Centrifugal blower vibration problem

Question

capacity of blower=120000 m^3/hr

temperature =450 degree C

BEARING=22220 CC W33,Plummer block=SOFN 220

NOW, WE ARE FACING VIBRATION PROBLEM.

hORIZONTAL Reading=19 peak to peak[13.0 mm/sec,RMS]

AXIAL READING READING IS 5.0 MM/SEC.

We have maintained all the criticle parameters.

blower system is simply supported,I mean blower is in the center [Both sides bearing]

Temperature of shaft is 80 deg.C

Its a new assembly.

What are the probable causes?

Is it required to balance the assembly AFTER comming in hot condition?Basicaly it was perfectly balanced perfectly in cold condition.

Wel-come to all answeres to give their experience.

Thanks in advance.

MOC of shaft is SS410.

Note: vibrations are comming from drive end side only.

fan is connected to the motor through fluid coupling.

Answer 1

Edit-

You are saying that the tiny (0.4mm ?) hot re-alignment is parallel with no angular component ?. I am not familiar with the bearing designations, however, if  journal bearings are employed they will both lift and also offset hydrodynamically.

Next -Would there be an electrically-induced problem with the drive motor ? Is the alignment set up with the motor in its electrical "center"  aka electrical axial position ? Is there a phasing irregularity ?

Were there  factory balancing runs of the blower and the motor ?

Do you have the right coupling ?

My brain is picked for now. Hope you fix it.

Initial-

Sometimes the manufacturer can furnish you with hot alignment compensation. That may get you into startup mode, but maybe not running mode.

I believe you will need to consider a hot alignment check because of the temperatures involved. There will be a little axial growth of the shaft, but there could be a differential vertical (or even lateral) growth of the bearing supports if they are not identical. This would include the compressor and the driver alike. The entire compressor frame may lift the compressor shaft to misalign with the cooler driver.  

Some misalignment could be resolved at your flexible coupling , but there are limits.

We did hot alignment and then added or removed shims in the cold condition to compensate for the vertical running condition. We compensated for the vertical first and then utilized jack screws for the horizontal (if any).

We had special jigs made to hold the dial indicatiors (of the time) so that they could be quickly employed at the coupling (or shaft) in the hot condition. Then we did some trig.

Next-

With some high pressure fans and blowers there can be an inherent aerodynamic vibration in the partial capacity condition. This occurrs when a system is installed for a future maximum capacity, but operated initially in a throttled condition. We utilized variable inlet vanes for this. (Speed control was too expensive).

Next-

Bad connections to a fan or blower will have detrimental effect on delivered performance. (This is called "System Effect"; I call it "Installation Effect") An uneven distribution of air into the inlet will create unequal loading, poor performance and even vibration. In these cases a modification to the inlet duct or obstructions will be needed.

Answer 2

It is required to balance the assembly after coming in hot condition.as blwer assembly is not perfectly installed to ground level it will caused to vibrations.as you have to see where the vibration occur & what is caused for that vibrations?

it is the case where practically observations are needed to solve vibration problem.

Nice question.keep it up.

Answer 3

WOW you can't get any dirtier than that!!! LOL

Answer 4

dont know