One of the blowers I have fixed is transferring vibrations to building structure.?

Question

I have two blowers of 10 HP each fixed on the terrace. One blower is very smooth running and silent whereas second blower is giving vibrations to building structure. Both the blowers are fixed on the same foundation. Dynamic balancing of impeller is ok. Level of pedestal bearings is ok. Pulley alignment is ok. Both the blowers are same, but one is giving vibrations. Help please.

Read many answers. Thanks for your valuable inputs. I want to add some details. 1. Blowers are centrifgal blowers. 2. Both the blowers are of the same capacity and size. 3. Both are fixed on the same foundation. 4. Anchor bolts are grouted properly. 5. No casing bolt or any other of the bolts is loose. 6. Dynamic balancing is properly done with my own hands on advanced machine. (I have25 years of experience in this field. I'm a mechanical engineer) 7. Impeller is properly fitted and there is no play between the shaft and impeller. The design of blower is very simple and same type of 6 more blowers are fixed in the another lab which are running very smooth and silently.

Answer 1

# Both the blowers are meant for same application?
Please read below::

# Biggest problem for vibration is Dunamic balancing.
As you are saying balancing is ok.On what basis?

-You can go for in-situ dynamic balancing.
If it is ok then you have a lot of check points:
a.
Looseness-of bearings-not properly mounted or not firmly secured with the use of adaptor sleeve.
Loose bearing padestals.
Looseness of the vanes.
LOOSE LOCKING of fan shaft.
Check the foundation bolts of casing /vibration isolator/motor.
Check the condition of motor [bearing/play/foundation bolts]
Check for the cracks on the foundation.
Check the suction cover for looseness of bolts/cracks.
Check the condition of belts.
Have a check on supports of suction and discharge ducts.
b. Check the alignment of fan pulley with the motor pulley.
Check rubbing of safety guard .
Check the suction condition i.e. both the blowers are having same damper opening.

Open the drain plug at the bottom and run the blower.
Check for any foreign matter.
Open the inspection cover and clean the fan if required.

#If you are having good vibro-meter , then take the RMS reading -axial ,radial.
filter the frequency one by one and study.that will give you the most probable cause.
# If the application is hot, then you have to go for hot alignment.Also check the blower cooling fan and padestal[locating ring for the bearing are firmly secured/proper size is there or not]
# Levelling of the shaft is of prime importanance.

# Monitor the flow,pressure and amperage of the fan.These can give a clue.
# Check the speed of the fan as it is pulley driven.

[Pl. read:
Gas Furnace Has Noisy Operation
Possible Causes

Higher pitched "squealing" sound may be caused by slipping blower belt or motor or shaft bearings in need of oiling
Lower pitched "rumble" sound may be caused by a poorly adjusted pilot light if this problem occurs with the burners off.
Lower pitched "rumble" sound may be caused by dirty gas burners if the problem occurs with the burners on.
Possible Repairs

Oil blower motor lubrication ports (usually at each end of shaft) with light weight oil
Check for proper belt tension. Belt should depress about 1" at center of span.
If too loose, tighten belt.
Replace frayed belt.
Adjust pilot light
Call furnace service technician to have burners adjusted or cleaned.]
#Click on:
http://www.hvacmechanic.com/forums/resservice/messages/26275.htm
http://www.spacepak.com/modules/lit_lib/upload/ESPD2-1105.pdf
http://www.thermopride.com/Manuals/ECM_with_OH6_I&O.pdf
http://www.apollohydroheat.com/lit/media/om/om_airhandler.pdf

Edit:
-What about the rpm of the machine?
Is there any VFD system?
If so check the requisite rpm and also check the direction of rotation.

Answer 2

Perhaps Foundation for blower is not adequate. The total weight of the foundation of blower should be more than weight of the blower. Vibration isolator pads are to be provided properly. Better to consult the blower supplier. Isolation of foundation of blower with building structural element if possible should be considered.

Answer 3

Check you foundation bolts. But it sound like somthing isn't balanced. I would check all the bolts around the casing as well. Your fan or turbine blade could be loose casuing the vibratiob as well. I would check the bolts first though just because it's easier to tighten a bolt then to take it all apart again.

Answer 4

You say the pulley alignment is okay. That implies that they are belt driven. Have you checked the belt to see if it has a flat spot in it. Many times the splice in a belt can cause a "rough" place that can cause vibrations. There is a segmented belt that can eliminate this problem.

http://www.fennerdrives.com/high_performance_composite_vbelts/powertwist_home.htm

Answer 5

Both was quiet before and both should be quiet now.
The cause may have been introduced after the balancing.
check for chips, paint or grease on blades, Is the motor running smooth?
Is the drive OK and not warn?
something may be skew.

for a start turn it slowly and watch for a wobble.

A bearing may be broken.

Answer 6

I'd bet my *** that one of the blades of the vibrating blower has a nick out of it or a paint drip.

Answer 7

Hope u found the fault and solved the problem, I wish that you let us know what it was & the solution