Air Dryer Basics
Keep Cool With Refrigerant Air Dryers
Across the country, the most common dryer present in compressed air systems is far and away the refrigerant air dryer. Throughout manufacturing and service industries, these machines are renowned workhorses. They are incredibly consistent, achieving dewpoints of ~38°F, which is more than enough to be used with pneumatic tools and other applications requiring moisture-free air. Air that has been dried by a refrigerant air dryer reaches ISO Quality classes 4 through 6. Please note that if you have not already been made aware of your ISO standards you shouldn’t have anything to worry about, but be sure to make sure you know before you purchase equipment. So this equipment is consistent and everywhere, but how exactly does this equipment function, and why do you need this equipment? For starters, when you compare this equipment with its main counterpart, the desiccant, refrigerant air dryers have: Lower capital investment; Lower operating and maintenance costs; Higher dew points (more moisture left in the air) Surprisingly enough, refrigerated air dryers use a refrigeration system to cool the air that is passing through. As this air cools, condensate is formed, and the air gets down to ~38°F, which explains the dewpoint. This process cools the air down to such a low temperature that moisture cannot be formed unless the air is below that temperature. So as long as your facility stays above 40°F, your compressed air will be dry and able to use without worry. After this condensate has formed, it is successfully drained out through a line in the bottom. Now that you have a basic idea of how these compressed air dryers operate let’s dive into the nitty gritty details about these machines. How Do These Refrigerant Air Dryers Work? Let’s start with the basics, how does water get into your compressed air system? It isn’t raining outside, but somehow all of this moisture is being created in your equipment. So as air exists around us, it exists at atmospheric pressure, about 14.6 PSI at sea level. So if you have 1 square foot of air at atmospheric pressure, and then you increase that pressure to 150 PSI, you are reducing the space that air exists into a tenth of its size. So all the water molecules floating around in that space have been forced into a much smaller area. As those molecules move into that smaller space, those like particles attract. So all of the water that was spaced out is combined with the air, but it is too hot after compression for the water vapor to condense. Once the air cools down, whether in the pipes, storage tank, or dryer, the water vapor condenses into liquid. Water is heavier than the air, so it falls to the bottom and must be removed. If your dryer is working properly there should be a condensate removal process in place to be filter and properly dispose of the water. Now that we have the concept set, let’s follow the airflow through a refrigerant air dryer. Incoming air enters an air-to-air heat exchanger where the air that enters is cooled off by outgoing air that has been cooled already. Next the air goes into an air-to-refrigerant heat exchanger that drops the temperature of the air down to 38ºF from the liquid refrigerant. The cooling of the air causes the moisture to collect and condense. This water is then collected and is drained away. The air then finishes its path through the dryer by entering the air-to-air heat exchanger to cool down the incoming air and prevent the pipes from sweating. Below is an illustration of this process working effectively and what happens when your system is not working as it should. Key Characteristics To Be Aware Of Maximum Pressure -Your dryer’s maximum pressure needs to be equal or higher than your compressor’s maximum pressure. Inlet Temperature – Each dryer has its own specified maximum inlet temperature, and surpassing this can damage your equipment. If your compressor has an aftercooler, it will make sure the compressed air is at a reasonable temperature. Maximum Flow -This refers to the max amount of air that can pass through your dryer. If your dryer is undersized this can cause significant pressure drops due to the air being unable to pass through. Maximum Room Temperature -Keep your environment in mind with your equipment. If it’s hot outside, you run the risk of overheating your dryer. Just make sure your ambient air temperature is more than 20ºF below your max inlet temperature. Refrigerant air dryers are the ideal solution for situations that: Ambient temperature is less than 50°C/122°F, Goal is to prevent condensation, Required pressure dew point is around 3°C-4°C/37°F-39°F. Calculating Your Pressure Dewpoint Temperature Determine your lowest ambient temperature Make sure to check areas that may be unheated areas underground and between buildings. Lower this temperature by 20°F This will give you your PDP that needs to be reached by your dryer If your lowest temperature is 65°F the your PDP would be 45°F What Are The Different Types of Refrigerant Air Dryers When it comes to selecting your refrigerant air dryer, there are a couple options that are available. With these options come differences, but not in how well they dry the air, but in how the equipment maintains