Management at Elgen Manufacturing Co. Inc., an HVAC and sheet metal manufacturer, serving HVAC contractors, fabricators and resellers, saw a need to improve the company’s process. Ductwork and assemblies are typically transported on open-air flatbeds, allowing debris and contamination to enter into the open ends of the ductwork. To protect from contamination, duct manufacturers often block the open ends with a stretch film and then seal it with tape. This approach is labor intensive, leaves a residue and adds expense.
Matthew Alberti, managing director of Elgen, knew there had to be a better solution. He envisioned using a polyethylene (PE) film with a pressure-sensitive adhesive (PSA) to make covering the ducts faster and easier. Alberti also knew that if Elgen could do this for their own products, then the company could likely manufacture a shrink wrap with PSA for use by other duct manufacturers as well. Elgen would be able to supply it to the industry through their distribution division, Capital Hardware Supply.
The biggest hurdle was finding a company who would work with Elgen to develop this drying solution. Upon meeting with Radiant Energy Systems, Alberti was told that the current drying technology used for making this product is a long convection dryer. Occasionally, infrared is used as a predryer. However, after working on the problem, studying the unique challenges the application presented and spending a few days testing various designs, Elgen and Radiant came up with a solution that would work not only in the lab setting but also on a production line.
The most commonly used technologies in the converting industry for drying water- or solvent-based coatings on different webs are hot air dryers (whether impingement or flotation) and infrared. Although hot air dryers are gentler, generally they are much longer in length because the drying rates are slower.
Infrared can deliver a lot more energy in a shorter space for the right process. Experience has shown that if infrared energy is too intense, it causes skinning of the coating (drying on top while it is still wet underneath), making the product unfit for sale. The combined technology of adding air to the process simultaneously with infrared is another possibility when the process has overlapping needs. Infrared provides the thermal energy to heat the water in the coating. Air provides the scrubbing action to break the boundary layer, helping in the drying process, and prevents skinning. The air also makes the process gentler, which is important while handling a temperature-sensitive substrate such as LDPE. Further, the drying system is designed so that when the line is operating, the air volume is optimized for the process. But when the line stops, the heaters turn off and the air automatically switches to a higher cooling volume to prevent overheating of the film.
Combination Heating Solution
After trials and testing to prove the theory, the solution was an infrared heater combined with an air-drying system. Designed, developed and manufactured by Radiant Energy Systems, this drying system uses the SFA heater, which is a stamped foil heater in combination with forced air. The drying system requires less space, produces a higher output and is available at a lower capital investment than a hot air dryer.
For Elgen, the SFA heater system was designed to run at 600 ft/min with a length of 25’ and a width of 72”, to be capable of handling various widths up to 60”. On some of the older lines in operation for making the same product, the hot air dryer would be about 120’ long.
The finished product requires different thicknesses of film to meet customer requirements. The film thickness ranges from 2 to 4.5 mils. The water-based adhesive is applied at a rate of 8 lbs/ream and is about 40 percent solids. The challenge was to come up with a compact dryer.
The infrared air dryers based on SFA heaters require precise control when dealing with heat-sensitive films. The multi-zone dryers address that issue. At each step, the web/coating temperature is measured and controlled with non-contact infrared thermometers to ensure that the film does not overheat. Running such a process requires vigilant operators, but the operators running this process line at Elgen are experienced.
Elgen is now producing shrink wrap with PSA and protecting their ductwork and assemblies with ease. End users receive the protected product and are able to easily remove the shrink wrap with PSA. In addition there is no sticky residue is left on the product. Other manufacturers are buying the shrink wrap through Capital Hardware Supply as well.