Compressed Air Super Air Knife vs. Blower-type Air Knife for Plastic Film Manufacturing

A plastic company produced many kinds of films and sheets.  They were having issues with one particular film, an OPS (Polystyrene) film which was 0.012” (300 microns) thick and 30” (762mm) wide.  As the material was extruded into a flat sheet, they would run it over a cold roll drum (Reference photo above).  The cold drum is a large cylinder that has chilled water running through it.  To keep the sheet on the surface of the cold drum, they used a blower air knife system.  With the blower air knife, they were having variation in thickness as well as stretch marks.  They heard about the EXAIR Super Air Knife, and they wanted me to do a comparison.  I was glad to compare the EXAIR 110230 30” Super Air Knife Kit to their blower-type air knife system.

Super Air Knife Kits include a Shim Set, Filter Separator, and Pressure Regulator.
  1. “Stretch” marks on the plastic film:
    • Blower System – Hot air is generated by the blower system. When the hot air hits the cool surface, it would cause an uneven hardening of the material, causing stretch marks.
    • Super Air Knife – It has a 40:1 amplification ratio. That means that 40 parts of the ambient air is entrained with 1 part of compressed air.  Being that the ambient air is much cooler than the hot air from the blower system, it actually aides in cooling.  There is no thermal shock to the sheet material, and hardening is consistent and faster.
  2. An even force across the plastic film:
    • Blower System – Their design had one 4” (102mm) line feeding into the side of the blower air knife. This would cause two issues for an even force.  As the velocity of the air hits the opposite side of the knife, the closed end, a turbulent air flow is developed.  Also, there would be a slight negative pressures at the entrance caused by the velocity of the air entering.  This chaotic turbulent flow caused an uneven force on the surface of the film.
    • Super Air Knife – The flow that is delivered from the Super Air Knife is laminar. This means that the force and velocity is consistent across the entire length, even on the target.  With this even force, the film was held evenly and securely on the cold drum.  With a filter, shim set, and regulator that is included in the kit, the force can be easily adjusted to the perfect requirement.
  3. Maintenance requirements:
    • Blower System – Preventative maintenance is a requirement. The blower filters have to be changed regularly, and the mechanical and electrical components have to be checked.  This requires downtime to the system.  In addition to this, blower motors are mechanical devices.  The bearings will wear and the motor will fail.  If a mechanical failure does occur, the downtime can cost days of operation.  These items should be checked quarterly as a PM which increases the cost of ownership.
    • Super Air Knife – No moving parts to wear out. The only maintenance would be to change the compressed air filter once a year.  There is no worry about catastrophic failure.
  4. Noise levels:
    • Blower System – With the blower motor and turbulent air flow, the system makes a lot of noise. They have a sound level near 93 dBA which would need PPE for nearby operators.
    • Super Air Knife – These units are very quiet. At a pressure of 100 PSIG (6.9 bar), the sound level is only 72 dBA.  No additional cost for PPE or the constant nagging disturbance of loud noises.
  5. Compact Design:
    • Blower System – The foot print of the blower is large and it takes up much floor space. The 4” (102mm) duct has to be ran to an oversized air knife (Reference photo below).  With the turbulent flow, the blower air knife has to be mounted close to the film surface.  So, it can make it difficult to optimize the placement.
    • Super Air Knife – With the compact design, the Super Air Knife has a large force in a small package. The model 110230 Super Air Knife has a footprint of 1 ¾” X 1 ½” X 30” long (44 X 38 X 762mm respectively) with only two ¼” NPT compressed air lines feeding it.  The force measurement is the same from 3” (76mm) to 12” (305mm) away from the surface; giving flexibility in placement.

When it comes to using the EXAIR Super Air Knives, it has many benefits over the blower-type air knives.  We can even include the initial purchase price in which the Super Air Knife would be about 1/10 the cost, and the company was able to increase production with a cooler blowing device.  They were delighted to remove the large blower-type system and replace it with a simple Super Air Knife.  If you would like to discuss the advantages of the Super Air Knife against a blower system, an EXAIR Application Engineer will be happy to assist.

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

Video Blog: Selecting the Right Air Knife

The following short video explains the differences between the three styles of Air Knives offered by EXAIR – The SuperStandard and Full-Flow

Please reach out to myself or one of our application engineers if you need help figuring which Air knife suits your application best!

Jordan Shouse
Application Engineer

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Compressed Air in Farming and Agriculture

I used to help my father-in-law around his farm and this city boy had his eyes opened when he realized it was more than shovels, tractors and livestock. Agriculture is vital for human existence and has become far more advanced over the centuries with a continual thirst for efficiency and technology. Agriculture is just like many other industries looking for continued ways to increase yield, improve quality, maximize labor and improve technology.

