Simple Solutions That Work! Issue 11

In general, there are two types of sand heaters used to prepare chemically bonded sand for molding and coremaking, and both are designed as fluid bed processes — meaning the sand is moved around the heating/cooling elements with compressed air or blower air. The more popular style is the electric-resistance fluid bed with compressed air fluidization, followed by water-pipe units in which hot or cold water is passed through piping, with fluidized sand moving around them with blower air. The popularity of the electric- resistance type heater is due primarily to cost (compared with water-pipe designs) and size. The heater and cooled with simple cooling tower water. Higher-kilowatt (150-500 kW) electric-resistance heaters can have a significant effect on demand charges; they obviously use a high volume of energy. Over time, these demand charges would make the water-pipe design the better choice. Electric-resistance type units are used in many industries for a variety of purposes, and commonly referred to as process heaters. They are used to heat granular materials with fluidization as well as liquids that are pumped through the unit. With normal maintenance and care, the electric-resistance style heater can be a very dependable and consistent piece of the no-bake molding process. DESIGN DETAILS These are a few of the critical fluidized-bed process components that need the operators’ attention: 1.Fluidizing membrane. Depending upon the sand grain size and temperature range, this membrane may be wire cloth or a simple canvas sandwiched between two support members. Both work equally well as long as they are specified for the purpose intended. It is important to keep the membrane in good condition. The most common problem for JACK PALMER President PALMER MANUFACTURING & SUPPLY, INC. ARTICLE TAKEAWAYS: • Understanding the Fluid Bed Processes & Components • Electric-Resistance Type Heaters vs Water-Pipe Based Heaters SELECTING & INSTALLING THE RIGHT SAND HEATER 57 electric-resistance units are much smaller that the water pipe- based designs, though both offer advantages. The electric-resistance heaters are less expensive and smaller but are not as accurate as the water-pipe units, due to the relative retention time in each. The electric- resistance heater can heat only; it cannot heat and cool like the water-pipe units. In higher- kilowatt sizes, the water-pipe units might be a better long-term choice because the initial capital costs are comparatively higher than the electric-resistance type. Operating costs also are much lower, as the water is normally heated with a natural gas-fired F or foundries that prepare chemically bonded sand for molds and cores, optimizing the process means understanding and evaluating the primary features and options for water-based and electric-resistance systems. Continued on next page MAKING YOUR INSTALLATION ASUCCESS