Compressed Air and Dew Point

Today’s discussion is on dew point of air as it has a significant impact on a compressed air system. The dew point is the temperature at which the water vapor in the air  can no longer stay in a vapor form, and condenses from a vapor into a liquid. The amount of water vapor contained in air is directly proportional to its temperature. The warmer the air the more space there is between molecules thus it is able to hold more water vapor.Capture

It is when air temperature drops below the dew point that issues develop in a compressed air system. Let’s take the example of a warm summer day at 90 F and 50% relative humidity. From the chart we see the dew point temperature to be 70 F. So at night, when all the equipment is shut down and the temperatures drop into the 60’s, water will condensate throughout the entire system. In the morning when the equipment is turned on, water blows through sensitive valving.

Compressing air will increase the dew point. Hot compressed air exiting the compressor and cooling while it makes its way through distribution systems is one reason for condensate in compressed air lines. Drying the compressed air is recommended to reduce or eliminate water condensate problems in a compressed air system.

There are several methods to dry out your compressed air. Each have their advantages and disadvantages. The following short review of the various options will help you decide which is best for your application.

After-coolers

The compressor’s after-cooler  which looks similar to a car’s radiator or the condenser in an air conditioner, is the first step to dryer air. It is placed at the compressor’s air outlet and uses either ambient air or water to cool the compressed air and condense some of the water vapor into a liquid that can be removed with a water separator.

The simplicity of design is a positive. The negative is that it can never cool below ambient but something above ambient depending on its capacity. After-cooler performance is rated by approach temperature, which is how closely the compressed air leaving the after-cooler will approach the temperature of the cooling medium used.

For example, if an air-cooled after-cooler is rated for a 10°F approach temperature, and the temperature of the ambient air is 90°F, the temperature of the air leaving the after-cooler will be 100°F. Assuming 50% relative humidity day the dew point will be 80 F.

Mechanical Water Separators

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Wet compressed air enters the separator and passes through a set of vanes that spins it in a vortex. Centrifugal force causes liquid to fly out of the compressed air stream and run down the inside of the filter bowl, where it can be drained off. These are installed at the point of use as a final defense before entering sensitive compressed air equipment. They are an inexpensive assurance of quality air. The ones EXAIR has also include a sintered bronze filter element to remove dirt and scale as well as water.

Deliquescent Dryer

A deliquescent dryer is basically a tank full of salt tablets. As the compressed air passes through the salt, the salt attracts water and dissolves into a brine that can be drained off. These are the least expensive dryers to purchase and maintain because they have no moving parts and require no power to run. The operating cost consists of the cost of more salt tablets.

Desiccant Air Dryers

These are similar to the deliquescent driers except they use a desiccant that attracts water but holds it. When they have reached their saturation limit they are either replaced or regenerated in one of three methods.

Operating cost of these dryers varies with the method used to remove water from or regenerate the desiccant.

Heatless regenerative dryers take a portion (about 15%) of the dry compressed air leaving the dryer and passes it through the desiccant to absorb the moisture out of it. Purchase cost economical but operational costs are high because if all the compressed air used to dry out the desiccant.

Heated purge regenerative dryers take advantage of the fact that hot air can hold more water than cold air. These dryers take about 5% of the dry compressed air leaving the dryer and pass it through an electric heater and then sends it through the wet desiccant bed. This dryer cost more than the heat less dryer but is offset by using half the compressed of that used by the heat less dryer.

Blower Purge Dryers

These are similar in concept to the had dryers found in restrooms but on a larger scale. Heated air is sent trough the desiccant with a blower. These are not quite as efficient because they are heating up ambient air which would not be as dry as compressed air.

Membrane Air Dryers

These dryers use pass the compressed air through a membrane with pores large enough to allow air molecules through but not large enough to allow water molecules through. The lower a dew point is needed, the more purge air is required. These

Refrigerated Air Dryers

Is an A/C system that refrigerate  the compressed air as close to freezing as possible in order to condense out as much water as possible then use a mechanical water separators to remove the condensed water. They require electricity to operate along with the associated cost of operation and maintenance.

