In the world of power generation, the reliability of alternators is paramount. Recently, we encountered a significant challenge with a 1875 KVA Marelli alternator: the rotor bearing journal had been damaged due to a bearing seizure caused by a remarkable seven times unbalance found in the rotor. This incident underscored the importance of effective maintenance and precise engineering.

The Challenge: Rotor Bearing Journal Damage

When the rotor bearing journal sustained damage, it became clear that immediate action was required. The primary issue was the bearing seizure, which not only affected performance but also posed risks for future operations. Understanding the root cause—excessive unbalance—was crucial for preventing similar problems down the line.

The Rebuilding Process

To restore the alternator to optimal condition, we chose to rebuild the damaged bearing journal using a medium-carbon alloy known for its toughness and fatigue resistance. This material was specifically selected for its ability to withstand the stresses that alternator components face during operation.

During the rebuilding process, we focused on achieving a Brinell Hardness (HB) of 200-300 in the bearing journal surface area. This hardness level is essential for ensuring wear resistance, which is critical for the longevity and reliability of the component. Additionally, we maintained the required surface roughness to promote effective bearing performance.

Magnetic Particle test

We ensure the refurbishment area of the shaft is thoroughly examined using Magnetic Particle Testing (MPT). This non-destructive testing method allows us to detect surface and near-surface defects effectively, ensuring the integrity and reliability of the shaft after refurbishment. By utilizing MPT, we can identify any potential issues before they compromise the performance and safety of the component.

Achieving Dynamic Balance

After the rebuilding and calibration of the shaft bearing journal, the next critical step was dynamic balancing of the rotor. The rotor, weighing 2100 kg, underwent a rigorous balancing process to meet the standards outlined in ISO 21940 for rotor balancing. Achieving the required balancing tolerance not only ensures smooth operation but also significantly reduces the likelihood of future bearing failures.

Conclusion: A Step Towards Enhanced Performance

The successful rebuilding of the 1875 KVA Marelli alternator rotor is a testament to our commitment to quality and reliability. By using high-strength materials, adhering to strict hardness standards, and ensuring precise dynamic balancing, we have effectively mitigated the risk of bearing failure in the future. This project not only enhances the performance of the alternator but also reinforces our dedication to providing dependable solutions in power generation.

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