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]

Is it 1x rpm of the fan showing up on the motor? I assume this is the case since 3750 is not likely a motor speed unles you have an electronic drive.

Does the belt lie horizontal between sheaves, vertical between sheaves, or at an angle?

Did you check axial on the motor as well? How about fan readings? Did you leave 'em out because they were much lower?

Was there a sudden increase?

 

[nisqually]

Most likely the fan RPM *is* showing up at the motor.
Motor RPM must be 3600 RPM. Belt is at an angle. Here are all readings at the biggest spike.

H V A
Bearing 1(RPM) .748(3750) .171(3600)
Bearing 2(RPM) .569(3750) .215(3600) .089(3750)
Bearing 3(RPM) .062(3750)
Bearing 4(RPM) .39 (3750)

New vibe program. First time readings taken on this fan.
I'm thinking fan shaft imbalance?? ---Nisqually--

 

[electricpete]

I wouldn't think fan unbalance would create vibration at the motor. I would think more likely pulley misalignment or eccentric fan sheave. Other opinions?

 

[electricpete]

also check belt tension

 

[mcdm]

is the unit mounted on anti vibration mounts i have had many cases where where the drive motor has been running at 10-15mm/sec(mainly vertical and axial planes ) and the fan bearings have been no more than 4-5mm/sec after further investigation i found that some of the av mounts were worn.
i agree with electripete and would suggest check the pulley arrangement

 

[MachineryWatch]

I agree with Pete. Probably fan sheave eccentricity or sheave misalignment.

Skip Hartman

http://www.machinerywatch.com

 

[Franko]

Nisqually - Did you solve your problem?
Is there a reason to use a pulley instead of a flexible coupling at 3600 rpm?
Anyway, I always first ask:
1. Are readings taken using a magnet mount? - If so, is hand-pressure also used - especially for horizontal readings as you won't stop the vibration, but will get more accurate readings.
2. Is a flat surface used for magnet or glued-on mounting, and are readings at bearing centerline-not at a long overhang?

We usually recommend tripping at 0.62 ips peak velocity.
I like to pass along this great on-line calculator:

http://www.wilcoxon.com/calculator.html

 

[Franko]

Nisqually - Did you solve your problem?
Is there a reason to use a pulley instead of a flexible coupling at 3600 rpm?
Anyway, I always first ask:
1. Are readings taken using a magnet mount? - If so, is hand-pressure also used - especially for horizontal readings as you won't stop the vibration, but will get more accurate readings.
2. Is a flat surface used for magnet or glued-on mounting, and are readings at bearing centerline-not at a long overhang?

We usually recommend tripping at 0.62 ips peak velocity.
I like to pass along this great on-line vibration unit conversion calculator:

http://www.wilcoxon.com/calculator.html

 

[nisqually]

Franko,

Thanks. I will try out the vibe calculator. I wish it could tell me how to lower the vibe on my equipment

Did you look at the picture? How do you use a flexible coupling with a belt driven fan? I thought that is for direct coupled fan/motors. I am new at this. Please explain. A link to a vendor website would be welcome.

I don't understand why the horizontal vibe is so high at bearing 1. The belt is attached at bearing 2 so I would expect the vibe to be higher there. But then again I am a rookie at this.

We took readings using a hand held "stinger" type probe tip. The readings are probably at bearing centerline for the fan shaft pillow block bearings but may not be so close to centerline of motor bearings. We we looking at overall vibration levels, not shock pulse although we have that information also.

Our vibe values are zero to peak. I am familiar with zero to peak, peak to peak and rms. What is ips? I thought that was iron pipe size.

Nisqually-rookie

 

[Franko]

Perhaps you would be better off with an industrial blower.

See: Gardner Denver:

http://www.gardnerdenver.com/GDCorpPortal/RouteRequest?route=to&id=1333

 

[Franko]

Ooops - forgor - ips is inches per second.

 

[micjk]

nisqually,
I have to agree, to an extent, with pete. check pulley runout (taperlocks are bad for this if not properly torqued) and alignment, one question though, doesn't pulley misalignment tend to show higher in the axial direction with the dominant peak on driver being the driven and visa-versa ( just asking). Roy Gariepy
Maintenance and Reliability Dept.
Bayer Corporation Dorlastan Fibers Div.
Goose Creek, South Carolina USA

 

[nisqually]

hi micjk,

I would very much like to understand what you are asking about pulley misalignment and the axial direction and driver versus driven but I don't. Can you please rephrase and try again? What do you mean driver being the driven and vice-versa?

-nisqually

 

[micjk]

if memory serves me correctly, often times with belt drive pulley misalignment axial data on the motor will show a dominant peak at the 1x frequency of the driven component and likewise the driven component will show dominant peak at motor 1x frequency. I added "just asking" in case other experts in this forum had different thoughts and could add some added input for educational value. i am also working on a fan with similar problem. Mine however has a few more forcing funtions involved. We defintelay have unbalance, along with looseness ( I have multiple harmonics of 1x driven component and found that the pillow block bearings have a .020 gap between housing and bearing support structure from center of housing to hold down bolt.) Hope this clears up my former post for you. Roy Gariepy
Maintenance and Reliability Dept.
Bayer Corporation Dorlastan Fibers Div.
Goose Creek, South Carolina USA

 

[electricpete]

It's a good point that Roy makes. A typical symptom for pulley misaligment would be 1x fan speed vib on the motor axial reading, and 1x motor speed vib on the fan axial reading. Still we probably shouldn't rule out misalignment based on the absence of axial vib.

 

[electricpete]

I should add that I don't have a bunch of experience with belt drives... we've only got a few at our plant.

 

[jmack]

Nisqually,
My suggestion would be to take phase readings. This will help to eliminate extensive time associated with the trial and error approach.

J MacK

 

[nisqually]

Excellent idea jmack. What I have is a "balancing kit" with the ability to take phase measurements and an instruction manual with the Commtest instrument vb1000-T.

OK then. Will the phase measurement tell me how much the sheave is wobbling, that is, rotating through an angle perpendicular to its axis of rotation? Am I making any sense?

 

[mcdm]

Hi nisqually i am using the commtest vb2000t kit and found help with phase @ universal technologies inc. interpreting unbalance/misalignment using relative motoion diagrams
any problems ill try to help