Hopefully this gives you a better understanding on how to qualify your compressed air.

Feel free to contact me at any time with questions or concerns, or if I can be of any further assistance. I genuinely appreciate the opportunity! 1-800-903-9247 or click on the live chat icon in the upper left hand corner.

Joe Panfalone

Application Engineer
Phone (513) 671-3322
Fax (513) 671-3363
Web: http://www.exair.com
Twitter: http://www.twitter.com/exair_jp
Facebook: http://www.facebook.com/exair

It’s Your Birthday…It’s Your Birthday

In an earlier post, I spoke about how I like my job and the people I work with. Here is a prime example of why I feel that way. As a father I’ve always enjoyed celebrating the kid’s and wife’s birthdays. But for me, my birthday is more or less just another day. No big deal.joebd2013

I turned 65 this week and had the most exceptional and memorable birthday ever. I was completely overwhelmed by all the attention I was given by my co-workers. The entire company took time out to present me with a birthday cake and sang a revised version of happy birthday strummed on the guitar by our lead engineer, and yes, everything they say about engineers is true.

The highlight of the day was the gifts they gave me. My hobby requires the use of lead which is hard to come by these days. Each employee presented me with a bag of scrap lead. AWESOME!

The adrenalin hardly subsided when they invited me out to dinner after work. Being of Italian descent, they took me to a nice Italian restaurant.

range

As if the gifts of lead were not enough, they presented me with a range bag with my name and company logo embroidered on it. It will be a life long reminder of a super group of people that collectively make a company.

I had a college professor once tell me that happy employees produce astounding results. The work environment at EXAIR is a happy one, which is why I was astounded on my birthday…

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Joe Panfalone
Application Engineer
Phone (513) 671-3322
Fax   (513) 671-3363
Web: www.exair.com
Twitter: www.twitter.com/exair_jp
Facebook: http://www.facebook.com/exair

The Last Of The Compressed Air Challenge Seminar Blogs (for now)

Last week, Lee Evans, Brian Farno, and I attended a seminar entitled “Fundamentals of Compressed Air Systems,” sponsored by the Compressed Air Challenge. Lee and Brian have already written great pieces on what we learned, and Joe Panfalone (even though he didn’t even go) has gotten in on the action too – leaving me to search desperately through my notes for something relevant to discuss. Here’s my initial takeaway: If your blog is published on Wednesday, try to attend the seminar you wish to write about on Tuesday, not Thursday.

One thing that my associates left me, though, was the subject of inappropriate uses of compressed air. According to the Compressed Air Challenge folks, 70% of the savings to be realized lie in measures on the “demand” side of your system. A big chunk of this is the aforementioned inappropriate uses, which were defined as applications that could be performed using alternate methods. The assumption is that these alternate methods are less costly from a compressed air usage standpoint – which is not always the only factor to consider:

*The floor needs to be swept at the end of the shift. It takes 10 minutes with a broom, or 5 minutes with a Super Blast Safety Air Gun (for instance, the Model 1214, which uses 91 SCFM @80psig). Let’s assume labor at a cost of $50/hr, and compressed air at a cost of $0.25/1000 SCF (Standard Cubic Feet):

-Broom: $4.17 labor (10 minutes @$25/hr) = $4.17
-Air: $2.19 labor (5 minutes @$25/hr) + $0.11 compressed air = $2.19

Other situations require a little more data, and math, to quantify. For instance, if vacuum is required for lifting, pick and place, mounting, etc., a central vacuum pump may have lower operating costs than those associated with the compressed air needs of E-Vac Vacuum Generators. When you factor in initial capital cost and maintenance expenses, the E-Vac still compares favorably, though, despite the potentially higher operating cost. I say “potentially,” because a system’s vacuum pump is often located some distance from the farthest point of use. That means it’s spending energy not only to provide vacuum to the remote points of use, but also to overcome the line loss in those lengths of piping. E-Vacs don’t have this problem, as they can be easily installed at the point of use, and sized appropriately.

