Intelligent Compressed Air: Maintaining an Efficient Compressor System

compressor

The electrical costs associated with generating compressed air make it the most expensive utility in any industrial facility. In order to help offset these costs, it’s imperative that the system is operating as efficiently as possible. I’d like to take a moment to walk you through some of the ways that you can work towards making your compressed air system more efficient.

The first step you should take is to identify and fix any leaks within the distribution piping. According to the Compressed Air Challenge, up to 30% of all compressed air generated is lost through leaks. This ends up accounting for nearly 10% of your overall energy costs!! To put leaks in perspective, take a look at the graphic below from the Best Practices for Compressed Air Systems handbook.

air leaks cost

Compressed air leaks don’t just waste energy, but they can also contribute to other operating losses. If enough air is lost through leaks, this can also cause a drop in system pressure. This can affect the functionality of other compressed air operated equipment and processes. This pressure drop can affect the efficiency of the equipment causing it to cycle on/off more frequently or to not work properly. This can lead to anything from rejected products to increased running time. With an increase in running time, there’s also the need for more frequent maintenance and unscheduled downtime.

You can perform a compressed air audit in your facility using an EXAIR Model 9061 Ultrasonic Leak Detector. If you’d prefer someone come in and do this for you, there are several companies that offer energy audit services where this will be a focal point of the process.

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EXAIR Ultrasonic Leak Detector

Speaking of maintenance, proper compressor maintenance is also critical to the overall efficiency of the system. Like all industrial equipment, a proper maintenance schedule is required in order to ensure things are operating at peak efficiency. Inadequate compressor maintenance can have a significant impact on energy consumption via lower compressor efficiency. A regular preventative maintenance schedule is required in order to keep things in good shape. The compressor, heat exchanger surfaces, lubricant, lubricant filter, air inlet filter, and dryer all need to be maintained. This can be done yourself or through a reputable compressor dealer. The costs associated with these services are outweighed in the improved reliability and performance of the compressor. A well-maintained system will not cause unexpected shutdowns and will also cost less to operate.

The manner in which you use your compressed air at the point of use should also be evaluated. Inefficient, homemade solutions are thought to be a cheap and quick solution. Unfortunately, the costs to supply these inefficient solutions with compressed air can quickly outweigh the costs of an engineered solution. An engineered compressed air nozzle such as EXAIR’s line of Super Air Nozzles are designed to utilize the coanda effect. Free, ambient air from the environment is entrained into the airflow along with the supplied compressed air. This maximizes the force and flow of the nozzle while keeping compressed air usage to a minimum.

Another method of making your compressed air system more efficient is actually quite simple: regulating the supply pressure. By installing pressure regulators at the point of use for each of your various point of use devices, you can reduce the consumption simply by reducing the pressure. This can’t be done for everything, but I’d be willing to bet that several tasks could be accomplished with the same level of efficiency at a reduced pressure. Most shop air runs at around 80-90 psig, but for general blowoff applications you can often get by operating at a lower pressure. Another simple, but often overlooked, method is to simply shut off the compressed air supply when not in use. If you haven’t yet performed an audit to identify compressed air leaks this is even more of a no-brainer. When operators go to lunch or during breaks, what’s stopping you from just simply turning a valve to shut off the supply of air? It seems simple and minute, but each step goes a long way towards reducing your overall air consumption and ultimately your energy costs.

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

 

Image taken from the Best Practices for Compressed Air Systems Handbook, 2nd Edition

Intelligent Compressed Air: Sliding-Vane Compressors

If you’re an active reader of the EXAIR blog, you’ve seen several posts over the last year about the various different types of air compressors. From the positive-displacement style of compressors (Rotary Scroll, Rotary Screw, Single and Double Acting Reciprocating Compressors,) as well as a review of a dynamic style (Centrifugal Compressors). In this blog, I’ll be discussing another of the positive-displacement variety: The Sliding-Vane Compressor.

