Expert Solutions for Crushing & Grinding Equipment Problems

Unplanned downtime of crushing equipment and grinding mills is a critical event that halts production and puts immense pressure on operations teams. A sudden stop or violent vibration requires immediate, accurate diagnosis to restore operation and prevent further damage.

This handbook provides a symptom-based troubleshooting guide for operators and maintenance personnel. It outlines a systematic approach to quickly identify the root causes of common faults in crushers and mills and provides clear, actionable solutions to minimize costly downtime.

In a high-pressure production environment, a fast and accurate diagnosis is essential. This guide is designed to be a practical tool used directly on the plant floor, moving logically from the observable symptom to the underlying cause and its resolution. It prioritizes safety and operational efficiency, helping teams move from reactive repair to proactive maintenance.

Why Would Equipment Suddenly Stop, and Where Should Inspection Begin?

A sudden stoppage of a primary crusher or grinding mill is one of the most serious faults, bringing the entire downstream process to a standstill. The cause can be electrical or mechanical, and a systematic check is the fastest way to identify the issue.

A sudden stop is typically caused by an electrical trip due to motor overload, a severe material blockage in the chamber, or a critical mechanical failure like a seized bearing. The initial inspection should always start at the electrical control panel, followed by a safe inspection of the machine’s chamber.

Before any inspection, all safety procedures must be followed. The equipment must be electrically isolated, locked out, and tagged out (LOTO) to prevent accidental startup.

Rapid Diagnostic Procedure for Sudden Stoppage

This table provides a step-by-step diagnostic sequence, starting with the most common and easiest-to-check causes.

Possible Cause	Inspection Point	Solution	Safety Precaution
Motor Overload Trip	Electrical control cabinet (check for fault codes/lights).	Reset the motor overload relay. If it trips again immediately, investigate the mechanical causes below.	ALWAYS de-energize and LOTO before opening panels or inspecting the machine.
Severe Material Jam	Crushing/grinding chamber. Check for oversized, uncrushable material (e.g., tramp metal) or packing of sticky/wet material.	Manually and safely clear the blockage. For tramp metal, review upstream screening and magnetic separation.	NEVER reach into the chamber. Use appropriate tools and cranes. Ensure machine is LOTO.
V-Belt Failure	Drive guard area. Check for broken or slipped V-belts.	Replace the entire set of V-belts. Check pulley alignment and belt tension.	Isolate and LOTO the machine before removing any guards.
Bearing Seizure	Main bearings. Check for extreme heat (use an IR thermometer), discoloration, or signs of metal fragments.	This is a critical failure requiring immediate, major repair and bearing replacement.	Do not touch hot bearings. Ensure the machine is fully stopped and isolated.

The Equipment Emits a Harsh Noise or Impact Sound. What Is Broken?

Abnormal noises are an early warning sign of a developing mechanical problem. A sharp, metallic impact is different from a high-pitched screech, and identifying the sound’s nature is key to diagnosis.

Loud, intermittent impact sounds usually indicate loose or broken internal components, such as liner plates or blow bars. A continuous grinding or screeching noise often points to a failing bearing or inadequate lubrication.

Ignoring these sounds can lead to catastrophic failure. The equipment should be stopped safely for inspection as soon as possible.

Diagnosing Faults by Sound

Different sounds point to different problems. A trained ear can quickly narrow down the potential causes.

• Sharp Metallic Bangs: This is often the sound of metal-on-metal impact. The most common cause is a broken or loose liner plate in a Jaw Crusher or Cone Crusher. It could also be a broken rotor component in an Impact Crusher. Stop the machine immediately, LOTO, and conduct an internal inspection of all wear parts. Tighten all bolts to the correct torque specification or replace broken components.
• High-Pitched Squealing or Screeching: This sound is a classic indicator of bearing distress. It can be caused by a lack of lubrication, contamination of the grease, or the beginning of a bearing failure. Use an infrared thermometer to check bearing temperatures and review lubrication schedules.
• Low, Rumbling Growl in a Mill: In a Ball Mill, a change from a sharp, crashing sound to a low rumble can indicate a “lazy” charge caused by worn lifter bars on the liners or incorrect slurry density. This signifies a drop in grinding efficiency.

Why Is the Equipment Vibrating So Much It Seems Unstable?

All crushing and grinding equipment has a normal operational vibration level. However, a sudden increase or excessive vibration is a serious symptom that indicates an imbalance or a structural issue that requires immediate attention.

Excessive vibration is most often caused by an unbalanced rotating assembly (e.g., a worn or broken rotor in an impact crusher), unevenly worn wear parts (liners), or a failing main bearing. In some cases, it can be caused by issues with the machine’s foundation or support structure.

Continuous operation under high vibration will cause fatigue damage to the machine’s structure and can lead to catastrophic failure of shafts and bearings.

Troubleshooting Excessive Vibration

A systematic approach is needed to isolate the source of the imbalance.

