Water and water vapor can cause big problems in a compressed air system. That\u2019s why compressed air dryers are a critical component of those systems. There are a few different types, and they all have their pros and cons. My colleague Jordan Shouse summed up the selection process pretty succinctly in a past blog: Compressed Air Dryers : What are they Good For?<\/a> I particularly enjoyed his reference to Edwin Starr\u2019s famous protest song, War (What Is It Good For?)<\/em><\/p>\n While they are all indeed \u201cgood for (as Jordan said)<\/em> absolutely A LOT\u201d, I wanted to take (another) deeper dive into one particular type. Membrane dryers are among the newer types of compressed air dryers. As the name suggests, they use a semi-permeable membrane whose structure allows molecules of certain fluids to pass through faster than others, thereby separating those certain fluids from the primary volume. Membrane separation technology is commonly used in:<\/p>\n A membrane dryer is made of a cylinder containing very small polymer tubes that have a special coating inside. This coating allows the above-mentioned water & water vapor to pass through more readily than the nitrogen, oxygen, and other trace gases found in the atmospheric air that the compressor has drawn in.<\/p>\n The advantages of membrane dryers are:<\/p>\n While environmental contamination isn\u2019t a concern, they are very sensitive to internal contamination, like oil & oil vapor. Membrane dryers are commonly supplied with coalescing filters to minimize any issues there.<\/p>\n One disadvantage (kind of) is their limited flow capacity: the highest capacity membrane dryers are capable of passing around 200 SCFM, meaning they can only be used in small-to-mid-sized systems. I said \u201ckind of\u201d above because, if a certain part of the compressed air system requires a different level of dry air than the rest of the plant, membrane dryers are an inexpensive and easy way to provide that. That\u2019s \u201ckind of\u201d an advantage, in that situation, actually.<\/p>\n Another disadvantage (kind of) is the amount of purge air they lose. Remember, membrane technology means certain fluids will pass through faster & more readily \u2013 but not exclusively \u2013 so they\u2019re going to lose some of that brand new compressed air along with the water vapor. And the lower you want the dew point to be, the more purge air will be lost. However, the purge air loss is minimal when they\u2019re discharging air dried to a dew point in the 40\u00b0F range, and that\u2019s perfectly acceptable in many industrial compressed air systems.<\/p>\n I want to help you get the most out of your compressed air system, so when you think of compressed air, think EXAIR! If you\u2019ve got questions, we\u2019re here to help. Give me a call<\/a>.<\/p>\n Russ Bowman, CCASS<\/p>\n Application Engineer\n
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