Tagged With "Loose"

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Air Handler Unit High Fan Free End Vibration

Avinash Thawani ·
Air Handler Unit Vibration Issue The vibration readings on the fan free end of the Air Handler AH-15050 have been significantly higher than the baseline during the last 20 days. RMS Acceleration has increased by 100% Raised noise floor in acceleration spectrum for Fan Free End. The spectrum peaks indicates a VFD speed change from 26Hz to 30Hz(gradually). Due to this change we are observing an increase in Accel RMS vibration. Currently the speed of the Motor is 28Hz. In the velocity spectrum...
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Balancing response at structural looseness/resonance

Kishore kumar ·
Dear members , Yesterday i have balance a fan ,it has dominant 1X r.pm 1500 .Initial balancing attempt is not success earlier two days before and production people given limited time due to their production demand . Yesterday i have received a call from the plant and after stopping the fan ,we observed some cracks on discharge duct and broken nut bolts at duct suction and discharge flange area .After repair we have examine static balance and found good condition and after motor trail with...
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Sub synchronous vibration and coupling failure

Thimba ·
Dear all, I’m monitoring a 40kW (2975rpm 2 pole) vertical lube oil pump. Please refer to the attached vibration data for the pump. On the 26 th Feb the coupling (Jaw coupling) was visually inspected and found the spider completely damaged and the coupling was replaced. Based on the spectra and time waveform is there any case for concern? What could be causing the modulation at around 3.5Hz? The pump bearing was replaced on 22/11/18 and the coupling was replaced at the time as well. Is there...
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FAN DE BEARING LOOSENESS

Rahul v dan ·
we have a found a fan De bearing looseness issue recently. Been monitoring since a while. Have observed change in spectra from past few days. Herewith Iam attaching both spectra of SAME DIRECTION.Any suggestions???
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What causes 1x vibration on Vertical Pump

haddadqaa ·
some causers of 1X vibration are 1-looseness 2-imbalance 3- wear in bushings (if applicable) Also, I'm looking for your experiences.
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Loose stator winding

Lampard Nguyen ·
Dear Experts,   There is wound rotor motor, 6 poles, 50Hz, 992rpm operating, 800KW, 6.6KV, coal milling motor. It was the first times I performed Vibartion analysis to that motor. In FFT velocity spectrum, It indicates some peaks of 2*FL and...
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Is this rub or looseness

jono jakarta ·
Dear Expert,   Please find the ppt   Thank you for your suggestion   Best Regards, Jono Jakarta
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Diagnosis rotating looseness in electric motors.

RAAL ·
Hello, Could you please recommend some other predictive technique other than mechanical vibrations, to diagnose rotating looseness (shaft or housing) in electric motors. Or if you think that the best thing is with mechanical vibrations, could you please give me some tips for the diagnosis of this type of failure, especially in electric Motor above 500 hp. Thanks
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Loose Rotor bars

ANIS VA ·
Hi everyone I post this issue related to Closed cooling water pump, i suspect that there is loose rotor bar. i attached all information in pdf file when i explain the problem details, Any feedback will be appreciated. thanks
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shaft looseness

Hossam 2 ·
Dear Experts what is the best way to detect the shaft wear under the bearing inner race or under the sleeve specially i face many problems like that but the only frequency shown in the spectrum is 1XTS. Example Overhung Fan variable speed motor (rated speed 1485 rpm) dominant frequency 1XTS (H=10 mm./sec....Vertical=6 mm./sec.....A=4 mm./sec) after balancing the vibration dropped to 2 mm./sec but in two days the vibration reached 36 mm./sec at horizontal direction 1XTS dominant vertical 25...
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Re: Loose stator winding

Lampard Nguyen ·
Please help me!
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Re: Loose stator winding

OLI ·
If possible let the sparky's check that all phases have the same voltage (at the motor if possible). It is the first I check when voltage is lower. It is to confirm that no breaker or connection is bad that is quite common for lower voltages. If you stop some time verify that the 100Hz drop instantly when power is cut. It is to confirm it is electrical and no other. Is it a lot of coal dust? Is this the only like this you have? Olov Good Vibrations since early 1950's, first patented...
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Re: Loose stator winding

