Intelligent Compressed Air: Membrane Dryers

A critical component on the supply side of your compressor system is the dryer. Atmospheric air contained within a compressed air system contains water vapor. The higher the temperature of the air, the more volume of moisture that air is capable of holding. As air is cooled, this water vapor can no longer be contained and this water falls out in the form of condensation. The temperature where this water will drop out is referred to as the dew point.

At a temperature of 75°F and 75% relative humidity, approximately 20 gallons of water will enter a 25HP compressor during a 24-hour period. As air is compressed, this water becomes concentrated. Since it’s heated during the compression process, this water stays in a vapor form. When this air cools further downstream, this vapor condenses into droplet form.

Moisture within the compressed air system can result in rust forming on the inside of the distribution piping, process failure due to clogged frozen lines in colder weather, false readings from instruments and controls, as well as issues with the point of use products installed within the system.

The solution to this problem is to install a dryer system. We’ve spent some time here on the EXAIR blog reviewing refrigerant dryers , desiccant dryers, deliquescent dryers, and heat of compression dryers. For the purposes of this blog, I’m going to focus on one of the newer styles on the market today: the membrane dryer.

Membrane Dryer

In a membrane dryer, compressed air is forced through a specially designed membrane that permits water vapor to pass through faster than the air. The water vapor is then purged along with a small amount of air while the rest of the compressed air passes through downstream. Generally, the dew point after the membrane dryer is reduced to about 40°F with even lower dew points also possible down to as low as -40°F!

With such low dew points possible, it makes a membrane dryer an optimal choice in outdoor applications that are susceptible to frost in colder climates. Membrane dryers also are able to be used in medical and dental applications where consistent reliability is critical.

A membrane dryer does not require a source of electricity in order to operate. The compact size makes it simple to install without requiring a lot of downtime and floor space. Since they have no moving parts, maintenance needed is minimal. Most often, this maintenance takes the form of checking/replacing filter elements just upstream of the membrane dryer. The membrane itself does need to be periodically replaced, an indicator on the membrane dryer will display when it needs to be changed. If particular instruments or processes in your facility are sensitive to moisture, a membrane dryer might be the best option.

However, there are some drawbacks to these types of dryers. They’re limited to low capacity installations, with models ranging from less than 1 SCFM up to 200 SCFM. This makes them more applicable for point-of-use installations than for an entire compressed air system. The nature in which the membrane dryer works necessitates some of the air to be purged out of the system along with the moisture. To achieve dew points as low as -40°F, this can equate to as much as 20% of the total airflow. When proper filtration isn’t installed upstream, oils and lubricants can ruin the dryer membrane and require premature replacement.

Make sure and ask plenty of questions of your compressor supplier during installation and maintenance of your system so you’re aware of the options out there. You’ll of course want to make sure that you’re using this air efficiently. For that, EXAIR’s wide range of engineered Intelligent Compressed Air Products fit the bill. With a variety of products available for same-day shipment from stock, we’ve got you covered.

Tyler Daniel
Application Engineer
Twitter: @EXAIR_TD


Membrane Dryer Schematic – From Compressed Air Challenge, Best Practices for Compressed Air Systems, Second Edition


No Matter The Size of The System, Air Leaks Should be Fixed

Just last night I was in my garage tinkering around with a vintage Coleman Camping lantern from 1949 that I am working on refurbishing. I grabbed my parts washing bin (A bread pan my wife let me have because she didn’t like the way it cooked bread) and was reminded that I had been soaking a helmet lock from a friends dirt bike in a penetrating oil. I removed the lock from the pan, wiped it down, then went to my trusty 30 gallon compressor to use a Safety Air Gun to blow the residual oil out of the lock.

When not in use my compressor stays turned off and I modified the factory outlet to include a quarter turn ball valve so that I can retain all air in the receiver tank and not have to charge the tank up every time that I use it. As I turned the valve on I was reminded that I have a rather large air leak that can drain the 30 gallon tank down from 150 psig to 60 psig within a few hours.

While my air system is almost as simple as it can be, single air hose real with an additional quick disconnect before the hose reel for small quick blow offs, it still has over a dozen connections within the system. While my worst offending leak is audible to my slightly aged ears there are other leaks that I cannot see or hear. That is unless I use one of two methods I know to find leaks.

The easiest is right out of our 6 Steps of Compressed Air Optimization, the Ultrasonic Leak Detector (ULD). The ULD is a versatile, low cost, hands free electronic device that will quickly and easily detect the general vicinity of a leak and then easily pinpoint the exact point of the leak. In conducting a test, it took right at twenty minutes to test each of the connections within my system and identify which connections had leaks. The actual repairs of the leaks around an hour. Before fixing though I timed the amount of time it took a friend to use the soapy water method to detect the same leaks.

