More Force is not Always Better for Cleaning Glass

Glass Annealing Machine with model 110230

A float glass company purchased an EXAIR model 110230 Super Air Knife kit to clean the surface of glass sheets.  The production manager watched the video of the performance of the Super Air Knife, and he was amazed at the efficiency, effectiveness, and safety that they could provide.  (We have many EXAIR Product videos here).  After they received the Super Air Knife, they mounted it after the annealing process to remove any specks of dirt and debris prior to the final visual inspection.  They were getting some false rejections from contamination that remained on the sheets, and they believed that they needed more force to better clean the surface of the glass.

The blowing system was operating at 73 PSIG (5 bar) air pressure, the maximum amount that could be supplied at the machine.  With the dynamics of the Super Air Knife, the blowing force could be increased by changing the shim thickness.  The plant manager contacted me about the characteristics in force and flow by changing from the standard 0.002” (0.05mm) thick shim to the 0.003” (0.08mm) or 0.004” (0.1mm) thick shim.  (These shims are Included in the shim set for aluminum Super Air Knife kits along with a 0.001” (0.025mm) thick shim).  As an Application Engineer at EXAIR, I was inquisitive about the application and wanted to do a “forensic” analysis of the system to generate the best suggestion.  So, I had him send me pictures of their setup.

With non-conductive materials like glass and plastic, static can be a huge issue.  Static forces can easily be generated and will cause dirt and debris to “stick” to a surface.  This attraction is very strong and will make it very difficult to remove.  If the static force can be neutralized, then the contamination can easily be removed from a non-conductive surface.

With this understanding, my initial suggestion for the company above was to remove the static charges from the surface of the glass with an EXAIR Static Eliminator.  With the complimentary design of the Super Air Knife, it is simple to mount an Ionizing Bar directly to the Super Air Knife that they currently installed.  I recommended a model 8030, 30” (762mm) long Gen4 Ionizing Bar, and a model 7960 Power Supply to transform the Super Air Knife into a Gen4 Super Ion Air Knife.  The positive and negative ions that are generated by the Gen4 Ionizing Bar can be carried by the laminar air flow of the Super Air Knife to treat the surface.  This combination can work well to remove static charges up to 20 feet (6m) away.  Once the static is removed, the force of the air stream would easily remove any dust or debris from the glass surface.

Gen4 Super Ion Air Knife

As an added note from the picture above, I recommended a different position for the Super Air Knife, or soon to be Gen4 Super Ion Air Knife to optimize the blowing area.  The glass company had the air knife positioned to blow straight across the surface of the glass.  For proper cleaning and better contact time, I suggested to mount the Super Air Knife with the Ionizing Bar about 6” (152mm) above the surface of the glass and angle it to about 45 degrees.  This would increase the contact angle and allow for a better blowing force to remove all the debris.  By adding the Gen4 Ionizing Bar and adjusting the blowing angle, they were able to reduce the air pressure from 73 PISG (5 bar) to 30 PSIG (2 bar); saving compressed air and reducing false rejections.

Pictures are always helpful in analyzing an application.  With the company above, we were able to optimize their cleaning process and reduce the total amount of compressed air required.  If you find that you need more force to clean a non-conductive surface, EXAIR Static Eliminators will resolve these static problems.  If you would like to discuss your application with an Application Engineer at EXAIR, we can go through the “forensics” analysis for optimization.

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

A Glass Company Needed a Vortex Tube to Keep Their Pyrometer Reading Accurately

Cooling with the Vortex Tube
Cooling with the Vortex Tube

A glass company was using a pyrometer to measure the temperature of the glass. As with many instruments, it is important to keep the electronics cool for proper operations.  In this case, they were having issues with the accuracy of the measurement.  They contacted EXAIR for a solution.

With their pyrometer, it was designed with a “cooling” device already. This was basically compressed air that would blow around the instrument.  Because of the surrounding area, the compressed air was heating up to 50 deg. C.  This additional heat would not cool the pyrometer properly, and it was causing unreliable readings.  He gave me the design specifications for cooling, and it was 40 liters per minute of compressed air at a maximum of 25 deg. C.  I told him that we had the perfect solution to keep his instrument cool, and it is the EXAIR Vortex Tube. Vortex Tubes are a low cost, reliable, maintenance-free solution that uses compressed air to power the Vortex Tube to produce cold air as low as -46 deg. C. They thrive in remote locations, high temperature environments, and harsh conditions with little to no worry about maintenance (other than providing a source of clean air). With a range of cooling capacities from 135 BTU/hr to 10,200 BTU/hr, I was sure that we could meet the requirements for proper cooling.

