9. Monitor and maintain a proper crusher speed. If proper drive belt tension is not maintained, the belts will slip and the crusher will slow down. A slowing crusher will cause incredibly high power peaks at a very low crusher throughput tonnage. Improper or neglected drive maintenance will result in a high-horsepower consumption at a low crusher throughput tonnage, and this inefficient use of connected horsepower will result in a higher-than-normal energy cost per ton of material crushed.
A speed sensor can be used to monitor the crusher countershaft speed, which will send a warning signal of a slowing crusher to the programmable logic controller, or it could be wired to simply turn on a warning lamp. When a warning is detected, the maintenance department can be dispatched to re-tighten the drive belts. When a speed sensor is used, drive belt life is extended and proper production levels can be maintained.
10. Determine the percentage of fines in the feed. “Fines in the crusher feed” is defined as material entering the top of the crusher, which is already equal to or smaller than the crusher’s closed-side discharge setting. As a rule of thumb, the maximum number of fines in the crusher feed should not exceed 25 percent for secondary crushers or 10 percent for tertiary crushers.
When there is an excessive quantity of fines in the feed, it is typically the result of a vibrating screen problem. This problem could be due to the fact that the screen is insufficient in size, or a screen that is sufficient in size yet is inefficient in operation. Re-crushing and re-handling product size material due to an insufficiently sized screen, inefficiencies due to the way the screen is set up or due to improper vibrating screen maintenance will lead to an excessive quantity of “fines in the crusher feed.” This will lead to inefficient use of connected crusher horsepower and a higher energy cost per ton of material crushed.
11. Limit the height from which the feed material drops. The maximum distance from which the feed material should fall from into the top of a small to mid-size cone crusher is 3 ft. When the feed material drops from a much greater distance, the stones tend to slam into the V-shaped crushing cavity with such velocity that it subjects the crusher to shock loads and extremely high stress levels. This situation is referred to as high-velocity wedging, and it can result in power overloads or force overloads – or both. This action puts undue stress and strain on the crusher components, and it results in increased maintenance repair costs and poor productivity.