BLOWER vibration issue


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
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



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Original Post

Is this blower part of a VSA plant that separates oxygen from air? If it is, then I have worked on a lot of these type of plants. The PLC readings are much lower than your measurements, so do you know why and which is correct? Assuming that the motor is direct drive to compressor without a gerabox, and that the compressor has 2-lobe rotors, then the vibrations from pulsation occur at multiples of 2x shaft speed. The pulsation vibration amplitudes will vary with load (static pressure differential). Vibration amplitudes can vary with speed because of a resonant structure, and because the load is affected by speed. There can be several natural frequencies within the operating speed range because of the flexible machine base and foundation and the large suction and discharge pipes. It looks like you have a metal grid shaft coupling, so torsional vibrations can also be a problem. One or more natural frequencies can change over time due to foundation grout and concrete anchor bolt deterioration, weld cracks, and loose fasteners. The oil soaked machine skid does not look well maintained for only 3-months of operation. You need to conduct variable speed and load tests, structural vibration tests, and possibly torsional vibration measurements to resolve a problem like this. A good starting point is to conduct a detailed inspection of base bolts, pipe expansion joints, pipe hangers to check for loose fasteners and cracks.

Hi Thanks a lot for your reply .
Currently We just have TK 81 in hand-- protable vibration analyzer. It cannot show any spectrum and waveform.But Would you like to help me explain how to indentify the issue with phase angle reading for me --a new hand. Thanks your help.
Today I also visually check these welds,but didnot found any problems. Maybe I need to do further check for these welds with Dye penetrant method.

Thanks again for your reply.


yes, It is the O2 blower of VSA plant.

For different reading , my understanding:
the reading from DCS is measured with Metrix Vib Proble which is installed at the DE of blower through screw connection. But use TK 81 to measure vibration , connect to machine frame through magnetic metal installed on the Bently velocity probe. And the measurement position is not very same between both. Is it right? ----any wrong pls correct me .
Walt---Your suggestion is very inportant for me.
I will do further test.



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Your recent pictures are not showing. Your spread sheet data is a bit confusing. There are repeated measurement points (rows). The plant PLC reading was 0.26 to 0.36 in/sec peak velocity at drive end vertical, while your TK81 was reading a filtered value of 0.929 in/sec peak velocity. Your TK81 unfiltered values should be a lot closer (and slightly higher) to the PLC values, and you should find out why not. I would be concerned if the TK81 numbers are real, that the 1xSS filtered levels are so high. I would do an internal inspection for rotor-to-rotor and rotor-to casing rubs.

The TK81 is about 25-year old technology that is inadequate for routine measurements and diagnostics on this type of machine. The PLC sensor is probably reading low and needs attention to verify that it is working correctly, within calibration, and that the scale factor used in the PLC is correct. Some of the early Metrix velocity transmitters had reliability issues.


I finally see that your data table has H, V, A measurement points at each of the four bearings (total = 12). I missed that because I only take measurements in the three directions on each end (total = 6 points). The reason is that the bearings are very close to each other, so there is little to be gained by more measurement points. You Columns H and K contain the TK81 overall levels and not the 1xSS values that I expected. You really need to measure 1xSS filtered values as well. Make a measurmement right next to the permanent Metrix sensor to see if your overall measurement has better agreement. Take measurements at the same point in the process cycle, since VSA vibration levels follow the pressure swings.

Getting back to your original question about the vibration levels going up while running at the same shaft speed; possible reasons include:
1) Increase in static pressure (delta-P across inlet to outlet) -- do you have enough process pressure gages to know this?
2) Deterioration in internal acoustical pulsation control elements (baffles, silencers, dampers, sieve screens/plates)
3) Looseness in base bolts, shim stock, pipe joints, and pipe hangers
4) Deterioration in grout and concrete anchor bolts
5) Cracks in base frame/skid, foundation beams, and pipe supports
6) Mechanical faults in compressor such as rotor rubs, timing gear failure, and bearing failure

Walt, thanks a lot for your help.
For 1X filter value during measuring the value is very low, so I didnot fill in spread sheet.
Before, I also try to measure with TK81 which is put near the metrix sensor ,the value measured with TK81 still is higher than the value from metrix sensor ( TK81 reading 0.4in/s , but Metrix reading 0.20in/s).

Yesterday I again met a strange matter on the blower.
Yesterday We re-adjust the motor VFD form 52HZ to 50HZ, the vibration reading from DCS drop to 0.16--0.21in/s peak from 0.26--0.32in/s.And the stable running status was kept for around 6 hours from noon to evening. But later, the vibraiton reading again went up and reached to 0.56in/s peak in around 4 hours. At that time operator again adjusted VFD frequency to original 52HZ. the vibration reading restored to original level 0.26---0.32in/s peak.
To this I feel it is very strange . At 50HZ the vibration began to go up . why the reading still may keep original level when adjust the frequecy from 50 to 52.