Mark R. ·
Cando, You may a soft foot situation going on here causing frame distortion and un-even air gap. Have you checked for that? The chances of a loose winding are slim. I know you can have loose coils and they will vibrate to the iron they will eventually ground out.
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Re: Loose stator winding

Walt Strong ·
" The amplitude of 2*FL frequency is 2.74 (mm/s) at NDE(Horizontal) motor position. You can see the spectrum in my attachment. With this condition, is there need to monitor vibration or shut-down and repair?" The peak at 49.75 Hz matches 3x shaft speed not FL. I don't think this is electrical, but it is probably mechanical looseness. The vibration level is quite low, so no action is warranted other than routine monitoring. The peak at 2xFL is probably electrical. The harmonics have very low...
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Re: Loose stator winding

abhiramkompella ·
I agree with Mr.Walt You have got 49.75 Hz in your spectrum with ur rpm it is of 3x running rpm it's not a 2xFL frequency... As per my knowledge inspect solo motor vibrations and also inspect for any soft foot problems in motor base...
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Re: Loose stator winding

Lampard Nguyen ·
Originally Posted by OLI: If possible let the sparky's check that all phases have the same voltage (at the motor if possible). It is the first I check when voltage is lower. It is to confirm that no breaker or connection is bad that is quite common for lower voltages. If you stop some time verify that the 100Hz drop instantly when power is cut. It is to confirm it is electrical and no other. Is it a lot of coal dust? Is this the only like this you have? Olov Dear OLI, Voltage and current...
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Re: Loose stator winding

Lampard Nguyen ·
Originally Posted by Mark R.: Cando, You may a soft foot situation going on here causing frame distortion and un-even air gap. Have you checked for that? The chances of a loose winding are slim. I know you can have loose coils and they will vibrate to the iron they will eventually ground out. Dear Mark, Air gap is good condition. Thanks
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Re: Loose stator winding

Lampard Nguyen ·
Originally Posted by Walt Strong: " The amplitude of 2*FL frequency is 2.74 (mm/s) at NDE(Horizontal) motor position. You can see the spectrum in my attachment. With this condition, is there need to monitor vibration or shut-down and repair?" The peak at 49.75 Hz matches 3x shaft speed not FL. I don't think this is electrical, but it is probably mechanical looseness. The vibration level is quite low, so no action is warranted other than routine monitoring. The peak at 2xFL is probably...
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Re: Loose stator winding

OLI ·
Did you check mounting/softfoot? Any findings in the spectra from electrical if you have that? Olov Good Vibrations since early 1950's, first patented vibrometer 1956 in the US. http://www.vtab.se
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Re: Loose stator winding

Walt Strong ·
Cando stated: " Thank you for your replying. Yes, i agree 49.75Hz is 3x harmonic. But 100Hz is 2FL. It is not 6x harmonic. I think 2FL is the frequency of magnetic force in motor. It indicates electrical looseness problem." Strong previously stated: "The peak at 2xFL is probably electrical. The harmonics have very low vibration levels, and even 2xFL amplitude is low. I would not take any maintenance actions, unless there was a significant change (increase) in amplitude of 2xFL or the...
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Re: Loose stator winding

Raul Rios ·
Hi Cando. The Approved Method of Charlotte says 1,25 mm/seg-rms DANGER value on 2XFL and 0,62 mm/seg-rms to 4XFL The 2FL can be produced as a result of ¨soft Foot. I am attaching a document. I hope I've helped Raúl Ríos www.ensayospredictivos.com.ve
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Re: Loose stator winding

Lampard Nguyen ·
Deall all, This is another fan motor, Wound rotor motor, 990 rpm, 6600V, 800KW. The symptom is similar with above motor. Could you please show me your opinion? Thank you so much! Regards,
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Re: Loose stator winding

Edwin de B ·
First: Be sure you do not pick up line frequency electric field by placing the probe cord over the body of the motor. You can pick up a big 2xFl with that. If that is not the case, and your 1xFl comes really from mechanical vibration, you should check for soft foot. Electrical/magnetic problems in stator windings also happen, but will show higher harmonics of the 2x Fl of higher amplitudes than you have here.
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Re: Loose stator winding

