Compare These Blowoffs

There are a variety of ways to blow the water from the bottles shown in the photo below, but which method is best? The following comparison of drilled pipe, flat air nozzles, a blower and the Super Air Knife proves that EXAIR has the best choice for your blowoff, cooling or drying application.

Our goal for each of the blowoff choices was to use the least amount of air possible to get the job done (lowest energy and noise level). Compressed air pressure required for each was 60 PSIG (4.1 BAR) which provided adequate velocity to blow the water off. The blower used had a ten horsepower electric motor and was a centrifugal type blower at 18,000 RPM. The table at the bottom of the page summarizes the overall performance. Since your actual part may have an odd configuration, holes or sharp edges, we took sound level measurements in free air (no impinging surface).

Drilled Pipe

This common blowoff is very inexpensive and easy to make. For this test, we used (2) drilled pipes, each with (25) 1/16" (1.6mm) diameter holes on 1/2" (13mm) centers. As shown in the test results below, the drilled pipe performed poorly. The initial cost of the drilled pipe is overshadowed by its high energy use. The holes are easily blocked and the noise level is excessive - both of which violate OSHA requirements. Velocity across the entire length was very inconsistent with spikes of air and numerous dead spots.

Flat Air Nozzles

As shown below, this inexpensive air nozzle was the worst performer. It is available in plastic, aluminum and stainless steel from several manufacturers. The flat air nozzle provides some entrainment, but suffers from many of the same problems as the drilled pipe. Operating cost and noise level are both high. Some manufacturers offer flat air nozzles where the holes can be blocked - an OSHA violation. Velocity was inconsistent with spikes of air.

Blower Air Knife

The blower proved to be an expensive, noisy option. As noted below, the purchase price is high. Operating cost was considerably lower than the drilled pipe and flat air nozzle, but was comparable to the EXAIR Super Air Knife. The large blower with its two 3" (76mm) diameter hoses requires significant mounting space compared to the others. Noise level was high at 90 dBA. There was no option for cycling it on and off to conserve energy like the other blowoffs. Costly bearing and filter maintenance along with downtime were also negative factors.

EXAIR Super Air Knife

The Super Air Knife did an exceptional job of removing the moisture on one pass due to the uniformity of the laminar airflow. The sound level was extremely low at 65 dBA. For this application, energy use was slightly higher than the blower but can be less than the blower if cycling on and off is possible. Safe operation is not an issue since the Super Air Knife cannot be dead-ended. Maintenance costs are low since there are no moving parts to wear out.

OSHA Maximum Allowable Noise Exposure

High noise levels are a common problem for many plants. Compressed air noise often exceeds OSHA (Occupational Safety and Health Administration) noise level exposure requirements, resulting in hearing loss to those working in close proximity. The sound level of the Super Air Knife is quiet at 69 dBA, even at high pressures of 80 PSIG (5.5 BAR). Using the Super Air Knife, it is possible to obtain hard-hitting force without the high noise.

Special Super Air Knives

EXAIR manufactures special Super Air Knives suited to specific application requirements. The shape, dimensions and materials of construction can be modified to fit existing machines and environments.

A special curved stainless steel Super Air Knife holds test tubes in place on a rotating index table.

This curved stainless steel Super Air Knife was manufactured for a laboratory that uses the force of the airflow to hold test tubes in place on a rotating index table. They were able to eliminate the mechanical clips and latches that slowed the test tube removal. This holding method minimized risk of tube breakage and eliminated any chance of puncturing the technician’s rubber gloves.

A PVC Super Air Knife designed to withstand a phosphorus environment.

EXAIR manufactures special Super Air Knives made of plastic. These products are engineered to work under normal operating pressures, providing the same performance as their aluminum and stainless steel counterparts.

This special PVC Super Air Knife was manufactured for a picture tube plant. The softer material was less likely to scratch the picture tube surface and was chemically resistant to the phosphorus which coated the inside.

A flat Super Air Knife, only 11/16" thick, blows plastic fibers from a mold used to make integrated circuit chips.

The flat Super Air Knife is used in a molding machine for integrated circuit chips. Prior to molding the black plastic shells around the silicon wafers, they blow the mold cavity clean of any fine plastic fibers left by the previous cycle. The flat design constructed of corrosion resistant stainless steel was made to fit the tight space of the molding machine.

The double-sided Super Air Knife provides two uniform sheets of laminar airflow.

The double-sided Super Air Knife provides two uniform sheets of air in opposite directions. It is ideal for blowing water from two or more columns of stacked parts (like printed circuit boards) as they are lifted out of a bath or the open halves of a mold. Each side operates independently.

Stainless steel Super Air Knife modified to include extra mounting holes.

As in this example, the Super Air Knife can be modified to include extra mounting holes to suit your application.

Super Air Knife Replaces fan Cooling

The Problem: A manufacturer of automotive electronics had a problem cooling computers as they exited a wave solder machine. In order to be handled and tested, the computers had to first be cooled to 81°F (27°C). Initially, they had tried banks of 6" (152mm) diameter axial fans across the 8' (2.5m) length of the cooling conveyor. It consisted of 16 fans blowing down from the top and 16 fans blowing up from the bottom at 7" (178mm) away from the surface. After traveling the full length of the conveyor with the fans running at full force (a five minute duration), the computers were still 108°F (42°C). Quality control personnel sat with an unacceptable backlog of computers waiting to be tested.

