About Double Acting Reciprocating Air Compressors

My colleague, Lee Evans, wrote a blog “About Single Acting Reciprocating Compressors”, and I wanted to extend that conversation to a more efficient relative, the double acting reciprocating compressor.   As you see in the chart below, this type of compressor falls within the same family under the category of positive displacement compressors.

Compressor Types

Positive displacement compressors increase air pressure by reducing air volume within a confined space.  The reciprocating type of air compressor uses a motor that turns a crank which pushes a piston inside a cylinder; like the engine in your car.  In a basic cycle, an intake valve opens to allow the ambient air into the cylinder, the gas gets trapped, and once it is compressed by the piston, the exhaust valve opens to discharge the compressed volume into a tank.  This method of compression happens for both the single and double acting reciprocating compressors.  With a single acting compressor, the air is compressed only on the up-stroke of the piston inside the cylinder.  The double acting compressor compresses the air on both the up-stroke and the down-stroke of the piston, doubling the capacity of a given cylinder size.  This “double” compression cycle is what makes this type of air compressor very efficient.  A single acting compressor will have an operating efficiency between 22 – 24 kW/100 cfm of air while the double acting compressor has an operating efficiency between 15 – 16 kW/100 cfm.  Therefore, electricity cost is less with a double-acting reciprocating air compressor to make the same amount of compressed air.

To explore the internals a bit closer, the mechanical linkage used to move the piston is slightly different as well as the additional intake and exhaust valves.   Instead of the connecting rod being attached directly to the piston as seen inside a single acting compressor, a crosshead is added between the compression piston and the connecting rod (view picture below).  The rod that connects the crosshead to the compression piston can be sealed to keep the cylinder completely encapsulated.  For every rotation of the electric motor, the air is being compressed twice.  With the added heat of compression, the double acting compressors are generally water-cooled.  Also, with the added mechanism between the crank and the piston, the rotational speeds are typically less.  Because of the larger size, water jackets, and added parts, the initial cost is more expensive than the single acting compressor, but the efficiency is much higher.

Double Acting Reciprocating Air Compressor

Double acting compressors are generally designed for rugged 100% continuous operations.  Dubbed the work horse of the compressor family, they are also known for their long service life.  They are commonly used in high pressure services in multistage styles and can come in lubricated and non-lubricated configurations.   With the dual compression, slow speed and inter-cooling, it makes this type of air compressor very proficient in making compressed air.

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

 

Photos:  used from Compressed Air Challenge Handbook

Finding Leaks and Saving Money with the Ultrasonic Leak Detector

Locate costly leaks in your compressed air system!  Sounds like the right thing to do.

The EXAIR Ultrasonic Leak Detector is a hand-held, high quality instrument that is used to locate costly leaks in a compressed air system.

Ultrasonic sound is the term applied to sound that is above the frequencies of normal human hearing capacity.  This typically begins at sounds over 20,000 Hz in frequency.  The Ultrasonic Leak Detector can detect sounds in this upper range and convert them to a range that is audible to people.

When a leak is present, the compressed air moves from the high pressure condition through the opening to the low pressure environment.  As the air passes through the opening, it speeds up and becomes turbulent in flow, and generates ultrasonic sound components. Because the audible sound of a small leak is very low and quiet, it typically gets drowned out by by surrounding plant noises, making leak detection by the human ear difficult if not impossible.

ULD_Pr

Detecting a Leak with the Ultrasonic Leak Detector

By using the Ultrasonic Leak Detector, the background noise can be filtered out and the ultrasonic noises can be detected, thus locating a leakage in the compressed air system. There are (3) sensitivity settings, x1, x10, and x100 along with an on/off thumb-wheel for fine sensitivity.  The unit comes with a parabola and tubular extension for added flexibility.

ULD_Kit

Model 9061 – Ultrasonic Leak Detector and Included Accessories

Finding just one small leak can pay for the unit-

A small leak equivalent to a 1/16″ diameter hole will leak approx 3.8 SCFM at 80 PSIG of line pressure.  Using a reasonable average cost of $0.25 per 1000 SCF of compressed air generation, we can calculate the cost of the leak as follows-

Capture

It is easy to see that utilizing the Ultrasonic Leak Detector, and identifying and fixing leaks is the right thing to do.  It is possible to find and fix enough leaks that a new compressor purchase can be avoided or an auxiliary back-up is not needed any more.