Sliding Vane2
Air enters from the right, and as the compression chamber volume reduces due to counterclockwise rotation, the pressure increases until the air discharges to the left

In positive-displacement type compressors, a given quantity of air or gas is trapped in a compression chamber. The volume of this air is then mechanically reduced, causing an increase in pressure. A sliding-vane compressor will consist of a circular stator that is housed in a cylindrical rotor. The rotor then has radially positioned slots where the vanes reside. While the rotor turns on its axis, the vanes will slide out and contact the bore of the stator wall. This creates compression in these “cells”. An inlet port is positioned to allow the air flow into each cell, allowing the cells to reach their maximum volume before reaching the discharge port. After passing by the inlet port, the size of the cell is reduced as rotation continues and each vane is then pushed back into its original slot in the rotor.  Compression will continue until the cell reaches the discharge port. The most common form of sliding-vane compressor is the lubricant injected variety. In these compressors, a lubricant is injected into the compression chamber to act as a lubricant between the vanes and the stator wall, remove the heat of compression, as well as to provide a seal. Lubricant injected sliding-vane compressors are generally sold in the range of 10-200 HP, with capacities ranging from 40-800 acfm.

Advantages of a lubricant injected sliding-vane compressor include:

  • Compact size
  • Relatively low purchase cost
  • Vibration-free operation does not require special foundations
  • Routine maintenance includes lubricant and filter changes

Some of the disadvantages that come with this type of compressor:

  • Less efficient than the rotary screw type
  • Lubricant carryover into the delivered air will require proper maintenance of an oil-removal filtration system
  • Will require periodic lubricant changes

With the host of different options in compressor types available on the market, EXAIR recommends talking to a reputable air compressor dealer in your area to help determine the most suitable setup based on your requirements. Once your system is up and running, be sure to contact an EXAIR Application Engineer to make sure you’re using that compressed air efficiently and intelligently!

Tyler Daniel

Application Engineer

E-mail: TylerDaniel@exair.com

Twitter: @EXAIR_TD

Diagram:  used from Compressed Air Challenge Handbook

People of Interest: Henri Coanda June 7, 1886 – November 25, 1972

Henri Coanda was born in Bucharest, Romania on June 7 1886 in a large family with five brothers and two sisters. His father, Constantin M. Coanda, was a decorated Romanian soldier and following in his footsteps he also enlisted in the military. He finished his military education with high honors, but his keen interest in flying and his desire to achieve this sent him down a much different path.

Coanda attended a technical university in Germany and also attended the Superior Aeronautical School in Paris where he graduated at the top of his class with the highest of honors. In less than a year, he had partnered with Gianni Caproni, another known aviator, to construct what was called the Coanda-1910. This aircraft was displayed in Paris at the Second International Aeronautical Exhibition. But, unlike other planes of this time, Coanda’s aircraft did not have a propeller. The plane had an oddly shaped front with built-in rotary blades arranged in a swirling pattern. It was driven by an internal turbine screw that would suck air in through the turbine while the exhausting gases exited from the rear, driving the plane forward by propulsion.

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As impressive as this jet engine was, no one believed that it could fly. It is not believed that it ever did achieve flight, despite some contradictory claims by Coanda himself, but was instead struck by disaster. It is rumored that as Coanda injected more fuel into the engine, he was surrounded by flames, thrown from the craft and was lucky to make it out alive. Coanda is not credited as the inventor of the first jet plane, but it is his technology that sky rocketed future aviation research and provided perspective into how jet engines should be built.

Coanda is most known today for his research into what is now known as the Coanda Effect, or propensity of a fluid to adhere to the walls of a convex surface. It is this principle that creates lift on an airplane wing and is also the driving force behind many of EXAIR’s Intelligent Compressed Air Products. If you’d like to discuss how the Coanda effect is utilized in a Super Air Knife, Super Air Amplifier, or Super Air Nozzle give us a call!

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

 

Jet Engine image courtesy of Luke Healy via Creative Commons License

Intelligent Compressed Air: Utilization of the Coanda Effect

Henri Coanda was a Romanian aeronautical engineer most known for his work developing what is today known as the Coanda effect. The Coanda effect is the propensity of a fluid to adhere to the walls of a curved surface. A moving stream of fluid will follow the curvature of the surface rather than continuing to travel in a straight line.  This effect is used in the design of an airplane wing to produce lift. The top of the wing is curved whereas the bottom of the wing remains straight. As the air comes across the wing, it adheres to the curved surface, causing it to slow down and create a higher pressure on the underside of the wing. This  is referred to as lift and is what allows an airplane to fly.