The soapy water method timed in at around thirty-five minutes for the same number of connections. This was due to a few of the fittings needing to be tested multiple times because of small leaks. It then took an additional fifteen minutes to wipe up all the soapy water that was now dripping down the air line and around the fittings.

While both methods found the same leaks and the ULD performed the task quicker and without any cleanup required, the true focus was on all leaks being repaired. My system has a dozen connection points for a two outlet compressed air system that are regulated and filtered at a single point. This system was draining a 30 gallon tank within a few hours which costs me every time I used my compressor and did not shut off the valve that shuts off the system.

This burden on my electrical bill was removed with less than two hours of labor and I can now leave the compressor fully charged and have air as soon as I need it rather than having to wait for the tank to charge up. Had this been in a production environment the cost could have crippled production resulting in catastrophic.

If you would like to discuss how leaks within your system can easily be found by using the ULD or would like to learn more about the other five steps in our Six Steps To Compressed Air Optimization, contact an Application Engineer.

Brian Farno
Application Engineer
Ph. 1-513-671-3322

Brian Farno
Application Engineer

Compressed Air Calculations, Optimization, and Tips

EXAIR uses our blog platform to communicate everything from new product announcements to personal interests to safe and efficient use of compressed air. We have recently passed our 5 year anniversary of posting blogs (hard for us to believe) and I thought it appropriate to share a few of the entries which explain some more of the technical aspects of compressed air.

Here is a good blog explaining EXAIR’s 6 steps to optimization, a useful process for improving your compressed air efficiency:

One of the Above 6 steps is to provide secondary storage, a receiver tank, to eliminate pressure drops from high use intermittent applications. This blog entry addresses how to size a receiver tank properly:

Here are 5 things everyone should know about compressed air, including how to calculate the cost of compressed air:

These next few entries address a common issue we regularly assist customers with, compressed air plumbing:

In a recent blog post we discuss how to improve the efficiency of your point of use applications:

Thanks for supporting our blog over the past 5 years, we appreciate it. If you need any support with your sustainability or safety initiatives, or with your compressed air applications please contact us.  

Have a great day,
Kirk Edwards

Improve Your Compressed Air System: Improve Point of Use Applications

While compressor controls and efficiency are an important part of any comprehensive compressed air audit, so too, are your point of use applications. Many times these point of use locations are quickly and inexpensively improved. The first step is to identify which area of your system you would like to improve first. Certainly you will have that “problem area”, the part of the plant you know is using compressed air more than it should. This area of your plant is usually outfitted with open tubes that have the ends crimped down as a homemade nozzle or the operators are using blow-guns with commercial grade nozzles or worse yet, no nozzle at all. It’s the area of the plant that may require hearing protection due to the loud hissing of air or where that pipe with drilled holes was the quickest and cheapest fix for the application (or so you thought).

Document these areas of the plant and address these points of use by measuring the current consumption. Many times, we find, the volume of air provided by open tubes, inefficient nozzles and drilled pipes is much more than is required for the application.  Accurate compressed air measurement will be important to properly calculate the compressed air cost and savings. These points of use can be retrofitted or optimized in a couple of ways. First, you can retrofit open tubes by placing a compression fitting and engineered air nozzle on it. This will both reduce the air consumption and noise levels within the plant. Drilled pipes have holes, or slots, along the length to provide a wide area blow off. These applications can show dramatic improvement by using compressed air knives or air amplifiers which are engineered to reduce air consumption, reduce noise and maintain OSHA Compliance for dead end pressure. The second way to improve these end use applications is to install pressure regulators and lower the end use pressure which will result in lower air use.

Don’t let these end use applications go unchallenged, just because they were this way when you joined the firm does not mean they should not, or cannot be improved upon. If you get the right folks involved and keep them updated about the actions or changes you are making, you will find advocates for the projects. Remember that quantifying the savings is key so don’t start without measuring how much air you are currently using at these problem areas. Flow meters on each leg of your system or at specific high use areas of the plant will prove invaluable to providing data expressed in dollars of savings to those making decisions within your firm. The compressed air supply side personnel will also be helpful in locating or prioritizing where to start saving compressed air. Keep employees and management informed of savings and improvements and the savings ball will have more potential to keep on rolling.


  • Measure – baseline the current conditions of compressed air use with flow meters
  • Upgrade – retrofit inefficient open blow offs, commercial grade nozzles, drilled pipes etc. with engineered  and intelligent compressed air products
  • Control air pressure – lower pressure results in lower air consumption

If you would like any assistance or support to improve your compressed air system, we’re here to help.

Kirk Edwards
Application Engineer