Intelligent Compressed Air: Membrane Dryers – What are they and How Do they Work?

Recently we have blogged about Compressed Air Dryers and the different types of systems.  We have reviewed the Desiccant and Refrigerant types of dryers, and today I will discuss the basics of  the Membrane type of dryers.

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.

Membrane Dryers are the newest type of compressed air dryer. Membranes are commonly used to separate gases, such as removing nitrogen from air. The membrane consists of a group of hollow fiber tubes.  The tubes are designed so that water vapor will permeate and pass through the membrane walls faster than the air.  The dry air continues on through the tubes and discharges into the downstream air system. A small amount of ‘sweep’ air is taken from the dry air to purge and remove the water vapor from inside the dryer that has passed through the membrane tubes.

Membrane Dryer
Typical Membrane Dryer Arrangement

Resultant dew points of 40°F are typical, and dew points down to -40°F are possible but require the use of more purge air, resulting in less final dry compressed air discharging to the system.

The typical advantages of Membrane Dryers are-

  1.  Low installation and operating costs
  2.  Can be installed outdoors
  3.  Can be used in hazardous locations
  4.  No moving parts

There are a few disadvantages to consider-

  1. Limited to low capacity systems
  2. High purge air losses (as high as 15-20% to achieve lowest pressure dew points
  3. Membrane can be fouled by lubricants and other contaminants, a coalescing type filter is required before the membrane dryer.

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.

Brian Bergmann
Application Engineer

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

 

 

 

Heat of Compression Dryers

A Heat of Compression regenerative desiccant dryer for compressed air

Before compressed air can be realistically utilized, it needs to be delivered to the point of use with proper volume and pressure, and it should also be clean and have some moisture removed.  We have information available regarding cleaning compressed air, but how do you dry the compressed air?  And why do you dry the compressed air?

Drying compressed air is akin to removing the humidity in the air when using an air conditioning system.  If the moisture is not removed, the effectiveness of the system is reduced and the ability to use the output of the system is reduced as well.

But, from a functional standpoint, what does this really mean?  What will take place in the compressed air system if the air is not dried and the moisture is allowed to remain?

The answer is in the simple fact that moisture is damaging.  Rust, increased wear of moving parts, discoloration, process failure due to clogging, frozen control lines in cold weather, false readings from instruments and controls – ALL of these can happen due to moisture in the compressed air.  It stands to reason, then, that if we want long-term operation of our compressed air products, having dry air is a must.

So, how can we remove the moisture in the compressed air?  One of the most common methods to remove moisture is a regenerative dryer, specifically, heat-of-compression type dryers.  A heat of compression type dryer is a regenerative desiccant dryer which uses the heat generated by the compression of the ambient air to regenerate the moisture removing capability of the desiccant used to dry the compressed air.

When using one of these dryers, the air is pulled directly from the outlet of the compressor with no cooling or treatment to the air and is fed through a desiccant bed in “Tank 1” where it regenerates the moisture removing capabilities of the desiccant inside the tank.  The compressed air is then fed through a regeneration cooler, a separator, and finally another desiccant bed, this time in “Tank 2”, where the moisture is removed.  The output of “Tank 2” is supplied to the facilities as clean, dry compressed air.  After enough time, “tank 1” and “tank 2” switch, allowing the hot output of the compressor to regenerate the desiccant in “tank 2” while utilizing the moisture removing capabilities of the desiccant in “tank 1”.

Heat of compression dryers offer a lower power cost when compared to other dryers, but they are only applicable for use with oil free compressor and to compressors with high discharge temperatures.  If output air temperatures from the compressor are too low, a temperature booster/heater is needed.

If you have questions about your compressed air system and how the end use devices are operating, contact an EXAIR Application Engineer.  We’ll be happy to discuss your system and ways to optimize your current setup.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

 

Heated Desiccant Dryer by Compressor1.  Creative Commons License

Super Air Knife Makes EVERYTHING Better

When we compare the EXAIR Super Air Knife to other methods of providing a curtain or sheet of air flow in terms of operating cost, efficiency, safety, and sound levels, the Super Air Knife is ALWAYS the clear choice.

The EXAIR Super Air Knife is the most efficient and quietest compressed air blow off product on the market today.

The Super Air Knives successfully replace these, and many other methods of providing a curtain or sheet of air flow all the time, while saving compressed air and decreasing noise.  The word “replace” oftentimes means “do the same job as.”

What you’re about to read is NOT one of those times.