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The Coanda effect is also the driving force behind many of EXAIR’s Intelligent Compressed Air Products. Throughout the catalog you’ll see us talking about air amplification ratios. EXAIR products are designed to take advantage of this phenomenon and entrain ambient air into the primary air stream. Compressed air is ejected through the small orifices creating air motion in their surroundings. Using just a small amount of compressed air as the power source, Super Air Knives, Air Nozzles, and Air Amplifiers all draw in “free” ambient air amplifying both the force and the volume of airflow.

Entrainment
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 air from the surrounding environment.

Super Air Knives provide the greatest amount of air amplification at a rate of 40:1, one part being the compressed air supply and 40 parts ambient air from the environment. The design of the Super Air Knife allows air to be entrained at the top and bottom of the knife, maximizing the overall volume of air. Super Air Nozzles and Super Air Amplifiers also use this effect to provide air amplification ratios of up to 25:1, depending on the model.

HowItWorks
Air Amplifiers use the Coanda Effect to generate high flow with low consumption.

The patented shim design of the Super Air Amplifier allows it to pull in dramatic amounts of free surrounding air while keeping sound levels as low as 69 dBA at 80 psig! The compressed air adheres to the Coanda profile of the plug and is directed at a high velocity through a ring-shaped nozzle. It adheres to the inside of the plug and is directed towards the outlet, inducing a high volume of surrounding air into the primary air stream. Take a look at this video below that demonstrates the air entrainment of a Super Air Amplifier with dry ice:

Utilizing the Coanda effect allows for massive compressed air savings. If you would like to discuss further how this effect is applied to our Super Air Knives, Air Amplifiers, and Air Nozzles give us a call. We’d be happy to help you replace an inefficient solution with an Engineered Intelligent Compressed Air Product.

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

Intelligent Compressed Air: Bernoulli’s Principle

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Daniel Bernoulli was a Swiss mathematician and physicist born in 1700. He is most known for the Bernoulli principle, published in his book Hydrodynamica in 1739. The Bernoulli’s principle states that an increase in speed of a fluid will result in a decrease in pressure. As a fluid moves from a wider pipe to a narrow one, the fluid begins to move faster. The given volume of the fluid moving from one point to another over a set amount of time will not change. In order for the same amount of fluid to pass through a smaller orifice, it must speed up. This is displayed quite well in the flow of a river. At wide, open spaces the river flows slowly. In areas that become narrow, for example by a canyon wall, the speed of the river’s flow increases dramatically.

The Bernoulli principle also provides an explanation for the lift that is created on an airplane wing. When air encounters an obstacle (in this case an airplane wing), its path will narrow as it flows around the object. As this stream of air speeds up, some of the energy from the random motion of the air molecules must be converted into energy of the stream’s forward flow. Pressure is created by the random motion of these air molecules. Transferring this energy into the stream flow then results in a drop in the air pressure. An airplane wing is shaped so that the air must move faster over it than under it. This causes the slower moving air underneath to exert more pressure on the wing than the air moving across the top. This is referred to as lift and is what allows an airplane to fly.

Temperatures are beginning to creep back up here in Cincinnati and just last week pitchers and catchers for the Cincinnati Reds reported for Spring Training. They’ll also be watching Bernoulli’s principle in action. The oft-dreaded (for batters, anyway) 12-6 curveball occurs due to the way the pitcher forces the ball to spin. Due to way he grips the ball across the laces and imparts this spinning motion, more air pressure forms on the top of the ball. This causes the bottom of the ball to accelerate downwards, resulting in the phenomenon that drives many baseball players crazy as they swing and miss due to a miscalculation of the ball’s position.

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Some of EXAIR’s products also utilize the Bernoulli Principle. As the high-velocity air exits the nozzle of a Super Air Knife, a low pressure area is created that draws in surrounding ambient air at a rate of 40:1. The same also occurs with the Super Air Amplifiers, Adjustable Air Amplifiers, and Air Nozzles. If you’d like to discuss the application of any of our Intelligent Compressed Air Products, give an Application Engineer a call today.

