Compressed Air System Equipment

Compressed air is a valuable utility and understanding what makes up a solid system is very important. Most all manufacturing facilities have a demand for compressed air, so today we’ll discuss how when managed well, and with the proper equipment, how valuable this utility can be.

The equipment begins with the compressor. Specifying which compressor is best for you is genuinely specific to your needs, and many times even your geography. How many “users” of the air, the distance the air has to travel, how many and how sharp of turns need to be made are all specific to your building and setup. Drastic temperature changes, night and day, and many times summer to winter, can effect the compressor as well. Here is a list of things to consider when purchasing or upgrading the compressor itself:

  1. What is the actual air requirement? (SCFM) – as a rule of thumb – every 1 HP = 4 SCFM
  2. How many shifts, and do these shifts vary in air consumption?
  3. Average and Maximum Flow requirements
  4. What about leaks?
  5. What about the future?
  6. What is the highest pressure needed and why?
  7. How far away form the source are the users?
  8. Would a receiver tank/intermittent storage in the loop benefit your situation?

Compressor: Once you fully have a grasp of your demand, you can now move on to the compressor. There are 5 main types of compressors. One of the most common is the single-stage lubricant injected rotary screw compressor. This compressor is also offered in 2 stage. The other 3 types are a) 2-stage double acting reciprocating compressor b) Lubricant free screw compressor and c) Centrifugal 3-stage compressor. Each of these compressors have their own unique characteristics, benefits and faults. We highly recommend getting a local Air compressor company or professional involved to ensure the correct type and size.

Dirty Inlet Filter: Once the compressor is specified, you will need to ensure you have the best solution for dirty, ambient air being pulled into the compressor. The air coming out, begins with the air coming in, so this filter needs careful consideration based upon your individual ambient conditions. We’ve all heard the saying “garbage in – garbage out”… This filter should be checked, washed or changed often.

Receiver tank: The compressor(s) feed into a receiver tank. Many times this is call the Control Receiver, or the wet tank or cooling tank. Receiver tanks take in the air from the compressor and hold it under pressure for future use. These tanks reduce the cycles on the compressor, and prevents excessive loading and unloading in the system. These are not used on every system, but should be.

Dryer: Regardless of where you are in the world, all atmospheric air has some amount of vapor which will begin to condense into water when the air is cooled to the saturation point (This saturation point is better known as the dew point). The amount of moisture in the air depends on the temperature and relative humidity. As a rule of thumb, the moisture in the air will double for every 20°F increase in temperature. Your dryer should be able to dry the air to a dew point that is at least 18°F below the lowest temperature at the use point of the air. The size and amount of dryers is completely dependent on your companies needs.

Coalescent filter: Right after the dryer, it is recommended to put this type of filter to remove any other condensate, oils, or lubricants from the compressor. Unwanted oil in in the system can effect the machines and tools being used with the air.

Once your pipes have been laid to your point of use areas be it a machine or tools, you will want to have another filter at the point of use. Regardless of the age of your system, piping corrosion will happen leading to particulate in your air lines. You will want to filter this out prior to the final use of the air. The style and size of these filters should be determined at the point of use for the air. If your end use utilizes an EXAIR product – we recommend using our Automatic Filter Separators.

As the final step prior to use, it is recommended to have a pressure regulator and gauge on the line. Over time, every system will deplete air with small leaks, added users, or dirty filters. The most common cause of failure with EXAIR products, is actually lack of the appropriate air at the point of use.

Please keep in mind that this is a fairly simplistic explanation of a common Compressed Air System. Some systems have multiple receiving tanks, refrigerant coolers, dryers, and many different types of filters. The main goal is having enough clean, dry air to ensure that machines and tools function at peak performance.

