About Air Compressors: Air Intake Best Practices

Take a second and think about where the air compressor is located within your facility.  It is more than likely not a major focal point displayed prominently in the floor layout. There is a better chance it is tucked away in a corner of the facility where operators seldom travel.  No matter the type of air compressor, it still has an intake where it pulls in the ambient air from around the compressor then sends it through some process and on the demand side of your compressed air system.  These intakes can easily be placed out of sight and out of mind especially in older facilities that were designed when compressors were loud and the piping layout kept them away from operators due to sound level restrictions.

Air Compressor
Antique Air Compressor (Not safe for use!)

That’s why your compressor manufacturer supplies a specific grade of air inlet/intake filter, and this is your first line of defense. If it’s dirty, your compressor is running harder, and costs you more to operate it.  If it’s damaged, you’re not only letting dirt into your system; you’re letting it foul & damage your compressor. It’s just like changing the air filter on your car, your car needs clean air to run correctly, so does your compressor and the entire demand side of your compressed air system.

According to the Compressed Air Challenge, as a compressor inlet filter becomes dirty, the pressure drop across the inlet increases, this is very similar to the point of use compressed air filters.  The inlet filter on the compressor is the only path the compressor has to pull in the air, when restricted the compressor can begin to starve for air very similar to if you only had a small straw to breath through and told to run a marathon.  A clogged inlet filter can give false symptoms to compressor technicians as well.

The effects can mimic inlet valve modulation which result in increased compression ratios. If we were to form an example based on a compressor with a positive displacement, if the filter pressure drop increases by 20″ H2O, a 5% reduction of the mass flow of air will be present without a reduction in the power being drawn by the compressor. This all leads to inefficiency which easily amounts to more than the cost to replace the depleted inlet air filter.

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Compressed Air System

Where you place the filter is just as important as how often you replace it.  There are some tips to be used when mounting the inlet filter.

  1. The filter can be placed on the compressor, but the inlet pipe should be coming from an external area to the compressor room or even the building if possible. The inlet should be free from any contaminants as well.  Some examples that are easy to overlook are nearby condensate discharges, other system exhausts and precipitation.
  2. Depending on the type of compressor being used, a lower intake air temperature can increase the mass flow of air due to the air density.  A compressor that is lubricant injected is not susceptible to this due to the air mixing with the warmer lubricant before being compressed.

If you would like to discuss improving your compressed air efficiency or any of EXAIR’s engineered solutions, I would enjoy hearing from you…give me a call.

Jordan Shouse
Application Engineer
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Images Courtesy of  the Compressed Air Challenge and thomasjackson1345 Creative Commons.

How a Centrifugal Compressor Works

Continuing our series on different types of air compressors, today’s blog will feature the centrifugal compressor.  The centrifugal compressor is classified as a dynamic compressor.  Dynamic compressors are designed to work with  a continuous flow of air that has its velocity increased by an impeller rotating at a very high speed.

The centrifugal compressor works by transforming the kinetic energy and velocity into pressure energy in the diffuser.  The air passes through the inlet guide vanes being drawn into the center of a rotating Impeller with radial blades and is then pushed outward from the center by centrifugal force. This radial movement of air results in a pressure rise and the generation of kinetic energy.  The kinetic energy is also converted into pressure by passing through the diffuser.

Centrifugal Pic 1
Sample Centrifugal Compressor

Multiple stages are required to raise the pressure to a sufficient level for typical industrial plant requirements.  Each stage takes up a part of the overall pressure rise of the compressor unit.  Depending on the pressure required for the application, a number of stages can be arranged in a series to achieve a higher pressure.

The most common centrifugal air compressor has two to four stages to generate pressures of 100 to 150 PSIG and incorporates a water cooled inter-cooler and separator between each stage to remove condensation and cool the air prior to entering the next stage.

Centrifugal compressors are the near middle of the road regarding efficiency, their typical operating cost is 16 to 20 kW/100 CFM.  The most efficient compressor type is the double-acting reciprocating and costs 15 to 16 kW/100 SCFM and the least is the Sliding Vane which costs 21 to 23 kW/100 SCFM.

Advantages of the centrifugal air compressor:

  • Up to 1500 HP systems are available
  • Price per HP drops as system size increases
  • Supplies lubricant-free air
  • Special installation pads are not required for installation

Disadvantages of the centrifugal air compressor

  • Costs more Initially
  • Requires specialized maintenance
  • Due to high rotational speeds (can exceed 50,000 RPM) precision high speed bearings and vibration monitoring are required

EXAIR recommends contacting a reputable air compressor dealer in your area to discuss your volume and pressure requirements to determine the best size & type air compressor for your needs.

