Manufacturing’s 4th Utility: Compressed Air System Components

In any manufacturing environment, compressed air is critical to the operation of many processes. You will often hear compressed air referred to as a “4th utility” in a manufacturing environment. The makeup of a compressed air system is usually divided into two primary parts: the supply side and the demand side. The supply side consists of components before and including the pressure/flow controller. The demand side then consists of all the components after the pressure/flow controller.

The first primary component in the system is the air compressor itself. 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.

Still on the supply side, but installed after the compressor, are aftercoolers, and compressed air dryers. An aftercooler is designed to cool the air down upon exiting from the compressor. During the compression, heat is generated that carries into the air supply. An aftercooler uses a fan to blow ambient air across coils to lower the compressed air temperature.

When air leaves the aftercooler, it is typically saturated since atmospheric air contains moisture. In higher temperatures, the air is capable of holding even more moisture. When this air is then cooled, it can no longer contain all of that moisture and is lost as condensation. The temperature at which the moisture can no longer be held is referred to as the dewpoint. Dryers are installed in the system to remove unwanted moisture from the air supply. Types of dryers available include: refrigerant dryers, desiccant dryers, and membrane dryers.

Also downstream of the compressor are filters used to remove particulate, condensate, and lubricant. Desiccant and deliquescent-type dryers require a pre-filter to protect the drying media from contamination that can quickly render it useless. A refrigerant-type dryer may not require a filter before/after, but any processes or components downstream can be impacted by contaminants in the compressed air system.

Moving on to the demand side, we have the distribution system made up of a network of compressed air piping, receiver tanks when necessary, and point of use filters/regulators. Compressed air piping is commonly available as schedule 40 steel pipe, copper pipe, and aluminum pipe. Some composite plastics are available as well, however PVC should NEVER be used for compressed air as some lubricants present in the air can act as a solvent and degrade the pipe over time.

Receiver tanks are installed in the distribution system to provide a source of compressed air close to the point of use, rather than relying on the output of the compressor. The receiver tank acts as a “battery” for the system, storing compressed air energy to be used in periods of peak demand. This helps to maintain a stable compressed air pressure. It improves the overall performance of the system and helps to prevent pressure drop.

Finally, we move on to the point-of-use. While particulate and oil removal filters may be installed at the compressor output, it is still often required to install secondary filtration immediately at the point-of-use to remove any residual debris, particulate, and oil. Receiver tanks and old piping are both notorious for delivering contaminants downstream, after the initial filters.

Regulator and filter

In any application necessitating the use of compressed air, pressure should be controlled to minimize the air consumption at the point of use. Pressure regulators are available to control the air pressure within the system and throttle the appropriate supply of air to any pneumatic device. While one advantage of a pressure regulator is certainly maintaining consistent pressure to your compressed air devices, using them to minimize your pressure can result in dramatic savings to your costs of compressed air. As pressure and flow are directly related, lowering the pressure supplied results in less compressed air usage.

EXAIR manufactures a wide variety of products utilizing this compressed air to help you with your process problems. If you’d like to discuss your compressed air system, or have an application that necessitates an Intelligent Compressed Air Product, give us a call.

Tyler Daniel, CCASS

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

Compressor Image courtesy of Compressor1 via Creative Commons License

Drying Supply Side Air With Heat of Compression Dryers

The supply side of a compressed air system has many critical parts that factor in to how well the system operates and how easily it can be maintained.   Dryers for the compressed air play a key role within the supply side are available in many form factors and fitments.  Today we will discuss heat of compression-type dryers.

Heat of compression-type dryer- Twin Tower Version

Heat of compression-type dryers are a regenerative desiccant dryer that take the heat from the act of compression to regenerate the desiccant.  By using this cycle they are grouped as a heat reactivated dryer rather than membrane technology, deliquescent type, or refrigerant type dryers.   They are also manufactured into two separate types.

The single vessel-type heat of compression-type dryer offers a no cycling action in order to provide continuous drying of throughput air.  The drying process is performed within a single pressure vessel with a rotating desiccant drum.  The vessel is divided into two air streams, one is a portion of air taken straight off the hot air exhaust from the air compressor which is used to provide the heat to dry the desiccant. The second air stream is the remainder of the air compressor output after it has been processed through the after-cooler. This same air stream passes through the drying section within the rotating desiccant drum where the air is then dried.  The hot air stream that was used for regeneration passes through a cooler just before it gets reintroduced to the main air stream all before entering the desiccant bed.  The air exits from the desiccant bed and is passed on to the next point in the supply side before distribution to the demand side of the system.

The  twin tower heat of compression-type dryer operates on the same theory and has a slightly different process.  This system divides the air process into two separate towers.  There is a saturated tower (vessel) that holds all of the desiccant.  This desiccant is regenerated by all of the hot air leaving the compressor discharge.  The total flow of compressed air then flows through an after-cooler before entering the second tower (vessel) which dries the air and then passes the air flow to the next stage within the supply side to then be distributed to the demand side of the system.