its own internal temperature. There are three main types of refrigerant air dryer: Non-Cycling Cycling Variable Speed Drive Non-Cycling Refrigerated Air Dryers The littlest amount of technology, so the cheapest version of a refrigerant air dryer that you are going to be able to find is the non-cycling refrigerant air dryer. The non-cycling dryers’ refrigeration stays on continuously while the compressor is running. So if the compressor is on, the dryer will be running. If the dryer runs for too long without a break, it can potentially lead to freezing in the pipes and rapid wear on your machine. However, if you have a smaller operation that does not need air all the time, these machines will work for you. If you just need clean dry air when you need it and don’t have a very large demand, overworking your machine won’t be the issue. Cycling Refrigerated Air Dryers The next step up is the cycling refrigerant air dryer. Cycling dryers cost more than their previous counterparts. That is because cycling dryers are designed to cycle the refrigeration on and off as needed to conserve energy and prevent excessive refrigeration when not being used. By cycling, it can prevent frost build up if the unit needs to run for a long period of time. These machines are great for the middle ground applications that may be running for a long time but do not have extremely high demand or operate for longer durations of time with typical flow. The technology in these dryers will be able to keep up with your demand as long as it is sized properly. VSD Refrigerated Air Dryers Variable Speed is the best of the best when it comes to compressed air technology. By being able to change operation speed to match demand, very little energy is wasted and you get the most out of your energy. A VSD refrigerant air dryer has a scroll compressor with a fixed element and an orbiting second element. This compact screw quietly spins so that it can perfectly match the demand. This style of refrigeration is used to combat the fact that most compressed air systems do not operate under static flow and temperature conditions. This variability in climate is matched by the variable speed refrigeration. The ability to match dryer energy consumption to air demand helps provide significant savings in operating costs. The price of saving on operating costs is a higher upfront payment for the necessary technology and machinery to achieve this energy saving. If you can afford to go with the price increase it will be worth every penny when you save on your energy bill for months to come. As with all the equipment, the more you pay the better the results you will get, but that doesn’t mean the cheaper option cannot do the job. Before You Buy When you are considering your options for drying your compressed air, there are pros and cons for every option. Your final choice should be what works best for your system and nothing else. Going with a refrigerant air dryer is going to cost you less, and if your main priority is condensate prevention then it is perfect for the job. Issues arise when dew points below 37°F are needed or the ambient air gets above 122°F. These conditions can cause your refrigerant air dryer to fail, by potentially freezing if the temperature gets too low or being unable to keep up with the present demand due to excess heat and moisture. If the relative humidity of the air surpasses 50%, then your dryer will no longer be properly rated for the environment and let moisture through. This moisture will damage your system and your equipment. If you need Class 3 Air or Higher, please look into our desiccant air dryers, because refrigerant air dryers do not meet the quality standards necessary for that level of air quality. If you have extreme temperatures, excess humidity, and low dew point requirements are all reasons you would want to consider a desiccant air dryer. Read more about why you might need help Keeping The Water Out with desiccant air dryers. Air Dryers are critical components of your process and you need to make sure you have the right type of dryer in place for your system. Protect your system and your wallet by keeping your air at the best quality and scheduling proper maintenance. Scheduled maintenance will always cost less than unforeseen downtime and issues. Time to Buy A Refrigerated Air Dryer Learn More From The Source From Atlas Copco From The Compressed Air Blog From Pneumatech More From Compressed Air Blog
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Keep The Water Out With Desiccant Air Dryers