To determine the correct size, I had to look at the temperature drop and the flow requirement. The Vortex Tube would have to decrease the incoming temperature from 50 deg. C to at least 25 deg. C.  This would equate to a minimum temperature drop of 25 deg. C.  With the chart below, I see that we are able to get a 29.7 deg. C temperature drop at a 70% Cold Fraction and 3 bar inlet pressure.  EXAIR Vortex Tubes are very adjustable to get different outlet temperatures by adjusting the inlet pressure and the Cold Fraction.  The Cold Fraction (CF) is the volume of cold air flow that will be coming out the cold end.  By adjusting a screw on the hot end of the Vortex Tube, the cold flow can be change to the desired CF.

Vortex Performance Chart
Vortex Performance Chart

The other requirement was the amount of air flow, 40 SLPM (Standard Liters per Minute).  In comparing the above information to the catalog data at 6.9 bar, we have to consider the difference in absolute pressures. With an atmospheric pressure of 1 bar, the equation looks like this:

VTflow = CAF/CF * (Catalog Pressure + 1 bar)/(Supply Pressure + 1 bar)

VTflow – Catalog Vortex Tube flow

CAF – Cold Air Flow

CF – Cold Fraction

Catalog Pressure – 6.9 bar

Supply Pressure – Chart above

From this equation, we can solve for the required Vortex Tube:

VTflow = 40 SLPM/0.7 * (6.9 bar + 1 bar) / (3 bar + 1 bar) = 112.9 SLPM.

In looking at the catalog information, this would equate to our model 3204 Vortex Tube which uses 113 SLPM of compressed air at 6.9 bar. So, after installing, the Vortex Tube was able to supply 20.3 deg. C air at a flow of 40 SLPM; keeping the pyrometer reading correctly and accurately.

Sometimes compressed air by itself is not enough to “cool” your instruments. The EXAIR Vortex Tubes can reduce the temperature of your compressed air to the desired requirement.  If you believe that your measuring equipment is being affected by temperature, please contact an Application Engineer at EXAIR to find the correct product for you.

 

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

High Temperature Air Amplifier Cools High Tech Mirror Glass

We recently worked with a customer that manufactures mirrors for the automotive industry.  Today’s mirrors are evolving and becoming more and more complex, including functions such as auto-dimming, and navigation and backup camera display.

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Mirror manufacturing involves many steps, one step is the application of the reflective material.  Silver can be deposited chemically, but other materials such as aluminum and gold, and for scientific grade mirrors, silicon oxides and silicon nitrides are applied via an evaporative process within a vacuum chamber.  The metal is heated under the condition of vacuum until it vaporizes and is then deposited on the glass.  Many layers may be deposited depending on the mirror type and reflective properties desired.

Our customer came to us and said they were interested in utilizing the Super Air Amplifier technology in the glass cooling process. After reviewing all of the details of the application, including the ambient temperature conditions, we recommended the EXAIR High Temperature Air Amplifier, model 121021, as the right choice for the cooling application.

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Model 121021, High Temperature Air Amplifier

The  model 121021 High Temperature Air Amplifier was developed for moving hot air and to be able withstand high temperature ambient conditions. This special design is rated for environments up to 700°F and its surface is protected from heat stress by a mil-spec coating process developed for the aircraft industry. It uses just 8.1 SCFM of 80 PSIG compressed air, has an amplification ration of 18:1, and a sound level of only 72 dBA. This highly efficient and quiet air amplifier was the right choice, and the customer has reported back that they ‘have been working good’ in the application. They are also used to circulate hot air in ovens or keep even temperatures on large rotational molds. They also solve heat/cooling problems in glass manufacturing, primary metals, heat treating and power generation. They are the right choice for rugged, high temperature processes.

EXAIR makes other specialty Air Amplifiers, including models made for specific customer applications.  These include designs with flange mounting for exhausting flue gases from a  furnace and a design with a PTFE plug to help pull sticky material through a process while preventing the material from depositing on the Air Amplifier.

To discuss your application and how an Air Amplifier would help out, feel free to contact EXAIR and one our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Mirror Photo Credit – Steve Damron – via Creative Commons Licensei