Lampard Nguyen ·
Originally Posted by Edwin de B: First: Be sure you do not pick up line frequency electric field by placing the probe cord over the body of the motor. You can pick up a big 2xFl with that. If that is not the case, and your 1xFl comes really from mechanical vibration, you should check for soft foot. Electrical/magnetic problems in stator windings also happen, but will show higher harmonics of the 2x Fl of higher amplitudes than you have here. Hello Edwin, We checked vibration on bearing...
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Re: Loose stator winding

Walt Strong ·
Cando, If you really want to be very thorough, then conduct impact test to identify possible motor natural frequency near 2xFL. Impact-response on motor housing in X-Y-Z directions and on cooling fan shroud. I have encountered and corrected several resonant vibrations associated with 2xFL on a various size and types of motors up to 4500 Hp. I have never encountered a "soft foot" condition that caused high vibration at 2xFL. I always consider it a possibility, because it is on the "Diagnostic...
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Re: Loose stator winding

Lampard Nguyen ·
Dear all, We shut-down motor yesterday, and uninstalled this machine. The problem you can see in my picture. Thank you. It's very interesting case.
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Re: Loose stator winding

Edwin de B ·
Thanks for sharing!
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Re: Is this rub or looseness

John from PA ·
Ever done a bump test on this machine?
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Re: Is this rub or looseness

Bill Kilbey ·
Can you acquire/plot TWF in acceleration? Do you have DEMOD/High Frequency Technique data?
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Re: Is this rub or looseness

seandude ·
I would tackle the misalignment first. Some couplings exhibit signs of rub with multiple harmonics when they are off this much, especially at 3600 RPM.
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Re: Is this rub or looseness

jono jakarta ·
Originally Posted by John from PA: Ever done a bump test on this machine? Dear John, I don't have tool for that Thank you
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Re: Is this rub or looseness

jono jakarta ·
Originally Posted by Bill Kilbey: Can you acquire/plot TWF in acceleration? Do you have DEMOD/High Frequency Technique data? Dear Bill, Please find the attachment. I hope this one what you need it Salam, Jono
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Re: Is this rub or looseness

Edwin de B ·
- Do you have older data from those points? Development in vibration says more than a one time reading - What is axial velocity of the motor? Has it developed too? Vibration caused by misalighnment or coupling shows on pump as well as motor. I also would like to get the 'subharmonic' 16 Hz explained. Are you sure the running speed is 50 Hz? There are very little causes for subharmonics. One is turbulance in pump flow. But that doesn't show the harmonics of it as you can see here. Another...
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Re: Is this rub or looseness

Ramos_ ·
Originally Posted by jono jakarta: Originally Posted by John from PA: Ever done a bump test on this machine? Dear John, I don't have tool for that Thank you Your normal single channel vibration analyzer can do the work. Capture FFT with Peak Hold averaging (if available) then use a wood to knock the casing. hope this helps
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Re: Is this rub or looseness

Rao Shahbaz ·
I would go with seandude to consider the misalignment first. rubbing would give high temperature or oil analysis can help you. take the thermogram of pump bearings- observe the difference.
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Re: Is this rub or looseness

Rao Shahbaz ·
have you done phase analysis across coupling?
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Re: Is this rub or looseness

Ron Brook ·
1/3 peaks are usually electrically induced due to a low phase voltage. This is a 3 phase motor and you are running on 50 Hz power, right? If you cut power, my guess is those harmonics would all go away. Check all three phases for voltage and current as soon as possible. Ron
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Re: Is this rub or looseness

Edwin de B ·
Hi Ron, I did not know about electric cause of 1/3X. But I would like to know all about is. Can you explain how it occurs? Thanks.
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Re: Is this rub or looseness