If you have been around air compressors before, you’ve most likely heard of needing to dry your compressed air. This is typically done with a refrigerated dryer, which uses cooling to remove moisture from the air, or by a desiccant air dryer. But just what exactly is this type, and how does it dry compressed air?What is Desiccant?Desiccant is an exceptionally adsorbent material due to its high affinity to water. In addition, they pull moisture from the air due to their hygroscopic properties. In other words, it can keep the area in immediate contact with the air dry by removing all the moisture into the center of the bead and containing it to allow more water to be adsorbed. This process continues until the beads become entirely saturated and need to be switched out.By using a desiccant air dryer, you can prevent wear and tear on your components that are highly sensitive to water. To be able to perform this process of air drying, specific materials need to be used. These materials are often chemically stable, but a few potentially toxic options require specific conditions to be used. The most commonly used desiccant includes but is not limited to: Silica Calcium Chloride Activated Charcoal Calcium Sulfate Due to the high quantities of water in compressed air and to extend desiccant life, these dryers often rely on two towers filled with desiccant. As the air passes over them, the water is adsorbed, and eventually, the beads will not be able to hold anymore. These towers are designed so that before the desiccant reaches full saturation, they will switch how the air flows between towers. One will go from removing moisture to being dried and vice versa.Depending on the style of the dryer, the way that the desiccant is dried differs. Just know that the desiccant needs to be dried when it is not in use to prevent early saturation and reduced performance from your dryer. We will detail the different types of desiccant air dryers and how they operate in just a bit.https://youtu.be/tEthstKYTYEIn Between The DesiccantAs we mentioned, these desiccant air dryers consist of two towers filled with an adsorbent material. When the air is being passed through the dryer, one building is dedicated to actively drying the air while the second tower is undergoing desiccant regeneration. This regeneration process is simply drying out the beads so they can absorb more moisture when the towers are switched back.Having a control panel that can automatically reverse the flow of air depending on the desiccant's saturation is hugely beneficial to the efficiency and longevity of the materials. This allows you to maximize your air-drying potential on each cycle. In addition, this provides for long drying and regeneration cycles. This alternation will continue until the beads can no longer retain moisture and the material needs to be switched out.The drying process is relatively straightforward with these dryers; the confusion comes when determining how you would like your desiccant to be regenerated. Differences arise between the models through the processes and what is used to regenerate the desiccant. The three main models of regeneration in dryers are: Heatless Pressure Swing Heated Regeneration Heat of Compression These dryers could be described as hot air regeneration, dry compressed air regeneration, and special drying systems. Although they may sound confusing, the processes of regeneration and their classifications are pretty self-explanatory. So let’s examine these machines on a closer level.Heatless Pressure Swing DryerHeatless Pressure dryers only use compressed air as purge air. Now, if you are unsure what purge air is, that is the air used to dry out the desiccant. In the case of a heatless dryer, a portion of the air that has been dried is redirected into the tower that is in the regeneration phase.By using dry compressed air, no extra energy is needed to dry the desiccant out. The problem arises when you consider how expensive compressed air is from an energy standpoint. Using the valuable compressed air as purge reduces the volume produced by your compressor as the air used to dry the desiccant is not cycled back through. These air dryers typically require a purge rate of around 17-20% of the total airflow.These dryers are classified under desiccant regeneration using compressed air; pretty self explanatory when you know how heatless works. This classification means the dryer uses a portion of dried compressed air that has just passed through and this saves extra energy costs that may be needed for other methods of desiccant regeneration.Heated Regenerative DryerCompressed air is such a valuable resource when it comes to cost, and if you are someone who does not want to waste much compressed air, a heated regenerative may be the best bet for you. These dryers use a hot air blower or an internal heating system to heat ambient air to the point of being able to regenerate the desiccant. These dryers often use less than 7% purge rate during this process, which is a lot lower than a heatless desiccant.It may come as a surprise, but these dryers are classified under hot air desiccant regeneration. A stream of hot air is passed through the saturated desiccant to remove the moisture from within the beads. This classification requires the use of a fan or internal electrical heating system to get the air up to the temperature that is needed while saving valuable compressed air. Rather than using air from in the system, heated atmospheric air is used to dry out the desiccant.Heat of CompressionUnlike the other forms of regeneration, heat of compression is much less common and that is due to the fact that it can only be used with oil-free compressors. This is because of the excess heat that comes off from an oil-free compressor due to the lack of something to remove heat in the compression chamber of the compressor. This heat would then be rerouted to the dryers so that regeneration can occur.Similar to heated regenerative