As a basic Crusher Operating Guide or guideline, you can alway assume the operating feed to the Standard cone crusher is normally scalped if over 25 percent of the desired crusher product is present in the new feed.
Since the range of feed size will often vary from approximately 12″ to 2″ in a given installation the crushing cavity must be selected to reduce these sizes efficiently. Where the top size of the feed is only 8″ the crushing cavity would be modified to reflect this smaller feed size. To meet these variations in size of feed and desired product size Standard cones can be equipped with various designs of fine, medium, coarse, or extra coarse crushing cavities.
As a guide in selecting the crushing cavity care is taken to obtain a design that will permit the topsize of the feed to enter the crusher in sufficient volume throughout the entire wear life of the liners.
Since the most efficient crushing action takes place when the feed is reduced in a series of 4 or 5 blows as it passes through the cavity, it becomes important to select a design that will effect some reduction in the upper portion of the cavity as well as the lower or parallel sizing zone. In other words, too large an opening for the feed will prevent crushing in the upper zones and can develop excessive power draw.
Since the crusher feed rate is governed by the power draw, an incorrect cavity can reduce the crusher capacity and, on occasion, create unnecessary maintenance. On the other hand, if the cavity will only accept the feed when the liners are new but as the liners wear the feed opening closes off reducing the feed rate, a more efficient cavity is required.
Since no two ores or crushing applications are exactly the same, a large number of cavity designs have become available through the years. Therefore, the optimum in cavity design is one which permits close to the rated power draw throughout the entire wear life and results in a scrap loss between 25 and 40 percent.
With the proper cavity design, maximum efficiency will be obtained if the feed is evenly distributed around the entire crushing cavity. Normally, guide yourself with the wide feed size range required in the Standard or secondary crushing stage is such that the crushing cavity is required to have a receiving opening considerably larger than the average portion of the feed.
For best results the feed should be regulated based on the crusher motor power draw. When handling the harder materials it is likely the crushing cavity in the Standard cone crusher will not be entirely filled up or “choked”. However, maximum capacity will be obtained under these conditions when cavity design and proper feed distribution methods are observed.