The Solution: The company removed the top and bottom fan banks and replaced them with (3) Model 110012 12" (305mm) Super Air Knives that were evenly spaced across the cooling section. Each Super Air Knife was angled so the computer and heat sink received the constant rush of airflow. With the conveyor at the same speed 1.6 FPM (0.5m/min), and Super Air Knives at only 40 PSIG, the computers were cooled to 81°F (27°C) in 90 seconds!

Comment: The laminar airflow of the Super Air Knives was the key to success in this application. Fan cooling could only provide random spikes of air at moderate velocities. The uniform sheet of air from the Super Air Knife quietly swept the heat away within the first 2' (610mm) of the conveyor. Low air consumption and the compact size of the Super Air Knife were an added bonus.

Air Shielding a Laser lens

The Problem: A dirty lens can affect the quality of cameras, sensors and lasers. Today’s visual inspection systems are highly accurate tools used to monitor dimensions, temperature, finish quality, labeling and much more. These products require clean lenses in order to provide the proper feedback to operators or other machinery within the process. The above laser lens is integral to a laser cleaning operation where a laser is used to clear away debris and provide a fresh surface. The laser cleaning operation in this case was creating debris which flew up and deposited on to the laser lens. Debris on the lens could affect the laser’s cleaning quality or become burned upon the lens and create the need for a replacement lens.

The Solution: A Model 110006 6” (152mm) Super Air Knife was installed just above the laser lens to blow air down and across the lens. The sheet of air created an invisible barrier the contaminants could not penetrate and kept them from depositing on to the lens. The quality of the laser cleaning has been consistently good and the need for replacement lenses due to debris deposition has been eliminated.

Comment: An air barrier is a common application for a Super Air Knife and can create a non-contact wiper with little or no obstruction. They have been used in similar applications to prevent debris from getting to many different sensors or cameras, to retain heat within an oven, or to deflect mist from a machine tool.

Bakery Creates Clean Break in Icing

The Problem: A bakery had a problem applying the icing to their snack cakes. As the baked sponge cakes moved down the conveyor, a continuous ribbon of icing was applied to the individual cakes. Trying to make a clean break in the icing was next to impossible. Mechanical blades required constant cleaning. Compressed air through a series of holes in drilled pipe used too much air, was noisy and didn't make a clean break in the icing.

The Solution: A Model 110018SS 18" (457mm) Stainless Steel Super Air Knife was installed across the conveyor. A photo eye is used to detect the space between the cakes and turn the compressed air on at the precise moment to apply uniform airflow and velocity against the ribbon of icing, creating a nice, clean break.

Comment: The Stainless Steel Super Air Knife was the best choice for this application. Since there was no contact with the icing, no additional cleaning was required. The laminar flow of the Super Air Knife has uniform velocity across the entire length and broke the ribbon of icing evenly. This would never have been possible with the spikes of air from a drilled pipe, nozzles or a blower.

Smoke Containment During Engine Test

The Problem: The last step in an engine assembly process is "burn-in" on a test stand. Each engine is connected to a dynamometer and run for a period of one to five minutes. Residual machining oil on the head produced smoke during the test, and the vent hood at the top of the stand had insufficient capacity to contain it.

The Solution: A Model 110024 24" (610mm) Super Air Knife was mounted on both sides of the test stand. The sheet or "wall" of air produced by the Super Air Knife, captured, contained and diluted the smoke while directing it towards the vent hood. The environmental problem was solved without obstructing the technicians observation of, or access to the stand.

Comment: The use of the Super Air Knife for containment and separation is becoming increasingly common. The advantage, as illustrated here, is the ability of the Super Air Knife to create a screen or barrier with no obstruction. Other typical applications in this mode are:

• Retaining heat in curing and drying ovens
• Protecting workers from coolant splatter
• Isolating industrial camera lenses from airborne contaminants

Drying Crates Following a Washing Operation

The Problem: A bottling plant places their filled bottles into plastic crates as a final step of their process. When the empty plastic crates are returned from the various retail markets, they must first be washed and sanitized prior to using them again. When the bottler put the crates through the washer, they exited the final rinse dripping wet. Bottles placed in the wet crates were eventually covered with water spots and many product labels were ruined.

The Solution: The company installed (3) Model 110018 18" (457mm) Super Air Knives to completely surround and blowoff the crates. Each Super Air Knife was placed on a wiping angle with the sheet of air blowing against the travel of the crates and directing the water downward toward the floor. The crates were dried and the bottles could be loaded immediately.

Comment: Super Air Knives were the best choice for this application. The uniform sheet of laminar airflow provided complete coverage so there were no dead spots when blowing across the inside and outside surfaces of the crate. The mounting used made it easy to rearrange and adjust the Super Air Knife depending on the size of the crate. Other companies have used a similar arrangement of the Super Air Knives to blowoff car batteries, blocks of cheese, milk cartons, buckets, and more.