EXAIR has many products used in the agriculture and food processing industries. The following details a few example by product line how we can influence efficiencies and quality of products:

Super Air Knife drying fruits and vegetables

Super Air Knives:

EXAIRs Super Air Knives are have ben used to help harvest apples and peaches. In this case they use our Super Air Knives to dry and blow off the fruit after the rinsing process just before the waxing process then again after waxing to blow off any remaining debris or moisture from the fruit before being packed.

A processing company using the Super Air Knife to clean a conveying belt equipped with a weighing system. Before the installation of the the Super Air Knife some of the cut vegetables being weighed would stick to the belt. Their solution was to clean the conveyor belt with EXAIR’s Super Air Knife to ensure continuous operation of the weighing and packaging systems.

Super Air Nozzles:

An onion farmer used EXAIR’s Model 1100 Super Air Nozzle to blow loose onion skins from the onions before packaging to improve the aesthetics to the customers.

Line Vacs:

A food packaging company repackages banana peppers from 55 gallon drums to 1 and 5 gallon containers using our Model 6066 3″ Stainless Steel Line Vac.

Using EXAIRs Model 150200 2″ Heavy Duty Line Vacs a feed stock manufacturer conveys various grains and feed stock simultaneously to a mixer which blends the ingredients. This reduced their blend time by 50%.

A grain processor used Model 142200 aluminum threaded Line Vac to convey small amounts of corn meal into a hopper which feeds into their inspection process.

A company producing worm eggs encapsulated in water soluble wax sold to farmers to enhance soil conditions. They eliminated a hand operation using Model 6081 1″ Aluminum Line Vac  to convey the worm eggs from one classifier to another.

EXAIR has several applications using Atomizing Spray nozzles to add moisture in growing environments . Greenhouses use our Atomizing spray nozzles to control humidity in the air and keep their soils moist to maintain optimal growing environments.

There are many other applications using compressed AIR on farms such as filling tires, cleaning equipment, blowing out water lines and more. Technology drives labor savings and improved quality prototypes are being designed and tested to use compressed air using drones to shoot pods filled with seeds, fertilizer and other nutrients into the soil. EXAIR will remain a strong influence in the growth of compressed air products helping to reduce the carbon footprint, enhance efficiencies and improve cost and quality within the agriculture and food processing industries.

If you have an application and you would like to talk please contact me or any of our qualified Application Engineers at 800.903.9247 and we will gladly help with our best recommendations.

Eric Kuhnash
Application Engineer
E-mail: EricKuhnash@exair.com
Twitter: Twitter: @EXAIR_EK

What Makes EXAIR’s Super Air Knife so Efficient

EXAIR Super Air Knives have been designed to improve upon performance characteristics of our original Standard Air Knife design, which was already a very good performer itself. The Super Air Knife design improves air consumption and noise exposure levels. Since they use less air, they cost less to operate. Because they operate quieter, they can contribute to a quieter environment and increase safety for your personnel. 

Compressed air is such a common utility in manufacturing environments (and more) that many of us take it for granted and may not be the best stewards of its use.  EXAIR Super Air Knives are the most efficient compressed air knife on the market today and help us all to use our compressed air more wisely.

If you have homemade air knives, pipe with drilled holes or manifolds with multiple nozzles, you are in a position to play the hero and save your company compressed air and money. 

Implementing a design which uses the free air surrounding us all, is a significant feature making the Super Air Knife efficient. This is done by utilizing entrainment to move the surrounding ambient air and amplify the blast of compressed air.

Diagram showing how the Super Air Knife works

Air Entrainment is the phenomenon that occurs when air/gas under pressure is released from a device in such a way that a low pressure is generated in the immediate area of the gas discharge.  Gas from the surrounding environment is then pulled into the discharged air stream, increasing its volumetric flow rate. Using this principle, a Super Air Knife increases the air flow without increasing the amount of compressed air used.

This phenomenon is prevalent in many of EXAIR’s products but shines the brightest with EXAIR’s Super Air Knife. The Super Air Knife Sports the highest entrainment ratio out of all of the products with a whopping 40:1 ratio, this makes for a very efficient use of compressed air. With an air consumption of only 2.9 SCFM per inch of air curtain at 80 psig then the air knife would be moving 116 SCFM per inch of air curtain. That’s a lot of air!

Also the fact that entraining ambient air is just moving the ambient air with the energy within compressed air makes process is extremely quiet. This is because the outer layers of the total developed flow are lower in velocity, and serve as a sound-attenuating boundary layer.  The sound level of a Super Air Knife at any length is only 69dBA.  That’s about as loud as someone talking at normal speech 3’ away from you.

Entrainment demonstration using a Super Air Knife

If you have any questions about compressed air systems or want more information on any of EXAIR’s products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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