A paper products manufacturer has a machine that treats a specialty product, and the process generates ozone (O3) at levels that would exceed personnel exposure limits, so they need to be contained.  They installed a long piece of drilled pipe to blow an air barrier, but they could only run the machine at about 65% of their desired capacity before the ozone level in the operators’ area exceeded their limits.

This company was familiar with several of our product lines already…they had several Cabinet Cooler Systems, a Reversible Drum Vac, and Super Air Knives in a variety of applications, so they knew how they worked.  Since the barrier needed to be 120″ long, though, this was going to be a much larger scale than they were used to.

Not only was the drilled pipe loud and inefficient, it was not particularly effective either.

Still, the installation of two Model 110060 60″ Aluminum Super Air Knives, coupled with our Model 110900 Air Knife Coupling Kit, was quick and easy.  Then came the good part: they found they were able to operate the machine at 100% capacity, while keeping the ozone at a safe level in the operators’ area.

EXAIR Super Air Knives provided a total solution: quiet, efficient, and most of all, EFFECTIVE.

Then came the better part:  The machine was pretty loud (we couldn’t do anything about that,) at 93dBA when it was running.  With the drilled pipe in operation, it was 94.5dBA.  When they took that out and installed the Super Air Knives, there was no net increase in noise level…it remained at 93dBA.

THEN came the even better part: Compressed air consumption was reduced to about 30% of what the drilled pipe was using.  Right in line with our table above.  Just another validation of the trustworthiness of our published data.  As EXAIR’s President is fond of saying, “Claims are easy, proof is hard.”

If you’re looking for a quiet, efficient – and effective – solution for a compressed air product application, give me a call.

Russ Bowman
Application Engineer
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Monitor Your Compressed Air System With EXAIR’s Digital Flowmeters

A topic that we’ve talked about here on the EXAIR blog discusses the costs of compressed air and how to use it more efficiently. How can you determine the costs of your compressed air? The first step you’ll need to take is to quantify the flow. In order to do that you’ll need a measurement tool such as the EXAIR Digital Flowmeter.

dfm_sizes
EXAIR’s family of Digital Flowmeters

The Digital Flowmeter is available from stock for use on Schedule 40 pipe with sizes ranging from ½”-4” I.D. Sizes up to 6” for Schedule 40 and ¾”-4” for copper pipe are also available. With a digital readout display, it’s easy to accurately monitor your compressed air usage throughout the facility. Creating a baseline of your usage will allow you to understand your compressed air demand, identify costly leaks, and replace inefficient air products.

The Digital Flowmeter installs in minutes with help from a drill guide and locating fixture to assist in mounting the Digital Flowmeter to the pipe. Two flow sensing probes are inserted into the drilled holes in the pipe. The meter then seals to the pipe once tightened. There is no need to cut, weld, or do any calibration once it is installed. With blocking rings also available, installation can be permanent or temporary.

The newest addition to this product line is the Digital Flowmeter with wireless capability. Using a ZigBee® mesh network protocol, data is transmitted to an Ethernet connected gateway. This allows you to mount the Digital Flowmeter in areas that you may not be able to easily access and wirelessly monitor and graph the usage with the EXAIR Logger software. Take a peek at this video blog for a demonstration of the use of a wireless Digital Flowmeter software to compare an open pipe to an engineered Air Nozzle.

wirelessdfmpr2_1670x574

In addition to communicating wirelessly with the gateway, the Digital Flowmeters can “piggyback” off of each other to extend their range. Each meter has a range of 100’. Using multiple Digital Flowmeters within the same ZigBee® mesh network, data can be passed from meter to meter to extend the distance over which the meters can operate. These can be installed on each major leg of your compressed air system to continuously monitor usage throughout the facility.

If you’d rather go with a hard-wired data collection method, the Digital Flowmeter is also available with a USB Data Logger. Simply remove the Data Logger from the Digital Flowmeter and connect it to the USB port of your computer. The data can then be viewed directly in the accompanying software or exported into Microsoft Excel.

dataloggerPRce_559wide
Digital Flowmeter w/ USB Data Logger installed

If you’d like to get a clear view of your compressed air usage, give us a call. An Application Engineer will be happy to work with you and get the proper Digital Flowmeters installed in your facility!