Vibmaster ·
Phase problems . Check connections.
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Re: Is this rub or looseness

jono jakarta ·
Originally Posted by Ron Brook: 1/3 peaks are usually electrically induced due to a low phase voltage. This is a 3 phase motor and you are running on 50 Hz power, right? If you cut power, my guess is those harmonics would all go away. Check all three phases for voltage and current as soon as possible. Ron Ron, The problem on the pump, not in the motor. I don't understand for what check 3 phases voltage and current Best Regards, Jono Jakarta
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Re: Is this rub or looseness

jono jakarta ·
Originally Posted by Vibmaster: Phase problems . Check connections. Vib, What do you mean phase problem? Why I should check the connection? Jono Jakarta
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Re: Is this rub or looseness

Ramos_ ·
Hi Jono, Pump overall vibration on DE is higher then NDE. There is dominant 2X at DE vertical which is indication of misalignment. The harmonics of 1/3 TS could be generated internally in the pump or transmitted from loose component or failure in disc pack / membrane of the coupling. Axially there is visible raised noised floor 60-80Hz which can attributed to some transient impacting that rings the natural frequency of the system. This can be from implosion brought by pump operation,...
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Re: Is this rub or looseness

jono jakarta ·
Originally Posted by Edwin de B: - Do you have older data from those points? Development in vibration says more than a one time reading - What is axial velocity of the motor? Has it developed too? Vibration caused by misalighnment or coupling shows on pump as well as motor. I also would like to get the 'subharmonic' 16 Hz explained. Are you sure the running speed is 50 Hz? There are very little causes for subharmonics. One is turbulance in pump flow. But that doesn't show the harmonics of it...
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Re: Is this rub or looseness

Bill Kilbey ·
Can you post the TWF from DEMOD? It looks like the 1/3 is more a modulation causing sidebands than a discrete 1/3 and harmonics. There does not appear to be a 1/3 on slide #11 at all, but a strong 2/3, which is most likely a sideband. Still not sure what the cause is, and probably not high enough to worry about.
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Re: Is this rub or looseness

jono jakarta ·
Originally Posted by Edwin de B: - What is axial velocity of the motor? Has it developed too? Vibration caused by misalighnment or coupling shows on pump as well as motor. In my opinion that leaves only looseness, based on the 1/3x with higher harmonics of it. I think you should check the mounting on the foundation first. Edwin, Please, Motor DE axial vs Pump DE axial
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Re: Is this rub or looseness

Ramos_ ·
The motor amplitude is low compare to pump, but based on your attached document..It looks like that there is COMMON transmitted source of external force that generates somewhat similar peaks across train component (motor - pump), and this could be from your metastream/john crane membrane coupling dynamic run-out or looseness..though I am not ruling out vibration from pump transmitted to motor. Should you recommend repair?? NO, you may want to increase your periodic monitoring frequency to...
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Re: Is this rub or looseness

Edwin de B ·
So all toghether: - Problem is in the pump. Not the motor. - Problem is not big, so can be left and monitored with higher frequency until it develops - cause is probably looseness. Might be of mounting of the pump on the foundation, or internal inside the pump (loose rotor)
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Re: Is this rub or looseness

Hubbe01 ·
Jono, an additional check for looseness is timewave form setup in Accelaration. Velocity timeforms are good to check Unbalance and misalignment. Set up your time waves to capture atleast 9 revelutions, say 250msec. If looseness will show impacts.
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Re: Is this rub or looseness

abok ·
Originally Posted by Edwin de B: So all toghether: - Problem is in the pump. Not the motor. - Problem is not big, so can be left and monitored with higher frequency until it develops - cause is probably looseness. Might be of mounting of the pump on the foundation, or internal inside the pump (loose rotor) Agreed. Still can be monitor with that amplitude. Phase reading cross coupling perhaps to confirm misalignment problem?
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Re: Is this rub or looseness

Gary Stacey ·
Looseness yes but perhaps a 'dynamic' looseness rather than foundation hence the 'busy' spectrum with a lot of harmonic content. As Has been said could be a developing coupling issue or bearing/housing clearence. However I do see where Edwin is coming from with the high 2x. Unlikely in my opinion to be mislalignment unless this has recently been worked on. Trend data would be useful as has been stated but misalignment is not usually a situation that 'develops'. Coupling lockup can give...
 
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