Hardgrove grindability index (HGI) | PPT SlideShare
8. PROCEDURE TO DETERMINE THE HGI VALUE The experimental procedure for the determination of hard grove grindability index HGI is as follow according to the ASTM standard ; • The 50gm sample of prescribed size 16+30 mesh is taken in the ball mill of HGI machine along with 8 iron balls. • Close the mouth of the ball mill, and set to rotate for exactly 60 revolutions.