An ethanol plant in North Dakota was burning through motor bearings at an alarming rate. 

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Maintenance personnel at Red Trail Energy’s ethanol plan in Richardson discovered that ball bearings inside several large motors were failing much sooner than they should.

Ethanol Plant

Failing Motors

Writing at Chemical Processing, Red Trail Energy’s Kent Glasser illustrated the problems the plant faced while trying to keep up failing motors. Replacing motor bearings isn’t cheap. In addition to paying a service center for parts and labor, the amount of time a motor is out of service quickly adds up to lost production and revenue.

The manager of the ethanol plant became concerned with those frequent high repair costs and called in a grounding system specialist to troubleshoot the three problematic motors.

Processing Motor

Scott Fisher, the Chief Operating Officer at Sustainable Grounding Systems, had a working history with Red Trail when a North Dakota electrical contractor hired him to evaluate the grounding systems of the plant.

Fisher arrived at the plant in May 2017 and took initial readings from a 30 HP and 150 HP centrifuge motors and a 400 HP fan motor. He discovered that the bearings in these motors had premature damage. These damages occurred much sooner than the ordinary wear and tear normally displayed by bearings operating properly.

Sustainable Grounding Systems is a nationally recognized company providing electrical grounding design, installations and inspections throughout the United States.  Contact Scott Fisher at  +1 (701) 721-3306 or email at [email protected]

A Familiar Suspect

His leading suspect? Stray currents from VFD-induced voltages built up on the motor shafts and discharged through the path of least resistance: the bearings.

Fisher’s solution was installing shaft grounding rings from AEGIS®. Split AEGIS® SGR rings were installed on the centrifuge motors and an AEGIS PRO Series Ring on the 400 HP motor.

AEGIS® PRO Series Rings

The AEGIS® PRO Series Rings are especially well-suited for these environments. They are designed for large frame, low-voltage motors of 500 HP or greater, medium-voltage motors, and 300 HP or larger DC motors.

AEGIS<sup>®</sup> PRO Series Rings for Medium Voltage MotorsTo learn more about how AEGIS® PRO Series shaft grounding rings offer maximum bearing protection, download this guide to best practices.

The follow-up readings from the motors showed significant improvement. Measurements as high as 19 volts dropped to less than 1.3 volts, which is too low to create premature damage to the bearings.

Reaping the Benefits

By starting a program to improve control of its production process, Red Trail Energy installed VFDs on all their motors. The company reaps several levels of a rapid payback on their investment.

First, VFDs provide several energy-saving functions that, with the money saved from using less energy, it eventually pays for itself. Playing the role of a soft starter, a VFD prevents damage to the motor caused by the sudden onrush of current during the startup procedure.

AEGIS® Rings – Prevent electrical fluting damage in bearings

In Sum

Finally, AEGIS® grounding rings protect motor bearings from damaging shaft currents. By preventing shaft current from reaching and damaging the bearings, shutdowns due to constant motor repair saves the company hundreds of thousands of dollars in lost revenue.

Read the entire story in Chemical Processing on-line