Drying Supply Side Air With Heat of Compression Dryers

The supply side of a compressed air system has many critical parts that factor in to how well the system operates and how easily it can be maintained.   Dryers for the compressed air play a key role within the supply side are available in many form factors and fitments.  Today we will discuss heat of compression-type dryers.

Heat of compression-type dryer- Twin Tower Version

Heat of compression-type dryers are a regenerative desiccant dryer that take the heat from the act of compression to regenerate the desiccant.  By using this cycle they are grouped as a heat reactivated dryer rather than membrane technology, deliquescent type, or refrigerant type dryers.   They are also manufactured into two separate types.

The single vessel-type heat of compression-type dryer offers a no cycling action in order to provide continuous drying of throughput air.  The drying process is performed within a single pressure vessel with a rotating desiccant drum.  The vessel is divided into two air streams, one is a portion of air taken straight off the hot air exhaust from the air compressor which is used to provide the heat to dry the desiccant. The second air stream is the remainder of the air compressor output after it has been processed through the after-cooler. This same air stream passes through the drying section within the rotating desiccant drum where the air is then dried.  The hot air stream that was used for regeneration passes through a cooler just before it gets reintroduced to the main air stream all before entering the desiccant bed.  The air exits from the desiccant bed and is passed on to the next point in the supply side before distribution to the demand side of the system.

The  twin tower heat of compression-type dryer operates on the same theory and has a slightly different process.  This system divides the air process into two separate towers.  There is a saturated tower (vessel) that holds all of the desiccant.  This desiccant is regenerated by all of the hot air leaving the compressor discharge.  The total flow of compressed air then flows through an after-cooler before entering the second tower (vessel) which dries the air and then passes the air flow to the next stage within the supply side to then be distributed to the demand side of the system.

The heat of compression-type dryers do require a large amount of heat and escalated temperatures in order to successfully perform the regeneration of the desiccant.  Due to this they are mainly observed being used on systems which are based on a lubricant-free rotary screw compressor or a centrifugal compressor.

No matter the type of dryer your system has in place, EXAIR still recommends to place a redundant point of use filter on the demand side of the system.  This helps to reduce contamination from piping, collection during dryer down time, and acts as a fail safe to protect your process.  If you would like to discuss supply side or demand side factors of your compressed air system please contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

Heat of compression image: Compressed Air Challenge: Drive down your energy costs with heat of compression recovery: https://www.plantservices.com/articles/2013/03-heat-of-compression-recovery/

O-Rings, Seals, Gaskets, Maintenace, Filtration – They All Matter

I’ve mentioned it before and I’ll say it again. You can’t teach experience. This was told to me by a mentor at a previous job and of course, younger me thought, “Yeah, yeah I know all I need to know.”  Well, younger me was an idiot and learned many things through experience. Sometimes I am still a slow learner and eventually, I remember those experiences and make decisions based on them. So what does this have to do with o-rings, seals, and gaskets?

I’m in the midst of a light construction project in my house and have reached a stage where some tools that I do not have would come in handy and make the job faster. Younger me would have justified purchasing a new one, experienced me understands a budget and reached out to my network of friends and a good friend said they had the tool I needed. This was a compressed air powered framing nail gun. Straight through nailing, no-problem, toe-nailing, no-problem, this thing won’t break a sweat and your arms will be stronger by the time you are done using it while your thumbs are screaming thank you for not smashing me a hundred times.

The Framing Nail Gun in question

This loan did come with two conditions, one was, he didn’t have any nails to give with it. This was not a problem as I wouldn’t expect a friend to give me free fasteners with a tool loan. The second is the one that concerned me, he said, it does leak a little air but it should still shoot just fine. After working in the compressed air industry for over a decade I have experienced this many times. At that point I knew if you could hear it, chances were it was a bad leak. Upon further inspection, there was a cylinder gasket and rubber spring that were in pieces.

Old Spring Bumper and Main Cylinder Gasket

Gasket pieces and dirty air can result in catastrophic failures.

Nothing that a trip to a local business couldn’t take care of.  A few new parts and discussion with their knowledgeable staff and I had the information needed to rebuild this nail gun to functioning status.

New vs. Old

Oddly enough, my experience and expertise with how the EXAIR products like the No-Drip Air Atomizing Liquid Spray Nozzles operate and how to rebuild them, provided a good foundation about how this tool worked. This repair ended up being very similar to the rebuild on a No-Drip Spray Nozzle.

This story is two-fold, filtration could have prevented a lot of the damage to this gun. This gun uses a good amount of air volume at an expedient pace so keeping it clean and clear of debris helps extend the lifetime of internal parts.  See my video on what happens without filtration below.

The second part is that maintaining and understanding processes to clean/rebuild are crucial to sustainable function of a machine. The cleaning process for this gun was fairly straightforward and using the correct lubricant for reassembly was another critical role. This culminated in a framing nail gun that can now be used to further my project and will more than likely live another decade before needing a rebuild again. That is if filtration and proper lubrication are followed.

Had I not obtained experiences throughout my career that helped me to understand how this tool functioned, the worth of a reliable network of vendors, and the necessity to complete tasks that take me out of my comfort zone I wouldn’t be in the place I am today. Because I have the experience and the network to ask for help it enables me to keep machines running that could have cost valuable production hours had this been a production environment.

EXAIR stocks rebuild kits, gaskets, shims, and parts for all of our product lines which may require a repair. For products which need to be cleaned in order to return back to new performance, we have the instructions or can do it for you here. From time to time they may need a repair or refurb in order to keep functioning at peak performance. If you want to build your trusted network or learn more about how to rebuild or clean EXAIR products, contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

About Dual Acting Reciprocating Compressors

When it comes to generating compressed air there are many types of compressors to utilize within a facility.  One of those types is a dual acting reciprocating compressor.  This is a type of positive displacement compressor that takes advantage of a piston style action and actually compresses air on both directions of the stroke.  Below you can see a video from a company that showcases how a dual acting compressor works and gives a good representation of how it is compressing the air on both directions of travel.

Dual_Recip
Click on this image for video

The reciprocating type of air compressor uses a motor that turns a crank which pushes a piston inside a cylinder; like the engine in your car.  In a basic cycle, an intake valve opens to allow the ambient air into the cylinder, the gas gets trapped, and once it is compressed by the piston, the exhaust valve opens to discharge the compressed volume into a tank.  This method of compression happens for both the single and double acting reciprocating compressors.

With a single acting compressor, the air is compressed only on the up-stroke of the piston inside the cylinder.  The double acting compressor compresses the air on both the up-stroke and the down-stroke of the piston, doubling the capacity of a given cylinder size.  This “double” compression cycle is what makes this type of air compressor very efficient.  A single acting compressor will have an operating efficiency between 100 cfm / 23 kW of air while the double acting compressor has an operating efficiency between 100 cfm 15.5 kW .  Therefore, electricity cost is less with a double-acting reciprocating air compressor to make the same amount of compressed air.

These compressors are ruggedly designed to be driven 100% of the time and to essentially be a Clydesdale of compressors.  They are commonly used with applications or systems requiring higher pressures and come in lubricated or non-lubricated models.

If you would like to discuss air compressors or how to efficiently utilize the air that your system is producing so that you aren’t giving your compressor an artificial load that isn’t needed, contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF