Value in the use of high alloy manganese is optimized when the material being reduced has a compressive strength value of 50k p.s.i. and a silica content of .5.

The optimum value we’ve experienced with our Xtralloy material has doubled service life under these material conditions. As both the strength and silica factors deviate one way or the other from either of these standards, the value in using high alloy manganese diminishes for different reasons. For example, a 20k p.s.i. material with a .2 silica content would reduce so easily that improved wear would be difficult to detect. On the other end of the scale, a material with an 80k p.s.i. strength value and a .8 silica content would be so difficult to fracture that the manganese casting would likely fail through fatigue being fully expended.

There’s a ratio of manganese content to carbon level that provides the most fatigue resistant manganese parts. As the intersect point between the highs and lows of those strength and abrasiveness scales deviate from the established optimum 50k and .5 values, the added benefit of the high alloy material reduces from a maximum service life increase of double. This information is based on data recorded during the development of Columbia Steel’s Xtralloy premium manganese steel.

The value in making cone liners with an increased feed opening is not about allowing for greater reduction ratios, but about insuring that the liner set provides a consistent output rate through full expenditure.

The concept is to remove steel where it’s not needed (at the feed end) and apply the wear steel where it is needed (at the discharge end). Most cone liners are removed when the feed opening closes off enough to reduce the output rate. A proper feed opening dimension that is in ratio with the thickness of the bowl and mantle, with proper feed size, will wear to full expenditure while maintaining a constant output rate.

Increasing the feed opening and thickness of cone parts takes considerable care in order to minimally affect the included angle between the liners, and not cause an adverse reaction to the size of feed material. Each category of crushing cavity -- fine, medium and coarse -- requires its own ratio of feed opening to length and thickness. In some cases, these categories of crushing are split even more finitely. This subject is closely related to determining the optimum feed size for a particular set of liners.

When it comes to crusher feed, the more uniform its shape and percentages of size range, the more effective the crusher becomes.

Range of feed material goes from small to large. The more of the feed product that can be removed that is equal to or smaller than the discharge setting, the more effective the crusher becomes. The large feed size maximum is best determined by putting nothing larger than three quarters the size of the effective feed opening. (This is not the largest opening of the feed end.) If that kind of sizing control can be accomplished, then the crusher needs to be flooded with enough volume of that material to keep the crusher filled at all times.

Woefully, this condition is rarely obtained. That is why choice of jaw, gyratory, cone and roll wear parts become so job specific. It’s difficult to control feed blends, types and sizes, and this has lead to the creation of many options in wear parts and machine types and sizes.

The more reduction stations in a crushing operation, the more effective each crusher becomes. Large volume mines have learned by experience that it usually takes 5 crushing stages to optimize the use of each crusher. Having that many stages of crushing is not viable in most cases, however, so the next best thing is to apply the best product, and proper wear parts, for the sizing job at hand.