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AEGIS® PRO Series Rings Protect Pulp and Paper Plant Motors from VFD-Caused Bearing Failure

Paper Roller

Downtime in paper plants due to VFD induced motor bearing damage can be extremely costly, not only in terms of repair costs for equipment, but in terms of lost production.

Paper making is very demanding. To ensure tight control over critical process parameters, many motors are controlled by variable frequency drives (VFDs or inverters). These drives can be used to control the motors driving all manner of pumps and fans, grinders, winders and rewinders, and a host of related equipment.


But while VFDs allow precise control of motor speed or torque, they can also damage motor bearings and cause costly unplanned downtime. These drives create voltages on the shafts of the motors they control — voltages that can discharge through motor bearings. The resulting electrical bearing damage can cause bearing failure and stop production.


So the VFD technology employed to improve paper making processes also creates damage that can shut them down instead.  Paper Rolling MachineThese preventable bearing failures can cost hundreds of thousands of dollars in damaged equipment, repair costs, and lost production.


AEGIS® Shaft Grounding Rings protect motor bearings (and coupled equipment) by channeling shaft voltage discharge currents away from bearings safely to ground


An AEGIS® iPRO Ring (below) protects a 1000 hp winder motor from VFD-sourced bearing damage by channeling destructive shaft voltage discharges away from its bearings and safely to ground.

An AEGIS® PRO Ring (below) protects a 1000 hp
winder motor from VFD-sourced bearing damage
by channeling destructive shaft voltage discharges
away from its bearings and safely to ground.

AEGIS® SGR Rings are sized for low voltage motors of less than 100 hp.  The AEGIS® PRO Series Rings provides the high current carrying capacity needed for larger and medium-voltage motors.


By preventing extremely costly process downtime, AEGIS® Rings generate an impressive return on investment.


For more information on the AEGIS® PRO Series Ring, click here.


To review ROI calculations for an AEGIS® PRO Series Ring, click here.


For a case study on the installation of AEGIS® PRO Series Rings at a paper plant, click here.

Vertical Pumps damaged by VFDsThe 2013 Public Works Manual featured a case study on a reverse osmosis plant whose vertical pumps suffered repeated bearing failures.  The failures were due to the variable frequency drives (VFDs) used to power the pumps.  VFDs can cause electrical current to flow through motor bearings, eventually causing fluting damage and bearing failure.

It took the plant two years, but they finally found the solution to their chronic fluting problem:  carrier insulation and AEGIS® Shaft Grounding Rings.  After that, the pumps ran for years without failure.

“If you install the rings beforehand, you avoid these problems altogether…
The cost is insignificant when you look at the total cost of a large project.”

To learn more, read the full article.

Garlock SGi™ with AEGIS™ SGR insideThe use of variable-frequency drives (VFDs) to control AC motors has increased dramatically in recent years. In addition to their low operating cost and high performance, they save energy. Today, the challenge facing system designers and engineers is to minimize damage to AC motors from shaft current. From its first minute of operation, a VFD induces destructive voltages that build up on the motor shaft until they find discharge paths to the frame (ground). In most cases, the motor bearings present the path of least resistance. Once voltage is sufficient to overcome the resistance of the oil film layer in the bearing, shaft current discharges, causing electrical discharge machining (EDM) pits and fusion craters in the race wall and ball bearings. This phenomenon continues until the bearings become so severely pitted that fluting, excessive noise, and failure occur. Continue reading

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