Crusher load in different crushing stages

The feed into crushing process varies a lot quite often. It’s a very important factor to consider while designing a crushing process. In the pri- mary stage, the feed into crusher varies from very fine feed to big blocks even in the same quarry. Thus, the capacity of primary stage isn’t stable all the time. For successful and continuous crushing operation, it’s important to have last crushers full all the time (see chapter choke feed). This is possible, if the external variation caused by the feed fragmentation is controlled. In practice, the use of stockpiles, screens, silos, buffers and process automation standardises the feed to final crusher, which give a chance to make consistent quality aggregates.

As a rule of thumb, crushing circuit should be designed so that the final crushing stage is under 100% load all the time. This comes true, if the secondary stage is under 80% load and primary under 70% load. This gives some extra capacity to early stage of crushing circuit to handle the interruptions caused by feed variation.