I'm sure most of you have noticed that horiziontally oriented, face mounted motors (Which make the motor rotor an over hung unbalance) can have high vibration outboard vert. Sometimes there are significant resonances also.


My question is this: Have you noticed a higher rate of bearing failure on such installations?

Vertical installations for face mounts, to me, have less noise, lower vibration levels, and fewer failures, not to mention they use less floor space. Agree/disagree?

Martin,

I have taken vibration readings on these types of motors for many months and I always called them out as having "looseness at the free end of the motor..." (not imbalance) because the vibration was highest in the vertical direction. My Recommendation? "Craddle the motor and anchor to the base." It never got done. But, (to answer your question) rarely have I ever seen a motor lose the ODE bearing because of this (analyze the waveform for impacts). Usually its the reducer or the pump (work unit) that gets failing vibe grade.

I did however see a similar type motor bolted to a screw compressor - the ODE bearing did fail after about 2 years of operation. It was later found through bearing post mortem analysis that the bearing showed signs of "misalignment".

I hope this helps.

DANV

Martin,

I don't agree that a C-face motor has an overhung motor rotor. The motor case is cantilevered, but the rotor has an outboard bearing for support. A true overhung rotor has its dominant mass beyond/outside the support bearings; such as a fan rotor.

Walt

Walt:
Yea, thats true. Typically though, an outboard bearing has some means of support, in this case it moves along with the rest of the motor case.

Do you think vertically mounted C face motors have a lower failure rate than horizontally mounted C face motors?

The NDE bearing is a c flange mounted motor usually has such no stresses that if rarely fails. This is due to the fact that the motor shaft,bearing, and bracket all move together, in phase, almost the same magnitudes.
The case of the motor that failed within 2 hours, check to make sure the bearing wasn't preloaded by an incorrect coulping spacing. This has been the case with man Cooper turbo compressors.
As far as vertically mounted, just make certain the fixed bearing can carry the load, since it will now support the entire static load of the shaft/coupling/etc. and also, if there is any dynamic loading from the driven equipment, say thrust from a fan, that too is now carried all by the one fixed bearing.
I once saw a footed motor mounted on a 45 degree angle in an OEM's machine and asked if he considered the added load on the fixed bearing. The look told me everything I needed to know.

Ron,

I've seen that look from gearbox owners with vertical drives that weren't designed for vertical applications.

Ron makes a good point about "everything moving together." Is there more stress on the bearings than if there were no vibration present? Surely. Is it significant? Probably not. I monitor a lot of machines with "high" vibration that never change and never fail.

Most of us are actually "machinery analysts" as opposed to simply being "vibration analysts."

I would not make the simple assumption that the outboard (NDE) bearing sees no load because everything is moving together. Motor rotor unbalance would load the bearing and so would misalignment at the drive end. I don't encounter many C-face motors, but I don't believe that they are immume to the same faults as other motor arrangements.

Walt

I was more interested not in vibration theory.. that conversation as we know, can go on forever, but rather in field experience with these installations.

Is there any reason to prefer one over the other? That is Horiz verses Vert C face mount?