Test ran a vertical Flygt pump/generator at the shop today. Ran it up to 1800 RPM and started hearing an awfull sound coming from the ODE bearing (NU 314). The noise was very sparatic and to me sound like the nu bearing was skidding. I took vibration data but really could not capture the noise besides somewhat in the waveform. Any input on what would cause bearing skidding and how to cure the problem ??

Thanks for any help.

What's a pump/generator and which end would be the drive end?
Horizontal or vertical? If horizontal, how much do you think the rotor weighs? Any belts on this machine? Grease or oil lub?

The typical reason for skidding would be not meeting the minimum load. Poor lubrication can contribute.

I have seen this on a another brand of similar pump type. It gave strange data, eventually it was resolved by a new bearing mount and it was a near brand new unit only a couple of weeks operation. Likely it was a problem with the casting and fitting of that bearing assy. Olov

quote:

What's a pump/generator and which end would be the drive end?
Horizontal or vertical? If horizontal, how much do you think the rotor weighs? Any belts on this machine? Grease or oil lub?

Flygt Makes vertical pumps that act as pumps or hydro generators. The Drive end connects to the turbine via a spring loaded spline shaft. This is a vertical unit, no belts. Grease lube.....

My concren is that the Nu bearing on the top of the motor is not recieving any radial load. I read somewhere elese that sometimes by inducing some unbalance to the rotor this can put enough lopad on the bearing. The rotor was balanced down to .1 mils in the shop a little extra unbalance wouldn't hurt it.

I agree with you. NU bearing (cylindrical roller bearing) in a vertical machine seems like asking for trouble. Seems like a very bad design. NU requires much more radial load to avoid skidding than similar size deep groove/conrad ball bearing. Also NU cannot be loaded in the axial direction to prevent skidding like a deep groove ball bearing can. As you say, adding some unbalance might help. If the machine goes to a shop, evaluate the possibility of putting a deep groove in instead of that NU.

It should get hot if it´s skidding? In my case a Grundfos vertical pump, it never got warm. I think it maybe only is the rollers rattling when not loaded as I and some others have found in CARB bearings that basically only is a variation of a roller bearing. In my pump case it may have been that the casing was oval due to the casting, swapping the cast part solved it. Making a minimal adjustment so the bearing is at an angle towards the shaft make it dead silent in the CARB case and what you do is getting it loaded. I agree the choice of having a roller bearing in that position don´t seem to be that good. Olov