Examining a typical cement clinker grinding mill , which can be considered to be representative of all tube mills, the components normally found as follows:
SHELL LINING PLATES
These plates are specially designed and incorporate contour features which inject movement into the ball charge during rotation of the mill. Properties required by the plates vary along the length of the mill.
For instance, at the inlet region of the mill there is likely to be less protection of the plates by ground products and the balls will be of largest size in use and therefore, toughness is of outmost importance. However, along the length of the mill, in second and third chambers, the ball size is considerably smaller and a protective layer of ground material is available and here wear resistance must be at a maximum.
END WALL LINING PLATES
These plates are fitted at the inlet region of the mill and as such are subjected to maximum impact by the large grinding media, therefore, the need to be manufactured in as tough a material as possible whilst at the same time obviously retaining a high degree of wear resistance.
Similar comments apply to slotted diaphragm plates particularly those separating first and second grinding chambers because in this region there is frequently a lack of protective ground material as it passes through the slotted plates. It is essential, however, to maintain a high level of hardness in these plates to avoid peening over the slots, thereby reducing mill throughput.
GRINDING BALLS AND CYLPEBS
This item is self-explanatory. Grinding balls vary in size from 12 to 100mm in diameter, the larger balls requiring increased resistance to repeated impact, smaller balls requiring maximum wear resistance. In the case of fine grinding, balls are occasionally replaced by cylpebs which cylindrical products with a height/diameter ratio of unity, the theory being that they posses a higher surface area/volume characteristic than the equivalent diameter grinding balls. Cylpebs are normally produced in sizes ranging from 12×12 to 30×30 mm.