Preventing Downtime and Spoilage in Paper Mills

Protect Pulp and Paper Plant Motors from VFD-Caused Bearing Failure and Prevent Downtime

Papermaking is very demanding. To ensure tight control over critical process parameters, many times variable frequency drives (VFDs or inverters) control motors. These drives control the motors driving all manner of pumps and fans, grinders, winders, and re-winders, and a host of related equipment.

 Downtime in paper plants due to VFD-induced motor bearing damage is extremely costly, not only regarding repair costs for equipment but lost production.

Potential (but avoidable) Pitfalls

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

So the VFD technology employed to improve papermaking processes also creates

AEGIS PRO Ring installed on Medium Voltage AC Motor

Damage that shuts them down instead! These preventable bearing failures cost hundreds of thousands of dollars in damaged equipment, repair costs, and lost production.

AEGIS PRO Series Ring

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

The AEGIS PRO Series design provides reliable shaft grounding for medium voltage large low voltage AC motors and large DC motor-driven applications to divert harmful shaft voltages to ground and extend bearing life.

Best Practice

Bearing Protection Handbook

To follow best practices, install the AEGIS PRO on the DE to discharge induced shaft voltages to ground and insulate the bearing on the opposite end (NDE) to stop high frequency circulating currents.  Large motors often have much higher induced shaft voltages and bearing currents.  The six circumferential rows of conductive microfiber provide the extra protection for these high current applications.

Designed for:

• Large frame low-voltage motors: 500 HP (375 kW) or greater
• Medium-voltage motors
• DC motors: 300 HP or greater

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

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 smaller HP motors, use AEGIS SGR Rings (2 rows of fibers) sized for low voltage motors to discharge capacitively-induced shaft voltage installed on the DE. Note that insulated bearings on the ODE are still needed on motors over 100 HP because of the HFCC in all VFD driven motors over 100 HP.

Motors up to 100 HP do not have HFCC and therefore only one AEGIS SGR Ring is needed.

More Information

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