Thank you for stopping by,

Brian Wages
Application Engineer
EXAIR Corporation
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Intelligent Compressed Air: Piping and Pressure Drop

Pressure drop is an unavoidable occurrence in compressed air systems. It’s caused by restrictions or obstructions to flow in your system, and that includes…well, everything:

  • No matter how big your header, drops, supply lines, etc. are, pressurized fluid encounters friction with the inside diameter of the conduit through which it flows.
  • Odds are, your header has at least a few elbows, wyes, tees, reducers, etc. Individually, the restrictions from these are usually quite small, but when you look at a system full of them, they can add up.
  • The type of piping your header is made of matters as well. Iron pipe WILL rust, which roughs up the inside wall of the pipe, which adds friction. Copper and aluminum aren’t near as bad, but there’s no such thing as a zero coefficient of friction.
  • Filters force the air flow through very small passages, torturous paths, or directional changes to remove particulates, moisture, and oil/oil vapor.
  • While not a restriction or obstruction, leaks in your system DO let out perfectly good compressed air before it can be used, so they can be included in our discussion.

Before you go off and redesign your air distribution header or remove your filters (DON’T do that!), it’s important to point that, historically, the highest pressure drops occur at or near the points of use:

  • Undersized hoses. The friction mentioned in the first ‘bullet’ above is compounded by increasing length, and decreasing diameter, of your air operated products’ supply lines. If your product’s performance is suffering, look up its rated air consumption and compare that to the flow rating of the length & diameter of the supply line.
  • Quick connect fittings. The push-to-connect types are particularly notorious for this…the air has to flow around the plug that stops flow when it’s disconnected. You can either replace them with threaded fittings, or if you still want the convenience of the quick connect, consider bushing up a size or two. A 3/8 NPT push to connect fitting will flow twice as much as a 1/4 NPT, and a 1/2 NPT will flow over three times as much as a 1/4 NPT fitting. In the EXAIR R&D room, Efficiency Lab, and shop, we actually use 3/4 NPT quick connects for a wide range of testing, demonstration, performance, etc.
  • Leaks. Even if they’re not big enough to cause a pressure drop, they’re still wasting compressed air. And if they ARE causing pressure drops, please stop reading this and go fix them, right now. Yeah; it’s that important.

Now, there are culprits on the supply side too: aftercoolers, dryers, and system filters can all contribute to pressure drops if they’re improperly sized, or, more often, improperly maintained. For troubleshooting, your first and best shot is to have pressure gauges at strategic locations…you can’t manage what you don’t measure. And not managing it can get costly:

  • Let’s say your compressor discharge header pressure is set to 100psig, but an undersized hose is only letting you get 65psig to an air operated product that really needs 80psig. You can increase your header pressure to 115-120psig to “push” more air through that hose, but keep in mind that all your other unregulated loads will get that pressure increase as well: pneumatic cylinders would operate faster, impact drivers will generate more torque, blow off devices will use more air (and get louder), etc.
  • Even if those things weren’t a problem, it’s going to cost you more. For every 2psi increase in your compressor’s discharge pressure, its power consumption increases by 1 percent. So, for the 20psi increase, it’s going to cost you about 10% more to operate that compressor. A larger diameter air hose, on the other hand, is a one time investment that doesn’t affect the rest of your compressed air system.
  • If you haven’t fixed the leaks I mentioned above yet, increasing your supply pressure will increase the leakage flow rate and, especially if the leak’s in a hose or hose fitting, it can tear that opening wider, compounding the leakage flow rate further.

EXAIR Corporation is keen on making sure you get the most out of our products, and your compressed air system. If you’ve got questions, we’ve got knowledge, and a wealth of resources to help…give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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Intelligent Compressed Air: Rotary Air Compressors

Air Compressor
Air Compressor and Storage Tanks

One thing that is found in virtually every industrial environment is an air compressor. Some uses for the compressed air generated are: powering pneumatic tools, packaging, automation equipment, conveyors, control systems, and various others. Pneumatic tools are favored because they tend to be smaller and more lightweight than electric tools, offer infinitely variable speed and torque, and can be safer than the hazards associated with electrical devices. In order to power these devices, compressed air must be generated.

There are two main categories of air compressors: positive-displacement and dynamic. In a positive-displacement type, a given quantity of air is trapped in a compression chamber. The volume of which it occupies is mechanically reduced (squished), causing a corresponding rise in pressure. In a dynamic compressor, velocity energy is imparted to continuously flowing air by a means of impellers rotating at a very high speed. The velocity energy is then converted into pressure energy. We’ve discussed the different styles of air compressors here on the EXAIR Blog in the past. Today I’d like to highlight the rotary compressors, one of the positive-displacement types of compressors.

