Tagged With "Broken Shaft"

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Re: Rotor broken bars problem, is it right?

Walt Strong ·
Cando, This is a very interesting case history, but I would like to understand the sequence of events. Did you remove the motor rotor after conducting the motor current spectrum analysis? If not, what was the reason for removing it? Did the motor current spectrum reveal eccentricity after the motor was reassembled with the damaged rotor or before it was removed? During the installation of the damaged rotor to put it back into service, I would assume that the following would have been...
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Re: Rotor broken bars problem, is it right?

Lampard Nguyen ·
Hello, Rotor was fall when we disassembled motor for replacing bearings and visual inspection of rotor also. It is only time based maitenance for this motor. But, unlucky, rotor was crasked. Current Signature analysis (both of rotor broekn bars FFT and eccentricity FFT which I attached above) is performed after maitenace to ensure motor can run with this rotor for ordering new rotor delay. Of course, we will monitor this motor operation by MCSA and vibration analyis. Firstly, we will do...
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Re: Rotor broken bars problem, is it right?

Howard Penrose ·
Cando Had you performed MCSA prior to this condition being found? It is often the case in cast aluminum rotors that casting voids exist that would cause the low level rotor bar (PPF) frequency that you are seeing. Some manufacturers have more prevalent cast rotor voids than others based upon their casting process. If that is the case and you are not seeing torsional issues, then you are probably OK. The notching in the rotor in this size machine most likely is not an issue as you have a...
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Re: Broken tooth symptoms in Gear box

John from PA ·
A B2SV10 is a double reduction gearbox with the 1st reduction being a bevel set and the 2nd reduction being a helical set. The "translation" of the model number is as follows: B = bevel helical 2 = two stages S= solid shaft V = vertical 10 = size ( not necessarily ratio ) The catalog indicates that the ratio can range from 6.271 to 13.683. The exact ratios available are 6.271, 6.875, 8.000, 8.842, 10.157, 11.045, 12.662 and 13.683. The repetition rate of the fault is 0.085 sec/cyc = 11.76...
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Re: Broken tooth symptoms in Gear box

vidya Sagar ·
Hi john, Thanks for the information. We opened the gearbox recently and found that one of the gear teeth in bevel gear(intermediate shaft) is having pitting.
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Broken Gear Shaft

Jenish ·
Dear Experts, Can anybody give any expert opinion about this Broken Shaft? It is from a stand gearbox of a rolling mill..
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Rotor broken bars problem, is it right?

Lampard Nguyen ·
Dear Experts, Could you please give me some advise about this photos, Is it rotor broken bars problem? I performed current signature analysis test for this motor. In my opinion, there is pole pass frequency peaks with low amplitude. Thank you so much! Regards,
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Re: Rotor broken bars problem, is it right?

edisonindia ·
It's a aluminum die cast rotor. Not really sure what your third picture shows. If you have the test equipment, you could do a growler test.
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Re: Rotor broken bars problem, is it right?

electricpete ·
First photo shows gouge in end ring. That could be the cause of the pole pass sidebands. Second photo shows gouge on od of bore. I look for something to judge the size of the gouge. I think the gouge shown in photo 2 is also shown in the third photo just above 26 (between 2 and 6). It doesn't appear to have penetrated to a bar. So I think it is confined to the bridge area above the bars. 3rd photo - I assume that white flash is just a reflection (maybe the photo is taken through a clear...
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Re: Rotor broken bars problem, is it right?

electricpete ·
Now I'm seeing the sideband was around 53 db below the main peak? Normally I start getting really interested at 45db. What load was that? Was there any trend?
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Re: Rotor broken bars problem, is it right?

Walt Strong ·
I am trying to understand the motor current spectrum. The dominant frequency is near 45 Hz which is not common 50 Hz or 60 Hz line frequency. So was the measurement made with the motor running with VFD at reduced speed and therefore at reduced load? Did you calculate the pole-pass sideband frequency and identify it on the plot? The interpretation of side-band amplitudes may be inconclusive, if the measurement was made at reduced speed and load. I had made a diagnosis of induced draft fan...
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Re: Rotor broken bars problem, is it right?

