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: Refrigerant Dryers

When we talk with customers about their EXAIR Products, we also discuss the quality of their compressed air. Many of our products have no moving parts and are considered maintenance-free when supplied with clean, moisture free compressed air. One of the most critical aspects of a compressed air distribution system is the dryer.

No matter where you are in the world, the atmospheric air will contain water vapor. Even in the driest place in the world, McMurdo Dry Valley in Antarctica, there is some moisture in the air. As this air cools to the saturation point, also known as dew point, the vapor will condense into liquid water. The amount of this moisture will vary depending on both the ambient temperature and the relative humidity. According to the Compressed Air Challenge, a general rule of thumb is that the amount of moisture air can hold at a saturated condition will double for every increase of 20°F. In regions or periods of warmer temperatures, this poses an even greater problem. Some problems that can be associated with moisture-laden compressed air include:

  • Increased wear of moving parts due to removal of lubrication
  • Formation of rust in piping and equipment
  • Can affect the color, adherence, and finish of paint that is applied using compressed air
  • Jeopardizes processes that are dependent upon pneumatic controls. A malfunction due to rust, scale, or clogged orifices can damage product or cause costly shutdowns
  • In colder temperatures, the moisture can freeze in the control lines

In order to remove moisture from the air after compression, a dryer must be installed at the outlet of the compressor. It is recommended to dry the compressed air to a dew point at least 18°F below the lowest ambient temperature to which the distribution system or end use is exposed. A dew point of 35-38°F is often sufficient and can be achieved by a refrigerated dryer (Best Practices for Compressed Air Systems). This makes the refrigerant dryer the most commonly used type in the industry.

A refrigerant dryer works by cooling the warm air that comes out of the compressor to 35-40°F. As the temperature decreases, moisture condenses and is removed from the compressed air supply. It’s then reheated to around ambient air temperatures (this helps to prevent condensation on the outside of distribution piping) and sent out to the distribution system.

With your air clean and dry at the point of use, you’re making sure you get the most out of EXAIR’s Intelligent Compressed Air Products without adhering to pesky maintenance procedures.

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

Compressor image courtesy of Tampere Hacklab via Flickr Creative Commons License

Why Dryers Are Needed in Compressed Air Systems

Air compressors are extremely proficient at compressing anything in the air they are intaking. With that air that is taken in, moisture is going to be present. The amount of moisture will all depend on where you are located geographically and the ambient conditions in the area. Here in Ohio, we experience all 4 seasons so the moisture content is higher in the air during the summer months, rather than the winter months. When this air is saturated with water vapor and the conditions are right, the air reaches a point it cannot hold any additional water vapor. This point is known as the dew point of the air and water vapor will begin to condense to form droplets.

When ambient air is compressed, heat is generated and the air increases in temperature. In most industrial compressed air systems, the air is then processed to an aftercooler, and that is where condensation begins to form. To remove the condensation, the air then goes into a 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 transferred will cause more liquid to condense out of the air. To address this moisture, compressed air dryers are used.

It is critical to the quality of the system and components downstream that actions are taken to prevent this condensation in the air. Condensation is generally detrimental to any point of use application and or the piping that conveys the air. Rust and/or corrosion can occur anywhere in the piping, leading to scale and contamination of the compressed air and processes. When trying to dry products off using compressed air or using the air to atomize a liquid such as paint, adding in these contaminants and moisture will cost production losses.

There are several options when it comes to the type of dryer that one may consider installing on their compressed air supply side.

• Refrigerant Dryer – the most commonly used type, the 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 of water vapor in the 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 I or any of our Application Engineers can help you determine the best solution.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

EXAIR Products: The Importance of Oil Removal Filters

Oil Removal Filter
Oil Removal Filters

EXAIR’s Intelligent Compressed Air Products have no moving parts and require no maintenance. Most EXAIR products require no direct maintenance, and will continue to require no maintenance if the supplied air is clean. Keeping air clean, in EXAIR’s case, can be done with a simple water/dirt or oil filter separator close to the application of the product – usually within 10 feet. The reason for the filters is that many products have very tight orifices that could get clogged from contaminants such as particulate, condensate, and lubricant.

Oil is commonly present in a compressed air supply, whether that’s intentional or not. Many air compressors are lubricated by a constant supply of oil, inevitably some of this oil ends up in the air supply. As the compressor wears, more oil is permitted to pass and ends up in the distribution system. While this is kept to a minimum with proper maintenance, it is impossible to prevent unless using an oil-free compressor.

Sometimes oil is present in the air supply intentionally. Many pneumatic devices require a precise amount of oil to keep the internal moving parts lubricated. In the case of EXAIR Intelligent Compressed Air Products, we recommend particulate-free, moisture-free, and oil-free air.

EXAIR offers a line of Oil Removal Filters. These coalescing style filters are used to remove very fine water vapor as well as any residual oil. These filters are highly recommended to be installed just prior to dryers that contain a media that would be compromised by lubricant passing through it. Coalescing filters utilize an element typically made up of glass fibers that “coalesce”, or combine, the fine water vapor and oil aerosols until the droplet size becomes large enough that it drops off into the filter bowl. With a coalescing filter, the most common cause of pressure drop increase is due to particulate clogging the element. Because of this, a particulate filter should always be installed just prior to coalescing filters. Check out this video demonstrating an Auto-Drain Filter and Oil-Removal Filter in action:

Without filtration, oil in the air supply will pass through the point of use device and into your product or process. The elimination of this problem is such a simple solution. Don’t neglect your compressed air system and ensure you’re delivering clean, dry, oil-free air to all of your EXAIR Intelligent Compressed Air Products.

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