During commissioning of a 6000volt, 2000kw Motor powered Forced Draft Fan, the Fan was center supported by Two Spherical Roller Bearings (22232),one at each end.

The fan was producing high noise when running at its rated load and speed of 1485 rpm. We suspected High Vibrations from unbalance or Misalignment. When measuring and analyzing vibrations at all the bearings in Three directions, the levels were NORMAL (Max. 1.9mm/s, at 758Hz in the Fan drive End bearing Axial).

Measurements at this specific bearing casing were very difficult, since the analyzer gave an overload signal in any direction of measurement, and we could not be able to take readings except after ISOLATING the base of the accelerometer.

Investigating the bearings showed serrations at the outer race with brownish marks on the rolling elements, (see attached Photos).

We suspected PASSING of CURRENT from the bearing casing through the bearing components ,or from rotor to casing, (Many Photographs of the Phenomena are available ).

The Question is :What are the possible Sources of this current leak?.

Click Here to See Bearing Fault Analysis

Procedure of Damage Progress in the Forced Draft Fan for
Unit #5 of Aboquir Power Station