Overview
Any thorough discussion of primary crusher selection must include a comparison of the two leading types: the standard gyratory crusher and the Blake jaw crusher. Although their applications often overlap in primary crushing, these machines are not competitors but rather complementary tools. Together, they address the vast majority of primary crushing needs. While specialized equipment like sledging rolls may outperform them in niche situations, very few primary crushing jobs can’t be effectively handled by one or both of these machines.
Both gyratory and jaw crushers can be engineered to process the toughest rock or ore economically mined or quarried. The jaw crusher, with its simple box-frame construction and toggle mechanism, is particularly suited for extra heavy-duty applications. Its design allows for reinforcement at a lower cost compared to the more complex shell castings of the gyratory unit. Although scenarios demanding extreme brute strength are rare, both types can be adapted for the vast range of materials encountered in practice. Reinforcing these machines for extra duty is generally a matter of using stronger metals or adding extra weight to the frame—changing the proportions of the working mechanism is seldom necessary.
In most cases, the decision between a gyratory and a jaw crusher is driven by performance criteria such as capacity, receiving opening size, and space constraints rather than by differences in inherent strength. To facilitate a quick and clear comparison for any specific application, it is helpful to list the key features of each type.
Features of the Gyratory Crusher
- High Capacity per Investment Dollar:
Gyratory crushers offer an impressive throughput relative to their cost. - Annular Discharge Opening:
This design minimizes slabbing, resulting in a more cubical product. - Optimized for Slabby Feed:
The shape of the receiving opening is ideal for handling thin, layered material—making it particularly effective with slabby feed. - Extended Receiving Opening:
The long, wide opening reduces the risk of bridging and supports dual-side discharge. - Low Flywheel Effect:
A lower flywheel impact reduces start-up surges and allows the machine to quickly shut down when overloads occur. - Ease of Maintenance:
Gyratory crushers can be serviced using a simple overhead crawl-type hoist, in contrast to the more complex crane operations needed for jaw crushers. - Faster Pinion Shaft Speeds:
These speeds allow for higher-speed motors and a lower gear reduction ratio. - Simplified Lubrication System:
Maintenance costs are further reduced with an economical lubrication setup. - Lower Foundation and Safety Costs:
Both the foundation requirements and the number of necessary safety guards are typically lower.
Features of the Jaw Crusher
- Large Receiving Opening per Investment Dollar:
Jaw crushers are designed to deliver a sizable feed opening, particularly well suited for blocky material. - Superior for Blocky Feed:
The rectangular opening is advantageous for handling chunky rock, giving the jaw crusher a clear edge—except in extremely large sizes. - Easy Adjustment for Wear Compensation:
Jaw crushers offer simple adjustments to offset liner wear, a benefit that is especially notable in larger units where a wider range of adjustment is available. - Consistent Throw:
Even with wear in the bearings, the jaw crusher maintains its original throw, ensuring consistent performance. - Better Handling of Sticky or Dirty Feed:
Without a diaphragm beneath the crushing chamber, the jaw crusher is less prone to clogging from sticky materials. - Simpler Routine Maintenance:
Daily repairs and maintenance are typically more straightforward, with major overhauls often requiring only a shutdown rather than extensive disassembly. - Cost-Effective Reinforcement:
When extra strength is needed for extremely hard or tough materials, additional reinforcement can be implemented at a lower cost compared to gyratory crushers. In standard (unreinforced) designs, jaw crushers are usually more robust.
Advantages and Disadvantages
Neither crusher type is ideal for very soft or “mushy” materials. However, the jaw crusher generally performs better with such feeds. For instance, loosely cemented minerals like soft sandstone are prone to packing and bridging in gyratory crushers, whereas jaw crushers can manage them if the material flows reasonably well. In applications involving soft materials, regardless of the crusher type, sluggish performance and the risk of chamber packing remain challenges.
When handling rock or ore that contains a significant amount of loam or similar contaminants, the jaw crusher tends to perform more reliably—provided the contaminant mix does not build up on the jaw plates. Gyratory crushers, on the other hand, should not be used with materials that exceed a minimal level of contamination, as even a small amount may cause issues with diaphragm packing.
Comparable Sizing and Selection
The term “comparable sizes” is frequently used to align gyratory and jaw crushers, though its precise definition can be elusive. In practice, this term refers to matching machines based on specific job requirements—whether prioritizing capacity, the size of the receiving opening, or other factors. Engineers and operators typically pair one gyratory crusher size with one jaw crusher size to determine which best fits their application. For primary crushing, the receiving opening is often the foremost consideration, with capacity being the next critical factor. One effective approach is to overlay scaled drawings of the openings to evaluate the effective feed size.
Handling Slabby Material
Materials with a slabby character—such as thinly stratified limestone or shale—tend to produce large slabs when crushed in a jaw crusher, particularly if some layers in the deposit are thinner than the crusher’s discharge setting. In contrast, the gyratory crusher, with its annular discharge and specially designed receiving opening, is better suited to handle slabby feed by breaking it more effectively. This distinct advantage makes the gyratory the preferred option when dealing with materials that have pronounced slab characteristics.
Conclusion
In summary, the choice between a gyratory and a jaw crusher should be based on a balanced evaluation of performance characteristics, space requirements, capital investment, and the specific nature of the feed material. While gyratory crushers excel in high-capacity, slab-friendly applications with lower foundation and maintenance costs, jaw crushers offer greater versatility with blocky feed, easier adjustments, and simpler routine maintenance. Ultimately, both machines serve as complementary assets in the realm of primary crushing, ensuring that nearly any crushing requirement can be met with at least a satisfactory degree of performance.