Mill Liners: The Cost Saver in Mill Liners

Factors influencing mill liner design:

Cost of liner and cost of installation.
Hardness and abrasiveness of the ore to be ground.
Type of grinding media (steel balls or pebbles).
Critical speed of mill.

		The cost of the liner must include the downtime while being installed and the cost of the bolts, gaskets etc. This combined cost is usually compared to the life in terms of tons milled.
		The hardness or abrasiveness of the ore will influence the choice of metal used. Hard abrasive rock will work harden the manganese steel.
		Using steel balls as a grinding media can sufficiently work harden manganese steel even if the ore is of a soft nature.
		The higher the critical speed, the greater will be the impact between the load and the liners also influencing work hardening of the liners.

Experience has shown that the grid type shell liner is the most economical liner to use in ball mills and semi-autogenous mills where there is high impact and abrasive conditions.

The lightness compared to the solid liner makes them faster and easier to install.

The grinding balls pack into the bars of the grid thereby exposing very little of the liner to attrition.

As a comparison between the solid and grid type liners, the metal loss is three times greater in the case of the solid liner.

Feed end and discharge end liners are also based on the grid design and are suitable for ball mills, autogenous mills and mills having a composite load of grinding balls and ore.

In a recent installation solid mill liners weighing 100 tons were replaced by grid liners weighing 47 tons, a saving in the freight and installation costs of 53 tons, in addition to the cost of a set of solid liners.

Depending on mill operation, the grid liner will equal or exceed the solid liner life.

Often it is found that the liner lengths can be increased when using the grid liners, thereby reducing the number of bolts, gaskets, etc.

There is an increase in the ball consumption until all the spaces between the bars are packed with balls, thereafter there is no further increase in ball consumption.

Advantages of the Grid Type Liner

They weigh 40% less and cost 50% less, and the life of the grid liner meets and exceeds the life of solid liners.

The grid liner uses the steel balls to protect itself from abrasion. It is far more economical to wear steel balls at 20 cents per lb rather than liners at 67 cents per lb.

		Grid liners are lighter and more easily handled.
		Grid liners are made from manganese steel, this work hardens well and is never brittle.
		Entrapment of balls in the grid presents an uneven rough surface to the load assisting in lifting of the load, ensuring a good tumbling action.
		Discard weight of grid liner is 80% lower than that of solid liners.
		Any liner can be made in the grid design.
		Grid liners are used in conventional, autogenous and semi-autogenous milling of ore.

Entrapment of balls in the grid presents an uneven rough surface to the load assisting in lifting of the load and ensuring a good tumpbling action.

Feed end and discharge end liners are also based on the grid design and are suitable for ball mills, autogenous mills and mills having a composite load of grinding balls and ore.

Would you like to see how Grid Liners can improve the economies in your operation? Just click here to complete an online analysis and we'll get back to you with a firm proposal.