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

 

River image courtesy of Sasori33 via Creative Commons License
Reds image courtesy of Lisa via Creative Commons License

Intelligent Compressed Air: Distribution Piping

air compressor

An important component of your compressed air system is the distribution piping. The piping will be the “veins” that connect your entire facility to the compressor. Before installing pipe, it is important to consider how the compressed air will be consumed at the point of use. Some end use devices must have adequate ventilation. For example, a paint booth will need to be installed near an outside wall to exhaust fumes. Depending on the layout of your facility, this may require long piping runs.  You’ll need to consider the types of fittings you’ll use, the size of the distribution piping, and whether you plan to add additional equipment in the next few years. If so, it is important that the system is designed to accommodate any potential expansion. This also helps to compensate for potential scale build-up (depending on the material of construction) that will restrict airflow through the pipe.

The first thing you’ll need to do is determine your air compressor’s maximum CFM and the necessary operating pressure for your point of use products. Keep in mind, operating at a lower pressure can dramatically reduce overall operating costs. Depending on a variety of factors (elevation, temperature, relative humidity) this can be different than what is listed on directly on the compressor. (For a discussion of how this impacts the capacity of your compressor, check out one of my previous blogs – Intelligent Compressed Air: SCFM, ACFM, ICFM, CFM – What do these terms mean?) Once you’ve determined your compressor’s maximum CFM, draw a schematic of the necessary piping and list out the length of each straight pipe run. Determine the total length of pipe needed for the system. Using a graph or chart, such as this one from Engineering Toolbox. Locate your compressor’s capacity on the y-axis and the required operating pressure along the x-axis. The point at which these values meet will be the recommended MINIMUM pipe size. If you plan on future expansion, now is a good time to move up to the next pipe size to avoid any potential headache.

Once you’ve determined the appropriate pipe size, you’ll need to consider how everything will begin to fit together. According to the “Best Practices for Compressed Air Systems” from the Compressed Air Challenge, the air should enter the compressed air header at a 45° angle, in the direction of flow and always through wide-radius elbows. A sharp angle anywhere in the piping system will result in an unnecessary pressure drop. When the air must make a sharp turn, it is forced to slow down. This causes turbulence within the pipe as the air slams into the insides of the pipe and wastes energy. A 90° bend can cause as much as 3-5 psi of pressure loss. Replacing 90° bends with 45° bends instead eliminates unnecessary pressure loss across the system.

Pressure drop through the pipe is caused by the friction of the air mass making contact with the inside walls of the pipe. This is a function of the volume of flow through the pipe. Larger diameter pipes will result in a lower pressure drop, and vice versa for smaller diameter pipes. The chart below from the “Compressed Air and Gas Institute Handbook” provides the pressure drop that can be expected at varying CFM for 2”, 3”, and 4” ID pipe.

pressure drop in pipe

You’ll then need to consider the different materials that are available. Some different materials that you’ll find are: steel piping (Schedule 40) both with or without galvanizing, stainless steel, copper, aluminum, and even some plastic piping systems are available.

While some companies do make plastic piping systems, plastic piping is not recommended to be used for compressed air. Some lubricants that are present in the air can act as a solvent and degrade the pipe over time. PVC should NEVER be used as a compressed air distribution pipe. While PVC piping is inexpensive and versatile, serious risk can occur when using with compressed air. PVC can become brittle with age and will eventually rupture due to the stress. Take a look at this inspection report –  an automotive supply store received fines totaling $13,200 as a result of an injury caused by shrapnel from a PVC pipe bursting.

Steel pipe is a traditional material used in many compressed air distribution systems.  It has a relatively low price compared to other materials and due to its familiarity is easy to install. It’s strong and durable on the outside. Its strength comes at a price, steel pipe is very heavy and requires anchors to properly suspend it. Steel pipe (not galvanized) is also susceptible to corrosion. This corrosion ends up in your supply air and can wreak havoc on your point-of-use products and can even contaminate your product. While galvanized steel pipe does reduce the potential for corrosion, this galvanizing coating can flake off over time and result in the exact same potential issues. Stainless Steel pipe eliminates the corrosion and rusting concerns while still maintaining the strength and durability of steel pipe. They can be more difficult to install as stainless steel pipe threads can be difficult to work with.

Copper piping is another potential option. Copper pipe is corrosion-free, easy to cut, and lightweight making it easy to suspend. These factors come at a significant increase in costs, however, which can prevent it from being a suitable solution for longer runs or larger ID pipe installations. Soldering of the connecting joints can be time consuming and does require a skilled laborer to do so, making copper piping a mid-level solution for your compressed air system.

