Simple Solutions That Work! Issue 5

If you need to clean up your casting operation and increase your profit margin at the same time, start at the areas that gen- erate the most airborne silica dust. The primary source of dust is the vibrating shakeout and sand car- ryover, coupled with the amount of sand still attached to the cast- ings after shakeout. When a green-sand mold is dumped onto a conventional vibrating shakeout, a large amount of fine silica dust is released into the workplace. It is difficult to capture all the steam laden with silica dust due to the amount of open area, so the foundry envi- ronment becomes dirty. The amount that is released is directly related to the sand tem- perature at shakeout. When the average sand temperature exceeds 100°C, the convection currents carry silica dust into the foundry atmosphere. The higher the sand temperature at shakeout, the greater will be the convection current velocity and amount of steam and dust to be captured. With a sand-to-metal ratio lower than 6.9:1, the average sand temperature will exceed 100°C. The convection current velocity increases significantly from 100°to 200°C (see chart). Theheat-affectedzoneof themold is the area where the moltenmetal comes into direct contact with the sand grains (mold face). As the sand expands in this zone, inter- nal stresses cause weak grains to fracture. Since sand quality varies around the world, the source of supply will directly impact the volume of fines generated from both mechanical and thermal aspects. Another important calculation tells us that for every kilo of metal poured into the mold, 15% by weight of new sand should be added to replenish the losses and keep the sand system in balance. Since the amount of cores may vary from job to job, using core sand as new sand additions can be a hit-or-miss method unless it is separated from the green sand and then metered back in at a given rate. REDUCE AIRBORNE SILICA & IMPROVE CASTING CLEANING FOR A SAFER ENVIRONMENT Mark Didion Product Manager DIDION International www.didion.com Article Takeaways: 1. Reduce airborne silica for a cleaner workplace 2. Improve casting cleaning and reduce disposal costs 4 SIMPLE SOLUTIONS THAT WORK! CONVENTION VELOCITY 200° C 100° C 25° C 5 & . 1 & 3 " 5 6 3 & CHART 1.1. As the sand temperature rises, so does the convection current velocity which affects the amount of effluent released into the foundry atmosphere.