Regardless of the type of air compressor you have, EXAIR’s Intelligent Compressed Air Products® can minimize your compressed air consumption, potentially reducing the size of compressor needed, reduce noise and still deliver powerful results!   If you would like to discuss highly efficient and quiet point of use compressed air products or any EXAIR product, we would enjoy hearing from you. 

Steve Harrison
Application Engineer
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Image Courtesy of  the Compressed Air Challenge

About Compressed Air Dryers – What Are They and Why Use Them

All atmospheric air contains some amount of water vapor.  When air is then cooled to saturation point, the vapor will begin to condense into liquid water. The saturation point is the condition where the the air can hold no more water vapor. The temperature at which this occurs is knows as the dew point.

When ambient air is compressed, heat is generated and the air becomes warmer. In industrial compressed air systems, the air is then routed to an aftercooler, and condensation  begins to take place. To remove the condensation, the air then goes into separator which traps the liquid water. The air leaving the aftercooler is typically saturated at the temperature of the discharge, and any additional cooling that occurs as the air is piped further downstream will cause more liquid to condense out of the air. To address this condensation, compressed air dryers are used.

It is important to dry the air and prevent condensation in the air. Many usages of the compressed air are impacted by liquid water being present. Rust and corrosion can occur in the compressed air piping, leading to scale and contamination at point -of -use processes. Processes such as drying operations and painting would see lower quality if water was deposited onto the parts.

dryers.png

There are many types of dryers – (see recent blogs for more information)

  • Refrigerant Dryer – most commonly used type, air is cooled in an air-to-refrigerant heat exchanger.
  • Regenerative-Desiccant Type – use a porous desiccant that adsorbs (adsorb means the moisture adheres to the desiccant, the desiccant does not change, and the moisture can then be driven off during a regeneration process).
  • Deliquescent Type – use a hygroscopic desiccant medium that absorbs (as opposed to adsorbs) moisture. The desiccant is dissolved into the liquid that is drawn out. Desiccant is used up, and needs to be replaced periodically.
  • Heat of Compression Type – are regenerative desiccant dryers that use the heat generated during compression to accomplish the desiccant regeneration.
  • Membrane Type– use special membranes that allow the water vapor to pass through faster than the dry air, reducing the amount water vapor in air stream.

The air should not be dried any more than is needed for the most stringent application, to reduce the costs associated with the drying process. A pressure dew point of 35°F to 38°F (1.7°C to 3.3°C) often is adequate for many industrial applications.  Lower dew points result in higher operating costs.

If you have questions about compressed air systems and dryers or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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About Rotary Scroll Compressors

The Rotary Scroll compressor is a popular style compressor and is used primarily for air conditioning refrigerant systems.  Recently, since it is very efficient, quiet and reliable it has been adopted by industrial air compressor manufacturer’s to expand their product offering for their smaller, high-efficiency product line.

They operate on the principle of two intermeshing spirals or scrolls with one being stationary while the other rotates or orbits in relation to it.  They are mounted with 180° phase displacement between them which forms air pockets having different volumes.  Air enters through the inlet port located in the rotating/orbiting scroll which fills the chambers and as is moved along and compressed along the scroll surfaces.

scroll compressor finalSome of the key advantages of a Rotary Scroll Compressor are:

  • Pulsation free delivery due to the continuous flow from the suction port to the outlet port.
  • No metal to metal contact thereby eliminating the need for lubrication
  • Low noise levels
  • Fewer moving parts means less maintenance
  • Energy Efficient
  • Air cooled

The largest disadvantage is they are available in a limited range of sizes and the largest SCFM outputs are around 100 SCFM.

This is exactly where EXAIR shines, we offer 15 product lines of highly efficient & quiet point of use compressed air products and accessories to compliment their limited output volume of air.  All EXAIR products are designed to use compressed air efficiently and quietly, many of which reduce the demand on your air compressor which will help control utility costs and possibly delay the need to add additional compressed air capacity.

As an example, EXAIR’s Super Air Knives deliver exceptional efficiency by entraining ambient air at ratios of up to 40:1 and they are able to deliver an even laminar flow of air ranging from a gentle breeze to exceptionally hard-hitting force.

Super Air Knife
EXAIR’s Super Air Knife entrains ambient air at a 40:1 ratio!

EXAIR’s Super Air Amplifiers are able to entrain ambient air at ratio’s up to 25:1.  The model 120024 – 4″ Super Air Amplifier developes output volumes up to 2,190 SCFM while consuming only 29.2 SCFM of compressed air @ 80 PSI which can easily be operated on a 100 SCFM output compressor.

Super Air Amplifier
EXAIR Air Amplifiers use a small amount of compressed air to create a tremendous amount of air flow.