desiccant air dryers, these dryers are considered hot air desiccant regeneration. The air just does not need to be heated up, at least not to the same degree. In this scenario the heat is simply moved from the compressor to the desiccant dryer to be used for the regeneration phase. This process can lower the dewpoint down to -50°F.How Do I Pick a Desiccant Air Dryer?When it comes to picking out a desiccant air dryer, there are few extra factors you are going to want to take into consideration, aside from the information you would be expected to know. As we know not all dryers are built the same, and different models excel in different environments and conditions. This variety of information that is needed can make it difficult to weed out the options that won’t work for you.Now these extra factors that you are going to want to focus on include: Pressure Drop Regeneration Costs Desiccant Use Pre-Filters After-Filter Valve Adjustments A few of these extra considerations may seem obvious, but it doesn’t hurt to make sure you have checked all of those factors. In order to understand what you should be looking for, we will go into all of them in further detail.Pressure DropWhen you are using a compressed air dryer, regardless of the style, it is going to create a pressure drop. This pressure drop will result in the air being produced to exit the dryer at a lower pressure than when it went in. For instance, if you need 90 PSI of air to operate and your dryer has a pressure drop of 2 PSI, then you will need the compressor to be outputting 92 PSI to ensure that with the pressure drop you are still meeting your requirements.Keep in mind, the bigger your compressor gets, the more expensive it is to increase the pressure on the air. Be sure to keep your necessary PSI and what your compressor is rated for when you are looking at an air dryer. It would be unfortunate to have all the information right but if you do not calculate for pressure drop, that can be the difference between your system working as expected or having problems due to inadequate pressure.Regeneration CostsRegeneration costs are dependent on the style of desiccant air dryer that you go with. If you select a heated air dryer, you will need to consider the energy costs needed to heat the regeneration air. Now if you have a heatless dryer your focus will not be on energy costs, instead it is on how much air is lost with purge air.Typically this is going to be between 15-20% of your compressed air that is being created, and that stuff does not come cheap. You are going to be losing up to a fifth of the compressed air you produce. Essentially your machine will only be outputting ⅘ of its total capacity when it is connected to a heatless desiccant dryer.Desiccant UseEven after going through the process of regeneration, the desiccant will eventually be worn down to the point where it no longer can hold any moisture and it is completely saturated. Once desiccant has reached this point, it will allow moisture to continue downstream and potentially cause problems at the point of use.It is important to keep in mind the cost of desiccant and the lifespan of the desiccant you choose. Knowing this information will allow you to stay on top of changing out the materials and knowing how much it will cost to properly operate and maintain your compressed air dryer. Typically these beads will need to be replaced every few years, but depending on your duty cycle that could change.Pre-FiltersCompressed air is naturally dirty, as all the particles that were existing in a large volume of space were compressed together. Pre-filters are a necessity to remove those contaminants before they reach the air dryer, especially your desiccant dryers. If other particulates make their way into the chamber, the desiccant can become contaminated or have reduced efficiency.When oil comes into contact with desiccant, it acts differently than water. Oil will coat the outside of the desiccant and prevent the water from being able to get through, both in and out. In order to prevent this from happening, it is strongly suggested to have filtration for water droplets and oil prior to your air dryer so that the dryer can do its job.After-FilterJust like you need the pre-filter to make sure the desiccant can do its job, you need an after filter to cover for the desiccant. Time can be detrimental to your desiccant and this will cause them to deteriorate and send desiccant-dust downstream. In order to protect against dust particles. The easiest way to do this would be the use of a particulate filter after the dryer to catch any particles that may be tagging along with the airstream that shouldn’t be.Valve AdjustmentsWhen it comes to your valves and making sure your equipment is set up properly, there are a few things you will want to change: Starting Pressure of Safety Valve: 1.05 times inlet pressure Pneumatic Shut-Off Valve: 0.3-0.5 MPA Adjust Ball Valve Q: About 4-6% of gas volume Some Last Minute RemindersCondensation is the killer of compressed air system. Issues can be caused downstream by the moisture that can be anything from clogging tools to creating fisheyes when you are trying to paint something. It can be expensive to replace these components or undergo