Central Midwest Limestone deposits tend to be relatively soft and nonabrasive so depending upon the seam and application, manganese liners can last for years. "How do I know when to change my liners?", is a question we often hear.

That question prompts us to suggest there are several related issues.

1. Maximizing Crusher Production

2. Correct Application of Liners

3. Maximizing Liner Wear

4. Gauging Liner Wear

If your cone has been in the plant for quite a while, perhaps its time to review the application since production demands, product specifications or feed material may have changed since the cone was installed or its last set of liners changed. If you are sure the operation is within factory recommended parameters then we're ready to select liners. If not, it might be worthwhile to take another look at your plant flow and the operation of units up and down stream of the crusher in question. You may be able to make some changes in plant flow that could be surprisingly beneficial to your operation.

Same concern for the liners as the crusher. What was happening in the plant flow the last time the liners were replaced might be different than today. There are also more choices today than ever before. Special liner configurations can solve or minimize crushing problems and higher manganese content can provide longer wear life. A competent and qualified supplier can provide an opinion of what might be appropriate in today's market. Profiles can be traced from worn liners and used to help make recommendations. Always replace liners in sets.

To maximize the wear life of your liner investment, keep fines out of the crusher. Packing a cone with fines prevents proper crushing action and can cause high amp draw, bowl float or ring bounce, accelerated wear and undesired gradation along with a reduction in throughput. Check your manual for factory recommendations, but in general provide an even, well centered feed that distributes material evenly around the crushing chamber. While head action is gyratory, the head does turn, but because the bowl does not, offset or uneven feed will cause pronounced uneven wear to the bowl on the heavier feed side. This makes it difficult to achieve target gradations because adjustments and crushing action is not the same all the way around the crushing chamber. Keep the crusher adjusted properly, not to close. Occasional adjustment will also keep the unit relatively free for when adjustments are required or liners needed. Nothing worse than a stuck bowl.

Now, how to tell when your liners are due for replacement. One way is to make marks on the crusher when a new liner is installed. Continue to make marks, maybe dates as well, as the bowl lowers. When you do make a change, mark that as well. Now on the next set of liners you'll have some relative idea of liner wear as the bowl drops.

But, the best way is to know your gradation, throughput and recirculating loads depending on your circuit. Remember that as you adjust liners to compensate for wear, the "throat" area of the liners also closes. This is a volumetric issue and a relatively small loss of throughput can add up to a lot of lost production. So if those liners take a long time to physically wear out you can be losing a lot of production or throughput and not even realize it! Know what the gradation and TPH are supposed to be and check it on some periodic basis.

Here is an example to illustrate the cost of a10% reduction in throughput due to liner wear.

Of course, there are additional costs associated with a liner change but the point is to gauge when your throughput and possibly gradations as well, fall off enough to justify replacing the liners. That's opposed to the point of view of maximizing metal utilization. If you get both, great! But we suggest if you check the numbers you will know for sure and you might be surprised.

When is the last time you checked!

Here's a quick little spread sheet to help you calculate your total cost of a liner change-out.

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