Want to lower HIGH horiz vibe readings ! 1

[nisqually]

Greetings -


- pulley
fan - -------------|||---shaft
- /\ /\ |
- brg4 brg3 | belt
|
motor|||pulley

What could cause high horizontal readings on the motor bearings? Pulley misalignment? Belts too tight? Belts too loose? The motor bearings are sealed and not regreasable. Shaft guard prevents getting horiz readings on fan shaft bearings at this moment. What course of action is recommended to bring down the horizontal vibe?? See numbers below. Questions are welcome. Answers are too.

ODE motor bearing .75 in/sec peak at 1XRPM (3750)
DE motor bearing .57 in/sec peak at 1xRPM (3750)

 

[electricpete]

Checking phase will certainly give good info.

I would like to take a moment to mention that there probably is no right approach for all situations. Depends on your situation. (Availability of the machine for running-tests, for shutdown maintenance, availability of maintenance vs predictive manpower etc).

I don't think that going after the belt/pulley system based on what you have already is trial and error. What else (besides belt/pulley system) is going to cause highest 1x-fan rpm appearing on the motor? And since pulley alignment and belt tension cannot be adjusted independently there's not much sense in discriminating between those. Add on a pulley runout test adds another 10 minutes.

OR... you could spend another week gathering and analysing data. And how much more conclusive will your diagnosis be? And by the way is that motor still shaking at 0.75ips the whole time your analysing? Just some food for thought. As I said, there is no single right answer.

 

[Franko]

May want to check Robinson Fan article:

http://www.robinsonfans.com/protect/ommanual.pdf

 

[nisqually]

thank you very much Franko. Millwrights replaced shaft bearings and belt and the readings are even worse at the motor and shaft bearings. also the motor mounting bolts are actually in the horizontal direction! I should have noticed that last time.

I notice robinson doesn't differentiate between horizontal and vertical, they just use radial. I find that interesting.

 

[electricpete]

You say the motor mounting bolts are in the horizontal direction. Can you explain that some more.

(Typically on fan applications I have seen vertical bolts mounting the motor to a light metal frame/baseplate and vertical jacking bolts which move the light metal frame/baseplate with respect to the pedestal.)

 

[nisqually]

sure. what I mean is the motor is bolted to the wall, not the floor. and it's bolted to a flimsy mounting plate that has no real jacking bolts so they can't get the proper tension on the belt for one thing.

I would very much like to figure out a new mounting arrangement for the millwrights if you know where I can look on the internet for mounting suggestions.

The readings are worse than last time.
4/09/03 in/sec rms overall machine vibration
3/26/03 in/sec rms (in parenthesis)
_____________
H V A
Bearing 1(RPM) .81 (.61) .23 (.13)
Bearing 2(RPM) .67 (.48) .30 (.17) .30 (.11)
Bearing 3(RPM) .31 .06 (.06)
Bearing 4(RPM) .19 .36 (.28)