Axial Float Problem in 275kw Motor

Insert 0.30mm shim somewhere?

Is the float the bearing itself or is the float within the bearing?

If the bearing is moving, yes, shim the bearing.

If it is the bearing itself. perhaps you could use a tapered roller bearing, oriented correctly, instead? These handle thrust loads much better.

I believe there is a ball-type bearing designed to handle thrust, also.

I'm surprised a motor of this size does not use some type of thrust bearing.

"I'm surprised a motor of this size does not use some type of thrust bearing."

Me too, that's the usual design for this kind of application. Did someone make this pump themselves and use an off-the-shelf industrial motor? If so, they apparently were not aware of the concept of a thrust bearing.

http://en.wikipedia.org/wiki/Thrust_bearing

There are other things you can do as well to reduce the thrust in axial pumps.

http://centrifugalpump.org/thrust_axial.html

Deep groove ball bearings can take thrust loads too.

when you say marathon , are you talking a hagglunds marathon motor , or an electric motor banded Marathon ???

please confirm

I don't know about hagglunds marathon motor. It's an electric motor of Marathon make.

No, I'm not talking about effect of thermal expansion. Its a result of simple check in cold and decoupled condition. Normally electric motors fitted with such bearings have axial float limited to about 0.1 mm.

Off late, checked 3 other motors of Marathon make (all 4 are new installations), found similar result, between 0.3 to 0.4 mm. Inquired with OEM (Marathon), they say up to 0.3 mm can be allowed.

Is the reply of OEM is satisfactory, when electric motors of other makes fitted with such bearings have axial float limited to about 0.1 mm?

very good answer

this is why many twin bearing shaft assemblies will have one captive bearing with interference fit , and another floating bearing to accomodate axial expansion due to thermal variations.

i sometimes use a spherical bearing on one end of a shaft which are great for both radial and axial loads , with the second bearing being a floating race , such as NU324 cylindrical roller.

these allow for up to 2.5 mm axial movement , and interference fit can be used on the races to prevent spun bearings which can occur in cases where a floating bearing fit is used

win-win situation

Call these people and talk the problem through with them.