maintenance. These costs can include: Labor for Repairs Parts for Repairs Damage to Products Production Downtime When you are relying on purge air to regenerate your desiccant, the purge rate is based on the nameplate and the rating there. The purge control on these machines is simply a crack or hole that feeds the air back into the towers. This allows for the air to have a fixed flow rate and pressure for the side that is being regenerated, without causing disparities in the flow of air.Applications:When it comes to dryers, you either need a desiccant or a refrigerated unit, and you should know which one you need when you go looking to get one. The point of switching from refrigerant to desiccant is determined by the quality of air you need, if you need air dryer to a critical degree then you should only be looking for a desiccant.The most common applications for desiccant air dryers are: Plastic Molding Electronics Production Power Plant Food & Beverage Laser Cutting The main thing you want to focus on is how the air is being used in your application. If it is an application where moisture will cause problems that can make your product unusable or have potentially catastrophic problems occur. When you are working in these industries moisture needs to be removed at all costs.Now you might not be in an industry where you need a desiccant dryer, but your location may make the difference between what dryer you need. If you live up north where the temperature can get really low, the ambient air can cool the pipes after the dryer and cause more moisture to drop out of the air because it is being cooled even more after being dried.In a refrigerant dryer the air would be below 40°F after it exits the dryer, but if the ambient air is below that it will cool it even more in the pipes.If you live in an environment where the temperature can get below freezing and your pipes go outdoors, then you will want to consider a desiccant even if your application is not one that needs one. You could also use desiccant seasonally if it was possible so that you did not have to use one year round, but would still be able to work through those challenging conditions.Before You BuySo before you go off and buy your own desiccant air dryer, let’s review why you may want to get one and the benefits that these dryers can provide.Traditionally, desiccant is stored in two towers so that while one is drying the air the other is being regenerated by purge air or heated air. This cycle of regeneration is dependent on demand, dew point, the moisture present in the desiccant, or a combination of factors. These dryers work year round with no problem due to the dew point can be made by a desiccant. These dryers have the capability to filter moisture in air that is as low as -100°F.The main advantages of these dryers are: Easy Maintenance Low Dewpoint Capabilities Excels At Second Stage Drying Most desiccant dryers come with an added bonus, a small sight-glass that lets you see a portion of desiccant beads. These beads are not used in the actual drying process but serve as an indicator for the moisture in the dryer. It will change color if there's too much water in the air to let you know you might want to change which tower is regenerating and drying. With this information, you can check and see how the dryer is performing at a glance.Now all that is left is for you to go out and get your desiccant dryer. At Warthog we carry the best desiccant dryers around, all it takes is a few clicks and you will be able to find anything you need here.Learn More From The SourceFrom Atlas CopcoFrom Quincy CompressorsFrom Mark CompressorsView All Desiccant Dryers
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The Basics of Dry Compressed Air Made Easy
Why Dry Compressed Air?Moisture is the enemy of productivity in your compressed air systems. Productivity is dependent on dry compressed air being adequately and consistently supplied to your tools and air system. The air around us is filled with little moisture particles that go unnoticed in our day-to-day lives. Once that air has been compressed, all the free-flowing particles and molecules are crammed into a small space and will start to combine and form what is called condensate.These water particles condensed together and become trapped in the air stream. The condensate will pool up in piping and tanks if it is not adequately treated. Build-up of condensate can be detrimental to the air system as a whole. It can create pressure drops and could even stop the whole process from working.Build Up Builds ProblemsThis build-up can happen due to a number of different variables, from the moisture in the ambient air to the dewpoint of the compressed air, the environment it is running in, and the outside temperature, to name only the big ones. The different degrees of quality determine the level to which your air will need to be dried.Internal condensate is the silent killer of air systems. From the outside perspective, everything seems to be running smoothly, but in reality, large quantities of condensate could be downstream from the compressor, wrecking productivity alongside the proficiency and lifespan of the compressor. This inability to see the condensate emphasizes the importance of maintaining a routine maintenance schedule. Avoid large-scale build-up and provide peace of mind for your company.https://www.youtube.com/watch?v=4SAh1jjQ6REProtecting Against Condensate Build-UpWhen you are working to protect against condensate build-up, it is a year-round endeavor. The more humid the ambient air is, the more water vapor will get pulled into the air compressor. More time and energy will be necessary to reach the same dryness level as normally achieved. This can cause wear and tear on the system and can be harmful to the overall life span of the machine. Not only can compressors and air systems have trouble during the summer with more humid air, but the dry cold air of winter can cause problems too, due to the lower quantity of moisture in the air.As it typically is, water is the enemy of equipment due to the problems it can cause internally or productivity-wise. It wears away at equipment over time and can become detrimental to productivity and operations because of this. The water can block airflow downstream resulting in less air being able to reach the end of the line and that means some pneumatic tools will not be receiving enough dry compressed air to operate properly. Keeping constant airflow is the key to keeping constant productivity, without it, the levels of pneumatic tool output will vary. Internal components can be hurt by water and condensation build-up:making dry compressed air vital.Condensate Isn't Just WaterWater build-up can exist unnoticed by users as it happens so gradually. Water hammer, which is when water in the pipes can slam into equipment or internal barriers and the sound resonating off sounds like a hammer banging, can occur from condensate build-up. Knocking other internal particulates loose and reintroducing them into the airstream. This can degrade the quality of the product air that is coming out at the end of the line and this may cause problems when dry compressed air is a necessity.Excess moisture can cause problems in several areas along an air system. It can be detrimental to the success of air tools, piping, dryers, air tanks, and all the other equipment that the air passes through. So when it comes to having dry compressed air, quality is something to consider with your dryer. The ramifications of the dryer can be felt all along the system, especially when the dryer does not work well. When considering a dryer it is important to look at specific aspects such as what cfm you need and how airflow can be affected by the dryer size and output.https://www.youtube.com/watch?v=ycW3FnRIwrMWhat to Consider When You Need Dry Compressed Air Whether you are looking to create an air system or modify your current one it is important to know the specifications of what you need so that you can ensure your system works properly and produces dry compressed air when you need it. When you are lining up your system it is important to know the following measurements and information about your system: Flow Rate or Compressor Size Ambient Temperature / Humidity Content Inlet Temperature Pressure Pressure Dew Point (PDP) Knowing this specific information is the key to your system’s success. With this, you can align the specific pieces you need to ensure that the airflow will be smooth and continuous when needed. Information like flow rate can be used to determine the speed at which the air will move through the system and to avoid drops in speed downstream.The water content/humidity in the ambient air is important and so is the temperature of the air. It can be difficult to cool air when it has been so compressed and all of the molecules are moving. So when the compressed air coming in is hot it can take even more time to cool down and can even slow down the system as the air moves slower.Temperature Adds UpTemperature plays an important role in the health of your air system, especially the air inlet. This temperature measures the temperature of the air as it enters and can affect the compression rate. If the air is warmer, it is harder to condense, causing problems with pressure and moisture in the air. When considering the pressure of your air system, it is important to note the pressure so you can maintain a consistent flow of dry compressed air downstream, and when more pressure is applied to the air, fewer moisture particles exist in the air due to the lack of space.Finally, Pressure Dew Point is another important factor to be considered. It is the standard used to measure the water content in compressed air and the temperature at which water begins condensing. It is the point at which the air can no longer hold any more water and it begins forming condensate. Different types of dryers can change the air's dewpoint and are something to consider as well. When you have dry compressed air, the temperature at which the water condensates, the dew point, is lowered so that the air has to drop in temperature for the moisture to turn to liquid.More Information on Dry Compressed Air VSD Dryers Desiccant Dryers Dryer Types Not Sure Where To Start?If you are looking to get started on obtaining your own dryer, click hereIf you need to learn more about air systems, click hereLooking for the Manufacturer’s details, click here
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