A company had a process where they galvanized metal sheets to protect them from corrosion. The system consisted of six baths to properly coat the metal. In order, it was a caustic wash, water rinse, pickling, water rinse, flux solution, and then zinc galvanizing. The sheets were 126” (3.2 meters) wide, and the sequence consisted of the parts being dipped into each bath for a certain length of time. The parts would then be raised above the solution to drip prior to moving to the next bath. This customer was looking for a better way to improve the process as well as to help reduce the drips and runs from the hot galvanizing, which were manually “rubbed” out before hardening. They contacted EXAIR to find a solution.
With similar applications, EXAIR has a great product for non-contact wiping flat surfaces. We call them Super Air Knives. I wrote a blog similar to this on a much smaller scale; “How a Super Air Knife Helps with Metal Etching“. The Super Air Knives 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, the Super Air Knives can entrain 40 parts of ambient air. With the Super Air Knives, we can generate a laminar flow to give an even force across the entire length. So, it is easy to set the correct force for different types of liquids and viscosities.
With the caustic solution and corrosive environment, I recommended our Super Air Knife in 316 Stainless Steel material for superior anti-corrosion qualities. EXAIR stocks 316 stainless steel Super Air Knives in many lengths. For this application, the width to cover this metal sheet was a bit outside our longest single air knife, which is 108” (2.7 meters). But, EXAIR does offer a Coupling Kit as a way of making our Super Air Knives even longer as multi-unit assemblies. We can couple the Super Air Knives together to reach across, and still keep the flow even. For this application, I recommended model 110054SS-316, 54” (1,372 mm) and model 110072SS-316 (1,829 mm) to be joined together with our coupling kit, model 10900SS-316, to accommodate the 126” (3.2 meters) width required for the application.
The customer decided to place one set of coupled Super Air Knives on each side of the material for the caustic bath, pickling bath, flux bath, and hot dip galvanizing bath. They mounted them above each tank, blowing at a compound angle, in and down toward the dip tank. The Super Air Knives would be turned on automatically only when the metal sheet was being removed from the solution. The excess liquid is forced back into the same dipping tank the material is drawn from. With a regulator, our customer is able to control the amount of force to get the best results without overusing the compressed air. Another benefit they enjoyed was that as more solution is removed from the material between each bath, the less liquid that is transferred from one solution bath to the next; thus, reducing cross-contamination dramatically.
After installing Super Air Knives in their system, they started to see a vast improvement in their process. The excess drips were removed without surface issues, and they were able to extend the life of their rinse tanks by 40%. As an added bonus, the Super Air Knives decreased the time at each bath, improving productivity without the additional labor cost. Less waste and faster production times are the solutions that the EXAIR Super Air Knives provide the customer. If you have a similar application and want to discuss how we can improve your dipping process, please speak to our Application Engineers. We’d be happy to help.
John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb
Photo: textured galvanized iron by makamuki0. Pixabay Content License
