Video blog : VariBlast Compact Safety Air Gun

The following short video is a brief overview of our VariBlast Compact Safety Air Gun. The VariBlast Compact Safety Air Gun’s unique design features a variable flow trigger allowing you to achieve varying levels of force from the same nozzle.

If you have any questions, please  contact an application engineer at 800-903-9247.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

Calculating Force and Pressure For Air Nozzles

I assisted with an application where logs were being shaved to make thin laminate.  Because the logs were non-concentric or entirely smooth, the beginning of the sheet was riddled with scrapes and defects until it was about 8 foot (2.4 meters) long.  This was a very quick process, and once good product was coming from a shaved log, the machine would divert the material from the scrap bin to the production feed line with a nip roll.  At the speeds that the material was traveling, they needed to kept pressure on the leading edge of the sheet so that it would not “curl” up before the nip roll closed and grabbed the sheet. The drive rolls were pushing the laminate product toward the nip roll and they needed to keep the curl pushed flat along a plate and wondered if we had a product that could accomplish this.

We suggested a series of 2” flat air nozzles, model 1122, to keep the product pressed down on the plate with the force from the airflow.  In their trial runs, they tried to find the correct amount of air pressure to keep the product flat.  Once they found the pressure required, they noticed that the thin and delicate laminate was getting damaged.  Of course, it was just at the beginning length when it was being held in place as it slid into the nip roll, approximately 3 feet (0.9 meters).  Like any company, they did not want to waste any more product and wondered if we had anything else that we could recommend.

Thus a question was presented, and a solution was needed.  In thinking about this, it took me to my Michigan days where snow was abundant.  When walking on snow, you would fall through, but if you had snow shoes, you could stay on top of the snow.  This brought me to the factors of Pressure and Force.  Like with the laminate, if a smaller area does damage to the product (boots through the snow), can we expand the area to keep it from being damaged (snow shoes on top of the snow).

Snow Shoes
Snow Shoes

With the application, we needed to apply the same force on the material.  The equation for force is F = P *A (Equation 1), where F – Force, P – Pressure, and A – Area.

We can do an equality statement from Equation 1 which shows F = P1 * A1 = P2 * A2 (Equation 2).  The amount of pressure required from other EXAIR products can be determined, i.e. if I can double the surface area, then I can reduce the pressure by ½.  For model 1122, we can determine the pressure that was generated from Equation 1 and from the catalog data:

Imperial Units of Model 1122                                                      S.I. Units of Model 1122

F = 1.4 lbf (catalog)                                                                       F = 0.624 Kg (catalog)

A1 = Length X Width                                                                    A1 = Length X Width

= 5 inches X 2 inches (catalog)                                                   = 12.7 cm X 5.1 cm (catalog)

= 10 in^2                                                                                         = 64.8 cm^2

P1 = F/A1 (Rearranging Equation 1)                                         P1 = F/A1 (Rearranging Equation 1)

= 1.4 lbf/10 in^2                                                                            = 0.624 Kg/64.8 cm^2

= 0.14 PSI (pounds per in^2)                                                     = 0.0096 Kg/cm^2

Super Air Amplifier
Super Air Amplifier

Now that we have all the information from model 1122, we can determine the pressure required for a different product to keep the force the same.  With the 2” Super Air Amplifier, model 120022, it has a much larger footprint than the 2” flat air nozzle, model 1122.  So, with Equation 2, we can determine the amount of pressure required.  We will use model 1122 for our P1 and A1, and we will use model 120022 for P2 and A2.  From the catalog data for model 120022, we get a target area as follows:

 

Imperial Units for Model 120022                                               S.I. Units for Model 120022

A2 = pi * (diameter/2)^2                                                              A2 = pi * (diameter/2)^2

= 3.14 * (5.15 in/2)^2                                                                    = 3.14 * (13.1 cm/2)^2

= 20.8 in^2                                                                                      = 134.7 cm^2

 

When we apply the information to Equation 2, we get the following information:

 

Imperial Units                                                                                  S.I. Units

P2 = P1 * A1 / A2                                                                              P2 = P1 * A1 / A2

=(0.14 PSI * 10 in^2) / 20.8 In^2                                               =(0.0096 Kg/cm^2 * 64.8cm^2) / 134.7 cm^2

= 0.067 PSI                                                                                       =0.0046 Kg/cm^2

 

Now that the area was increased like the snow shoes above, the pressure was reduced and no additional waste was incurred.  Sometimes you have to think outside the igloo.  As with any application or product, you can always contact us at EXAIR for help.

 

John Ball
Application Engineer
johnball@exair.com
twitter.com/exair_jb

 

Image courtesy of VasenkaPhotography. Creative Comment License

Things Are Not Always As They Seem

A magician got a job on a cruise ship, entertaining the passengers on deck throughout the day, and performing a big nightly after dinner show. The Captain sat in the front row, and brought his pet parrot to see the show every night. After a couple of performances, the parrot started to figure out some of the magician’s tricks, and would cry out “The card’s up his sleeve!” “The ball’s in his other hand!” “There’s a fake bottom in the box!”  This irritated the magician to no end, but despite his protests, the Captain continued to bring the parrot to every show.

Then one night, the ship hit an iceberg and sank. The magician and the parrot ended up in the same lifeboat, where they sat, quietly glaring at each other. Hour upon hour passed in complete silence. Just before dawn, the parrot finally said “OK; I give up. What did you do with the ship?”

Magicians, of course, are the masters of all things “not as they seem,” using sleight-of-hand to create illusions or distractions. That means we see what they want us to see, we’re entertained, and their mission is accomplished.

The laws of physics mean that things are not always as they might seem as well. This morning, I had the pleasure of discussing an Air Knife application with a customer who intended to mount a Standard Air Knife as close as possible to his material, in order to provide the highest possible force from the air flow. The thought was, the closer the better, right? Well…

It turns out, this Air Knife was tested at distances from 3mm – 30mm (about 1/8” – 1”) from the target. The amount of force applied actually INCREASED with the distance over that range. His thinking was, with the velocity of the air flow being the highest, right at the outlet of the Air Knife, this would be where the force was greatest too. And, all other things being equal, this would be true.

The velocity of the air flow exiting our Air Knives can be as high as 13,000 feet per minute, and it’s not slowing down one bit over an inch of travel…not to any degree that we have an instrument to measure, anyway. The Standard Air Knife, however, entrains air from the surrounding environment…in fact, at 6″ away, it’s actually entrained 30 TIMES the amount of air that’s being supplied from your compressed air system. This is a TREMENDOUS increase in the mass flow rate. So, if you have a BUNCH more air hitting the target at the same speed, it’s going to exert a proportionately higher force.

How Std AK works

After explaining this to my customer (who installs these on chemical processing machinery), he was then able to enlighten HIS clients to the benefits of letting a little physics do the heavy (or not so heavy) lifting. In this case, the unexpected increase in force they got by moving the Air Knife about ½” away meant they could actually lower their compressed air supply pressure, conserving a great deal of air in this continuous blowing application.

Do you want to know how EXAIR, our Intelligent Compressed Air Products, and the laws of physics can work wonders in your facility, give us a call. No sleight-of-hand or prestidigitation required, but we’re willing to learn!

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