We’ve seen in recent blogs that Compressed Air Dryers are an important part of a compressed air system, to remove water and moisture to prevent condensation further downstream in the system. Moisture laden compressed air can cause issues such as increased wear of moving parts due to lubrication removal, formation of rust in piping and equipment, quality defects in painting processes, and frozen pipes in colder climates. The three main types of dryers are – Refrigerant, Desiccant, and Membrane. For this blog, we will review the basics of the Refrigerant type of dryer.
All atmospheric air that a compressed air system takes in contains water vapor, which is naturally present in the air. At 75°F and 75% relative humidity, 20 gallons of water will enter a typical 25 hp compressor in a 24 hour period of operation. When the the air is compressed, the water becomes concentrated and because the air is heated due to the compression, the water remains in vapor form. Warmer air is able to hold more water vapor, and generally an increase in temperature of 20°F results in a doubling of amount of moisture the air can hold. The problem is that further downstream in the system, the air cools, and the vapor begins to condense into water droplets. To avoid this issue, a dryer is used.
Refrigerant Type dryers cool the air to remove the condensed moisture and then the air is reheated and discharged. When the air leaves the compressor aftercooler and moisture separator (which removes the initial condensed moisture) the air is typically saturated, meaning it cannot hold anymore water vapor. Any further cooling of the air will cause the moisture to condense and drop out. The Refrigerant drying process is to cool the air to 35-40°F and then remove the condensed moisture. The air is then reheated via an air to air heat exchanger (which utilizes the heat of the incoming compressed air) and then discharged. The dewpoint of the air is 35-40°F which is sufficient for most general industrial plant air applications. As long as the compressed air stays above the 35-40°F temperature, no further condensation will occur.
The typical advantages of Refrigerated Dryers are-
– Low initial capital cost
– Relatively low operating cost
– Low maintenance costs
If you have questions about getting the most from your compressed air system, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
Today, I would like to discuss a question that comes up time and time again over the years. “What happens when I put water through a Super Air Knife?” That raised another question from myself of what about a Super Air Wipe?
The answer is quite simple, it will come out, just not as good as compressed air does. The engineering and design for Super Air Knives were all based around compressed air use. With any good product of course comes the question in time, how else can we use this? A number of applications for the Super Air Knife is blowing moisture off a part that has been applied through a series of wash/rinse nozzles. What if the knife could apply the liquid and then a second knife could remove the liquid. Below are some images from testing that was done on a Stainless Steel Super Air Knife at various gap sizes and various pressures. The “best” performance visually was from operating the air knife with .004″ gap and approximately a 17 PSIG inlet pressure (this is for a 12″ Super Air Knife).
As you can see in the photos, the water does flow fairly well immediately out of the knife, and becomes more turbulent as it gets further away from the knife. The stream actually begins to break up and thus the effective distance of the knife may be reduced when using it to flow liquids. This is not going to perform like a pressure washer, the maximum distance for the stream of liquid before it completely fell off was around 10′ from the discharge point. If this were to be used to remove loose debris or to cover a part in water to help cool the part the stream would be more than enough to perform.
As noted above the operating pressure was fairly low, and the gap was at a .004″ thickness. I recently tested a 1″ Stainless Steel Super Air Wipe as well. The shim gap was once again set to .004″ thick to permit a better flow and a low pressure, approximately 10-12 psig inlet pressure. As you can see the flow of water is not as smooth as the air flow out of a Super Air Wipe but if a light rinsing process was needed, or a water cooling process, this would work well.
So the answer to the main question at hand is yes, a Super Air Knife and Super Air Wipe will both operate with a pressurized liquid source under the correct circumstances. While they do not operate exactly like they do with compressed air, the results still prove useful in certain applications.
Last week I pointed out the important locations for measuring your compressed air system pressure throughout your compressed air system. One of the critical points to measure system pressure was before and after each filter. This leads into another question that I receive every once in a while, “How do I tell when the filter needs to be changed?” The answer to this is easy, when you see more than a 5 PSIG pressure drop across the filter. This means that the element within the filter has become clogged with sediment or debris and is restricting the volume available to your downstream products.
This can lead to decreased performance, downtime, and even the possibility of passing contaminants through the filter to downstream point of use components. In order to maintain an optimal performance when using EXAIR filter separators and oil removal filters, monitoring the compressed air pressure before and after the unit is ideal.
Replacement filter elements are readily available from stock, as well as complete rebuild kits for the filter units. Changing the filters out can be done fairly easily and we even offer a video of how to do it.
The life expectancy of a filter element on the compressed air is directly related to the quality of air and the frequency of use, meaning it can vary greatly. If you tie a new filter onto the end of a compressed air drop that has not been used in years, you may get a surprise by the filter clogging rather quickly. However, if you maintain your compressor and your piping system properly then the filters should last a long time. Generally we recommend checking your filters every 6 months.
If you have questions about where and why to filter your compressed air contact us.
Over the year that I have worked at EXAIR so far I have had a fair share of calls come in from movie production / filming crews that are looking for ways to keep the camera lenses clean and clear of water during the wet shoots they are doing. Several film houses and production crews have had exceptional results using our Air Knives.
Let’s say you are shooting a film in the rain, or a pool shot, anything involving liquid flying toward the lens of the camera. You will probably already have your camera in a protective case, or poncho, to keep it from getting wet but you can’t put anything over the lens to protect it from getting droplets on the lens which will ruin the shot. (Similar to this video of a not so fun track day.)
What the crews will do is mount our Air Knife across the top of the camera lens blowing downward to create a barrier of air for the lens. This won’t disturb the shot or the focus like a protective sheet of Lexan or glass could. What the air stream will do is help keep all the droplets off the lens and blow the water away from it. A Super Air Knife or Full Flow Air Knife typically works just fine and doesn’t consume a lot of compressed air or nitrogen. Which is generally present on most shots or you can get it very easily from a rented compressor. If the video above would have been a filmed shot from a stationary point the film would have been nice and clear if an EXAIR Air Knife would have been present to blow off the rain. It could have even turned out something like this.
So if you are filming a movie and debris or water on the lens is a problem just give us a call. We’ll help you size the appropriate Air Knife for the lens you are using.
Oh yeah. That second video is me.