Vibration Characteristic of Lobe Blower

Element Generating Vibration in rotary lobe blower :

1. Blower Inherent characteristic
a. Impacting bearing loads excite component/system natural frequency.
b. Pressure pulsations set up vibration at four times running speed

2. Rotary lobe blower has very close clearances between the impeller and the housing. The impeller contact will
setup vibrations as follows :
a. Impeller to impeller frontal lobe contact-if contact is between only one set of lobes, the vibration frequency
will be 1x rpm, if both sets of lobes contact, the vibration frequency will be 2x rpm.
b. Impeller to cylinder contact-the vibration frequency will depend on the number of impeller tips contacting
the cylinder which could range from one to four times the RPM.
c. Impeller to head plate contact-the vibration frequency will be erratic and unsteady.

3. Damaged gears will generate vibrations at gear mesh frequency (GMF)

4. Damaged gear will generate vibrations at bearing frequency (BPFI,BPFO, FTF, BSF)

5. Rotor unbalance and bent shaft will generate vibrations at 1x rpm.

6. Blower/driver coupling misalignment will generate vibrations at 1x RPM and 2xRPM

7. Acoustic resonance in the blower inlet/discharge piping will generate vibrations at 4x RPM.

8. Operation of rotary blower at or near system torsional may cause impeller lobe contact and increase vibration

9. External piping if not properly isolated will transmit vibrations into the blower

10. Foundation design and method of mounting has considerable effect on blower vibrations.