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

Back Blow Air Nozzles Clean Inside Diameters

They say time flies when you’re having fun. Maybe that’s why I found it a little hard to believe it’s been almost two years since we introduced the Back Blow Air Nozzles. They’ve become yet another “textbook” solution to a great many applications:

*Model 1004SS M4 Back Blow Air Nozzles are used to dry the inside of a closed cylinder after a zinc bonding process.  They’re also fitted to Model 1204SS-12-CS M4 Back Blow Safety Air Gun to remove chips & cutting fluid from freshly cut pipe ends.

*Our Model 1006SS 1/4 NPT Back Blow Air Nozzle won Plant Engineering Magazine’s “Product Of The Year” Bronze Award in 2015, and are successfully employed in a wide range of uses:

  • Blowing out splined bores by a gear manufacturer
  • Quickly cleaning out spindles between tool changes by a CNC machinery operator
  • Removing the last bits of powder from spent toner cartridges by a printing equipment recycler

*The Model 1008SS 1 NPT Back Blow Air Nozzle is becoming famous in hydraulic cylinder repair shops…after a cylinder bore is honed, one quick pass of the powerful blast it produces cleans bores from 2″ to 16″.  We can even put it on the Model 1219SS Super Blast Back Blow Safety Air Gun, with a 1ft, 3ft, or 6ft extension.

EXAIR Back Blow Air Nozzles come in three sizes, for bores from 1/4″ to 16″ in diameter!

If you want to see how they work, check out this video:

I could have sworn Lee Evans just made that video, but apparently, it’s over a year old now.  Time does indeed fly, and I promise we’re having fun!  If you’d like to find out more about how a Back Blow Air Nozzle – or any of our engineered compressed air products (old or new) – can make your operations quieter, more efficient (and hence, probably, more fun,) give me a call.

Russ Bowman
Application Engineer
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Super Air Wipe Helps Shield a Lens

Super Air Wipe Kit

A tier 2 automotive company makes small metal boxes with a process which includes laser welding and a vision inspection system. The machine was programmed to weld different components onto the metal enclosure. During the welding operation, an optical sensor would check the quality of the welds. The vision system used a lens to protect the sensor from welding slag and debris. After a few operations, they started seeing false positives in the welding areas, and the metal enclosure would be flagged for rejection. In investigating the issue, they found that the lens was getting dirty from the welding operation. Because of the sensitivity of the sensor, it would detect the debris and marks on the lens and signal for poor weld. The lens was doing its part in protecting the sensor from damage; but, they needed a way to shield the lens from dirt and slag during the welding operation and visual inspection.

With this process, the machine would weld metal fasteners onto an enclosure by laser. The optical sensor would move along the welded areas to check the quality. In a lead/lag operation, the vision system would check the welds after a few seconds of cooling. So, both operations were occurring at the same time but at different intervals. When they started to see the rejection rate increase, they would have to stop the operation, clean the lens, and verify the integrity of the welds. In some cases, they would have to replace the 1 ¼” diameter lens especially if a piece of welding slag marred the surface. With incorrect rejections and lens cleaning, downtime was hurting their production rates and cost.

This customer wanted to use compressed air because it is a powerful and invisible way to create a shield. Since EXAIR is a leader in efficient and effective ways to use compressed air, they contacted us for help. Initially, I suggested a Super Air Knife to deflect any slag and debris from the lens surface. I showed a prior solution to a very similar issue; “Air Shielding a Laser Lens” (Reference below). But, because of the proximity to the part and the limitation in space, the Super Air Knife  configuration in the solution below would make it impossible to use. They were looking for a product that could be mounted either flush or behind the surface of the lens and still protect it.

Air Shielding a Laser Lens

To accommodate for this request, we had to direct the compressed air stream at an angle. EXAIR manufacturers a product that can do just that, the Super Air Wipe. The design of the Super Air Wipe blows compressed air at a 30-degree angle toward the center in a 360-degree air pattern, just like a cone. It can be placed around the lens and still be able to create a “wall” of air to block any slag or debris from hitting the lens.

I recommended the model 2452SS, 2” Super Air Wipe Kit. This Super Air Wipe has the body, braided hose, hardware, and shims that is made from stainless steel. It can handle the high heat loads from the welding process as well as to allow for easy cleanup after a day of operating. The kit includes a filter, to keep the compressed air clean; a regulator, to finely tune the force requirement; and a shim set. The shim set includes two additional sets of shims that can be added to increase the force of protection if needed. With the kit, the customer can “dial” in the correct amount of force needed to keep the lens clean without using excessive amount of compressed air.