The last (and I thought, most highlighted) inappropriate use they covered was cabinet cooling. It was explained that even though a vortex tube cooler may cost less, the air consumed will cost more than the electricity required by a refrigerant-based unit. Now, we don’t dispute that…the following comparison shows as much:

Then, the instructor went a bit further (pre-empting a question from Brian, Lee, and I) to validate cabinet cooling as an appropriate use, but only when: the environment was not conducive to a refrigerant-based unit (high ambient temperatures, dusty/dirty/aggressive atmosphere, etc.), AND thermostat control was used. They took great pains to not promote any particular brands of equipment in the presentation of the seminar, but the photo they used to illustrate this was unmistakably an EXAIR NEMA 4 Cabinet Cooler with Electronic Temperature Control. That was worth the price of admission for me.

If you have questions about whether you’re using your compressed air appropriately, or even to its maximum efficiency, give us a call. If we can’t find the answer mathematically from the data available, we can gather the data in our Efficiency Lab. Math doesn’t lie, and neither will we.

Russ Bowman
Application Engineer
EXAIR Corporation
(513)671-3322 local
(800)923-9247 toll free
(513)671-3363 fax
Web: http://www.exair.com
Blog: https://blog.exair.com/
Twitter: twitter.com/exair_rb
Facebook: http://www.facebook.com/exair

Understanding Gas Flow and Measurements

Both gas and liquid flows can be measured in volumetric or mass flow rates. With non-compressible liquids these two measurements are very nearly the same sans the effects of temperature. With compressible gasses though, they are very different. The same mass under different pressures will occupy dissimilar volumes.

To demonstrate this, take a folded fluffy comforter and weigh it. Then stuff into one of those storage bags that you suck down with a vacuum cleaner. The physical size becomes very much smaller but the weight (mass) stays the same.

When measuring a flow of a compressible gas through a pipe you are measuring volumetric flow. Unlike non-compressible liquids, it is of little value unless it is converted to mass flow which would be dictated by the pressure it is under. For example the utility company charges by the cubic foot of natural gas and gallons for water. With water you actually get a gallon as measured by the meter. With gas though, the mass you receive depends on pressure it is under.

To effectively measure gas flows, their volumetric flow rate has to be converted to standard conditions for temperature and pressure. Simply put, it is the volume it would occupy at atmospheric pressure (14.7 psi) and defined as standard cubic feet per minute (SCFM).

Convert flow from CFM to SCFM

 Qg = Q x P/14.7

Qg=Gas flow in standard cubic feet per minute (SCFM)

Q=Volume flow rate in cubic feet per minute (CFM)

P=Line pressure absolute (gage pressure +14.7).

Example: Convert gas flow expressed in cubic feet per minute (CFM) to units of standard cubic feet per minute (SCFM).

 Given:

Q = 20 CFM

P = 114.7 (100 psi gage reading +14.7)

Qg = Q x P/14.7     = 20 CFM x 114.7/ 14.7      = 156 SCFM

Flow meters used to measure gasses usually are calibrated for readings at atmospheric pressure. When the flow is under pressure, they provide a chart of factors associated with various pressures to multiply against the visual reading.

Joe Panfalone
Application Engineer
Phone (513) 671-3322
Fax   (513) 671-3363
Web: www.exair.com
Twitter: www.twitter.com/exair_jp
Facebook: http://www.facebook.com/exair

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Tis the Season For Static

We are approaching the dry winter season and with it the problems of static electricity. At our house, we have a sofa with a synthetic fabric covering that is absolutely horrendous for generating static electricity. After a couple of jolts, the dog no longer comes around us when we are sitting on that couch.

