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Metal Casting Technologies : December 2007
METAL Casting Technologies December 2007 53 CONDUCTION LOSSES Conduction loss is often the first thought regarding furnace efficiency. The loss of heat through the insulation of a furnace is apparent from the hot casing, and is ongoing. The solution seems obvious, increase the thermal insulation. The total conduction losses are made up of the sum of losses through the roof, walls, base and doors. Typical conduction losses for our example furnace are shown in Figure 3. In our example furnace, the total conduction loss represents less than 2% of the furnace rating. You will note that the bottom losses are almost equal to the sum of the roof, door and wall losses combined and are clearly disproportionate to the area. That is because the requirements are different. In the bottom area, the main issues are strength of material, wear resistance, and maintaining the freeze plane in the hot face layer. The losses to this area are typically under 1% of the rating and may well be a secondary consideration compared to the fitness for purpose of the refractory materials in this important area. We can apply higher insulating designs in the roof and walls by being smarter rather than just making it thicker. This is evident in the lower losses for those areas in the previous graph (Figure 3). The following pictures (Figures 4 & 5) show a Thermcon design modular roof construction which has a low thermal conductivity compared to older conventional cast designs. This design has the added advantage of pre-casting the roof panels on the floor in advance with good control of the casting process. The modules are fixed into position with minimal disruption during construction of the furnace, without the usual shuttering and delays associated with casting in position. Figure 4. Installation of Low Loss Pre-Cast Roof Panels Figure 5. Roof Completed in a Day Beckwith Macbro Resin Coated Sands All grades of resin coated sand used for shell molding and shell cores for ferrous and non-ferrous applications PRODUCTS ■ Range of resin strengths from 1.0% to 5.0% ■ Silica, Zircon, Chromite coated sands or blended mixes ■ Coated Sands of different AFS typically from 50-90 AFS ■ Thermal Reclaimed Coated Sands SERVICES ■ Full technical and trouble shooting service. ■ On-site shell core and shell molding facility to evaluate the product applications. ■ Laboratory facility to ensure product quality. Contact : Rob Dalla Via (Resin Coated Sand Manager) 30 Devon Road Devon Meadows, Melbourne Telephone : +61 3 5995 4244 Mobile : 0417 332 723 Fax: +61 3 5995 5030 E-mail: email@example.com Website: www.beckwithmacbro.com.au