In these days I met a high vibration issue on blower. Detailed as following.
Blower :GARDNER DENVER CycloBlower 9CDL23.
Driving motor : 1780rpm ,60HZ.
The motor speed is controlled by VFD.
The blower has been run for three months from commissioning to now. VFD setting value 53HZ. And the vibration reading from DCS always keep 0.19--0.23 inch/s peak measured with Metrix Vib Proble Which is installed at the DE of blower.
But a week ago the vibration began to go up slowly and reach to 0.50inch/s peak. At that time we check the process system , didnot find any change existing. So We try to lower the running frequency from 53HZ to 52HZ ,then the vibration droped to 0.26-0.34 inch/s peak. And at that time I measued some vibration data (pls see attachment)with TK81. Today we again try to adjust this motor frequency from 52HZ to 50HZ, Now the vibration reading from DCS drop to 0.16--0.21in/s peak And after this adjustment I again measured the Vib data with TK81.
Below is some vib reading measured with TK81
Oxygen blower TECO AEHD-VSAO1 Motor : 60HZ ,1780 RPM ,1200kg,380 Volt. 2009.9.23 2009.9.29
Compressor Data Collection Unit
1. VIBRATION DATA
VFD (CPM) HZ 52HZ(1542rpm) 4X(6168) 2X(3084) 50HZ(1483rpm) 2X(2966rpm) 4X(5932)
plant PLC peak reading in/sec 0.26-0.36 0.16-0.21
Drive End, Drive Rotor, Horizontal ①(Max. / Min.) in/sec 0.756(0.77) (0.44@6209) (0.032@3087) 0.45
Drive End, Drive Rotor, Vertical ②(Max. / Min.) in/sec 0.929 0.614@6209 0.0392@3033 0.567 0.103@2979 <0.1
Drive End, Drive Rotor, Axial ③(Max. / Min.) in/sec
Drive End, Non-Drive Rotor, Horizontal⑦(Max. / Min.) in/sec
Drive End, Non-Drive Rotor, Vertical⑧(Max. / Min.) in/sec 0.568 0.285@6181 0.0308@3033 0.76 0.174@2965 <0.1
Drive End, Non-Drive Rotor, Axial ⑨(Max. / Min.) in/sec
Non-Drive End, Drive Rotor, Horizontal④(Max. / Min.) in/sec 0.511 0.99 0.034@2979 0.517@5965
Non-Drive End, Drive Rotor, Vertical⑤(Max. / Min.) in/sec 0.939 0.273@6238 0.427@3080 1.064 0.741@2979 <0.1
Non-Drive End, Drive Rotor, Axial ⑥(Max. / Min.) in/sec
Non-Drive End, Non-Drive Rotor, Horizontal⑩(Max. / Min.) in/sec 0.469 0.891 0.048@2985 0.571@5965
Non-Drive End, Non-Drive Rotor, Vertica l⑾ in/sec 1.195 0.519@6281 0.469@3080 1.175 0.764@2965 <0.1
Non-Drive End, Non-Drive Rotor, Axial ⑿ in/sec
For above issue. In my opinion there are two possible reason .
1. Machine nature vibration frequecy is changed due to machine issue ,as bearing wearing........
2. machine mounting frame nature vibration frequecy is changed due to frame stiffness change--------is it possible? Will the frame stiffness be able to change after run the blower for 3 months? ----somebody has this kind of experience for this kind of welding machine mounting frame?
In addition, from those vib data measured with TK 81 you can see that at 53hz the 4X vibration is very high but at 50hz the 4X vib is very low, and every reading <0.1in/s peak.
Any thought and comments from you will be