If you have questions regarding the Ultrasonic Leak Detector, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Intelligent Compressed Air: Save $$ With a Leak Prevention Program

waste

Don’t let leaks drive up your utility bill

The generation of compressed air accounts for approximately 1/3 of all energy costs in an industrial facility. According to the Compressed Air Challenge, about 30% of that compressed air is lost through leaks. This means nearly 10% of your facility’s energy costs are simply wasted through poor connections, faulty air valves, improper installation, etc. In addition to simply wasting money, compressed air leaks can also contribute to a variety of other operating losses. A leak can cause a drop in system pressure. When this occurs, end users may not operate as efficiently, having an adverse effect on production. This same drop in system pressure will also cause the equipment to cycle on/off more often, shortening the life of your compressor and other equipment. If the leaks cause an issue in supply volume, it may lead to the belief that more compressor capacity is necessary, further increasing your operating costs.

To put leaks in perspective (assuming energy costs of .10/ kWh), the Compressed Air Challenge states this:

  • A $200/year leak cannot be felt or heard
  • A $800/year leak can be felt, but not heard
  • A $1,400/year leak can be felt and heard.

If you walk through your facility, how many leaks can you hear?

We know that a large portion of the compressed air is being wasted, but what do we do about it? A proper leak prevention plan is the key to success. Since these leaks are impossible to see and some cannot even be heard, you need a tool to help assist you. EXAIR’s model 9061 Ultrasonic Leak Detector is the right tool for the job. When compressed air leaks through a pipe, it creates an ultrasonic signature due to turbulence. While this sound is not always detectable by the human ear, this meter will allow you to locate leaks up to 20’ away.

 

ultrasonic_2

Model 9061 with parabola attachment

The first step will be locating the leaks using an Ultrasonic Leak Detector and tagging them throughout the facility. Don’t let this overwhelm you!! If you have a larger facility, break it up into sections that can be completed in 1 day. This will allow you to decide which areas of the plant should be looked at first. Once you’ve located and tagged all of the leaks, rate them under two separate criteria so that you can prioritize what to fix first. Rate them based on the difficulty that it will take to fix them and also by the severity of the leak. Those that are severe yet easy to fix would make sense to begin fixing first. Those that may require a period of shutdown can be planned to fix at a more appropriate time.

ULD_Kit

Accessories that come with the Ultrasonic Leak Detector

When you’ve had the opportunity to fix them, don’t just forget about it. When new piping is installed, new lines are added, or anything involving compressed air is installed there is the potential for new leaks to develop. Set this as one of your regular PM activities and complete your own compressed air audit once a year. Implementing the process and maintaining it are the keys to your success.

If you have questions about developing a leak program or how to use the Ultrasonic Leak Detector, give us a call. An Application Engineer will be happy to help with the process and recommend additional methods to save on your compressed air supply.

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

The Cost of Compressed Air Leaks Create the Need to Find and Fix

Leaks can cost you

As margins get tighter and cost of manufacturing climbs, industries are looking into other areas to be more economical.  A big focus today is in the compressed air systems.  Compressed air is considered to be the “forth” utility behind gas, water, and electricity.  It is a necessary system to run pneumatic systems, but it is the least efficient of the utilities.  For every $1.00 that is put into making compressed air, you only get roughly 5¢ of work from it.  So, it is very important to use this utility as efficiently as possible.

One of the largest problems affecting compressed air systems is leaks.  That quiet little hissing sound coming from the pipe lines is costing the company much money.  A university study was conducted to find the percentage of air leaks in a typical manufacturing plant.  In a poorly maintained system, they found on average that 30% of the compressor capacity is lost through air leaks.  In relation to the amount of electricity required to make compressed air, for every ten power plants producing electricity, there is one power plant producing electricity just for air leaks.  A majority of companies do not have a leak prevention program; so, many of these companies have poorly maintained systems. This creates a large amount of waste caused by simple air leaks.  To put a dollar value on it, a leak that you cannot physically hear can cost you as much as $130/year.  That is just for one inaudible leak in hundreds of feet of compressed air lines.  For the leaks that you can hear, you can tell by the chart below the amount of money that can be wasted by the size of the hole.  Unlike a hydraulic system, compressed air will not leave a tell-tale sign of a leak. You have to locate them by some other means.

**Note 1

Most leaks occur where you have threaded fittings, connections, hoses, and pneumatic components like valves, regulators, and drains.  The Optimization products from EXAIR are designed to help optimize your complete compressed air system.  The most effective way is to find and eliminate air leaks, and EXAIR has two products that can help do this.  The Ultrasonic Leak Detectors can find the air leaks, and the Digital Flowmeters can monitor your system for air leaks.  With both of these products included in a leak prevention program, you will be able to keep your compressed air system running optimally and reduce the wasted cost in air leaks and overusing the air compressor.

