RTO Fan/Motor Base Vibration question

[plcsoftvsd]

My two cents....

a) Hope the base bolts of motor and fan have been tightened.

b) Just to rule out that temperature is an issue,..is it possible to run the fan with cold air at the rpm where the vibration is maximum.

c) Decouple the fan and run the motor at full speed and see the trend of vibration.

 

[kamenges]

What is your vibration spectrum? Is there a single, very dominant frequency or is there a frequency profile? The actual vibration frequency can narrow your search significantly.

Keith

 

[Tark]

Might try cleaning the fan blades and see if that changes anything. From the picture they appear to be a bit dirty.

 

[Russ]

Here is some vibration trending data. It's interesting that the initial success occurred while the outlet manifold, and fan bearings were cool.
I have repeatedly checked anchor bolts, bearing bolts, motor bolts. Due to the vibration levels I have snugged up some motor base anchor bolts about every quarter.
Here is the vibration trend. One point to note. After I realized the resonance issue I increased the minimum speed during online operation above the range to minimize its effect on the equipment until the vibration problem was resolved.

 

[leitmotif]

Seems to me the first thing I would do is get that bearing lube system into spec. You state each bearing requires .8 gal per minute but then later state the overall flow of the lube oil pump was .5 gpm (was it??). High oil temp was "cured" by a cooler. So in my mind you pump thick oil in and get thin oil out of bearings. I would be concerned by a fairly high delta T across the bearings and would use more flow ie at least .8 gpm.

Have there been any changes to the exhaust side of fan ducting??
Have you any data on system flow and pressures upstream and downstream of fan?

What is the RPM of the fan??

What about erosion of the blades? Seems to me this could change the blade configuration thus the direction and velocity of the air and create different loading on the fan and or housing.

Dan Bentler

 

[milldrone]

Might try cleaning the fan blades and see if that changes anything.

I had a fan that ran 24/7 most of it's life. The interesting thing about this fan was when it would stop it was always out of balance for a few days afterwards. Then it would be ok after that. The problem was the accumultaion of dust would fall off the blades on the half of the fan that gravity would not hold the dust in place. After running for a few days the "balancing" dust was replenished.

I don't see any mention of the type of impeller design. Backward incline impellers can have a very nasty charateristic of "vibrating" or pulsing if the flow through the fan is reduced in certain apps.

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