For your blow off needs EXAIR’s Super Air Nozzle lineup has an offering that will fit nearly any need or application you may have.  Nozzles are available in sizes from M4 x 0.5 to  1 1/4 NPT and forces that range from 2 ounces of force up to 23 Lbs at 12″ from the discharge.  We offer sixty two nozzles that could all be operated easily from the limited discharge or a rotary scroll compressor.

nozzlescascadeosha
Family of Nozzles

If you need to reduce your compressed air consumption or you are looking for expert advice on safe, quiet and efficient point of use compressed air products give us a call.  We would enjoy hearing from you!

Steve Harrison
Application Engineer
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Starting a Leak Prevention Program

Since all compressed air systems will have some amount of leakage, it is a good idea to set up a Leak Prevention Program.  Keeping the leakage losses to a minimum will save on compressed air generation costs,and reduce compressor operation time which can extend its life and lower maintenance costs.

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There are generally two types of leak prevention programs:

  • Leak Tag type programs
  • Seek-and-Repair type programs

Of the two types, the easiest would be the Seek-and-Repair method.  It involves finding leaks and then repairing them immediately. For the Leak Tag method, a leak is identified, tagged, and then logged for repair at the next opportune time.  Instead of a log system, the tag may be a two part tag.  The leak is tagged and one part of the tag stays with the leak, and the other is removed and brought to the maintenance department. This part of the tag has space for information such as the location, size, and description of the leak.

The best approach will depend on factors such as company size and resources, type of business, and the culture and best practices already in place. It is common to utilize both types where each is most appropriate.

A successful Leak Prevention Program consists of several important components:

  • Baseline compressed air usage – knowing the initial compressed air usage will allow for comparison after the program has been followed for measured improvement.
  • Establishment of initial leak loss – See this blog for more details.
  • Determine the cost of air leaks – One of the most important components of the program. The cost of leaks can be used to track the savings as well as promote the importance of the program. Also a tool to obtain the needed resources to perform the program.
  • Identify the leaks – Leaks can be found using many methods.  Most common is the use of an Ultrasonic Leak Detector, like the EXAIR Model 9061.  See this blog for more details. An inexpensive handheld meter will locate a leak and indicate the size of the leak.

    ULD_Pr
    Using the Model 9061 Ultrasonic Leak Detector to search for leaks in a piping system
  • Document the leaks – Note the location and type, its size, and estimated cost. Leak tags can be used, but a master leak list is best.  Under Seek-and-Repair type, leaks should still be noted in order to track the number and effectiveness of the program.
  • Prioritize and plan the repairs – Typically fix the biggest leaks first, unless operations prevent access to these leaks until a suitable time.
  • Document the repairs – By putting a cost with each leak and keeping track of the total savings, it is possible to provide proof of the program effectiveness and garner additional support for keeping the program going. Also, it is possible to find trends and recurring problems that will need a more permanent solution.
  • Compare and publish results – Comparing the original baseline to the current system results will provide a measure of the effectiveness of the program and the calculate a cost savings. The results are to be shared with management to validate the program and ensure the program will continue.
  • Repeat As Needed – If the results are not satisfactory, perform the process again. Also, new leaks can develop, so a periodic review should be performed to achieve and maintain maximum system efficiency.

In summary – an effective compressed air system leak prevention and repair program is critical in sustaining the efficiency, reliability, and cost effectiveness of an compressed air system.

If you have questions about a Leak Prevention Program or any of the 16 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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General Good Ideas For The Compressor Room

When considering your compressor room all too often the phrase applies “out of sight and out of mind”.  Of course, we all know that is not a good approach to the compressor room or really anything in life.  Unfortunately, many of us take for granted that very system that delivers the power to keep our machines, equipment and tools operating.

Air Compressor
Compressor Room Located Outdoors

So, what can we do keep the ‘lungs” of our plants performing reliably and efficiently?  Since this Blog is about “General Good Ideas For The Compressor Room”, I have some points below for your consideration.

  • Ideally the compressor room should be centrally located to minimize the length of the pipes and allows for easier noise control. With long piping runs leaks become more likely and frictional losses are increased.
  • The compressor room should be sized to allow for easy maintenance and future expansion.
  • For efficient operation air compressors need clean intake air. Intake air that is dusty, dirty or contains gaseous contamination will reduce the efficiency and possibly the longevity of your equipment.
  • The compressor room needs adequate ventilation since air compressors generate significant heat. If excessive heat is allowed to build up it reduces the efficiency of the air compressor raising utility costs, causes compressor lubricant to break down prematurely that could possibly result in increased maintenance and compressor failure.
  • What is the velocity of the air through the main headers? If the speed is above 1200 FPM many dryers have reduced efficiency and speeds greater than this can also carry moisture past the drainage drop legs.
  • Excess friction caused by too small of a diameter piping creates pressure loss, which reduces efficiency and if the compressor is ran above its pressure rating to overcome the frictional losses increases energy consumption, maintenance costs and down time.

