Oil level in the vertical motor lower bearing

[bopsyseng]

I have large (1750 hp)vertical AC motor on a pump. The oil gauge has standstill level and operating level bands. Before starting the motor the oil level was at the middle of standstill level however, after starting the motor the oil is 1/2" higher than top of the operating level band. No leaks or change in the operating temperature (150'F). PLease let me hear your thoughts.

 

[automatic2]

no change in operating temperature, that will be your key indicator. If your fluid had excessive detergents or other additives, you may see higher than normal foaming, which would indicate higher on the sight, and a subsequent rise in temp. Your looking Ok. As a general rule, the bearing should not be higher than 1/3 submerged to prevent churning. Again a temp rise would indicate this.

 

[bopsyseng]

We have not noticed any foaming. The standstill oil level mark will 1/2 submerge the bearing. The operating level is not suppose to change much however, we are noticing 1/2" increase.

 

[automatic2]

your spinning bearing will act somewhat like a centrifugal pump. As the clearances betwee housing and fluid reduce, the efficiency of this 'pump' increases. The results are fluids accumulating in voids. Electric motors drive bearings at elevated speeds (and temps, thus requiring 'C' class clearances). Care must be taken at these speeds to prevent overly flooding the bearing which can bring on a condition of churning. This condition is usually accompanied by temp rise.

Is it possible that sediments may be creating a damning effect in the housing, thereby allowing fluid accumulation at the sight port?, or the opposite, a metal deflector has been omitted in assembly, or broken away, that had been used to shield the sight port from pumped fluid flows.