So Many Holes

I remember the book and movie about a young teenager who gets sent to a prison/ work camp that all they do is dig holes. Yeah, there’s a much deeper story line there and that isn’t the point of this blog. The point is, that movie is all I thought of when I encountered this customer’s nozzle solution. Their ejector nozzle on a recycling conveyor was using too much air and was too noisy.

Upon receiving the nozzle to do a free EXAIR Efficiency Lab, we were absolutely amazed at the level of care taken to make something like this. The nozzle was purpose built and definitely got the job done, it also drained their compressed air system at times and made a lot of noise while it did the work. So what did this nozzle look like, now keep in mind, this was not the customer’s design, it was a solution from the machine manufacturer.

For an idea, the customer nozzle was a 3″ overall length, and had a total of 162 holes in it. There were two inlets for 3/8″ push to connect tubing. The holes were very cleanly drilled and we used a discharge through orifice chart to estimate the consumption before testing. Operating pressure were tested at 80 psig inlet pressure.

Discharge through an orifice table.

Our estimations were taken from the table above. We used a pin gauge to determine the hole size and it came close to a 1/32″ diameter. With the table below we selected the 1.34 CFM per hole and used a 0.61 multiplier as the holes appeared to have crisp edges.

Estimation Calculation

Then, we went to our lab and tested. The volumetric flow came out to be measured at 130.71 SCFM. This reassured us that our level of estimation is correct. We then measured the noise level at 95.3 dBA from 3′ away. Lastly, we tested what could replace the nozzle and came up with a 3″ Super Air Knife with a .004″ thick shim installed. To reach this solution we actually tested in a similar setup to the customer’s for functionality as they sent us some of their material.

Now for the savings, since this customer was focused on air savings, that’s what we focused on. The 3″ Super Air Knife w/ .004″ thick shim installed utilizes 5.8 SCFM per inch of knife length when operated at 80 psig inlet pressure. So the consumption looks like below

That’s an astounding amount of air saved for each nozzle that is replaced on this line. The line has 4 nozzles that they want to immediately change out. For a single nozzle, the savings and simple ROI looks like the table below.

Air Savings / Simple ROI

That’s right, they will save 115.02 SCFM per minute of operation. These units operate for seconds at a time so the amount of actual savings is still to be determined after a time study. In videos shared, there was not many seconds out of a minute where one of the four nozzles was not activated. Once the final operation per minute is received we can rework our calculations and see how many hours of line operation it will take to pay back each knife purchase.

If you have any point of use blowoff or part ejection and even have a “nice looking” blowoff in place, don’t hesitate to reach out. These are still very different from our Engineered Solutions. We will help you as much as we can and provide test data, pictures, and even video of testing when possible.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

“It’s Not Rocket Science”, or How Compressed Air Has Straightforward Applications In Aerospace

On the submarine I served on, many of us used math, specific to our jobs. Torpedo (and missile) fire control, navigation, reactor operations…even meal cooking…involved certain formulas to accomplish particular tasks. One formula we all knew and kept near & dear to our hearts, though, was:

Number of surfaces = Number of dives

And those who fly aircraft and spacecraft, in – and out of – the atmosphere, have a similar formula:

Number of landings = Number of takeoffs

While this certainly requires a great deal of skill of the operators (as does diving and surfacing a submarine), it also takes a great deal of technical acumen in the engineering and construction of those aircraft & spacecraft (and warships). Terms like “aircraft grade” inspire a high degree of confidence in the integrity of materials, and rightly so – the quality standards that manufacturers and suppliers are held accountable to are stringent and inviolate. That’s why aerospace professionals need reliable, durable, and effective equipment to do their jobs.

EXAIR Corporation has been providing this kind of equipment to the aerospace industry (and others) since 1983. Here are some examples of the applications we’ve worked with “steely eyed missile men” to solve:

  • A jet engine manufacturer makes a titanium assembly consisting of a honeycomb shaped extrusion bonded to a rigid sheet. The cells of the honeycomb are only 1/8” wide, and 3/8” deep. After fabrication, they’re washed & rinsed, and the tiny cells tend to hold water. They would invert & tap the assembly to try to get the water out, but that wasn’t always effective and occasionally led to damaging the assembly. To reduce the chance of damage (and loss) of an assembly, they built a cleaning station, using EXAIR Model HP1125 2” High Power Super Air Nozzles and Model 9040 Foot Pedals, for hands-free control of the high force blow out of the honeycomb cells. The results were increased production, decreased defects, and lower labor costs.
  • A machine shop makes composite material parts for the aerospace industry. Static charge would build up, causing the shavings to cling to most of the surfaces inside the machine. The vacuum system was unable to overcome the force of the static charge to remove it, so they called EXAIR. Our expertise in static elimination led to the specification of a Model 8494 Gen4 Stay Set Ion Air Jet System to direct ionized air onto the tool during cutting. This eliminated the static as it was generated on the shavings, allowing the vacuum system to perform as advertised. Not only did it make for a cleaner work station, the air flow provided cooling for the cutting tool, improving performance & extending life.
  • If a company works with metal parts, there’s a decent chance they operate a welding machine, and those things make smoke & fumes that, at best, are a nuisance, and at worst, are toxic. An airplane repair shop that has to weld in tight spaces needed a convenient, portable, compact way to evacuate the welding smoke and fumes. They chose a Model 120024 4” Super Air Amplifier. They’re capable of pulling in over 700 SCFM, and with a sound level of only 73dBA and lightweight aluminum construction, they’re an ideal fit for this application.
  • Certain satellites have components whose batteries must be fully charged to ensure that everything works just right. Because of the heat that charging generates, they couldn’t be charged with the spacecraft on the launch pad without cooling. Conventional methods of providing cold air (refrigerant based or cold water chillers) are too bulky, so they instead use a Model 3230 Medium Vortex Tube, capable of providing 2,000 Btu/hr worth of cooling air flow. This enables them to charge the battery until just prior to launch, making sure the batteries are as fully charged as possible, prior to deployment.
  • While the lion’s share of Vortex Tube applications involve the use of their cold flow, a number of folks do use the hot air flow, with great success. A major material supplier to the aircraft & aerospace industry makes a flexible, porous strand of material that, after fabrication, passes through a wash tank prior to cutting to size. They wanted to speed up the drying time, but it was impractical to use electrically powered hot air blowers or heat guns. By using an EXAIR Model 3275 Large Vortex Tube set to a 70% Cold Fraction, they’re able to blow a little over 22 SCFM of 220°F air onto the strand, which effectively dries it to their specification, quickly & safely.
These are some of the EXAIR Intelligent Compressed Air Products used in the aerospace industry.

Exacting jobs call for safe, efficient, and reliable tools. Even if your job “isn’t rocket science”, the value of the right tool cannot be stressed enough. If you use – or want to use – compressed air for such a task, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
Visit us on the Web
Follow me on Twitter
Like us on Facebook

“Math Wall” image courtesy of João Trindade, Creative Commons License

The Effect of Back Pressure on a Vortex Tube Part 2, Calculating Btu/Hr.

My previous blog post was about how Vortex Tubes react when there is back pressure due to a restriction on either the hot or cold discharge of the Vortex Tube.  In it I mentioned that there is a formula to calculate what the cooling capacity (Btu/Hr) will be if there is no way to avoid operating the Vortex Tube without back pressure on the discharge. That is the calculation focus of this blog – calculating Btu/hr of a Vortex Tube with back pressure.

To continue with the same example, the calculations from the previous blog are shown below.  Last time the example Vortex Tube was operating at 100 psig inlet pressure, 50% cold fraction, and 10 psi of back pressure. We will need some additional information to determine the Btu/Hr capacity. The additional information needed is the temperature of the supplied compressed air as well as the ambient air temperature desired to maintain.  For the example the inlet compressed air will be 70°F and desired ambient air temperature to maintain will be 90°F.

(100 psig + 14.7 psia) / (10 psig + 14.7 psia) = X / 14.7 psia
4.6437 = X / 14.7
X= 14.7 * 4.6437
X = 68.2628
(Values have been rounded for display purposes)

The calculation above gives the compensated operating pressure (X = 68.2628) which will be needed for the BTU/hr calculation. The rated air consumption value of the Vortex Tube will also need to be known.  A 30 SCFM rated generator will be used for this example, the normal BTU capacity of a Vortex Tube with a 30 SCFM generator is 2,000 BTU/hr.

