How can you design of ball mill?

Answer 1

*Ball mills are generally smaller in diameter relative to their lengths (i.e. low aspect ratio) when compared with AG and SAG units;

* Ball mills have comparatively high charge densities when compared to AG and SAG mills; and

* Ball mills are rubber lined more often than AG and SAG mills.

The progressive increase in the size of ball mills has led to an ongoing requirement for more accurate and reliable analysis of mill structures (the trunnions, heads, mill shell sections and connections between these components) for a number of reasons:

* Higher levels of reliability have been called for because of the higher capital costs involved, higher levels of availability required and reduced levels of plant redundancy;

* Increased sizes have put more pressure on manufacturing constraints (for example, the maximum size of castings, machining capabilities and so forth). As a result, sizes cannot be indefinitely scaled up, leading to greater pressure to limit section sizes and thicknesses, and hence leading to higher general stress levels, which of necessity are closer to design criteria;

* As sizes have increased, the stresses at non-axisymetric features such as manholes have increased, so that more rigorous analysis of these features becomes necessary;

* The increasing sizes have required that mill structures be manufactured from a larger number of components bolted together. The bolted joints now include radial head joints and longitudinal flange joints (also non-axisymetric structures), as well as the circumferential head and shell joints.

* Those very large ball mills with geared drives typically use large outstand gears, which can have a significant effect on the stresses in the main mill structure. Consequently, these gears need to be modelled as part of the main mill analysis, in sufficient detail to establish the effect of the gear and gear loading on the mill structure. Separate analysis of the gear structure is usually carried out.