Issue link: https://www.e-digitaleditions.com/i/954267
24 POWDER COATING, March 2018 A dding infrared (IR) to a powder coating system can provide many benefits, but there are several things that must be taken into consider- ation before you take that step. Most importantly, there needs to be an un- derstanding of what IR is, how it differs from convection, and how it can help your process. While IR isn't the answer for every pro- ject, it is often the best choice for curing products consistently and efficiently. Using IR can lead to line speed increases, curing time decreases, energy conserva- tion, and other cost savings. This article will define terms, dispel misconceptions, and discuss costs to help you choose the right oven for your application. Explaining some terms There is a lot of misinformation on I R ' s c a p a b i l i t i e s . S o m e o f t h e s e misconceptions include: • IR only heats what it sees in its direct line of sight. • IR only works on flat surfaces. • IR ovens are more costly to operate than convection ovens. • IR ovens require more maintenance than convection ovens. • IR is harmful to the oven operator. These mistruths can be dispelled simply by learning what IR is and how it works within a powder coating system. Let's start by taking a closer look at the several different types of IR emitters. An emitter gives off different wavelengths that equals the intensity of the energy or heat. This is directly related to a coating's emissivity, which is the amount of heat wavelength given off from an IR emitter source and how much of the energy is absorbed. Emissivity is a ratio of energy radiated from a material's surface to that radiated from a black body (a perfect emitter) at the same temperature and wavelength under the same area and viewing condi- tions. A perfect emitter value is 1; a per- fect reflector is 0. Most coatings and materials fall in between 0 and 1. For example, most organic paints and coat- ings have an emitter value between 0.92 and 0.95. The closer to the perfect emit- ter value of 1, the better the absorption of radiated energy because emissivity is equal to the absorptivity in a thermal dynamic equilibrium. Put simply, the better the coating absorbs, the quicker it gets hot. The key is matching the right IR for the coating and process. There are a few types of IR, including gas fired; gas catalytic (medium to long wavelength); gas radiant (medium wavelength), which is gas fired over a ce- ramic mold; and electric. Electric can emit short, medium, and long wave- lengths depending on the type of emit- ter used. For example: • Short wavelength with a T3 emitter — used for pinpoint accuracy, rapid heat-up, and instantaneous cool down. It offers infinitely adjustable power and a long life of over 5,000 hours for the tube. • Medium wavelength with a tubular el- ement emitter — a reliable nickel chromium resistance coil is housed in a quartz tube, providing a nonvertical burn design. This is most effective in applications requiring surface temper- atures in the 120°F to 325°F (49°C to 163°C) range. • Medium wavelength with a coil emit- ter — a sheathed tubular element with nickel chromium resistance coil packed in magnesium oxide. This is ideal for applications with complex geometric part profiles and tempera- ture requirements of 250°F to 450°F (121°C to 232°C). • Long wavelength with a cone emitter — utilizes a high-grade chromium wire that is helically wrapped around a ceramic cone-shaped core. This is pop- ular for heat-sensitive substrates such as wood and plastic. It is an excellent choice for applications requiring tem- peratures of 300°F (149°C) and below. Infrared Equipment Division of IHEA This column is provided to you by members of the Infrared Equipment Division (IRED) of the Industrial Heating Equipment Association (IHEA). The group includes infrared (IR) curing equipment suppliers from throughout North America. We publish the column three times a year to give you the latest information about IR curing techniques and equipment. Contact information is at the end of the column. Most IR manufacturers offer testing for free or for a fee. Any IRED member can assist you in finding solutions to curing problems and best practices for finishing of coatings. This issue's column was submitted by IRED member Marty Powell, Carlisle Fluid Technologies, Scottsdale, Ariz. How IR can improve productivity in your plant IR Curing ShopTalk