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hello my friends we have two id fans for cement kiln from the last maintenance we replace both bearings for both fans and we clean the fans with sand blast just the surface after the operation we get high vibration axial and horizontal especially horizontal at certain speed that some time cause the line to stop the limit of horizontal vibration is set at 5.0 mm.s at max speed 960 rpm

Tags: VIBRATION

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Share the latest vibration data and spectrum.. People cannot say anything about the root cause unless they the data and spectrum.

In general, high 1X shows imbalance which is common issue in ID Fans. however, if you are getting high Axial vibration levels as well then this could be miss alignment. 

Also, when you said certain speed, do you mean the reading during run up or coast down? or there is a VFD?

RM

5x?...how many blades the impeller?

1x, there is the unbalance, is clare.

how many blades per impeller
there is an imbalance, it is clear
but, regarding the last photo, many nx armonics indicated like bearing/housing looseness...
we see high 14x armonic, probably 14 impeller blades?
but the sideband from 6x to 18x is look like a rotor bar problem about motor...?
many things, but just my opinion

RM

As others stated, mechanical looseness is present. The sidebands are most likely from the outer or inner race spinning. When the bearing spins in the housing/shaft, it is turning at a different speed which will create a frequency very close to running speed. Have seen worn gear couplings exhibit this same pattern.

Down and dirty way of checking. Dial indicator on shaft of interest at top dead center, long bar and block/s of wood, gently pry up on shaft and record total indicator movement. Most taper bore bearing will have .003-.004" of designed in roller clearance, the bearing fit to the housing another .001-.002" that adds up to .004-.006" of total allowable shaft play

Dave

RM

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