Shurafa ·
Nice photos. I like these clear pictures. Regards-Ali M. Al-Shurafa
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Re: Rotor broken bars problem, is it right?

edisonindia ·
If the motor was not having any issues like stalling, overcurrent, current oscillation or excessive temperatures, I would run it. pete It is not cost effective to repair die cast rotors. Best to replace them, if found defective. I had replaced a few die cast rotor windings with copper for a set of 6.6 KV motors about 2 decades back, but that was a special case since the OEM had gone bust and the client was desperate.
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Re: Rotor broken bars problem, is it right?

Lampard Nguyen ·
Hello, Thank so much for all recommendation. Some information about this case: - Motor is driven by VSD with line frequency supplies to motor is 45.1 Hz. - Motor has been running with 67% FLA. - Rotor was fall when maintenance, It caused some incisions on rotor which you can see on my photos. We don't have any spare part to replace for motor. Therefore, motor must run with crashed rotor. So, we want to perform MCSA for diagnostic rotor condition. With this result, I think there is not bad...
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Re: Rotor broken bars problem, is it right?

electricpete ·
I agree, based on: 1 - Apparently you have run the motor since the damage to take the current signature. 2 - You have a vsd, so the rotor doesn't see the severe duty of direct on line start. 3 - you are planning to continue monitoring. If you see an increasing trend in sideband under similar conditions that might be a time to be concerned. If damage occurred while stationary, I'm curious what created the mark around the circumfence of rotor at that location. Maybe the od got dinged and...
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Broken tooth symptoms in Gear box

vidya Sagar ·
Hi Friends, In one of the gearbox am finding symptoms of broken tooth(Correct me if am wrong). Gearbox Make: Flender Type :B2SV10 Input RPM :1489 Gearbox Ratio:1:10 I doesn't have teeth details of the gearbox.Please find the time wave form and acceleration spectrum.Vibration levels are less than 2 mm/sec at Gearbox in all directions. Thanks in advance Regards Sagar
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Re: Broken tooth symptoms in Gear box

Walt Strong ·
John, Great analysis with not much to start with! Walt
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Re: Broken tooth symptoms in Gear box

Rao Shahbaz ·
Re: Broken tooth symptoms in Gear box
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Re: Broken tooth symptoms in Gear box

Akhil Rathore ·
superb
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Re: Broken tooth symptoms in Gear box

vibramac ·
Well done John, you cannot bet experience!!!!!!
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Re: Broken tooth symptoms in Gear box

John from PA ·
Thanks for the positive comments!
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Rotor broken bars?

Lampard Nguyen ·
Dear Experts, We have a squirrel cage inductance motor, 400V VFD, 220KW. The load is Roll which driven by Gear-box in Paper factory. We carried out MCSA and Vibration analysis for this motor. The opposition of MCSA and Vibration result was making me confuse so much. - MCSA indicates rotor broken bars problem with high peaks at pole pass sidebands. - There is no symptom in vibration spectrum. We can see result in my attachment. Please give me your oppinion! Thank you! Regards,
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Re: Rotor broken bars?

Dave Reynolds ·
To diagnose rotor bar problems in vibration spectrum: Identify actual running speed and subtract it from synchronous speed 1800-1775=25 rpm of slip, now multiply the slip rpm X the number of poles in the motor 4 poles x 25=100 cpm pole pass sidebands IF the motor truly has a rotor bar problem, then you should see the pole pass sidebands around 1x 2x 3x 4x 4x 5x rpm or some combination of the harmonics. Keep in mind your bin spacing on spectrum, you must have good resolution to see these...
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Re: Rotor broken bars?