Seeing the dog’s hair stand on end is humorous but in manufacturing it can be devastating. Here is a very well produced video  put out by the Chemical Safety Board. It demonstrates how a chemical distributor did everything right but something as innocuous as a hinge caused a devastating fire.

The harmful effects of static electricity are not confined to flammable liquids, in the production process they can affect vision systems, impair packaging, transfer systems, and electronics assembly just to mention a few.

EXAIR has a complete line of static eliminators that can help you control static electricity in your operation. Give one of our application engineers a call at 1-800-903-9247 and they will help you choose the most appropriate product. Then EXAIR provides a 30 day evaluation period. Should within that time you are not satisfied you can return it for full credit.

Joe Panfalone
Application Engineer

Phone (513) 671-3322
Fax   (513) 671-3363
Web: www.exair.com
Twitter: www.twitter.com/exair_jp
Facebook: http://www.facebook.com/exair

Safety Matters

I just came back from a safety training meeting on lockout/tag-out. At first I wondered why I needed to attend as I sit in front of a computer all day. I came from the meeting with a real appreciation for why my company insists that all employees attend. While I may not be directly involved, I do venture out in the shop. Having a working knowledge on safety not only protects me but provides an additional set of eyes for potential issues.

Did you know that of the 125 million US workers, 4,547 died on the job in 2010 and 3.6 million had reportable injuries.  – Some sobering statistics that I do not plan to be part of.

OSHA recently released the top ten citations for 2010. They are:

Subject

Code

Number

Of Citations

Scaffolding, Construction  29CFR 1926.451

8,371

Fall Protection,Construction  29CFR 1926.501

7,559

Hazard Communication, General Industry  29CFR 1910.1200

6,633

Respiratory Protection,General Industry  29CFR 1910.134

3,932

Ladders, Construction  29CFR 1926.1053

3,820

Lockout / Tag out, General Industry  29CFR 1910.147

3,531

Electrical Wiring Methods, General Industry…  29CFR 1910.305

3,381

Powered Industrial Trucks, General Industry..  29CFR 1910.178

3,224

Electrical Systems Design,General Industry…  29CFR 1910.303

2,770

You can find a copy of 29 CFR on the Department of Labor’s website. They also have a plethora of manuals and training info.

I hope the company that you work for is as concerned for its employees as mine is.

Joe Panfalone
Application Engineer

Phone (513) 671-3322
Fax   (513) 671-3363
Web: www.exair.com
Twitter: www.twitter.com/exair_jp
Facebook: http://www.facebook.com/exair

Keep Your Pressure Up and Your Risk Down

Keeping up with all the new products EXAIR has been introducing has been somewhat daunting for me. My co-workers claim it is due to the age of my internal hard drive.  I would like to think that it is so filled with decades of knowledge that it has slowed down my internal processor. It is undeniable though, that EXAIR continues to launch new products to better serve the industrial compressed air community.

When we recently introduced our Atto Nozzle, which is about the size of a grain of rice, I started receiving application calls needing to replace open miniature copper tubing which presents issues with the OSHA directive of 30 psi maximum dead-end pressure. When operating the small open copper tubes at 30 psi they were not able to achieve sufficient air flow. Going to anything larger was not an option due to space constraints.

With the Atto Nozzle,  the orifices are nestled between the protective fins and there are multiple orifices. This makes it impervious to blockage so higher air pressures can be used to provide an effective blow off. Higher inlet pressures equal higher velocity air and sufficient volume to continue to get the job done while still maintaining OSHA compliance. All of EXAIR’s Super Air Nozzles have these features to allow you to keep your pressure up and get the job done while maintaining or increasing the safety to your personnel.

If would like to discuss your application with one of our engineers call us at 1-800-903-9247

Joe Panfalone
Application Engineer

Phone (513) 671-3322
Fax   (513) 671-3363
Web: www.exair.com
Twitter: www.twitter.com/exair_jp
Facebook: http://www.facebook.com/exair