EXAIR Ultrasonic Leak Detector:

When a leak occurs, it emits an ultrasonic noise caused by turbulence.  These ultrasonic noises can be at a frequency above that which is audible for human hearing.  The EXAIR Ultrasonic Leak Detector can pick up these frequencies and make the leaks audible.  With three sensitivity ranges and LED display, you can find very minute leaks in your compressed air system.  It comes with two attachments; the parabola to locate leaks up to 20 feet away, and the tube attachment to define the exact location in the pipe line.  Once you find a leak, it can be marked for fixing.

EXAIR’s Digital Flowmeter w/ USB Data Logger

EXAIR Digital Flowmeter:

With the Digital Flowmeters, you can continuously monitor for waste.  Air leaks can occur at any time within any section of your pneumatic area.  You can do systematic checks by isolating sections with the Digital Flowmeter and watching for a flow reading.  Another way to monitor your system would be to compare the results over time.  With the Digital Flowmeters, we have a couple of options for recording the air flow data.  We have the USB Datalogger for setting certain time increments to record the air flows.  Once the information is recorded, you can connect the USB to your computer, and with the downloadable software, you can view the information and export it into an Excel spread sheet.  We also offer a wireless capability option with the Digital Flowmeters.  You can have multiple flow meters communicating through a gateway to monitor and record the flow information onto your computer system.  If you find that the flow starts trending upward for the same process, then you know that you have a leak.  It can also give you a preventive measure if your pneumatic system is starting to fail.

Compressed air leaks will rob you in performance, compressor life, and electrical cost.  It is important to have a leak prevention program to check for leaks periodically as they can happen at any time.  The EXAIR Ultrasonic Leak Detector and the Digital Flowmeters will help you accomplish this and optimize your compressed air system.  Once you find and fix all your leaks, you can then focus on improving the efficiency of your blow-off devices with EXAIR products and save yourself even more money.

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

 

**Note 1: Chart was published by Compressed Air Challenge in April 1998 – Rev. 0

Video Blog: The Monetary Benefits of an Engineered Solution

This video highlights the value and benefits of an engineered blow off solution.  We take a homemade open pipe blowoff and replace it with an EXAIR model 1100 Super Air Nozzle.  This air nozzle is then controlled through our Electronic Flow Controller, allowing for intermittent On/Off of the compressed air flow.  And, these solutions are wirelessly monitored via Zigbee network using our Wireless Digital Flowmeter.  Implementing these solutions results in a compressed air reduction of over 90%!!!

 

Full calculations along with supporting flow values (pulled from the same data shown in the video above) are shown below.

Screengrab of the flow values shown in the video above. Click for larger image.

The open pipe:

The first compressed air flow values to show up on the EXAIR Logger are for the open pipe blow off.  At 1 BAR operating pressure, this “solution” consumes 22.3 SCFM of compressed air.  At a cost of $0.25 for every 1,000 cubic feet of compressed air, this nozzle will cost $695.76 to operate 8 hours per day, 5 days per week, 52 weeks per year.

The engineered EXAIR Super Air Nozzle

Model 1100 EXAIR Super Air Nozzles consumes 4.7 SCFM at an operating pressure of 1 BAR – a reduction of 79% compared to the open pipe.  These savings prove out in terms of operating cost as well – $146.64 per year, compared to $695.76.

The engineered EXAIR Super Air Nozzle with Electronic Flow Control (EFC)

By controlling the “ON” time for this application with an EFC, we are only blowing for 32% of the time for each minute of operation which changes the required compressed air flow from 4.7 SCFM to a peak value of 1.5 SCFM. This control saves an additional 68% of compressed air flow.  And, these savings are compounded by eliminating the need for constant compressed air flow.  Total annual operating cost for the EXAIR 1100 Super Air Nozzle with Electronic Flow Control is just $46.80.

Implementing an engineered solution can have a TREMENDOUS impact on energy costs and operating costs in your facility.  Compressed air is the most expensive utility to produce and consume, making the impact of proper solutions of high value to any business.  Let us help you utilize engineered compressed air solutions in your facility by contacting an EXAIR Application Engineer today.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

What’s So “Super” About The Super Air Amplifier?

EXAIR Intelligent Compressed Air Products such as (left to right) the Air Wipe, Super Air Knife, Super Air Nozzle, and Air Amplifier are engineered to entrain enormous amounts of free air from the surrounding environment.

“Free air” from the surrounding environment?  You might think it’s too good to be true, and if you think you’re getting something for nothing, you’re right.  If you consider, though, that it’s oftentimes preferable to work smarter, not harder, then the use of engineered compressed air products is too good NOT to be true.  Case in point: the Super Air Amplifier.

The Coanda Effect is the “work smarter, not harder” part of the Super Air Amplifier

Simple and low cost, (hey, “engineered” doesn’t necessarily mean “complex and expensive”) the EXAIR Super Air Amplifier uses a small amount of compressed air to generate a tremendous amount of air flow through entrainment.  How much do they pull in?  Depending on the model, they entrain air at rates of 12:1 (for the 3/4″ Model 120020) to 25:1 (4″ & 8″ Models 120024 & 120028, respectively.)  The larger diameters mean there’s more cross sectional area to entrain air, so there is indeed efficiency to scale, size-wise.  There are a couple of great visuals in this video, if you want to see the entrainment in action (1:50) or the difference that the entrainment makes (1:30):

 

Where can you use a Super Air Amplifier?  The easy answer is, anyplace you want a consistent, reliable air flow.  The pressure supply can be regulated from a “blast to a breeze,” depending on the needs of your application.  The patented shim can be replaced for even higher performance, while maintaining the efficiency that makes it so valuable.  The balanced flow makes for incredibly quiet operation…no more noisy fans, blowers, or open-end compressed air pipes.  The body (3/4″ to 4″ sizes) is cast with a 2-hole flange for ease of installation.

When can you use a Super Air Amplifier?  Another easy answer: anytime you want.  If you need a continuous air flow, there are no moving parts to wear or electrical components to burn out.  Supply them clean, dry air, and they’ll run darn near indefinitely, maintenance free.

Alternately, if you need intermittent air flow, starting & stopping operation is as simple as opening & closing a valve in the compressed air supply line.  They produce rated flow immediately, and cut it off just as fast.

Some of the more popular applications are ventilation/exhaust, cooling, drying, cleaning, and dust collection.  There are five distinct models to choose from, and they’re all in stock.  We’re also happy to discuss special requirements that might lead to a custom product too.  Our Application Engineers work with Design & Production all the time to meet specific needs of particular situations.

If you’d like to find out more about letting the Super Air Amplifier, or any of EXAIR’s Intelligent Compressed Air Products work smarter for you, give me a call.

Russ Bowman
Application Engineer
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Crescent Hammers, Phillips Head Punches, and Other Cautionary Tales

I don’t want to sound “preachy,” but I’m a stickler for using the right tool for the job. Case in point: just the other day, I noticed (OK; my wife told me about) a loose drawer handle. I went to my toolbox in the garage to get a flat-head screwdriver, even though the drawer in question had a selection of butter knives, any one of which could have been used to tighten that screw.

I can trace this, without doubt or hesitation, to my service in the US Navy, under the direction of Senior Chief Cooper.  Proper tool selection & use was VERY important to him.  He stressed the issues of safety, quality, and performance, but if that didn’t work, he’d make his point with an offer to demonstrate the use of a specific tool (a ball peen hammer) on a sensitive part of your anatomy (it’s exactly the part you’re thinking of.)  At that point, it would have been unwise (and unsafe) to question whether that was a proper use of the tool or not.

Only one of these is a hammer………………..….only one of these is a punch………………..…..only one of these is a chisel.
Choose wisely.

Likewise, there are safety, quality, and performance issues associated with compressed air blow offs.  At EXAIR, we’re ALL sticklers about this, and we get calls all the time to discuss ways to get more out of compressed air systems by using the right products.  Here’s a “textbook” example:

A hose manufacturer contacted me to find out more about our Air Wipes, and how they might be a better fit for their various cleaning & drying applications (spoiler alert: they are.)  The blow offs they were using were made of modular hose, designed (and very successfully used) for coolant spraying in machine tools.

Only one of these is a compressed air blow off. Again…choose wisely.

The selection process was two-fold: they purchased one Model 2401 1″ Super Air Wipe to verify performance, and they sent in some of their modular hose assemblies for Efficiency Lab testing.  The first part was just as important as the second because, no matter how much air they were going to save (another spoiler alert: it was significant,) it wouldn’t matter if it didn’t get the job done.  At the station shown above, the Super Air Wipe resulted in superior performance, and a compressed air cost savings of over $400.00 annually.  For that one station.  Based on that, they outfitted TWENTY FIVE stations with engineered product sized for their different hoses, using our Model 2400 (1/2″), 2401 (1″), 2402 (2″) and 2403 (3″) Super Air Wipes.

If you’d like to find out how using the right product for the job can help your operation, give me a call.

Russ Bowman
Application Engineer
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