Another lightweight material that is becoming increasingly more common in industry is aluminum piping. Like copper, aluminum is lightweight and anti-corrosion. They’re easy to connect with push-to-lock connectors and are ideal for clean air applications. Aluminum pipe remains leak-free over time and can dramatically reduce compressed air costs. While the initial cost can be high, eliminating potential leaks can help to recoup some of the initial investment. Aluminum pipe is also coated on the inside to prevent corrosion. While an aluminum piping system may be the most expensive, its easy installation and adaptability make it an excellent choice.

It can be easy to become overwhelmed with the variety of options at your disposal. Your facility layout, overall budget, and compressed air requirements will allow you to make the best choice. Once you’ve selected and installed your distribution piping, look to the EXAIR website for all of your point-of-use compressed air needs!

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

Super Air Wipe Helps Shield a Lens

Super Air Wipe Kit

A tier 2 automotive company makes small metal boxes with a process which includes laser welding and a vision inspection system. The machine was programmed to weld different components onto the metal enclosure. During the welding operation, an optical sensor would check the quality of the welds. The vision system used a lens to protect the sensor from welding slag and debris. After a few operations, they started seeing false positives in the welding areas, and the metal enclosure would be flagged for rejection. In investigating the issue, they found that the lens was getting dirty from the welding operation. Because of the sensitivity of the sensor, it would detect the debris and marks on the lens and signal for poor weld. The lens was doing its part in protecting the sensor from damage; but, they needed a way to shield the lens from dirt and slag during the welding operation and visual inspection.

With this process, the machine would weld metal fasteners onto an enclosure by laser. The optical sensor would move along the welded areas to check the quality. In a lead/lag operation, the vision system would check the welds after a few seconds of cooling. So, both operations were occurring at the same time but at different intervals. When they started to see the rejection rate increase, they would have to stop the operation, clean the lens, and verify the integrity of the welds. In some cases, they would have to replace the 1 ¼” diameter lens especially if a piece of welding slag marred the surface. With incorrect rejections and lens cleaning, downtime was hurting their production rates and cost.

This customer wanted to use compressed air because it is a powerful and invisible way to create a shield. Since EXAIR is a leader in efficient and effective ways to use compressed air, they contacted us for help. Initially, I suggested a Super Air Knife to deflect any slag and debris from the lens surface. I showed a prior solution to a very similar issue; “Air Shielding a Laser Lens” (Reference below). But, because of the proximity to the part and the limitation in space, the Super Air Knife  configuration in the solution below would make it impossible to use. They were looking for a product that could be mounted either flush or behind the surface of the lens and still protect it.

Air Shielding a Laser Lens

To accommodate for this request, we had to direct the compressed air stream at an angle. EXAIR manufacturers a product that can do just that, the Super Air Wipe. The design of the Super Air Wipe blows compressed air at a 30-degree angle toward the center in a 360-degree air pattern, just like a cone. It can be placed around the lens and still be able to create a “wall” of air to block any slag or debris from hitting the lens.

I recommended the model 2452SS, 2” Super Air Wipe Kit. This Super Air Wipe has the body, braided hose, hardware, and shims that is made from stainless steel. It can handle the high heat loads from the welding process as well as to allow for easy cleanup after a day of operating. The kit includes a filter, to keep the compressed air clean; a regulator, to finely tune the force requirement; and a shim set. The shim set includes two additional sets of shims that can be added to increase the force of protection if needed. With the kit, the customer can “dial” in the correct amount of force needed to keep the lens clean without using excessive amount of compressed air.

As an added benefit of saving compressed air, the Super Air Wipe uses the Coanda effect to maximize the entrainment of ambient air into the compressed air stream. This makes the unit very efficient and very powerful. The Super Air Wipe was mounted just behind the lens like the customer required (Reference mock picture below), and the sensor could examine the welds without any interference with the metal enclosure.

Laser Lens mock drawing

Visual inspections systems are highly accurate pieces of equipment, and a dirty lens will affect the performance. EXAIR has many ways to keep the lens clean with a non-contact invisible barrier to protect sensors, cameras, and lasers. If you have a similar application, you can contact an Application Engineer to determine the best way to keep the lens clean and your equipment functional. After mounting the Super Air Wipe, the customer above eliminated any false rejections, and dramatically decreased any downtime for cleaning or replacing the lens in his welding machine.

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