Why is a Jaw Crusher with Pre-screening More Cost-Effective?This is what many people want to know.
In mining crushing and aggregate production sites, many customers encounter the following problems: high soil content and fine powder in the stone lead to easy clogging of the crusher after feeding, high mud content in the finished product, and accelerated equipment wear. The key to solving these problems lies in the pre-screening function of the jaw crusher—commonly known as the soil discharge belt.
I. Working Principle of Pre-screening
The pre-screening system of a jaw crusher typically consists of a vibrating feeder (bar screen) and a bypass belt (soil discharge belt).
When raw materials enter the crusher, the vibrating feeder first performs pre-screening:
Materials larger than the screen bar gaps (coarse material) continue to enter the crushing chamber and are crushed by the jaw plates.
Materials smaller than the screen bar gaps (fine material, mud, stone powder) fall directly through the screen bar gaps onto the bypass belt and are directly discharged.
The entire process is completed simultaneously during the feeding stage, requiring no additional equipment and not affecting the continuous operation of the crusher.
II. Why is a Jaw Crusher with Pre-screening More Cost-Effective?
- Increased Output
This is the most direct effect. If the raw material contains 20%-30% of small-diameter materials or soil that already meet standards, these materials will occupy the effective working space of the crusher if they enter the crushing chamber, resulting in a reduction in the amount of large materials that actually need to be crushed.
Pre-screening separates these materials in advance, allowing the crushing chamber to be used entirely for crushing large materials, effectively increasing production capacity by 15%-30%.
- Improved Finished Product Quality
If raw materials containing soil enter the crushing chamber directly, the soil will mix into the finished aggregate during the crushing process, resulting in excessive mud content in the finished product. For concrete mixing plants and asphalt mixing plants, aggregate with excessive mud content is substandard.
Pre-screening separates soil and fine powder before crushing, resulting in high-cleanliness and well-graded finished aggregate that directly meets high-quality aggregate standards.
- Prevents Blockages
During the rainy season or when high-soil-content stones (such as weathered rock and mountain stone) enter the crushing chamber, the damp soil and fine powder easily adhere to the jaw plates and crushing chamber walls, causing poor material flow and potentially leading to blockage and shutdown.
Pre-screening removes soil and fine materials in advance, keeping the crushing chamber clear and significantly reducing the risk of blockages.
- Reduces Equipment Load and Wear
Soil and fine powder do not need to be crushed. If they enter the crushing chamber, they not only waste crushing force but also:
Increase jaw plate wear (fine particles in soil are abrasive)
Increase the load on bearings and eccentric shafts
Accelerate equipment aging
Pre-screening reduces ineffective crushing, extending jaw plate life by 20%-40% and significantly reducing overall equipment maintenance costs.
- Reduces Dust
Soil and fine powder are repeatedly squeezed and ground in the crushing chamber, generating a large amount of dust. Pre-screening separates these materials in advance, ensuring that only large stones are crushed in the crushing chamber, reducing dust generation by 30%-50% and improving the on-site working environment.
III. Case Study
Background: A granite crushing plant in Jiangxi Province. Raw materials are sourced from open-pit mining, with a soil content of approximately 25% and a particle size of 0-600mm.
Before Modification: A conventional jaw crusher (without pre-screening) was used, with all soil entering the crushing chamber.
Output: Approximately 170 tons/hour
Jaw plate life: Approximately 500 hours
Finished product mud content: 8%-12% (some exceeding the standard)
Cavity clogging frequency: 2-3 times per week
After Modification: Replaced with a jaw crusher equipped with a pre-screening device; the pre-screening gap is 50mm.
Output: Increased to 220 tons/hour (+29%)
Jaw plate life: Extended to 700 hours (+40%)
Finished product mud content: Reduced to 2%-4%
Cavity blockage frequency: Basically eliminated
Dust concentration: Reduced by approximately 40%
Economic benefits: After the upgrade, the monthly jaw plate replacement cost will be reduced by approximately 20,000 yuan, and the additional revenue from increased production will be approximately 50,000 yuan/month. The investment payback period is less than 2 months.
IV. Selection Recommendations
Scenarios where pre-screening is strongly recommended:
- Raw material with soil content > 15%
- Warmed rock, mountain stone, and other materials with high impurity content
- Rainy season construction (wet materials)
- Construction waste recycling
- Projects with high requirements for the cleanliness of finished aggregates
Scenarios where pre-screening is not required:
- Clean raw material with soil content < 10%
- Clean stone directly screened after blasting
- Short-term projects with limited budgets
V. Summary
The pre-screening function (exhaust belt) of the jaw crusher is a low-cost, high-return design. It achieves a comprehensive effect of increased production, improved quality, reduced consumption, and reduced dust by separating soil and fine materials before crushing. For materials with high soil content, pre-screening is not just an added bonus, but an essential configuration.
All Suhman mobile jaw crushers come standard with a pre-screening function, which can flexibly adjust the screen bar gap according to material characteristics to ensure optimal performance under different operating conditions.
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