle time for the air compressor is roughly 60%.  To calculate the hours of running time per year, I used 250 days/year at 16 hours/day for two shifts.  So operating hours equal 250 * 16 * 0.60 = 2,400 hours per year.  The electrical rate at this facility is $0.10/KWh.  With these factors, the annual cost for operating the air compressor can be calculated by Equation 1:

Cost = 100hp * 0.746 KW/hp * 2,400hr * $0.10/KWh / 0.95 = $18,846 per year in just electrical costs.

So, what is an air compressor?  The answer is a pneumatic device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored as pressurized air.  Efficiency in using compressed air is very important.  EXAIR has been manufacturing Intelligent Compressed Air Products since 1983.  We are able to save you money by reducing the amount of compressed air you use.  If you need alternative ways to save money when you are using your air compressor, an Application Engineer at EXAIR will be happy to help you.  We even have a Cost Savings Calculator to find the annual savings and payback period; and you will be amazed at how much money can be saved. 

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Photo: Technical Illustration of a portable single-stage air compressor by Brain S. Elliot.  Creative Commons CC BY-SA 4.0

EXAIR’s Calculator Library

If there is one thing you can always count on it’s a good calculator, and EXAIR offers you 3 — right on our website!!! The calculator library consists of an Air Savings Calculator, an EFC Calculator, and a Cabinet Cooler sizing calculator. All 3 of these add exceptional value and insight into our products. Let’s take a minute and look at each of these calculators in a little more detail.

The Air Saving Calculator allows you to compare a current product, to one of our products based upon overall cost. In order to make this effective for you, you will need to know the SCFM that your current solution is using. With that information, we can factor in the cost of our product and the SCFM consumption of this new solution, and give you an Air and Cost savings number. For example, if you are using a 1/4″ open pipe for blow off, you would be using @ 40 SCFM (not going to mention the OSHA violations – that’s for another blog). By placing one of our Super Air Nozzles on this open pipe, we will save you so much air (SCFM) that you can quickly see (above) that this one nozzle, can save you up to $1350 per year… One Nozzle!!!

The next calculator is the EFC calculator. An EFC is an Electronic Flow Control that can help you quickly automate your process. The EFC will allow you to use air only when it’s necessary and cut down on consumption. For example, if your conveyor has dead space between products, the EFC will shut the air flow off during the dead space. The calculator will tell you how much money you can save by installing the EFC. This will even tell you how long it will take to pay off the initial cost of the EFC unit. To use this calculator you will need the SCFM being consumed, the % of time that the product needs to be on, the purchase price of the EFC (this varies by size, call for details, or see on the link), and your cost of compressed air. We have $0.25 in this blank as a general standard, but if you know your actual, you will get a more concise answer. Your cost could be much higher, I’d be surprised if it is lower. The Example to the left shows the effects of a $1200 EFC that runs a product at 80 SCFM, and needs to be on 45% of the day. The EFC turns off the air the other 55% of the day when there is no reason to run the air. This pays for itself in 76 days, and adds $3960 to the bottom line each and every year.

The 3rd and final calculator that EXAIR offers online is the most used. It is our Cabinet Cooler System Calculator. Electrical cabinets get hot, and will overheat your electronics. Our Cabinet Coolers are the most efficient method to cool these cabinets, and eliminate electronic damage from overheating. There are no moving parts in these Cabinet Coolers, and the Vortex based system cools these with little to no maintenance. You simply need to supply these with clean, dry, compressed air. As you can imagine, these cabinets come in all sizes, and there are all sorts of various electronics that can be inside of these. We need the measurements and temperatures so that we can calculate the correct size Cabinet Cooler system for you. Our Cabinet Coolers have large size differences, from as little as 4 SCFM and 275 Btu/hr, up to 80 SCFM and 5600 Btu/hr, and we can go larger than this if necessary. The good thing about this calculator is that all of the information you need to enter is readily available to you as long as you have a a tape measure and a thermometer.

We do encourage everyone to take advantage of these on-line tools, however always remember that experienced application engineers like me, are here M-F 7AM-4PM EST to help you in any way possible.

Thank you for stopping by,

Brian Wages

Application Engineer

EXAIR Corporation
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Cover photo by Peggy_Marco licensed by Pixabay

Understand the ROI of Your EXAIR Products With Our FREE Efficiency Lab Service

Many facilities may not have the means to test the air consumption of their blowoff solutions. With compressed air being the most expensive utility in a manufacturing facility, it’s important to identify places where you can save money on your overall operating costs. EXAIR manufacturers a wide variety of products intended to help you reduce your compressed air usage. If you’re not able to accurately measure the consumption in your own shop, we invite you to send the products into EXAIR for testing.

