Protecting bearings against electrical discharge from shaft

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Flowserve Corporation has announced the release of new Bearing Gard bearing isolator upgrade technology. Enhanced with the latest in electrical grounding capabilities, this technology is designed to extend bearing life and reduce operating costs for motors driven by Variable Frequency Drives (VFDs).

In recent years, VFDs have grown in popularity because of their ability to deliver greater system efficiency, extend motor life and optimize operating costs. However, VFDs operate by delivering power to the motor in a series of positive and negative pulses, which often results in unbalanced voltage that can accumulate in the motor shaft until it can find a path to ground.

Without proper grounding between the shaft and the motor housing, the bearings often become the path to ground. The resulting electrical discharge can drastically damage or even destroy the bearings in just a few months of service. Flowserve developed new Bearing Gard technology to directly address this challenge. With integrated electrical grounding protection in place, substantial elimination of shaft voltage is achieved, which helps to significantly extend bearing life.

The new Bearing Gard - with electrical grounding technology - dramatically increases electric motor reliability by guarding against the two main causes for premature motor failure: 1) bearing contamination and 2) damage due to electrical discharge.

The Bearing Gard is uniquely capable of resisting contamination at the entry point with its patented triple combination of static shut-off, O-ring-protected rotor/stator interface, and oversized contamination channels.


The newly added and industry-leading AEGIS grounding ring technology is designed to provide protection against bearing damage due to electrical discharge and/or fluting. The AEGIS grounding ring technology provides current-diversion methods, discharging harmful shaft voltage to the ground instead of through the bearing.

Key features include:

  • Static-sealing technology, preventing contamination under shut-off conditions
  • 360-degree grounding contact
  • Protection against bearing lubrication breakdown due to electrical discharge machining and contamination

Static shut-off design to increase reliability by preventing O-ring binding while providing large standard axial movement available in the industry