At present, the next days are Chinese nationaly holiday, So after this holiday we will do a check for the blower. (check main shaft runout , open gear side & drive side cover to check internal situation , so that we firstly ensure the blower is in good condition.

Walt, thanks again for your help.


In our company there are a lot of GARDNER DENVER CycloBlowers to be used. In these years we also met much blower to be damaged ahead of sechdule. some is damaged after runing for 2 months. the most damaged part is bearing at the drive end. And it seems the damage was caused by great axial force. Although we have already taken much time to do detailed check such as pipe stress, soft foot, alignment seems that we just got a little of improvement,not obvious.
To this type of blower it is very important to run under the disign PDI between inlet and outlet. now I am thinking if these blowers are running out of the design PDI. Because the outlet pressure transmitter is not installed close to blower outlet nozzle but is installed at the downstream of outlet silencer and cooler . it is far from the blower . then the piece of pipe pressure drop is not considered. And I also am trying to do some calculation. Found that the oulet Temp is higher than calculated Adiabatic TEMP based the PDI from DCS, inlet P&T.

Walt, pls help me take a look at if my doubt is right .


I guess you are working on your national holiday! I don't have direct experience with the GD Cyclo machines, since I the VSA plants and other that I worked had twin 2-lube (straight) blowers. The VSA plant that I am familiar with had one fresh air positive pressure blower and three vacuum blowers that had water injection. It also had one or two blowers/compressors for the oxygen. Does your problem blower run with positive or negative pressure? There are plenty of potential contributors to premature drive-end bearing failure including:
1) Wrong bearing, incorretly installed
2) Wrong shaft seal, incorrectly installed
3) Wrong bearing lube oil, incorrect oil level
4) Excessive static pressure or temperature
5) Blower Case distortion caused by soft-foot
6) Poor shaft alignment (radial and angular), incorrect shaft end gap, undersized shims, and weak base bolts and washers
7) Shaft coupling wear/damage and poor lubrication (meteal grid type)
8) Timing gears not set correctly
9) Rotor-to-rotor or rotor-to-case rubs
10) High vibrations that cause case to twist (out-of-phase motion end to end)


#11 on my previous list is Shaft Current that causes electrical discharge through bearings by producing EDM. This is a common problem with motors with VFD control. I have seen shaft current go across metal grid coupling and destroy gearbox bearings quickly. I recommend a thorough inspection of failed bearings to find possible (general or specific) cause of failure. The overall vibration monitor and the TK81 are poor tools to detect developing bearing faults in the presence of high pulsation vibrations. A word of caution; the high vibrations may not be directly related to the drive end bearing failure!

we have many GD blowers , some is installed at indoor. some is installed at outside. To these outside blowers we found that once it is heavy rain the blower will has high vibration happening, And sometimes some blowers was tripped by high vibration . at first we doubt it was caused by the big rain droplet hitting the vibration sensor . And we made a rain shield just for the vibration sensor. Over time when it is heavy rain again the high vibration still happened. So now we had to think of another reason . it maybe is real vibration , when it is heavy rain the rain as cooling medium will cool down the machine casing quickly ,this will lead to high TEMP difference between inside rotor and casing , cause the fit clearance was changed suddenly . Result in the high vibration happening.

Dear friends, Did you met this kind of situation before? And share your thought to me.

Updated infomation about this blower.

Last Friday we took a thoro inpection for this blower, Details as following:
1.Check drive shaft movement and run out
shaft movement reading is 0.001inch same as original commissioning record/ coupling run out reading is normal , less than 0.002inch.
2.Check oil sump of both side of O2 blower if there is any abnormal thing existing
No any dirt and metal were found from draining oil .
3.check alignment ,soft foot etc.
alignment inspection result is within our requirement, soft foot also is less than 0.002inch
4.(4) Re-do this VFD TEST (after reinforcing the frame did not re-do VFD test on last time)
Pls see new VFD TEST result under normal operating status
48hz----0.2inch/s, 49hz----0.56inch/s,50hz----0.52inch/s,51hz----0.29inch/s,52hz----0.22inch/s,53hz-----0.23inch/s,54hz----0.31inch/s(from these view 49hz&50hz are not used during future operating.)
And It seems the resonance area already is changed after reinforcing the machine frame on last time. Below is VFD test result during commissioning .
( Raise the frequency from 50Hz to 57Hz. Found that from 50 to 55Hz, the vibration raised from 0.18in/sec to 0.36in/sec; 56Hz, raised to more than 0.5in/sec; 57 Hz, 0.7in/sec. So we suggest that the frequency should be controlled no more than 55Hz during daily operation. )
5.check all the welds of machine frame ,it is ok
6.check all the mounting bolt on the machine&frame , it also is ok

In other words after finishing this inspection we still didnot find the real reason of high vibration which happed on last time.
Currently the machine still run with 52 hz, and the vibration keep 0.23-0.27inch/s peak.

Any comments&thoughts from you will be appreciated


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