A couple of years ago, the plant manager decreed that all motors over 10HP would have vibration monitoring. Because problems can be nipped in the bud and nipped during scheduled downtime rather than during an unexpected failure, this has dramatically improved equipment availability and plant output. In nearly every case, the motor pedestal was weak or the motor wasn’t mounted properly. In one case, the foundation had cracked and was replaced with one made of reinforced concrete. But one motor in particular has no foundation or pedestal problems but continues to vibrate.
What should you check?
Motor vibration can result from causes other than motor mounting problems. Using a good laser alignment system, and ensure the motor is properly aligned to its load. If it still vibrates after that alignment, some possible causes include:
- Coupling problems. A common example is a misaligned belt or sheave.
- Load mounting problems. If the motor drives a load that vibrates due to poor mounting, that vibration will be felt at the motor.
- Load lubrication deficiencies. A common example is a gearbox with lubrication problems. For a quick check, look at the gearbox temperature. It should not be appreciably 100°F (assuming the typical production floor ambient temperature).
- Load design problems. A common example is an air distribution system in which the compressor outlet piping is too small. In addition to causing high air velocity (over 30 fps) it could also cause vibration feedback from the downstream piping.
