Jaw Crusher Feeding Issues Explained: Causes and
Solutions for Material Backflow and Discharge Blockage
Many users have recently reported issues of material backflow and no discharge during the operation of jaw crushers. These problems not only reduce production efficiency but also pose risks to equipment safety. This article provides a comprehensive analysis of these common failures, using jaw crushers as a case study, and offers practical solutions to help users maintain stable equipment performance.
1. Material Backflow in Jaw Crushers: Causes and Solutions
1.1 What Is Material Backflow?
Material backflow refers to a situation where the crushed material fails to discharge properly and flows back toward the feed inlet, sometimes even ejecting out, which may lead to blockages or safety hazards.
1.2 Common Causes of Backflow
✅ Equipment Design or Wear Issues
- Mismatched dimensions of key parts such as jaw plates, toggle plates, or the inner cavity;
- Excessive wear on jaw plates may increase the angle between the jaws beyond twice the material’s friction angle, reducing effective clamping force and causing upward material displacement.
✅ Uneven Force Distribution
- Vertical forces generated by the moving jaw may become imbalanced, especially the upward force component, which tends to push material toward the inlet.
✅ Oversized Discharge Opening
- Contrary to popular belief, a wider discharge opening may increase the risk of backflow by reducing friction and material confinement.
✅ Large Particle Size Variance in Feed Material
- Irregular feed sizes disrupt smooth flow, and larger pieces can obstruct smaller ones, forcing material backward.
1.3 Solutions for Backflow
✅ Optimize Equipment Design and Setup
- Regularly inspect and correct key part dimensions;
- Replace heavily worn jaw plates;
- Install wedge-shaped spacers between the jaw and moving jaw plate to reduce the angle, keeping it below twice the friction angle to eliminate upward backflow forces.
✅ Improve Feeding and Crushing Process
- Pre-screening: Use a vibrating screen to ensure uniform feed size;
- Adjust feed rate and size to prevent overload;
- Consider a multi-stage crushing setup (primary + secondary) for better handling of irregular materials.
✅ Safety Measures
- Install protective guards above the feed opening to prevent injury from ejected material.
2. Discharge Blockage (No Material Output): Causes and Solutions
2.1 What Is a No-Discharge Problem?
This occurs when crushed material fails to leave the crushing cavity, causing blockage or jamming, which may even force a shutdown of the equipment.
2.2 Common Causes of Discharge Blockage
✅ High Moisture or Impurities in Material
- Wet or muddy materials tend to stick to the cavity walls, leading to accumulation and blockage.
✅ Overfeeding or High Feed Rate
- Excessive or too rapid feeding overwhelms the discharge section, causing material buildup inside the crushing chamber.
✅ Presence of Uncrushable Items
- Metal scraps, iron blocks, or overly hard materials may damage jaw plates and hinder discharge.
✅ Incorrect Motor Wiring or Configuration
- Issues such as reverse motor rotation or improper star-delta connection may cause mechanical reversal or insufficient torque.
✅ Low Operating Voltage
- Insufficient voltage leads to weak motor output, slowing down or completely stopping the discharge process.
2.3 Solutions for No-Discharge Issues
✅ Ensure Stable Power Supply
- Check for proper wiring and correct motor connections;
- Upgrade power supply if voltage is consistently below rated levels;
- Use voltage regulators or stabilizers to ensure consistent power delivery.
✅ Control Feeding Parameters
- Feed continuously and evenly based on equipment specifications;
- Avoid sudden surges in material input.
✅ Pre-screen and Remove Impurities
- Remove iron, stones, and other non-crushable items before feeding;
- Dry or screen moist materials prior to crushing to reduce clogging.
✅ Match the Right Equipment to the Material
- Ensure the crusher model fits the required feed size and crushing capacity;
- Always refer to the user manual for guidelines on feed size and output expectations.
✅ Follow Operating Procedures
- Only trained personnel should operate jaw crushers;
- Avoid unauthorized modifications to settings or running parameters.
3. Equipment Usage and Maintenance Tips
- Perform regular maintenance on jaw plates, bearings, belts, and motors;
- Clean the crushing cavity after each shift;
- Use pre-screening systems to improve material quality;
- Keep operation logs and establish a regular maintenance schedule.
4. Frequently Asked Questions (FAQ)
Q1: Is frequent backflow a sign of poor equipment quality?
Not necessarily. Backflow may result from improper setup, worn components, or feed issues. Start by checking jaw plate angles and wear levels before suspecting manufacturing defects.
Q2: Can jaw crushers handle wet materials?
Wet materials can cause clogging or discharge issues. Solutions include drying the material beforehand, using pre-screeners, or lowering feed rate with larger discharge settings.
Q3: What should I do if the motor is running in reverse?
Stop the machine immediately. Check motor wiring, especially for 3-phase power. Have a qualified electrician correct any reverse wiring or star-delta configuration errors.
5. Conclusion
Jaw crusher issues like backflow and no-discharge are common but manageable. By understanding their root causes and applying appropriate fixes, users can maintain smooth and efficient crusher operations. Regular inspections, proper feeding, and adherence to operating procedures are key to avoiding downtime and extending equipment life.
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