Mar 30, 2020 Aggregates blog

How to improve jaw crusher performance and productivity

Washington Luiz
Washington Luiz
Global Support Manager, Crusher consumables
Everyone wants to get the most out of their equipment, and jaw crusher operators are no exception. There are several factors that affect crusher performance and thus the whole circuit. Here are a few things that can help you avoid production losses.
Installed C130 jaw crusher

Avoid bridging

Continuous bridging in the feeding area of jaw crushers is a common problem.

What is it?

Bridging means stones blocking the flow from entering or moving down in the crushing chamber. It can be caused by just one stone that is larger than the feed opening, or then many average-sized stones of crossing against each other and blocking the crusher’s feed.

Why it is a problem?

Bridging can cause a significant loss of production that oftentimes goes unnoticed. It is relevant to keep an eye on bridging in the feeding area of a primary crusher as it can take several minutes to resolve the issue (big rock being removed, fragmented or directed to the chamber). If it occurs say ten times in a day, it quickly leads to one hour of lost production.

If that happens, for instance, in a Metso crusher model C130 with 352 short ton per hour (stph) working capacity and assuming a USD 12 /short ton , the daily loss can easily add up to four thousand dollars.

How to prevent bridging?

Bridging can be avoided by implementing a tight control of the blasting grid to avoid generating oversize material, training the truck loader operator to separate the oversize material at the pit and the primary crushing plant operator visualizing the flow of material to the crusher and controlling the stones’ speed and direction by varying feeder speed and using the hydraulic hammer installed in the area.

Example of bridging. One large rock blocks the crusher.
Example of bridging.

Apply the proper jaw die profile

There are many kinds of rocks, differing in crushability, abrasiveness, flakiness, etc. Choosing the best combination of fixed and movable jaw dies profiles will help to optimize production when crushing difficult material. A Rock of low crushability requires a closer nip angle to keep the capacity as designed. A highly abrasive rock requires thicker and heavier jaw dies that last longer, thus avoiding loss of production due to frequent stops to replace them. Flaky rock requires toothed jaw dies to crush it into more cubical pieces, avoiding stops due to bridging and belt cutting along the crushing circuit.

Having the appropriate jaw die profile saves more than 20% of production capacity that would otherwise be a loss. Let’s use the same example scenario as in the first one with the C130 model. We would have approximately a 70 stph reduction in production, in other words, a decrease of USD 4000 to 8000 in revenue for one day.

Monitor the condition of jaws

Besides being an important item for the machine’s performance, the jaw crusher’s jaws are responsible for front frame and swing jaw protection. Wear generally causes loss in production due to increased crushing angle, loss of tooth profile, reduction of the CSS to compensate the possible lamellar effect, etc. That is why it needs to be monitored throughout the crusher’s lifecycle.

As excessive wear can cause a 10–20% reduction in production, it is important to find the optimal time for the jaw turn or change in terms of cost and benefit. Again, with the same scenario with C130, we would have approximately a 70 stph reduction in production, in other words, a decrease of USD 4000 to 8000 in revenue for one day.

Chart of optimal change time for jaw plates.
Illustrative figure.

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