Customer Case: Abnormal Noise & Vibration Failure of Ball Cage CV Universal Shaft Coupling

1. Customer & Equipment Overview

The customer is a large heavy-duty building materials enterprise with a 24-hour continuous production line for ore crushing and aggregate conveying. The faulty equipment is the main drive system of the belt conveyor, equipped with a 132 kW motor. A ball cage universal coupling is adopted at the transmission part to compensate for installation deviation, dynamic displacement and angular misalignment during operation, serving as the core transmission component of the whole conveyor line.

Operating under heavy load impact, frequent start-stop and heavy dust conditions, the coupling requires high sealing performance, wear resistance and load capacity. After one year of operation, regular abnormal noise and excessive vibration occurred at the transmission end. Conventional maintenance such as bolt tightening and grease refilling failed to solve the problem completely. There were risks of coupling jamming, fracture and production line shutdown. The customer commissioned our technical team for on-site inspection and rectification.

2. Fault Phenomenon

The fault shows typical characteristics of ball cage coupling failure. Abnormal noise is slight under no-load condition. When the equipment starts with load, materials climb or impact load occurs, dull, regular "clunking" impact noise appears at the transmission end. As the fault worsens, the noise intensifies under full load. The vibration at the input end of the reducer rises continuously with periodic body jitter. The impact at start and stop becomes obvious, accompanied by instantaneous torque fluctuation. If the equipment continues running with faults, steel ball seizure, raceway spalling and universal joint failure may occur, leading to coupling breakage and shutdown, causing direct production losses.

3. On-site Inspection & Testing

Our technicians conducted no-load / full-load comparison tests, acoustic diagnosis, vibration measurement and disassembly inspection. Motor faults, reducer bearing damage and unbalanced belt tension were ruled out one by one. The root cause was confirmed to be the failure of the ball cage coupling itself.

Disassembly inspection revealed that the sealing structure of the original coupling aged and failed. A large amount of dust and impurities entered the cavity, causing grease caking and deterioration and loss of lubrication protection. Long-term dry friction resulted in steel ball wear, pitting and scratching on inner and outer raceways, with excessive assembly clearance. In addition, dynamic angular misalignment existed during operation. The worn steel balls rolled unsmoothly and stuck intermittently. Recurring rigid impact under load fluctuation generated persistent abnormal noise and periodic vibration. The measured vibration value exceeded the allowable standard seriously.

4. Root Cause Analysis

Three core causes were summarized: First, the original coupling had insufficient sealing grade and wear resistance, which could not adapt to the harsh environment with heavy dust, heavy impact and continuous angular compensation, prone to dust ingress and wear. Second, sealing rings were damaged without timely replacement. Dust invasion destroyed the lubrication system and triggered dry wear, gradually aggravating component wear. Third, routine maintenance was inadequate. The site only performed simple tightening and grease refilling, without regular inspection of sealing status, cavity cleaning and wear clearance detection. Minor hidden dangers accumulated and eventually developed into structural transmission faults.

5. Rectification Solutions

To ensure continuous production, we formulated a rapid rectification plan:

1.Replace with a new heavy-duty upgraded ball cage coupling with reinforced double-layer dust-proof sealing structure to improve wear resistance, impact resistance and anti-dust performance.

2.Fill high-performance extreme-pressure heavy-duty grease to maintain stable lubrication under variable angles and high loads and eliminate dry friction.

3.Re-calibrate installation accuracy with professional instruments to optimize shaft alignment and dynamic angular offset, reducing continuous compensation load and wear of the coupling.

4.Develop a special maintenance plan for the customer, specifying quarterly seal inspection, semi-annual grease replenishment and annual disassembly inspection, to prevent fault recurrence.

6. Rectification Result & Case Summary

After rectification, the equipment runs smoothly under no-load and full-load conditions, free of abnormal noise, jamming and periodic vibration. Torque output remains stable and vibration readings return to the standard range. The equipment has been operating stably for more than 12 months without recurrence of faults. Maintenance frequency, shutdown risks and production losses are greatly reduced.

This case demonstrates that abnormal noise of ball cage couplings under heavy dust and heavy load conditions is mostly triggered by sealing failure, loss of lubrication and excessive clearance caused by component wear. Proper product selection matching working conditions, precise installation alignment and standardized periodic maintenance are critical to eliminating coupling faults and ensuring long-term stable operation of heavy-duty transmission equipment.