When testing aggregates, ores, coal, or coke in geotechnical or construction materials testing laboratories, sample preparation often involves the reduction of particle sizes from the initial bulk or field sample. Many of these materials are hard, tough, or brittle, so crushing them into smaller sizes is an ideal application for robust, rugged, and durable jaw crushers.
All jaw crushers operate on the same straightforward principle; two hard-faced heavy plates or jaws crush large particles between them. One powered jaw reciprocates in an elliptical motion opposite a stationary jaw mounted in the frame.
During an operating cycle, the gap between the two jaws opens; a particle drops in, and the jaws close in and crush the particle. Further crushing of the fractured pieces continues until particles are small enough to fall through the bottom opening by gravity. The jaws face each other at a slight vertical angle, so particles become smaller as they progress toward the bottom.
A simple adjustment of the distance between the two jaws regulates the final sample size. The term, "final size" can be a little vague. It refers to the approximate maximum particle size at completion of crushing, but the size range and distribution can vary considerably based on the material properties of the sample.
Many factors make laboratory jaw crushers the optimum selection for effective and efficient primary crushing of hard, brittle, rock-like materials.
Jaw crushers can also have some disadvantages compared to other types of size reduction.
How to Choose:
The selection of the best jaw crusher for your application will naturally be governed by the particle size, volume, and properties of your bulk material, along with the desired particle size and quantity of the final sample. The size of the jaw plates limits the particle size capacity and determines the size of the feed opening. In general, maximum particle sizes are about 70-80% of the feed opening, but this can vary by manufacturer and model. Jaw materials are available in a variety of materials to adapt to the hardness and toughness properties of samples and to extend service life.
Our Recommendations:
Small Crushers: For applications where reduced quantities of materials with smaller top sizes and final sizes are needed, these smaller jaw crushers fit the bill. Their compact size allows easy positioning anywhere in the lab, even on a benchtop.
¹ Final Size is an approximate maximum particle size of the material after crushing with the opening set to its minimum clearance. Particle size distribution will vary by material type.Medium Crushers: These useful models have the capacity, size, and power to meet most primary crushing functions in the lab. Options for voltage configurations add to their versatility.
¹ Final Size is an approximate maximum particle size of the material after crushing with the opening set to its minimum clearance. Particle size distribution will vary by material type.Large Crushers: When size, capacity, and throughput are the most sought-after features, these units are the best choice. Some models can be ordered with gasoline or Diesel engines for mobile on-site work at remote locations or pilot plants.
We hope this blog post has helped you select the right jaw crusher. Please contact the testing experts at Gilson to discuss your application.
Standard Test Methods, Specifications, and Practices
Individual test methods and specifications referenced in our product descriptions, blog articles, and videos are available for review or purchase from the professional organizations noted.
Jaw Crushers are primary crushers used in the first stage of the crushing process. They feature a V-shaped cavity (called the crushing chamber) that is formed by a moving piece of steel and a stationary piece of steel (called jaw dies). Material to be crushed enters the top of the chamber, where it is squeezed between the moving piece of steel and the stationary piece of steel as it makes its way down the chamber toward the discharge at the bottom.
Jaw Crushers typically have a reduction ratio of 6:1, which means a 30” feed will be reduced down to 5” at the smallest size. The product size can be adjusted by opening or closing the gap between the jaw dies at the smallest point. This is referred to as the closed-side setting. If you need a smaller product size, move the jaw dies closer together to decrease the closed-side setting. If you need a larger product size, move the jaw dies further apart to increase the closed-side setting.
A compression-type crusher, Jaw Crushers are ideal for processing hard rock like dolomite, limestone, sandstone and river gravel, as well as material that is fairly abrasive. They are also a good choice for construction and demolition debris recycling applications for processing reinforced concrete, bricks, ceramics and more. Jaw Crushers are not the best choice for lightweight or sticky material.
Jaw Crushers are not a shaping crusher. Because they typically produce an elongated, flat and slabby product, Jaw Crushers are usually followed by a secondary crusher, such as a cone, impactor or roll crusher, for refining and further size reduction.
These crushers come in a range of styles and sizes and are capable of
handling low tonnages, such as in sampling applications, as well as
large lumps at high capacity. If you are considering a Jaw Crusher for
your application, here’s how to choose the right one.
Like other types of crushers, Jaw Crushers are sized based on the material to be crushed. This includes:
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- A description of the material to be processed
- Physical characteristics of the material
- Maximum feed size
- Desired product size
- Desired feed rate (or tons per hour)
The characteristics of the feed material are extremely important. Not
only do they help to determine the size of the Jaw Crusher required to
do the job, but they also help to determine the materials of
construction of the wear components.
A Jaw Crusher is sized so that the maximum feed size is 80% of the gape and width openings. The gape is the measurement between the two jaw dies, while the width is the measurement between the two side plates. For example, if the maximum feed size is 29”x49”, the crusher gape would be 32” and the width would be 54”.
By sizing the Jaw Crusher slightly larger than the largest feed size, you reduce the risk of large lumps getting stuck in the crushing chamber or sitting on top of the crushing chamber, stalling production.
The characteristics of the feed material also help to determine if a
Jaw Crusher is even the best type of crusher for the job, or if another
type of crusher would be better suited. Lab testing can provide an
analysis of the material that can be shared with the equipment
manufacturer for sizing the crusher.
In addition to the material to be processed, you also want to consider the environment in which the crusher will be operating. This includes factors such as:
- Method of extracting the raw material
- Method of feeding the raw material to the crusher (typically Jaw Crushers are fed by Vibrating Grizzly Feeders, Wobbler Feeders and scalping screens)
- Does it need to fit into an existing structure or integrate with existing equipment?
- Is it an aggregate plant or a recycling plant?
- Is going to be a stationary structure? Does it need to be installed on a chassis as part of a portable plant? Does it need to be skid-mounted for modularity?
- Future production increases
- Site footprint
- Plant height restrictions, if any
- Operating hours per day
Another consideration is the method of adjusting the closed-side setting: manually with shims or hydraulically with the push of a button. Shim-adjust Jaw Crushers are lower in capital cost, but they require a complete plant shutdown when product-size adjustments need to be made, as well as someone to physically make the adjustments.
You also want to consider if tramp metal relief is necessary. If
there is a chance you could accidentally process a large piece of metal,
such as a bucket tooth, on through to the Jaw Crusher, you may want to
consider a hydraulic Jaw Crusher with tramp relief over a shim-adjust
Jaw Crusher. The toggle on a shim-adjust Jaw Crusher can break in the
event an uncrushable material enters the chamber, whereas the hydraulics
on a hydraulic-adjust Jaw Crusher will relieve to pass the material.
Contact us to discuss your requirements of Jaw crusher machine. Our experienced sales team can help you identify the options that best suit your needs.