Simple Solutions That Work! Issue 9

BACK-2-BASICS 17 LATEST RESIN COATED SAND TECHNOLOGY Large strides have been made in emissions reduction of Shell Sand. However, low emission grades have brought challenges to those using the technology in hot and humid conditions. The first generation of low emission sands are susceptible to sand lumping or clumping in these extreme conditions. Properties are maintained once lumps are broken back into free flowing sand, but these lumps have the potential to clog sand transport systems and create down time. Issues such as these called for a more robust, second generation of low emission shell sand, now branded as EcoFlo. The second generation utilizes hexa lowering technology along with other additives to improve flowability under hot and humid conditions. PERFORMANCE COMPARISON Conventional, first generation low emission, and second generation low emission sand grades were compared using identical sand, resin type, and resin content. Melt Point and Hot Tensile Strength properties were compiled to compare core making properties, Table 1. Melt Point is a gauge of reactivity and how quickly the resin coated sand mix will cure. Custom Coat and E-Series grades are very similar while EcoFlo grades exhibit a higher Melt Point. Foundry tests have shown that cure speeds can be maintained with a simple resin modification in the EcoFlo mix. Hot Tensile Strength is a measures of handling strength. A reduction in strength is noted with the low emission grades. In practice, a slight resin addition is applied to maintain the handling strengths. The emission reduction is significant enough that Table 1. Modifications of Custom Coat 80-3.25 NAME CUSTOM COAT E-SERIES ECOFLO Melt Point, °F 227 230 238 Hot Tensile Strength, psi 299 223 250 a lower core making emission profile is still maintained despite increases in resin level. Note EcoFlo exhibits strengths higher than E-Series, yet still a reduction in strength vs Custom Coat grades. In a production environment, similar productivity levels can be achieved with each of these resin coated sand technologies. EMISSIONS The core making emissions were compared for the three different technologies. In the testing, air samples were taken from directly from above a core box during a standardized core making cycle. Figures 1 and 2 display the results for ammonia and formaldehyde emissions, respectively. Note the concentrations are dependent on the air movement, exhaust conditions, and core making cycles. Concentrations will differ from each operation; the numbers should be taken as comparative only. As expected, the E-Series sand grade showed drastic reduction in core making emissions, over 70% in ammonia and over 90% reduction in formaldehyde. The EcoFlo sand grade mimicked the ammonia emissions with over 70% reduction. Formaldehyde emission reduction was not as significant as E-Series but still resulted in around a 70% reduction vs Custom Coat grades. Continued on page 16 Figure 1. Ammonia emission comparison of conventional, E-Series and EcoFlo RCS technologies.