Efficient Utilization of Rock Crushing Equipment Wear Liners

Jan. 22, 2018

Article by: Russ Coverdale

Successful rock crushing hinges on efficiency.

Many factors contribute to that efficiency - from plant design, to safety in operations, to seasonal optimizations - but the underlying goal, always, is to maximize the value of each system component.

That’s why utilizing rock crushing equipment liners well is central to profitable production. Liners come in many forms, such as bowls, mantles, jaw dies, cheek plates, curtain liners, blow bars, to name a few, and therefore they are one of the most frequently replaced system components in rock crushing – and, too often, they aren’t utilized to their full value.

That can lead to costly inefficiencies in your system.

But, you can avoid this. Here’s what you need to know about rock crushing equipment liners, including:

  • How long they should last
  • How to calculate liner utilization
  • How to maximize liner life, and
  • How to avoid the most common liner mistake.

Armed with this knowledge, you’ll be able to boost your efficiency in using rock crushing equipment liners—and that will impact the success of your entire operation.

Let’s get started.

How Long Should Liners Last?

Given that wear liners are one of the most frequently replaced components in the crushing system, how long can you expect your liners to last?

Well, the short answer is: it depends.

Several factors affect liner life, but the most notable is the type of stone you process. Rock liners are responsible for providing the immediate dynamic contact on the stone as it’s being crushed and this means that the type of material the liners interact with has a direct and notable effect on longevity.

Liners might last for years when used to crush soft rock materials, such as talc, onyx, alabaster, or soft limestone. Harder, abrasive minerals, like granite, however, may wear out liners within a month.

Other factors, such as continuity of run time, may come into play as well, but the primary determinant toward the life of liners is the combination of hardness/abrasivity of the mineral being crushed.

How to Measure Liner Utilization

Replacing liners at the correct time reduces your costs. If you use the liners too long, you may wear through the liners entirely and begin to damage the crusher head itself, which can end up being costly. Replace them too early and the cost shifts to the waste of precious production time, as well as the costs associated with premature liner replacement. 

More likely, though, is that liners wear unevenly, forcing replacement to protect the machine although full utilization isn’t realized. 

To achieve full liner utilization, it’s critical that you understand what the targeted utilization goals should be, and how to measure progress.

Typically, in a Metso HP-style crusher, the optimal utilization target is 50 to 55% of the liner. For a Symons-style crusher, targeted utilization should be 60 to 65% to maximize liner use before replacement is required. 

To calculate liner utilization, weigh the liners before they’re installed. Upon removal, weigh them again. Utilization percentage is calculated by subtracting the used weight from the original weight, then dividing the difference by the original weight.

With that in mind, there are four methods to tell when a liner has met utilization goals and should be replaced. Each of these methods is accurate enough to rely on for replacement timing, if appropriate factors are known.

Monitor Production

This means monitoring the amount of stone going through the crusher. In the case of cone crushers, as the liners wear down, the feed opening at the top of the crusher will constrict, and you’ll lose throughput as the opening decreases and crushing cavity volume is reduced. When you have 10% production loss, compared to peak production, it’s time to change your liners. Failing to do so at that point will cost money in lost production and, if the liner wears too thin, could cause severe damage to internal crusher components.

Physical Measurement on the Exterior of the Crusher

A second way to monitor usage one a cone crusher is to measure from the dust cover down to the top of the adjustment ring. The distance will start at a certain height (maybe six inches), and will decrease as adjusted down for wear—it may be two-and-a-half inches at full utility. Make a physical mark on the exterior that signifies full utility and, when the mark is reached, you’ll know that it’s time to change the liners.

Measure Crusher Hours

This requires an understanding of the crusher and the stone being crushed. For example, a certain crusher may operate for 200 hours before it needs to be changed. Some crushers have an hour meter to monitor time.

Measure Total Tons Through the Crusher

This, again, requires an understanding of the crusher and material it’s fed. Depending on those factors, there is an expected cumulative throughput that the crusher will process before liners will need to be replaced. Measuring total tons through the crusher against that number will provide an accurate notification for timing liner replacement. 

How to Maximize Liner Life

There’s nothing to be done about the physical reality of the crushing pressure and abrasion that liners are subjected to; with use, liners will inevitably wear down.

That being said, there are two factors that can help to maximize the life of liners:

Break Them In

Breaking-in the manganese in a cone-crusher liner will gradually make the liner material more dense and hard, in a process called “work-hardening”. So, when you replace liners avoid going back to full production levels right away.

Instead, here’s what we recommend: when you install a new set of liners, operate the crusher at 50% of its full load capacity for six hours. After six hours, open up to 75% of capacity for two hours. At that point, the manganese should have solidified to its maximum density. Then, you can go to full operation, and your liners will function more efficiently.

Keep a Continuous Feed

Sometimes, starting and stopping feed to a crusher is unavoidable, but liners will last longer with fewer interruptions in feed. The concentric spinning motion, inherent in the head of a cone crushers while it’s not crushing, requires resistance to stop. When the feed is re-introduced, resistance is applied and the spinning motion comes to an abrupt halt while beginning to slowly rotate the opposite direction. 

This start/stop process prematurely removes liner material and can shorten normal wear life. So, avoid stops as much as possible. Continuous feed reduces the amount of abrupt halts and improves the life of liners.

How to Avoid the Most Common Mistake

Finally, to utilize rock crushing equipment liners as efficiently as possible, it’s vital to avoid the most common liner mistake: selecting and using incorrect liners for your particular application.

This, essentially, comes down to the necessity of using liners that are correctly sized relative to the feed size. This may seem obvious, but incorrectly sized liners are surprisingly common and counterproductive.

If the liner is too large for the feed size, the lower portion of the liner will wear out before the upper portion is worn out. If the liner is too small for the feed size, the upper portion of the liner will wear out before the lower portion. 

Either way, you’re wasting valuable liner, and robbing efficiency from your process. Make sure that your crusher has a correctly sized liner that matches your specific feed size and local crushing conditions.

Start Utilizing Your Liners Properly

The key to successful rock crushing lies in sweeping aside systemic inefficiency. We hope this information about rock crushing equipment liners enables you to do just that, through maximized utilization of your wear liners.

Make sure your crusher wear liners are correctly utilized—contact Mellott Company for a complete liner study service.

Given the gradations for feed and discharge, we can calculate wear liner utilization. We can even identify asymmetric wear, by studying the worn liner profile, to enable you to accurately fit the proper liner to your specific crushing application.

Get in touch with Mellott Company today, and tune your rock crushing system for increased efficiency and success.

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