The use of sand substitution to solve the free silica problem in foundry atmospheres

Field tests were carried out to compare the air quailty in a gray iron foundry before and after changing the molding material from the standard silica based sand to the mineral olivine. Olivine is a magnesium iron silicate (Mg, Fe) SiO4 which occurs in nature and contains little or no free silica. Data were collected using standard OSHA approved methods to determine the total dust and the respirable limit for the alpha-quartz particle loading levels. Additional samples were taken using a cascade impactor and filter tape samplers. The foundry was surveyed once before the substitution of olivine and three times after the changeover. The study demonstrates that the partial substitution of olivine can reduce the concentration of free silica to acceptable health levels. However, contamination from processes using silica sand must be controlled.