Panta ·
Lampard, like Dave said you must cut spectrum or Fmax. should be at 5-6 speed of motor to see good patern and good haystaks . At figure 6 it should be rotor bar pass frequency pick at 1470 Hz and one pick left like twice line frequency sideband . Good luck .
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Re: Rotor broken bars?

Lampard Nguyen ·
Dear all, Thank you so much for your recommendations. I have just performed RIC (rotor influence check) for this motor. RIC profile indicates some erratic relate to rotor broken bar issue. I think that there is problem of rotor. It's a interesting case-study! Thank you! Best regards,
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Re: Finish Mill Stand Gearbox

Monitor man ·
Originally Posted by Phil2425: I am seeing 1x impacting in waveform data from a gearbox. We have opened the box up to replace a faulty bearing. We inspected the gearsets and did not find any signs of broken or cracked gear teeth. I know that other stand and other mills have a 1x during operation. Does anyone else have any experience with this. If you have a cardon shaft check the u-joint cross can be damaged. There for the "clear" time signal
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Finish Mill Stand Gearbox

Phil2425 ·
I am seeing 1x impacting in waveform data from a gearbox. We have opened the box up to replace a faulty bearing. We inspected the gearsets and did not find any signs of broken or cracked gear teeth. I know that other stand and other mills have a 1x...
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Re: Finish Mill Stand Gearbox

John from PA ·
What I see is an overall of 0.0641 in/sec pk, which is not alarming in itself, but I do see a crest factor of slightly over 4. Is this behavior something recent or has this been this way for some time? Any idea is there has been an upward trend of the crest factor? Can you take the gearbox out of service and inspect the teeth using a dye penetrant method? Audibly, does the gearbox have a pronounced "knocking".
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Re: Finish Mill Stand Gearbox

Phil2425 ·
There is not an audible knock. You can just feel a 1x thud when operating. We changed spindle components and it got somewhat better. Just very curious as to what it is.
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Re: Finish Mill Stand Gearbox

Phil2425 ·
The Crest Factor has always ran between 3 - 4.
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Re: Finish Mill Stand Gearbox

John from PA ·
Is the behavior of the impacting in the waveform something recent? Or perhaps first time observed? In light of the overall amplitude of 0.06 I'd be inclined to just watch carefully. However, if that evidence of impacting in the waveform just suddenly started I would have some concerns. By the way, what are the speeds and tooth counts of this gearbox?
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Re: Finish Mill Stand Gearbox

Bill Kilbey ·
Take some PeakVue readings, it may be much more clear.
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Re: Finish Mill Stand Gearbox

Ramos_ ·
Looking at the TWF, there are 3-4 teeth that is creating modulation that is why they appear like as 1X peak sidebands on the FFT and also look like an impacting. Crest factor will also be increased as Pk is getting higher than RMS reading (CF = Pk/RMS), especially when there is impacting. For this case, some recommended actions can be: 1. John's suggestion is good if it's possible. I worked in Cement plant before and periodically we stopped cement ball mills and can do inspection. Boroscopic...
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Re: Finish Mill Stand Gearbox

Phil2425 ·
I have been taking Demod data and there is no signs of impacting or defects in the high freq data.
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Re: Finish Mill Stand Gearbox

Bill Kilbey ·
Can you post that DEMOD or PeakVue TWF data?
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Re: Finish Mill Stand Gearboxes

Phil2425 ·
Here are the images. This data is taken in the vertical plane. Impacting is at the turning speed of the bottom pinion output shaft. This shaft has 2 gears on it. A 51T and a 28T gear. The 51T is the Bull that is driven by the input pinion from motor and the 28T mates up with a Top Pinion 28T and those drive the Rolls.
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Finish Mill Stand Gearboxes

Phil2425 ·
I am seeing a 1x vibration in our Finish Mill Stand Gearboxes. I know that a broken or cracked gear tooth will cause this issue, however we have opened up a box and did not see ay signs of a cracked or broken gear. Some of our other stands...
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Pole Pass Reading in Standard Route Readings

oju ·
Was wondering how many here take high res readings to monitor pole pass in their standard route readings? If so have you found issues?
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Re: Pole Pass Reading in Standard Route Readings

