The SAG grinding ball size is usually about 125mm. But more and more mining company adopt bigger size, like 135~150mm. Adopting the bigger size ball, the energy consumption of SAG mill will be lower, and the capacity will increase.

SAG mill

7.5x3.2m SAG mill inner

View for 7.5×3.2m SAG mill inner

100mm SAG mill grinding balls

                                                              100mm SAG mill grinding balls

some mining company adopt SAG mill grinding copper ore. the feeding size is less than 250mm, the discharged product size is less than 12.5mm.  At first stage, they load diameter 125mm, 100mm and 75mm balls totally 100t, the capacity is only 220t/h.  Then they change the grinding ball load quantity and size, such as diameter 130mm, 110mm, 90mm, 75mm, totally 120t, the capacity is up to 280t/h. Then they increase the grate plate sieve size, and make the grinding ball size to be diameter 150mm,  the SAG mill capacity is up to 400t/h.

Although we increase the grinding ball size, the capacity of SAG mill will be increased a lot, we shall pay attention that, the weight of diameter 125mm is 7.8 kgs, and the weight of 150mm ball is 13.6 kgs.

When a grinding ball with a diameter of 150mm or above is used, the semi-autogenous mill load must be effectively controlled, otherwise the mill liner is very easy to be broken by the steel grinding balls. According to the production plan to stop and get the mill to empty, to check, need to take the standard control process, for example: 1, if the mill can change speed, should establish a grinding empty system, according to the load weight of the mill to reduce the speed of the mill;  2, when using a large diameter steel ball, the thickness of the mill drum wear liner should be increased accordingly.