Tech Tip: Sizing the Jaw Crusher

Why is selecting and maintaining the proper jaw crusher closed-side setting (CSS) so important to crushing efficiency?

“The right jaw crusher CSS directly affects the flow of the rest of the crushing circuits – allowing the primary jaw to produce material that’s ideal for secondary crushing,” says Jarrod Adcock, product manager for Superior Industries.

Follow CSS Basics

First off, for those new to crushing, the closed-side setting (CSS) on a jaw crusher is the distance between the jaw liners at the bottom of the crushing chamber when the machine is operating. The CSS determines the product size of the material produced by the jaw.

By consulting with your crusher manufacturer (and your machine manual), producers can pinpoint the right CSS for the primary crusher, and for the circuits to follow. Importantly, selecting (and maintaining) the right CSS impacts overall material flow, production capacity, product gradation, power draw and wear.

Control Feed Size & Fine Materials

Proper feed material and proper crusher settings go hand in hand within overall crushing efficiency.

Make sure that your feed size is correct for the crusher you operate, and eliminate the fines being fed into the jaw. By pulling out the fines, you will ensure processing efficiency and a higher quality material at the discharge point.

Crushed material that is similar in size to the CSS offers the best particle shape – while material that is smaller than the CSS contains more elongated particles, as it has passed through the machine without being crushed.

Proper scalping helps remove fines from the feed material. “When we design a primary jaw circuit, we normally place a grizzly feeder ahead of the jaw crusher to pull out the fine materials,” says Adcock. “That’s why it helps to work with a manufacturer who offers all the components of a plant and understands optimum material flow from one circuit to the next,” he stresses.

Maintain Desired Settings

Maintaining correct crusher settings supports plant productivity.

Consider the example of an operation who neglects daily CSS monitoring while also dealing with the issue of excessive liner wear. As the liners wear, the closed-side setting keeps expanding. That means that material going to a secondary cone crushing circuit keeps getting larger. This may overload the cone, and if the operator “opens up” the cone to accept larger material, this will directly affect the efficiency of the tertiary circuit. It becomes “a domino effect of lost production efficiency.”

Producers should check the CSS daily – and at the same time, inspect the liners too – making it a two-birds-with-one-stone maintenance advantage.

Streamline CSS Adjustments

While older-style crushers involve costly time and labor to change settings via a manual shim adjustment, modern crushers make it much easier with two styles of making setting adjustments. The first is a hydraulic-adjusted wedge system that operates with the push of a button. As the opposing wedges go against one another, the hydraulic cylinders open or retract the CSS, making it a simple operation.

The second option is the use of a hydraulic toggle plate, which eliminates the opposing wedge system, while adding hydraulic cylinders to the backside of the crusher to operate the CSS system. The hydraulic system will react to a tramp event or to excessive force, and the cylinders will retract the CSS, letting material pass through before returning to the original setting.

Optimum crushing efficiency at the primary jaw crushing circuit leads to similar performance in all the circuits that follow – delivering greater productivity, profitability, and the lowest costs per ton.

Tech Tip: Selecting Jaw CSS

Maintain the Right Closed Side Settings

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