All you have to do is contact an EXAIR Application Engineer and ship them straight to our warehouse in Cincinnati, Ohio. Once we receive it, our engineers will complete some in-depth testing to determine the compressed air consumption, sound level, and force that your current solution provides. With this information, we’ll be able to compare it to an EXAIR Engineered solution. This way we ensure that you receive the best, safest solution possible also capable of saving money through reduced air consumption and improved efficiency.  We’ll send you back a comprehensive report that’ll help you to make the best decision for your company.

This video below shows our EXAIR Efficiency Lab and some examples of the different types of products we’ve tested in the past:

This service is something that we offer to our customers completely free of charge. This way, you can rest assured that in going with a new solution from EXAIR, you’re getting the most bang for your buck. Oftentimes, it’s not known just how much some of these products cost to operate. It’s just compressed air, air is free right?? Compressed air is certainly not free, but in fact rather costly as a 4th utility in an industrial plant.

Making sure that you understand the products used within your various applications is even more critical in a time where everything in life is rapidly getting more expensive. By ensuring you’re using the best possible blowoff solutions for your processes, you can save a dramatic amount of energy that would otherwise be wasted.

If you think there’s anything in your facility that could be using too much air, we’re here to help. Reach out to an Application Engineer for more information on how we can help save you money!

Tyler Daniel, CCASS

Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD

How to Calculate ROI (Return on Investment)

You may have asked…why should I switch over to an engineered compressed air product if my system already works? Or…How can your products be much different?

Manufacturing has always been an advocate for cost savings, where they even have job positions solely focused on cost savings. Return on Investment (ROI) is a metric they look toward to help make good decisions for cost savings.  The term is used to determine the financial benefits associated with the use of more efficient products or processes compared to what you are currently using. This is like looking at your homes heating costs and then changing out to energy efficient windows and better insulation. The upfront cost might be high but the amount of money you will save over time is worth it.

ROI Calculation

How is ROI calculated? It is very simple to calculate out the potential savings of using an EXAIR Intelligent Compressed Air® Product. We have easy to use calculators on our websites Resources where filling in a few blanks will result in an ROI when switching to a EXAIR product! Here they Are, Calculators.

I’ll go ahead and break down the simple ROI calculations for replacing open blow offs with an EXAIR Super Air Nozzle:

  • ¼” Copper Pipe consumes 33 SCFM at 80 psig (denoted below as CP)
  • A Model 1100 ¼” Super Air Nozzle can be used to replace and only uses 14 SCFM at 80 psig (denoted below as EP)

Calculation:

(CP air consumption) * (60 min/hr) * (8 hr/day) * (5 days/week) * (52 weeks/year) = SCF used per year for Copper Pipe  

(33) * (60) * (8) * (5) * (52) = 4,118,400 SCF

(EP air consumption) * (60 min/hr) * (8 hr/day) * (5 days/week) * (52 weeks/year) = SCF used per year for EXAIR Product  

               (14) * (60) * (8) * (5) * (52) = 1,747,200 SCF

Air Savings:

SCF used per year for Copper Pipe – SCF used per year for EXAIR Product = SCF Savings

               4,118,400 SCF – 1,747,200 SCF = 2,371,200 SCF in savings

If you know the facilities cost to generate 1,000 SCF of compressed air you can calculate out how much this will save. If not, you can use $0.25 to generate 1,000 SCF which is the value used by the U.S. Department of Energy to estimate costs.

Yearly Savings:

                (SCF Saved) * (Cost / 1000 SCF) = Yearly Savings

                                (2,371,200 SCF) * ($0.25 / 1000 SCF) = $592.80 annual Savings

With the simple investment of $42 (as of date published) you can calculate out the time it will take to pay off the unit.

Time Until payoff:

                (Yearly Savings) / (5 days/week * 52 weeks/year) = Daily Savings

                                ($592.80/year) / (5 days/week * 52 weeks/year) = $2.28 per day

                (Cost of EXAIR Unit) / (Daily Savings) = Days until product has been paid off

                                ($42) / ($2.28/day) = 17.9 days  

As you can see it doesn’t have to take long for the nozzle to pay for itself, and then continue to contribute toward your bottom line. 

If you have any questions about compressed air systems or want more information on any of EXAIR’s products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.

Jordan Shouse
Application Engineer

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Hand Holding money Image from Pictures of Money Creative Commons license