As an added benefit of saving compressed air, the Super Air Wipe uses the Coanda effect to maximize the entrainment of ambient air into the compressed air stream. This makes the unit very efficient and very powerful. The Super Air Wipe was mounted just behind the lens like the customer required (Reference mock picture below), and the sensor could examine the welds without any interference with the metal enclosure.

Laser Lens mock drawing

Visual inspections systems are highly accurate pieces of equipment, and a dirty lens will affect the performance. EXAIR has many ways to keep the lens clean with a non-contact invisible barrier to protect sensors, cameras, and lasers. If you have a similar application, you can contact an Application Engineer to determine the best way to keep the lens clean and your equipment functional. After mounting the Super Air Wipe, the customer above eliminated any false rejections, and dramatically decreased any downtime for cleaning or replacing the lens in his welding machine.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Keys to an Efficient Compressed Air System

How do I make our compressed air system efficient?

This is a critical question which plagues facilities maintenance, engineering, and operational personnel.  There are concerns over what is most important, how to approach efficiency implementation, and available products/services to assist in implementation.  In order to address these concerns (and others), we must first look at what a compressed air system is designed to do and the common disruptions which lead to inefficiency.

The primary object of a compressed air system is to transport the compressed air from its point of production (the compressors) to its point of use (applications) in sufficient quantity and quality, and at adequate pressure for proper operation of air-driven devices.[1]  In order for a compressed air system to do so, the compressed air must be able to reach its intended destination in proper volume and pressure.  And, in order to do this, pressure drops due to improper plumbing must be eliminated, and compressed air leakage must be eliminated/kept to a minimum.

But, before these can be properly addressed, we must create a pressure profile to determine baseline operating pressures and system needs.  After developing a pressure profile and creating a target system operating pressure, we can move on to the items mentioned above – plumbing and leaks.

Proper plumbing and leakage elimination

The transportation of the compressed air happens primarily via piping, fittings, valves, and hoses – each of which must be properly sized for the compressed air-driven device at the point of use.  If the compressed air piping/plumbing is undersized, increased system (main line) pressures will be needed, which in-turn create an unnecessary increase in energy costs.

In addition to the increased energy costs mentioned above, operating the system at a higher pressure will cause all end use devices to consume more air and leakage rates to increase.  This increase is referred to as artificial demand, and can consume as much as 30% of the compressed air in an inefficient compressed air system.[2]

But, artificial demand isn’t limited to increased consumption due to higher system pressures.  Leaks in the compressed air system place a tremendous strain on maintaining proper pressures and end-use performance.  The more leaks in the system, the higher the main line pressure must be to provide proper pressure and flow to end use devices.  So, if we can reduce leakage in the system, we can reduce the overall system pressure, significantly reducing energy cost.

 

How to implement solutions

Understanding the impact of an efficient compressed air system is only half of the equation.  The other half comes down to implementation of the solutions mentioned above.  In order to maintain the desired system pressure we must have proper plumbing in place, reduce leaks, and perhaps most importantly, take advantage of engineered solutions for point-of-use compressed air demand.

The EXAIR Ultrasonic Leak Detector being used to check for leaks

Once proper plumbing is confirmed and no artificial demands are occurring due to elevated system pressures, leaks in the system should be addressed.  Compressed air leaks are common at connection points and can be found using an ultrasonic noise sensing device such as our Ultrasonic Leak Detector (ULD).  The ULD will reduce the ultrasonic sound to an audible level, allowing you to tag leaks and repair them.  We have a video showing the function and use of the ULD here, and an excellent writeup about the financial impact of finding and fixing leaks here.

The EXAIR catalog – full of engineered solutions for point-of-use compressed air products.

With proper plumbing in place and leaks fixed, we can now turn our attention to the biggest use of compressed air within the system – the intended point of use.  This is the end point in the compressed air system where the air is designed to be used.  This can be for blow off purposes, cleaning, conveying, cooling, or even static elimination.

These points of use are what we at EXAIR have spent the last 34 years engineering and perfecting.  We’ve developed designs which maximize the use of compressed air, reduce consumption to absolute minimums, and add safety for effected personnel.  All of our products meet OSHA dead end pressure requirements and are manufactured to RoHS, CE, UL, and REACH compliance.

If you’re interested in maximizing the efficiency of your compressed air system, contact one of our Application Engineers.  We’ll help walk you through the pressure profile, leak detection, and point-of-use engineered solutions.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

 

[1] Compressed Air Handbook, Compressed Air & Gas Institute, pg. 204

[2] Energy Tips – Compressed Air, U.S. Department of Energy