In one of our open circuit cement mill (Rated capacity 100 tph) section we have installed a pregrinder (Vertical Roller Pre-grinding mill ) and a Sepax air separator.The pre-grinder 3mm passing product , which is fed in cement ball mill.The typical granulometry of pre-grinder 3mm passing product is as given under: +3mm=6.90%,+1mm=6.91%,+0.6mm=12.23%,+0.212mm=37.57%,+0.09mm=51.24%, +0.045mm=64.78% We are facing problem of material spillage from mill feed clinker weigh feeder while feeding the above said size distribution pregrinder product to cement ball mill.Feed hopper is concrete hopper having capacity of 600 MT and clinker weigh feeder is 200tph capacity.Please give your valuable suggestions to stop the material spillage from the said mill clinker weigh feeder.