Possible Cause	Inspection Point	Solution	Safety Precaution
Unbalanced Rotor	Impact crusher rotor. Check for broken, cracked, or unevenly worn blow bars. Check for material buildup on one side of the rotor.	Replace blow bars in a full set to maintain balance. Clean any material buildup.	ALWAYS LOTO before inspection. A rotor can move unexpectedly.
Uneven Liner Wear	Crusher/mill chamber. Visually inspect the wear profile of the manganese liners or mill liners.	Rotate or replace wear parts to ensure the wear profile is even around the chamber.	Follow the manufacturer’s procedure for liner replacement. Wear parts are extremely heavy.
Foundation Issues	Mounting bolts and support structure. Check for loose foundation anchor bolts. Look for cracks in the concrete or steel structure.	Tighten all foundation bolts to the correct torque. If structural issues are found, consult a civil engineer.	This work should be done during a planned shutdown.
Main Bearing Failure	Main eccentric shaft bearings. A failing bearing can cause erratic movement and severe vibration.	Monitor bearing temperatures. If failure is suspected, schedule an immediate replacement.	Isolate machine. High vibration can make the area around the machine unsafe.

Why Is the Final Product Size Out of Spec, Either Too Coarse or Too Fine?

Consistently producing the correct product size is essential for the efficiency of the entire plant. When the product gradation suddenly changes, it points to a problem with either the machine’s settings or its wear parts.

An incorrect product size is usually caused by worn-out wear parts (liners, blow bars, hammers), an incorrect machine setting (like the Closed Side Setting on a cone crusher), or a change in feed conditions. In grinding circuits, it can also be due to inefficient classification.

This is often a process issue rather than a mechanical failure, but it has a direct impact on profitability.

Correcting Product Size Issues

• Inspect Wear Parts: The first step is to perform a visual inspection of all primary wear parts. As liners or blow bars wear, the geometry of the crushing chamber changes, which directly affects the product size. If the profile is significantly worn, replace the parts.
• Verify Machine Settings: For crushers with adjustable settings, like the Closed Side Setting (CSS) on a cone crusher, verify that the setting is correct and has not shifted during operation. Calibrate the sensor or perform a manual check (e.g., a lead sinker test).
• Check Feed Conditions: A significant change in the feed material (e.g., wetter, stickier, or finer) can impact the crusher’s performance and product shape. Ensure upstream screens are not blinded, which would allow excess fine material to bypass and enter the crusher.
• Review Grinding Circuit Classification: In a Ball Mill circuit, producing a product that is too coarse is often a problem with the Hydrocyclone classifiers. Check cyclone pressures, inspect for worn internal components (apex, vortex finder), and verify slurry density.

The Bearing Temperature Alarm Is On. Should an Immediate Shutdown Occur?

Bearing temperature is a critical indicator of machine health. An alarm indicates that a bearing is generating excessive heat, which is a symptom of a serious underlying problem.

Yes, a high-temperature alarm on a critical bearing (like a main or eccentric bearing) warrants an immediate and controlled shutdown of the equipment. Continued operation risks catastrophic bearing failure, which can destroy the shaft and housing, leading to extremely costly and lengthy repairs.

While an immediate shutdown is necessary, the cause must be diagnosed before restarting.

Diagnosing Bearing Overheating

Possible Cause	Inspection Point	Solution	Safety Precaution
Lack of Lubrication	Grease lines, lubrication pump, grease levels.	Check for blocked or broken grease lines. Ensure the auto-lube system is functioning and the reservoir is full. Manually purge the bearing with fresh grease.	Do not touch hot bearing housings. Use appropriate PPE.
Incorrect Lubricant	Lubrication records and grease gun/system.	Verify that the correct type and grade of grease/oil (e.g., EP2 for heavy loads) is being used as per the manufacturer’s specification.	Using the wrong lubricant can be as damaging as using none.
Contamination	Bearing seals. Inspect for damage or wear that could allow dust and water to enter.	If contamination is suspected, the bearing may need to be flushed and repacked with new grease. Replace damaged seals.	Work area must be clean to prevent further contamination during maintenance.
Over-Lubrication	The bearing housing.	Over-greasing can cause the rolling elements to churn the grease, generating excess heat. Follow specifications for lubrication quantity and frequency.

How to Move from “Firefighting” to Prevention: A Daily Maintenance Checklist?

The most effective way to reduce unplanned downtime is to transition from a reactive “breakdown-repair” model to a proactive, preventive maintenance culture. A simple daily checklist is the foundation of this strategy.

A robust preventive maintenance program is built on frequent, routine inspections of key components. This allows operators to identify and address small issues before they escalate into major failures, saving enormous amounts of time and money.

This checklist should be performed by the operator at the start of every shift. It is a rapid health check for the equipment.

Daily Operator Inspection Checklist

Checkpoint	What to Look For	Action if Abnormal
1. Visual Walk-around	Leaks (oil/grease), loose bolts, cracks in structure, guard damage.	Report immediately to maintenance. Tighten loose guards if safe to do so.
2. Lubrication System	Correct levels in oil/grease reservoirs. No fault lights on auto-lube panel. Evidence of fresh grease at bearing seals.	Top up lubricants. Report any system faults.
3. V-Belts / Drive	Proper tension (no excessive sag). Signs of cracking, fraying, or glazing.	Report for tensioning or replacement.
4. Wear Parts (Internal)	When safe and visible, look for broken or excessively worn liners/blow bars.	Report to supervisor for scheduled replacement.
5. Temperature (Post-Startup)	Use an IR gun to take baseline temperatures of key bearings.	Note any temperature that is significantly higher than normal and report it.
6. Sound (During Operation)	Listen for any new or unusual noises (banging, squealing, grinding).	Report the specific sound and location immediately.

Conclusion

Systematic troubleshooting based on clear symptoms is the key to minimizing downtime for crushing and grinding equipment. By moving from symptom to cause, teams can perform repairs efficiently and safely.