Now that your compressor room is shipshape in Bristol fashion, you might think that all is well.  While that may be true, chances are there are other significant additional savings to be had.  EXAIR specializes in point of use compressed air products that are highly efficient and quiet!  If you have any blow-offs that are open tube or howl as loud as the ghost of Christmas yet to come, check out EXAIR’s Super Air Nozzles.  They are highly efficient and quiet, in fact they meet OSHA Standard 29 CFR – 1941.95 for maximum allowable noise and OSHA Standard 29 CFR 1910.242 (b) for higher than 30 PSIG blow-off pressure.  All of EXAIR’s compressed air products are engineered to minimize compressed air consumption and take advantage of the Coanda effect.  Simply stated EXAIR’s highly engineered, intelligent designs entrain (combine) ambient air with the compressed air supply which saves you money!

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EXAIR Super Air Nozzle entrainment

EXAIR also offers the Ultra Sonic Leak Detector.  Simply point the device at a suspected leak which are typically found at unions, pipes, valves and fittings from up to 20’ away.   Plants that are not maintaining their plumbing can waste up to 30% of their compressors output through undetected leaks.

ultrasonic_2
EXAIR Ultra Sonic Leak Detector

EXAIR has a complete optimization product line that the Ultra Sonic Leak Detector is in that includes the Electronic Flow Control, Digital Flowmeter’s and a Digital Sound Level Meter.  All designed to either increase the safety or efficiency of your compressed air usage.

EXAIR has 15 other product lines all designed to increase your process efficiency and save you money by using you compressed air supply efficiently.  Why not visit the EXAIR website or call and request a free catalog?

When you are looking for expert advice on safe, quiet and efficient point of use compressed air products give us a call.   We would enjoy hearing from you!

Steve Harrison
Application Engineer
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Image taken from the Best Practices for Compressed Air Systems Handbook, 2nd Edition

Intelligent Compressed Air: Single Acting Reciprocating Air Compressors

Of all the types of air compressors on the market, you can’t beat the single acting reciprocating air compressor for simplicity:

Piston goes down: air is pulled in. Piston goes up: air is pushed out.

This simplicity is key to a couple of major advantages:

  • Price: they can cost 20-40% less than a similar rated (but more efficient) rotary screw model, up to about 5HP sizes.  This makes them great choices for home hobbyists and small industrial or commercial settings.
  • High pressure: It’s common to see reciprocating compressors that are capable of generating up to 3,000 psig.  Because the power is transmitted in the same direction as the fluid flow, they can handle the mechanical stresses necessary for this much better than other types of air compressors, which may need special modifications for that kind of performance.
  • Durability: out of necessity, their construction is very robust and rugged.  A good regimen of preventive maintenance will keep them running for a good, long time.  Speaking of which…
  • Maintenance (preventive): if you change your car’s oil and brake pads yourself, you have most of the know-how – and tools – to perform regular upkeep on a reciprocating air compressor.  There’s really not that much to them:

    The internals of a single acting reciprocating compressor.

Those advantages are buffered, though, by certain drawbacks:

  • Efficiency, part 1: The real work (compressing the air) only happens on the upstroke.  They’re less efficient than their dual acting counterparts, which compress on the downstroke too.
  • Efficiency, part 2: As size increases, efficiency decreases.  As stated above, smaller sizes usually cost appreciably less than more efficient (rotary screw, vane, centrifugal, etc.) types, but as you approach 25HP or higher, the cost difference just isn’t there, and the benefits of those other types start to weigh heavier in the decision.
  •  Maintenance (corrective):  Whereas they’re easy to maintain, if/when something does break, the parts (robust and rugged as they are) can get pretty pricey.
  • Noise: No way around it; these things are LOUD.  Most of the time, you’ll find them in a remote area of the facility, and/or in their own (usually sound-insulated) room.
  • High temperature:  When air is compressed, the temperature rises due to all the friction of those molecules getting shoved together…that’s going to happen with any air compressor.  All the metal moving parts in constant contact with each other, in a reciprocating model, add even more heat.
  • Oil in the air: If you’re moving a piston back & forth in a cylinder, you have to keep it lubed properly, which means you have oil adjacent to the air chamber.  Which means, no matter how well it’s built, you’re likely going to have oil IN the air chamber.

All that said, the benefits certainly do sell a good number of these compressors, quite often into situations where it just wouldn’t make sense to use any other type.  If you’re in the market for an air compressor,  you’ll want to find a local reputable air compressor dealer, and discuss your needs with them.  If those needs entail the use of engineered compressed air products, though, please feel free to give me a call to discuss.  We can make sure you’re going to ask your compressor folks the right questions.

Russ Bowman
Application Engineer
EXAIR Corporation
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