I have a new record at my site

MOTOR.doc (170 Kb, 217 downloads) a lil bit o' noise

have the motor bearings greased.. check again after, see how vibration amplitude repsonds to greasing.

motor rpm has alot to do with amplitude you have in your waveform.

Possibly run another month, depends on how it reacts to greasing.

Mike

How critical is this machine to operations? Is there a spare that can be brought on line if (when) this one fails? With your waveform showing an increase from about 2 to 160 g's pk-pk I wouldn't be predicting any future for this bearing. If I were monitoring it, I would tell my customer to change the bearing as soon as possible and let him know that the bearing is running on borrowed time. You've marked BPFO, do any other brg components show up in the data? Even if grease dampens the vibration, it won't fix the fault. Depending on what the motor is driving and the coupling type, the motor may run for a while without failure IF the driven unit can help support the drive end of the motor but I wouldn't take the chance unless you just have too.

Wow, that is scary. I'll bet it sounds like a jackhammer.

Out of curiosity, is the bearing housing temperature elevated at all?

Thanks for the replys. I probably should have titled this thread : "Look what I found / can you top this?" or something. It is a 5 HP motor driving a small pump. There is no on-line spare, so we have already scheduled it for replacement as soon as a new motor arrives. I just wanted to share with the board our site record. And yes, it is singing a sweet song

Not for long. Have you spectral profile data in g's? Interesting to predict exact time of failure or see how close one can get. Just a fun thing.

Here you go, Sam

motor_accel.doc (26 Kb, 131 downloads)

Congratulations, I think. Wow! My recent record is 35 g's on a 70 hp motor (10 pole - 715 rpm).

3MP075.doc (56 Kb, 69 downloads)

For a 5 hp motor driving a pump, if you keep it greased, 1-3 months, maybe longer. If you have clearance, and lubrication, and the cage doesn't come apart, it will run until something else (motor rotor, pump impeller) locks up.

And wow is a good term:

I expected to see some different stuff from what was displayed in the g's spectrum, however, dearly beloved - get the head-stone ready: born nn aaa 199n, died 19 JAN 2008. Seriously, it could go anytime but can't see it here next week.

That one is getting pretty bad but I think I may have you beat. Here is a 5 hp as well with an overhung fan.

2.5 months prior to these readings it looked like yours. Good Luck!

steam_fan.doc (48 Kb, 69 downloads)

This one actually never failed before they replaced the unit. They bought a new pump and motor assembly so the old bearing was never removed. I kept writing this up as an immediate priority and it was like the Energizer Bunny. Kept going and going. Thank goodness these guys already have faith in me or this my have blown any credibility since it never flew apart like I thought that it would.

Tyrone_Waveforms.doc (214 Kb, 64 downloads)

When I see high vibration at high frequency (like above 2000Hz) I get concerned about the frequency response of the mounted transducer system.

Bill stated the obvious. When you see those data presented with such levels and wonder about the system used and how things were done there is a question posed; is the data valid and reliable?

Regardless, giving the benefit of doubt, the thing must be bad at those magnitudes unless ??? Most 100 mV/g transducers will stand 50 g's, some 80 but you have to consider - how can anything on the planet stand 80!!!!!!!!!

My data was collected with a 2-pole magnet from a flat cast on the drive end horizontal. I won't argue over the accuracy of the data, but I can tell you I could hear the buzz from 75 yards away, and it is in an area populated with several pcs of rotating equipment.

If the motor is mounted on rigid foundation and if the motor casing/body is stiff enough and you are measuring vibration very close to bearing then with 40 Gs pk-pk value motor would run for max of 15 days.
With litte stiffness would survive for one month to one and a half month.

bye
Arun K

Send flowers on Fri to ensure they arrive Sat.

The high g-levels in the original machine are being generated at 2300 Hz. Given the mathematical relationship of acceleration to frequency, 80 g's at this frequency is not going to be as damaging as 80 g's generated at 1000 Hz (for example).

A practical example is the "slab lines" in a bad stretch of concrete interstate highway. What happens here is the individual slabs tilt down at the leading edge, and thus up at the trailing edge. Each joint becomes a "fault" in essence (you can see them plainly if you look back in your rearview mirror). Anyways, the faster I go, the smoother the ride. The slower I drive, the harder the jarring is.

This isn't a perfect example, but it illustrates the point somewhat that high g-levels at higher frequencies are not as bad as the same g-levels at lower frequencies. Plus, on small machines, the mass is relatively low, so the forces generated are proportionally lower.

All true and good points, Rusty.

Now, how many days would you give this thing? If I were on call, I would want it changed by the time I left on Friday.

quote:

, the faster I go, the smoother the ride. The slower I drive, the harder the jarring is.

The ride is not at the point of contact with the tire. Do you think the g level is higher or lower at high speeds? That suspension on that Arkansas Beamer must be doing something.

Of course I know that no one in Arkansas would violate a law by going above the speed limit