Modification of Mill Liner

Mill Specification: Φ6.4x3.3m SAG Mill

Problems Description:

1) Cracking of mill liner was found after running the mill in a few days.

2) The serive life of mill liner is less than three month.

3) By listening the grinding sound, we can hear the sound of lots of steel balls knocking the mill liners.

4) Production efficiency of mill is low.

Reasons analysis:

1) Wrong designing of shell liners: the cone angle of mill liner lifter bar is too small, which leading the grinding media wrongly to the shell liner working surface instead of the area of ore gathering and result in the damage of mill liner. All these will influence the service life of mill liner and production efficiency of mills.

2) Wrong designing of end liner and grate liner: The lifter bar is too narrow, this will also shorten the service life of mill liner.

Solutions:

1) Proper designing of the cone angle of mill liner lifter bar, the lifter bar will lead the grinding media falling down in a proper path.

2) Increase the size of mill liner lifter bar, prolong the service period of the lifter bar maximumly.

3) Cylinder liners are designed as a spacing configurations of high & low rectangular lifting bars, the design can increase the space volume of grinding ball and large processing ore.

4) Strength the lifter bar of end liner and grate liner.

Mill Specification: Φ5.5x2.4m

Problems Description:

1) Cracking and arching deformation of mill liner was found after running the mill for a few days.

2) Breakage of fixing bolt caused by the arching deformation of mill liner.

Reasons analysis:

1) The quality of the mill liner is not qualified because the material is not right. The mechanical property of the mill liner can not meet the mill working condition, so caused the

breakage of the mill liner.

2) Wrong structure designing of mill liner.

Solution:

1) Adopt pearlite wear-resistant chrome-molybdenum as material of mill liner HMCB and HMCB02 series, the hardness standard is HB325-375, impact energy≥55J.

2) Design and transformation of shell liner according to the designing standard of SAG mill liner.

3) Add the monitoring frequency of mill grinding sound, add the feeding timely when the filling is not sufficient.

Feedback from the client:

CIC did the optimization and modification of mill liners and solved the problems of mill liner cracking and arching transformation. The service life of the mill liner is prolonged after improving. We get a good reputation from our customer.

Mill Specification:

Φ6×3m SAG mill (first stage) and Φ4.27×7.3m overflow ball mill (second stage)

Problems Description:

Φ6×3m constant speed SAG mill (first stage) and Φ4.27×7.3m overflow ball mill (second stage) is applied to crush and separate gold ore in mining processing factory of Dulan Jinhui Mining Co., Ltd. Protodikonov's Hardness of ore is f=10-12, feeding material size is small, and 80-120mm material covers about 18% (see Fig. 1). Max. diameter of milling balls in the two kinds of mills is Φ120mm. All materials of mill liners are HMCB02, and the structure of mill end liners are all segmentation design of two loops. For the SAG mill, overflow type for discharging minerals, and cylinder liners are designed as the spacing configuration of high & low rectangular lifting bars. The rated output per hour of each mill is 100ton/h, and the actual output per hour of each mill reached 91.6 ton/h, now the output per hour of each mill is 65ton/h. We found that cylinder liners in the high lifting bars places are worn seriously after running for 45 days (see fig. 2). The electroacoustic system reflected the sound of milling is heavy (electro-acoustic output signal is 4mA). For the Φ4.27×7.3m overflow ball mill, the working faces of cylinder liners are designed as a geometric shape with a single wave peak. The thickness of the wave peak is 116mm, and the thickness of the wave valley is 50mm. The difference between wave peak and valley is 66mm. The electroacoustic system reflected the sound of milling is clear (electro-acoustic output signal is 11mA). So for SAG, wearing speed and conditions of liners are abnormal, and output per hour of each mill cannot reach the requirement, and milling sound is abnormal. And for the overflow ball mill, the milling sound is also abnormal.

Solution:

SAG Mill - based on the detailed condition on-site, the CIC designed the lifting bars of cylinder liners to high trapezoid(see fig. 3 & 4), in order to effectively lift medium in the mill and guide the milling balls to be thrown on the working faces of material enrichment area on the bottom of the mill and achieve high-efficiency crushing of feeding material. The optimized plan can dramatically prolong the service life of mill liners, decrease output per hour (successful examples: Φ6.4×4.88m SAG in Tonghua Corporation Xinqiao Mining Co., Ltd and Φ7×3.5m SAG in Jiangtong Corporation Yinshan Mining Co., Ltd.). For the mill end liners, we designed them as segmentation structures in three loops (see Fig. 5). Actual running experience shows that mill end liners in the inside loop are all not needed to replace after being applied to our optimized design plan (successful example, Φ6.4×4.88m SAG in Tonghua Corporation Xinqiao Mining Co., Ltd.).

Overflow ball mill - base on the features of the ore and sufficiently play the grinding function of overflow ball mill, we suggested the size of main milling balls is Φ80mm, and designed the liners as double wave peaks (see Fig. 6) and the difference between wave peak and valley is 50mm. Meanwhile, the CIC designed the end mill liner as a segmentation structure in three loops in order that decreases the weight of residual scrapping end liners in the inside loop (successful example,  Φ4.27×6.1m overflow ball mill in Fengyuan Molybdenum

Industry Co., Ltd.).