The heat of compression-type dryers do require a large amount of heat and escalated temperatures in order to successfully perform the regeneration of the desiccant.  Due to this they are mainly observed being used on systems which are based on a lubricant-free rotary screw compressor or a centrifugal compressor.

No matter the type of dryer your system has in place, EXAIR still recommends to place a redundant point of use filter on the demand side of the system.  This helps to reduce contamination from piping, collection during dryer down time, and acts as a fail safe to protect your process.  If you would like to discuss supply side or demand side factors of your compressed air system please contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

Heat of compression image: Compressed Air Challenge: Drive down your energy costs with heat of compression recovery: https://www.plantservices.com/articles/2013/03-heat-of-compression-recovery/

Compressed Air Efficiency Results in Better Business!

Time and time again we write about how compressed air is considered the fourth utility in a manufacturing setting. Compressed air is a great resource to use, however it needs to be used responsibly!

How you use it in your business is important, for a couple of key considerations:

The Cost of Compressed Air

Compressed air isn’t free.  Heck, it isn’t even cheap.  According to a Tip Sheet on the U.S. Department of Energy’s website, some companies estimate the cost of generation at $0.18 – $0.30 per 1,000 cubic feet of air.  A typical industrial air compressor will make 4-5 Standard Cubic Feet per Minute per horsepower.  Let’s be generous and assume that our 100HP compressor puts out 500 SCFM and is fully loaded 85% of the time over two shifts per day, five days a week:

500 SCFM X $0.18/1,000 SCF X 60 min/hr X 16 hr/day X 5 days/week X 52 weeks/year =

$22,464.00 estimated annual compressed air cost

So to minimize the compressed air use and the over all generation costs there are six easy steps to follow!

  1. Measure: the air consumption You must create a baseline to understand your demand requirements. How can you measure your improvements if you do not understand your total demand or baseline? Installing an EXAIR Flow Meter to your main air lines will help identify the amount of compressed air demand you have and help identify areas of concern.
  2. Find and fix leaks in the system: The repair of compressed air leaks is one of easiest ways to gain energy savings. In most cases all you need is a keen sense of hearing to locate a leak. Once a you have confirmed a leak then the make the necessary repairs. Harder to find leaks may require tools such as EXAIR’s Ultrasonic Leak Detector. This is a hand held high quality instrument that can be used to locate costly air leaks.
  3. Upgrade your blow off, cooling and drying operations: Updating your compressed air process tooling can save you energy and help you comply with OSHA noise and safety regulations. An example would be to replace old blow off or open pipe systems with EXAIR Safety Air Nozzles. Replacing open copper tubes or pipes can amount up to 80% air savings. You achieve lower sound levels and significant energy savings.
  4. Turn off the compressed air when it isn’t in use: It sounds obvious but how many times has an operator left for a break or lunch and doesn’t shut off the compressed air for his/her station? The minutes add up to a significant amount of time annually meaning there is opportunity for energy savings. The use of solenoid valves will help but EXAIR’s Electronic Flow Control (EFC) will dramatically reduce compressed air costs with the use of a photoelectric sensor and timing control.
  5. Use intermediate storage of compressed air near the point of use: The use of storage receivers can improve your overall system efficiency in a number of ways. For example, using a main air receiver at the compressor room can make load/unload compressor control more efficient. Localizing receiver tanks such as EXAIR’s 9500-60 sixty gallon receiver tank by the point of use for a high demand process will stabilize the demand fluctuations allowing a more fluid operation.
  6. Control the air pressure at the point of use to minimize air consumption: The use of pressure regulators will resolve this issue. Using regulators you can control the amount of air being processed at each point of use. EXAIR offers different sized pressure regulators depending upon your air line and process requirements. Regulating the compressed air to the minimum amount required and will reduce your overall demand resulting in annual savings and a payback schedule.

Health & Safety

Injuries and illnesses can be big expenses for business as well. Inefficient use of compressed air can be downright unsafe.  Open ended blow offs present serious hazards, if dead-ended…the pressurized (energized) flow can break the skin and cause a deadly air embolism.  Even some air nozzles that can’t be dead ended (see examples of cross-drilled nozzles on right) cause a different safety hazard, hearing loss due to noise exposure.  This is another case where EXAIR can help.  Not only are our Intelligent Compressed Air Products fully OSHA compliant in regard to dead end pressure, their efficient design also makes them much quieter than other devices.

Efficient use of compressed air can make a big difference in the workplace – not only to your financial bottom line, but to everyone’s safety, health, and livelihood.  If you’d like to find out more about how EXAIR can help, give me a call.

Jordan Shouse
Application Engineer

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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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