Walt Strong ·
I usually make two measurements on the motor case near the terminal box. The first measurement is a high-resolution low frequency velocity spectrum for confirming motor speed and to detect rotor pole-pass sidebands. The second measurement is high-frequency acceleration to detect rotor bar and stator slot passing frequencies along with modulation sidebands. I have detected both electrical and mechanical faults with these type of measurements. There may be other ways to accomplish the...
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Re: Pole Pass Reading in Standard Route Readings

Gary Stacey ·
I do not generally take a high res reading to look specifically for PP symptoms. I will if other issues such as audible modulation make me suspect there may be a developing rotor bar issue or if rotor dynamic eccentricity is suspected. Be interested to know what problems you have detected with the high frequency acceleration reading Walt? I don't doubt you have! Textbook states that RBF with 2x line frequency sidebands = rotor bar issues but I have not had much success with it. I quite often...
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Re: Pole Pass Reading in Standard Route Readings

Dave Reynolds ·
Agree with Gary, we have low frequency hi resolution reading on ALL of our machines, only take it when we have driver and driven speeds that are 100 rpm or less speed difference, hear an audible noise or higher than usual vibration values. Keep in mind, IF you have broken/loose rotor bars, the motor will have poor performance, lose HP, draw higher than normal amps, have a modulating noise coming from the motor, will run hotter than a normal motor, time waveform will have modulation and will...
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Re: Pole Pass Reading in Standard Route Readings

Walt Strong ·
"I will if other issues such as audible modulation make me suspect there may be a developing rotor bar issue or if rotor dynamic eccentricity is suspected." Gary, if you want to rely upon your hearing and some other means of detecting rotor dynamic eccentricity that is fine. If it is convenient for you to go back to the machine and make additional measurements that is fine. If you're making a decision not to take certain data because some faults are very unlikely that is fine. Most of the...
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Re: Pole Pass Reading in Standard Route Readings

Gary Stacey ·
Sorry should have added that I do take high res readings if there has been any change in the routine data such as harmonics, increasing overall etc. With my standard data set we will see 'skirts' around 1x 2x etc which would also prompt investigation. As with Dave I have seen very little by way of rotor bar problems in my 20 years of collecting data. I am just traking one now on a smallish motor - previously we had only ever seen the issue on large FD/ID fan motors and we collected routine...
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Re: Pole Pass Reading in Standard Route Readings

electricpete ·
I agree with above. One thing to add is "dynamic eccentricity". We've recently tossed around the idea of whether dynamic eccentricity can cause increased pole pass sidebands around FL in current under load. We had lots of discussion on that but a main point for Gary and I was that we've never seen that. On the other hand, I have seen pole pass sidebands around 1x in vibration on vertical motor at least twice where subsequent refurbishment showed loose housing fit on lower bearing, and the...
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Re: Pole Pass Reading in Standard Route Readings

Walt Strong ·
"On the other hand, I have seen pole pass sidebands around 1x in vibration on vertical motor at least twice where subsequent refurbishment showed loose housing fit on lower bearing, and the symtpom went away after refurbishment. I attributed that to dynamic eccentricity. (btw nothing ever showed in current sidebands)" I have made similar diagnosis on two different motors, one with ball bearings and the other with journal bearings. The diagnosis was confirmed by bearing repairs, and there was...
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Re: Finish Mill Stand Gearboxes

John from PA ·
Can you post some data? The fact of the matter is it would be rare to see a gearbox that didn't have some 1X. Amplitudes matter. Have you investigated alignment issues, type of coupling and its behavior, etc. You might do better posting this in the vibration related forum at https://www.maintenance.org/for...on-alignment-balance
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Re: Finish Mill Stand Gearboxes

Phil2425 ·
The 1x impacts are visible in time domain. Spectral data does not show it as much.
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