Tag: steel sheet blowoff

Removing Coolant From Cold Rolling Operations

Published on by John BallLeave a comment

An overseas company had a cold rolling process where they would make metal sheets of different thicknesses and widths.  They were having issues with their machine removing the excess coolant from the surface that was used in the process.  Like with too many applications, they made their own home-made air knives.  They found that they had reduced production rates, increased quality failures, and amplified noise levels.  They contacted EXAIR to help resolve these issues.    

To go into the details of the application, the cold rolling process uses work rolls to “squeeze” the metal to a thinner gauge.  This squeezing creates heat up to 350oF (177oC).  So, before each work roll, they would spray a coolant to help remove the heat.  The amount of coolant is very important to get the proper cooling and metal gauge.  After the work rolls, the coolant has to be removed before the next work roll operation.  Their system was designed for 3,300 ft/min (1000 m/min), but they could only run it at half the speed as they could not remove enough coolant from the surface.  For each work roll, they used three homemade compressed air knives that were made from 54” (1372mm) pipes with drilled holes.  They laid one on top and one on bottom just after the work rolls.  After the trial, they had to add another one on top to try and remove the remaining coolant that was missed by the first one.  Each home-made knife used 440 SCFM (744 M3/hr) of compressed air at 100 PSIG (6.9 bar) during the cold rolling operation.

Super Air Knife

With similar solutions, EXAIR has a great product for non-contact wiping for flat surfaces, the Super Air Knives.  They use compressed air to generate a force at varying degrees.  With the engineered design, we are able to add free ambient air at a rate of 40:1.  For every one part of compressed air, we can entrain 40 parts of ambient air.  By adding this mass to the airstream, we can generate a hard-hitting force.  Generally, with a drilled pipe, they have an entrainment near 4 to 5:1 which requires more compressed air to get that same force.  Also, with the Super Air Knives, we can generate a laminar flow to give an even force across the entire length. 

For this application, I was worried about the setup of their home-made air knives.  With the position of being straight across, the coolant liquid could build up to a heavier amount in front of the knives, which could allow for some of the coolant to bypass.  This would be the reason for the second drilled pipe on top.  The bottom unit worked fine as gravity was helping to remove the coolant from the surface.  But they were using a lot of compressed air with high noise levels.  I was able to help them to create a more effective blow-off design and to save a lot of compressed air. 

Chevron Style

In my discussion, I mentioned that with high-speed operations, the setup is important for great non-contact wiping.  For this customer, I recommend the Chevron style which mounts two Super Air Knives as an inverted “V”.  Now we can cut the amount of coolant in half.  Half of the sheet means half of the weight of coolant.  For the top, I recommend two pieces, model 110036 36” (914mm) Aluminum Super Air Knife, and a single piece, model 110054 54” (1,372mm) Aluminum Super Air Knife, for the bottom.  We were able to solve their issues with their cold rolling process. 

As they started their operation, they were able to increase the production rates, and removed the need for the extra air knife.  With the Super Air Knives, we were able to save them 877 SCFM (1,490 M3/hr) of compressed air at 100 PSIG (6.9 bar), as compared to the total amount of 1,320 SCFM (2,232 M3/hr) for the three home-made air knives.  With a 24-hour operation, the Super Air Knives saved them a lot of money.  The Return on Investment, ROI, was less than 30 days.  As a note, the Super Air Knife only has a noise level of 72 dBA at 100 PSIG. 

If you are looking to improve your blow-off application to increase production rates, reduce waste and improve safety, the EXAIR Super Air Knives can provide that solution.  With the customer above, the development happened immediately with a short ROI.  If you have a similar application and want to discuss it with an Application Engineer at EXAIR, you can contact us directly.  We’d be happy to help you.

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

Photo: Steel Roll Alignment by Jean-Etienne Minh-Duy Poirrier.  Creative Commons 2.0

2″ Flat Super Air Nozzle Produces High Force to Clean Steel Sheet

Published on by Tyler DanielLeave a comment

I recently worked with a customer at a company that manufactures steel sheets. They grind, polish, and then shot blast the steel sheets. As the material exits the shot blasting chamber, some of the media still sticks to the steel and is carrying over into additional processes. To mitigate this, they installed a 1” pipe with drilled holes at the exit of the conveyor to remove the excess media and keep it contained inside of the machine. While this worked, it was using a substantial amount of compressed air which was resulting in a pressure drop across the rest of the facility when this machine was in operation.

Although their current method was doing the job for them, they couldn’t live with the increased compressed air consumption. After searching the internet, they came across the EXAIR website and were interested in learning about other blowoff methods. Typically for an application involving a wide sheet of moving material we’d look towards one of our Super Air Knives, available from stock in lengths from 3”-108”. But, in this case there was some friction between the shot blasting media and the stainless steel sheet that required brute force. They needed something that was going to give them an increased amount of force, but still reduce their overall consumption.

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(10) HP1125 2″ High Power Flat Nozzles installed on 1″ pipe manifold

I recommended our HP1125 High Power 2” Flat Nozzle. With a .025” thick shim installed, the HP1125 nozzle will produce 2.2 lbs of force when operated at 80 psig. This was more than enough to remove the shot blasting media. They’re also much quieter than an open blowoff, producing a sound level of just 83 dBA. While this wasn’t a motivating factor for them, the reduction in noise was definitely welcomed. They placed some on order and replaced the 1/4″ open holes with (10) Model HP1125 2” Flat Super Air Nozzles.

For comparison, (10) 1/4″ holes will consume 690 SCFM at 80 PSIG while (10) of the HP1125 comes in at just 370 SCFM. By simply installing the HP1125 (which conveniently also has a 1/4 NPT air inlet), they reduced their compressed air consumption by a whopping 46%!! By reducing air consumption they eliminated the system pressure drop, they were also able to increase the force as the compressor was able to maintain the 80 PSIG pressure at the header pipe. This also alleviated the pressure drops experienced elsewhere in the plant.

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HP1125 2″ High Power Flat Super Air Nozzle

At EXAIR we have a wide-range of different products suited to a number of different blowoff  applications. From 4mm nozzles producing just 2 ozs of force, all the way up to our largest nozzle capable of delivering 23 lbs of force and everything in between. No matter the application, EXAIR has something capable of taking care of the job. Odds are it’ll be safer, quieter, and more efficient!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD