Case Study: Reduce Voltage in Coal Production Motors
Background
A leading coal production company approached Nye about a motor at their truck load out that experienced bearing failures from fluting corrosion on the raceways. Fluting is caused by electrostatic discharge through the inner and outer bearing races. The bearing failure was occuring in a variable speed motor used to drive a conveyor belt via speed reducers. The motor runs 20-40 hours per week at a speed of 1600-2200 rpms, and uses open, deep groove ball bearings. The company had twelve motors with the bearing failure problem, leading to costly down times.
Challenges
- Which grease can lower the induced voltage on the rotor shaft under 3 volts and stop the motor bearings from voltage-induced failure?
Solution
NyoGel® 758G
A stiff, lithium soap thickened, light viscosity, ester grease.
- Electrically conductive
- Excellent performance in demanding bearing applications
- Good channeling abilities
| Product | Chemistry | Temp Range (°C) | Oil Separation (24 hrs @ 100°C) | Evaporation (24 hrs @ 100°C) |
|---|---|---|---|---|
| NYOGEL 758G | Ester / Lithium Soap | -40 to 150 | 0% | 0.18% |
Results
The coal company tested NyoGel® 758G and found that the grease was able to lower the voltage induced on the rotor shaft from 17 volts down to .8 volts. After running for two weeks, the voltage reading was reading .31 volts without bearing failure. The hours until failure on the fan end bearing improved from the 400-450 range to over 1200 hours. The lubricant increased the life of the bearing by 300% and helped the motors achieve good mechanical performance.
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