Grinding media wear rate calculation in ball mill. kominuter ball-mill. the mill was operated for 694 hr. during which time 4825 lb. 2188 kg. of 5-in. 139.7-mm. balls were added. the original ball load in the mill was 6614 lb. 3000 kg. and the load at the end of the 694 hr. was 6338 lb. 2874.8.