Abnormal vibration in vertical grinding mills (moulins verticaux) is a common issue that affects equipment stability and production efficiency. It is crucial to accurately diagnose the cause of vibration and address it quickly. The following outlines three main situations that cause abnormal vibration and their mechanisms:
1. Impact Vibration Caused by Running Empty
Phenomenon and Cause: When the mill runs without material or under no load, the grinding rollers and the grinding table (or ring) lose the buffering effect of the material. As a result, direct metal-to-metal contact and impact occur. This “hard contact” condition not only creates loud impact noise but is also the direct source of severe vibration.
Core Solution: To fundamentally prevent this problem, modern large vertical grinding mills are equipped with grinding roller limiters. These devices automatically restrict the downward travel of the rollers when they detect an overly thin material layer or a feed interruption. This effectively prevents direct contact between the rollers and the grinding table, thereby avoiding impact vibration from running empty.
2. Unstable Material Layer Due to Overly Fine Feed
Phenomenon and Cause: Stable operation of a vertical mill relies on forming a uniform and stable material bed on the grinding table. However, if the feed particle size is too fine (far below the design limit) or the required product fineness is too high, the material can easily be blown away by the air flow. Consequently, it becomes difficult to form an effective grinding bed. In this situation, the grinding rollers “bounce” on the unstable thin material layer, causing the equipment to operate similarly to an empty run and leading to periodic vibration.
Core Solution: Strictly control the feed particle size and product fineness requirements to ensure they remain within the equipment’s design limits. For special ultra-fine grinding needs, it is necessary to select specially designed mill types or adjust process parameters such as air volume and rotation speed to re-establish a stable material layer.
3. Structural Vibration Caused by Loose Mechanical Connections
Phenomenon and Cause: After long-term operation, key fasteners such as foundation bolts, roller tie-rod bolts, and shell connection bolts may loosen due to vibration. Loose mechanical connections compromise the overall integrity and rigidity of the equipment structure. As a result, the relative movement between components increases, leading to abnormal vibration. This type of vibration is often accompanied by irregular noise and can accelerate fatigue damage to other parts, posing a serious safety risk.
Core Solution: Establish and strictly implement a regular tightening and inspection system. Especially after major maintenance or before restarting following a prolonged shutdown, it is essential to systematically check and retighten the preload force of all critical bolts to ensure the reliability of mechanical connections.
Summary and Recommendations
Vibration in a vertical grinding mill is a key indicator of its operational health. When abnormal vibration occurs, operators should follow the principle of “observe first, analyze second, then act”:
Immediate Check: First, verify whether the material feed has stopped to rule out empty running.
Process Verification: Confirm whether the material particle size or fineness requirements are abnormal.
Mechanical Inspection: Systematically check the tightness of bolts at all key locations.
By following this targeted troubleshooting process—from simple to complex—most vibration faults can be quickly identified. This approach helps prevent minor issues from developing into major failures, ensuring production continuity and equipment safety.
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