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Case Studies

Case:

Gearboxes Crippled by Domino Failures


A gearbox on a high-speed conveyor system was expected to run continuously for 10 years with routine lubrication and inspection. After only 3 years, it suffered catastrophic failure. Investigation revealed a domino chain of failures: initial shaft misalignment increased load on bearings, which overheated and degraded lubricant. Contaminated lubricant accelerated gear tooth wear, leading to progressive vibration spikes and eventual gearbox seizure.

Case:

A large steel rolling mill relied on a gearbox containing cylindrical roller bearings to transmit heavy loads at relatively low speeds. These bearings were designed for long service life under clean lubrication conditions. However, after only 14 months of operation (instead of the expected 5โ€“7 years), operators reported rising vibration, noise, and temperature from the gearbox.

Case:

In a chemical processing facility, horizontal centrifugal pumps were used to transport high-temperature liquids across various stages of production. Each pump relied on thrust ball bearings to absorb axial loads generated by the impeller. Despite an expected bearing life of 3โ€“5 years, several pumps began showing signs of distress after only nine months. Maintenance teams observed abnormal vibration, elevated temperatures, and audible knocking, prompting a detailed failure investigation.

Case:

A mid-sized manufacturing facility operated a 200 HP vertical motor driving a process pump. The motor was 9 years old, running nearly 24/7, with thrust ball bearings supporting axial load from the pump column. The motorโ€™s insulation system had degraded due to prolonged thermal stress, vibration, and moisture ingress. During a scheduled outage, megger testing was skipped because the motor was considered โ€œstill running fine.โ€

Case:

A major automotive manufacturer began seeing premature thrust ball bearing failures in a new line of passenger vehicles equipped with high-torque, compact automatic transmissions. These transmissions used thrust ball bearings to handle combined axial and radial loads from the torque converter and gear train. After just 30,000โ€“40,000 miles of service, failures began appearing in warranty claims, with drivers reporting grinding noise, excessive vibration, and transmission overheating.

Case:

A fleet of delivery vehicles began experiencing premature wheel bearing failures within 18โ€“24 months of service, well below the expected lifespan of 5โ€“7 years. The wheel bearings in question were thrust ball bearing assemblies supporting both axial and radial loads. Maintenance logs revealed that during a service campaign, the original OEM-specified high-temperature lithium-complex grease had been replaced by a general-purpose calcium-based grease due to a supply substitution.

Case:

A fleet of long-haul heavy-duty trucks began experiencing premature wheel hub failures after approximately 180,000 miles of operation, well short of the expected 500,000-mile service life. The hubs used thrust ball bearings to carry combined axial and radial loads from both steering and trailer weight. Investigations revealed that due to overloading beyond the rated axle capacity, the thrust ball bearings were consistently subjected to forces exceeding their design limit.

Case:

A food processing plant operated a conveyor line driven by an induction motor coupled through a gearbox. The gearbox used self-aligning ball bearings designed for a maximum speed of 3,600 RPM. Due to a control loop fault in the Variable Frequency Drive (VFD), the conveyor motor intermittently spiked to 4,500โ€“5,000 RPM for short bursts. Operators did not notice these speed excursions since the line was still producing at normal throughput.

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