Positive-displacement compressors are broken into two categories: reciprocating and rotary. The rotary compressors are available in lubricant-injected or lubricant-free varieties. Both styles utilize two inter-meshing rotors that have an inlet port at one end and a discharge port at the other. Air flows through the inlet port and is trapped between the lobes and the stator. As the rotation continues, the point inter-meshing begins to move along the length of the rotors. This reduces the space that is occupied by the air, resulting in an increase in pressure.

In the lubricant-injected varieties, the compression chamber is lubricated between the inter-meshing rotors and bearings. This lubricant protects the inter-meshing rotors and associated bearings. It eliminates most of the heat caused by compression and acts as a seal between the meshing rotors and between the rotor and stator. Some advantages of the lubricant-injected rotary compressor include a compact size, relatively low initial cost, vibration free operation, and simple routine maintenance (replacing lubricant and filter changes). Some drawbacks to this style of compressor include lower efficiency when compared with water-cooled reciprocating compressors, lubricant carry over must be removed from the air supply with a coalescing filter, and varying efficiency depending on the control mode used.

In the lubricant-free varieties, the inter-meshing rotors have very tight tolerances and are not allowed to touch. Since there is no fluid to remove the heat of compression, they typically have two stages of compression with an inter-cooler between and an after cooler after the second stage. Lubricant-free compressors are beneficial as they supply clean, oil-free compressed air. They are, however, more expensive and less efficient to operate than the lubricant-injected variety.

Each of these compressors can deliver air to your Intelligent Compressed Air Products. If you’re looking to reduce your compressed air consumption and increase the safety of your processes contact an EXAIR Application Engineer today. We’ll be happy to discuss the options with you and make sure you’re getting the most out of your compressed air usage.

Tyler Daniel
Application Engineer
Twitter: @EXAIR_TD

EXAIR Digital Flowmeters With Wireless Capability

“You can’t manage what you don’t measure” is a well-known axiom in engineering & process improvement circles.  We talk to callers every day who are keen on conserving compressed air use in their facilities by making a few tweaks, considering a complete overhaul, or more often, some point in between.  Bottom line (literally) is, compressed air isn’t cheap, so small gains in efficiency can add up.  And large gains can be complete game-changers…following our Six Steps To Optimizing Your Compressed Air System has resulted in users being able to shut down 50 and 100 HP air compressors, saving thousands of dollar A MONTH in operating costs.

Step #1 is measurement, and that’s where the EXAIR Digital Flowmeter comes in.  They’re easy to install, highly accurate, extremely reliable, and available for just about any size pipe used for compressed air distribution.  They can output a 4-20mA signal straight from their PCB board, or serial comms (RS485) through an optional control board.  USB Data Loggers and Summing Remote Displays have proven to be value-added accessories for data management as well.

Summing Remote Display (left) for remote indication and totalizing data. USB Data Logger takes data from the Digital Flowmeter to your computer and outputs to its own software (shown above) or Microsoft Excel.

If you want to go wireless, we can do that too: using ZigBee mesh network protocol, a radio module is installed in the Digital Flowmeter with wireless gateway to transmit data to an Ethernet connected gateway.  The transmitting range is 100 ft (30 meters,) and the data can be passed from one radio module to another, allowing for multiple Digital Flowmeter installations to extend the distance over which they can communicate with the computer you’re using for central monitoring.  Advantages include:

  • Wireless monitoring of EXAIR Digital Flowmeters throughout your plant.
  • Prevents unwanted joining upon the network.
  • Monitoring software is included at no extra charge.
  • Measures & transmits both current air usage, and cumulative air usage data.
  • 128 bit encryption for wireless transmissions.
  • Comes configured & programmed, out of the box, available for installation on 1/2″ to 4″ SCH40 iron pipe, or 3/4″ to 4″ Type L copper pipe.

Digital Flowmeter w/ Wireless Capability, Gateway, and Drill Guide Kit

If you’d like to find out more about how easy it is to measure, manage, and optimize your compressed air usage, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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