First, determine the new consumption rate by establishing a ratio of the compensated pressure (68.2628 psi) against the rated pressure (100 psi) at absolute conditions (14.7 psia).

(68.2628 PSIG + 14.7 (atmospheric pressure)) / (100 PSIG (rated pressure) + 14.7) = .7233
.7233 x 30 SCFM  = 21.7 SCFM Input 

Second, the volumetric flow of cold air at the previously mentioned cold fraction (50%) will be calculated.  To do this multiply the cold fraction setting (50%) of the Vortex Tube by the compensated input consumption (21.7 SCFM) of the Vortex Tube.

50% cold fraction x 21.7 SCFM input = 10.85 SCFM of cold air flow

Third, the temperature of air that will be produced by the Vortex Tube will need to be calculated.  For this consult the Vortex Tube performance chart which is shown below. To simplify the example the compensated operating pressure (68.2628 psi) will be rounded to 70 psig and to obtain the 70 psig value the mean between 80 psig and 60 psig performance from the chart will be used.

Cold Fraction
EXAIR Vortex Tube Performance Chart

For the example: A 70 psig inlet pressure at 50% cold fraction will produce approximately an 88°F drop.
Fourth, subtract the temperature drop (88°F) from the temperature of the supplied compressed air temperature (70°F).

70°F Supply air – 88°F drop = -18°F Output Air Temperature

Fifth,  determine the difference between the temperature of the air being produced by the Vortex Tube (-18°F) and the ambient air temperature that is desired (90°F).

90°F ambient – -18°F air generated = 108°F difference.

The sixth and final step in the calculation is to apply the answers obtained above into a refrigeration formula to calculate BTU/hr.

1.0746 (BTU/hr. constant for air) x 10.85 SCFM of cold air flow x 108°F ΔT = 1,259 BTU/hr.

In summary, if a 2,000 BTU/hr. Vortex tube is operated at 100 psig inlet pressure, 50% cold fraction, 70°F inlet air to maintain a 90°F ambient condition with 10 psi of back pressure on the outlets of the Vortex Tube the cooling capacity will be de-rated to 1,259 BTU/hr.  That is a 37% reduction in performance.  If a back pressure cannot be avoided and the cooling capacity needed is known then it is possible to compensate and ensure the cooling capacity can still be achieved.  The ideal scenario for a Vortex Tube to remain at optimal performance is to operate with no back pressure on the cold or hot outlet.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF

How Much Force Does It Take?

In case you weren’t aware, the answer to “How much force does it take?” is always going to be, ALL OF IT.   At least that is what we generally think when trying to blow product off a conveyor belt or diverting parts into bin, etc. Speed and efficiency play a direct role in to what nozzle or blow off device you should use in order to get the job done and be able to repeat the process.

The question we are often asked by customers is, “How much force to I need to move this?”  That is a question that we cannot often answer without asking more questions.  The good part of this is, there is a formula to calculate just how much force you need to move an object.   A good video explaining friction is shown below.

In order to answer the question of how much force do I need, we really need to know all of the following:

Weight of the object
Distance from target
Is it on an incline or level
Distance needed to move
Then, the usually unknown variable, the coefficient of friction between the target and what it is sitting on.

Often times it is the thought process of, my target weighs 5 pounds, I need 5 pounds of force in order to move it from the center of this conveyor belt to the edge, this is not the case.   If you wanted to lift the object over a break between two conveyors then you would need slightly more than 5 pounds in order to ensure you are lifting the front edge of the unit high enough to meet the other conveyor.

Whether you know all of the variables or only a few, if you need to get an object moved and you want to try using compressed air to do so, give us a call and we will help you find the best engineered solution for your application.  Then, we’ll back all stock products with a 30 day guarantee if you don’t like how the system performs – but rest assured, we get it right almost every time.

30 Day Guarantee
The EXAIR 30 Day Guarantee

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF