Tagged With "Enveloping"

Topic

CSI/MHM adjustable envelope alarms

tcvib ·
All, I have been a CSI/Emerson user most of my career. Never really used autostat due to the complexity of it. I have recently started using SKF and find their envelope alarm editing very user friendly. I can pull what data I would like to build my alarm from and generate the alarm using the data I selected. I generally look back through my history and find a period of good operation and select 8 or 9 FFT to build my alarm from. Once the alarm is generated I go in and fine tune my alarms...
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Re: CSI/MHM adjustable envelope alarms

Alvaro Loayza ·
Hello, I work with Emerson technology. You are right about overall alarms, you can set them manually in your trend. But if you want to check spectra alarms. Band alarms I think is the tool you would want to use. You have to set them manually. So the question is. Is there any way to get a bunch of "good" spectra (typical baseline start up measurements) to make an alarm limit set automatically? I'm sure you can make it for overall values and trying to find out how. But I haven't checked for...
Topic

TWA : gearbox

azizsuahid ·
Machine: Helical type Gearbox Location: 4 TWA H, 4 EN3 H, input nde Type: Single reduction 1480 / 349 cpm, TWA setting lor 3200/ end f. 2800cpm. Result pk pk 50g. Obvious modulation at input speed. Envelope ~40 gE pk-pk for two weeks Suggestion: to stop plant by mid june which is 4 weeks from now juz to replace the gearbox. I have a feeling to replace It by next week. But i am also facing downtime n production target. Thank you for reading and kindly comment...
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Re: TWA : gearbox

John from PA ·
The rate at which the bursts occur would indicate that the most likely source is related to the 1480 RPM input shaft. If you have the equipment and the access to the machine I would suggest an examination of the input shaft area with a strobe light. Examine the coupling area carefully including the keyway. The speeds of 1480/349 could be obtained by a 106 x 25 tooth combination which is a hunting tooth combination. Depending on the accuracy of those numbers the tooth combination might be...
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Re: TWA : gearbox

John from PA ·
Has that box ever been apart? And if so has anyone paid attention to the phase of assembly, of which there are 6 based on the 18 x 78 tooth combination? What is the past history of the problem? Something new or something that has been there for an extended period and is now getting worse?
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Re: TWA : gearbox

azizsuahid ·
thanks i dont have that access. its a diffrnt type of coupling for a 2MW motor tooth 18/78. i simply put approx. actual speeds.
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Re: TWA : gearbox

azizsuahid ·
1. Yes , many times, every 3 years, overhaul with new bearings and other things except the gears and housing. the gears have been for more than 10 years. no clear signs of wears. no oil analysis being carried out for years. 2. i am not aware the phase of assembly. i found your attached article regarding the phase which i will go through it 3. 3 weeks ago, there was a problem on the blower anchor bolt which we found it was a crack. we already fixed that by adding extra support. i 4. Readings...
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Re: TWA : gearbox

Walt Strong ·
"Based on TWA, can one conclude by saying impacts on the bearings or gears are too high and danger. meaning to say, the gearbox might fail in one week. " I would be surprised if any knowledgeable person on this BB would agree with this statement! You are putting way too much trust in one SMALL piece of data! Walt
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Re: TWA : gearbox

azizsuahid ·
noted and i will get more data
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Re: TWA : gearbox

azizsuahid ·
gearbox tag 2141.1A was replaced last month with inner race + bsf faults today gearbox tag 2141.1B is under investigation. see attachment. thanks for thorough reading and kindly comment.
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Re: Vibration motor(bearing)

Akhil Rathore ·
bearing numbers mentioned in post & in attached picture are different as BPFO is differs for both the mentioned brg nos
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Re: Vibration motor(bearing)

Sin ·
Thank AKHIL RATHORE , I'll check it.
Topic

Vibration motor(bearing)

Sin ·
Hi all! Motor have: DE bearing: NU332 NDE bearing: NU330 - 6330 I use omnitrend (pruftechnik), it has bearings (attached files). I choose bearing true or false? Can you help me explain signature of attached files? Thank all^^
Topic

envelope band pass filter

aziz58 ·
hi dear all as u know some analyzer have ability to set various band pass filter and F max for envelope spectrum . what is best setting of them according machine speed and defects frequency ? I saw different suggestion .is there any standard ? best regards
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Re: envelope band pass filter

Dave Reynolds ·
filter for envelope readings If you put the above search into the magnifying glass at the top of the page close to your name, it will search for your answer, lots of info on this subject in the boards Dave
Topic

300 Hz and harmonics at envelope spect. (DC Motor)

Onur Gün ·
I have never seen an envelope spectrum like that. At full wave rectified DC motors, we normally see 300 Hz peak but with harmonics at the envelope spectrum is not common for me. What can be the problem or are there any problem? NDE Envelope Spectrum NDE Velocity Spectrum NDE Accel. Spectrum DE Envelope Spectrum DE Velocity Spectrum DE Accel. Spectrum DE Envelope Spectrum
Topic

Envelope alarms/Severity Assessment and changing bearings

Costa Ilic ·
Hello to all, I believe some of you are in dilemma but I hope so meany of you are much more experience than I am. Making decision of changing bearing base on envelope alarms is not always the best approach but if all envelope filter are set up correctly and it is nice development of bearing fault frequency over life ob bearing what your you advice and do you have a reference to point out for correlation amplitude in envelope spectrum with level of fault in bearing. I am referring to regular...
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Re: Envelope alarms/Severity Assessment and changing bearings

Costa Ilic ·
Thank you BECAR , Your answer is something that I expected, there is no simple and cross-platform rule. I was hoping that there is someone with more experience or knowledge from me or someone has some rule of thumb at least that have been proven in practice...
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Re: Envelope alarms/Severity Assessment and changing bearings

Becar ·
There is such a variety of machine types that envelope standards will never be something to rely on. The only way is setting alarms for each individual machine seperately according history of measurement, experience etc.
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Re: Envelope alarms/Severity Assessment and changing bearings

Rotating Guy ·
Hi, I am using enveloping for deeper analysis but sometimes it doesn't needed or i mean it is confusing, i do usually basic TWF and Spectrum and i can get the bearing fault, usually before i go replacement of bearing i check the amount of impacting if it get worsen. regards
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Re: Envelope alarms/Severity Assessment and changing bearings

Costa Ilic ·
Hello to all, What we are referring here envelope analysis is something we use but not for making decisions in future, using it just as a tool of an early indication of a problem but most of the time we trust more TWF and Spectrum, interesting. Can we say envelope analysis is not so practical tool?
Topic

When to use filter 1, filter 2, filter 3 and filter 4 of the SKF acceleration enveloping (gE)?

jorgeluis-2000 ·
Good evening, I would be very grateful when I used filter 1, filter 2, filter 3 and filter 4 with the SKF acceleration enveloping (gE)? and what accelerometers to use in each of these filters to detect faults in the bearings?. SKF uses 4 filters: Filter 1 = 300 - 6 Kcpm Filter 2 = 3 K - 60 K pm Filter 3 = 30 K - 600 Kcpm Filter 4 = 300 K - 2.4 Mcpm As the failure progresses, is the filter changed or are these filters used only for early failures? and not to follow the progress of the...
Topic

RMS o Peak to Peak Acceleration Enveloping Alarm?

jorgeluis-2000 ·
Messrs. Forum: Good evening, I will greatly appreciate a query regarding the attached SKF (Acceleration Enveloping (gE) Alarm), there is confusion about it, in vita that literature has been found where it says that the values of Enveloping Severity in this table are Global Values (RMS) of gE and there are other literatures where it says that these values of Enveloping Severity of the table correspond to values Peak to Peak of gE. Please your technical support.
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

Becar ·
Very good question! I am not a big fan of the ˝table˝ envelope analysis (I don't use it) but I know this SKF enveloping alarm table and I know the confusion about it. Can you provide some source, where you have seen that the values in the table should be RMS values? As the table comes from SKF, I think you should accept the SKF literature only. But here is one thing that bothers me. Per my experience the values in the table should be closer to RMS than P-P. That is why I never used it for...
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

Akhil Rathore ·
Hi Can you attach the literature where the gE values are said to be in RMS. SKF table is in pk-pk. Thanks Akhil
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

DBTCMP ·
SKF gE is always measured in Peak to peak never rms and 1 average.
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

Rotating Guy ·
Hi, g is always at P-P, i used RMS for velocity spectrum. regards,
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

DBTCMP ·
Don’t know who claimed gE was measured in rms, that is just wrong. I work for a skf distributor and skf have always told us Peak to peak. Also remember only one average to be taken,
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

Akhil Rathore ·
That literature is still awaited...!!! Meanwhile you can see this Webinar recording..watch it till the end. http://hiresmedia.skf.com/camp...sentation_html5.html
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

jorgeluis-2000 ·
Good afternoon, attached an extract of a Thesis that I found on the Internet (in Spanish), in the Envelope spectrum says Ge peak to peak but in the spectrum note says global value 3,814 gE RMS and this has created confusion, it is assumed that the global value should I say 3,814 gE peak to peak or 3,814 gE RMS ?. I will appreciate your comments. Greetings.
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

DBTCMP ·
Again as I said RMS is of little use with gE, always use peak or if possible true peak. the reason for this is impacting get avergaed out and are of little use. Please find from skf technical newsletter. Quote- gE why not to average. Fast Fourier Transform (FFT) relies on a signal consistently repeating itself with time and averaging is used for standard Condition monitoring as it allows the data to become more statistically correct. However the process of averaging when applied to gE...
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

Akhil Rathore ·
As per the spectrum you've attached the gE value recorded is 3.814 & the Y axis shows the measurement in Pk-Pk. I dont know why he wrote gE RMS below the spectrum when he measured it in pk-pk. Also if he mathematically converts 3.814 pk-pk to RMS the value will change. So I would personally consider the comment below the spectrum a Typo error mentioning it in RMS. Thanks Akhil
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

DBTCMP ·
That’s true but the document is aimed at the technologies initial basic use. The Lubrication capability was a field engineers discovery in later years. I I myself use gE for Lubrication purposes in my field work but still have it setup to detect in peak. i don’t speak Spanish so cannot decipher what that document is outlining.
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Re: RMS o Peak to Peak Acceleration Enveloping Alarm?

Becar ·
@DBTCMP The SKF newsletter doesn't consider that some people (not me) use Envelope / Peakvue / Demudulation for lubrication issues also. In that case the RMS value is a lot more important than P-P.
Topic

Demodulation Vs Acceleration Enveloping

Raul Rios ·
Hi all! I have a doubt in relation to both techniques. Are they similar algorithms? How are both techniques different? The gE (ENV) in a commercial unit that is associated with the speed of rotation and the size of the bearing? What is the best techniques? Thank you for your kind comments. Regards, Raul Rios
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Re: Demodulation Vs Acceleration Enveloping

Rotating Guy ·
Hi Raul, I prefer to use acceleration enveloping for rolling element the demodulation for gears. regards, RG
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Re: Demodulation Vs Acceleration Enveloping

Raul Rios ·
Thank a lot for your input...but, ¿Why? ¿What is the difference?
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Re: Demodulation Vs Acceleration Enveloping

OLI ·
Same question, same answer. In principle they are based on this theory but may be different depending on implementation by different brands and instruments: https://en.wikipedia.org/wiki/Demodulation It should depend on that you have some modulation to demodulate and your filters are set so there are some signal left to work on basically. From start the rectification suppressed the noise from cavitation so you could find bearing faults in cavitating pumps since those are mostly extinct by...
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Re: Demodulation Vs Acceleration Enveloping

John from PA ·
There are some good online materials that discuss this topic in depth. Basic information on the technique, go to https://www.bksv.com/media/doc/bo0501.pdf More in depth, go to https://apps.dtic.mil/dtic/tr/fulltext/u2/a311546.pdf
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Re: Demodulation Vs Acceleration Enveloping

Raul Rios ·
Thank you all for your kind comments. Regards,
Topic

Strange harmonics on horizontal pump

Kamilu ·
Hi all, it is my first post here, thank you in advance for all the answers. I have been monitoring 45 kW pump, ~1480 RPM and i have seen strange harmonics approx. at ~6,31 RPM, strongest on DE pump and motor side. I have checked bearings in manufacturer catalog and it says that these should be : Motor : 6313 DE/NDE Pump: QJ 313 DE / 2213 NDE None of the bearings fault frequencies match with 6,31 harmonics. The closest one are 2x BPFO motor bearing at 6,142, and pump BSF at 6,661. Pump vane...
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Re: Strange harmonics on horizontal pump

Becar ·
Hello. I am sorry to say that but your spectrums are a mess and from that point you are talking all wrong. Why do you use Orders for X axis, after that Hz, and again Orders...? You are saying a couple of times you have harmonics of 6,31 RPM. This is not true. You have harmonics of 6,31 x Orders. It is close to bearing frequencies you mention but could also be close to vane pass frequency. You should check the exact number of vanes, verify your rotation frequency. For a motor bearing check I...
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Re: Strange harmonics on horizontal pump

Kamilu ·
Thanks for your reply and sorry for my mistakes. I'm an intern and i try to learn vibration analysis on my own using only Internet and books. I've made new measurments with higher number of lines but lower frequency for velocity spectrum and figured out that shaft speed is 1486 RPM what makes these harmonics 6,28 X Orders. Now the closest bearing frequency is pump DE BPFI - 6,547 X Orders. But i have to tell you that i'm not sure if bearings installed are the same that in manufacturer...
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Re: Strange harmonics on horizontal pump

Becar ·
It is a pitty you don't have the ability of time waveform. From the data available, I would say the worst thing is the envelope spectrum on the pump (the last one). The look is similar to bearing fault frequencies which can't be confirmed from your info. The question is, why those frequencies are more obvious on the motor velocity signal than on the pump. It could be because of some construction instabilities or because of a bad coupling alignment. However envelope spectrum on the motor...
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Re: When to change a bearing?

JJ13 ·
The defects may not be visible with the naked eye. John gave a good resource on bearing failure stage. We typically wait until a bearing defect shows in velocity before changing. Our plant is not typical though, because we have 3 down days a week. It is also worth mentioning that a bearing in stage 2 failure can have less than 10% of the bearing life left. Depending on the service of the bearing it is not always advisable to allow it to degrade to a point of seeing defects with the naked eye.
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Re: When to change a bearing?

John from PA ·
A good discussion of the four stages of bearing failure can be found at https://reliabilityweb.com/art...e_stages_responses/. It sounds like the approach you describe is catching the bearing at the 2nd stage where clear visual indicators of distress are often not present. If the operation of the machine permits it generally is advisable to operate to stage 3. That gives a better indicator of the actual cause of failure, especially if the bearing is analyzed by the bearing OEM.
Topic

When to change a bearing?

MARCO20002000 ·
Messrs. Forum: Good afternoon, I would appreciate sharing information about when to change a bearing? I commented that we have a company that monitors the condition of the bearings and in their vibrational analysis reports they only analyze the acceleration envelope spectra and have placed as alarm limits of SKF Acceleration Envelope. We have disassembled the bearings that supposedly had wear detected by the Acceleration Envelope and no anomaly was found. I will appreciate your technical ...
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Re: When to change a bearing?

Ron Stiemsma ·
Also depend on the machine. Worked at an aluminum rolling mill where bearing defects would also be seen in the aluminum product. Very costly so we changed those as soon as the spike energy data indicated something was wrong. (no visible indication) Now I am in the power industry and we usually wait until the higher harmonics start to show up in the normal spectrum. It also depends on what the trend is doing. I have bearings with defects that have been steady for years.
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Re: When to change a bearing?

Ralph Stewart ·
Why do they use only or report only the use acceleration enveloping for analysis and making decisions on faults? Would it not be better to use velocity as the main source of analysis and the making of a decision to replace the bearing? Sounds like someone might be making the wrong choice in their choice of units, Fmax, Resolution, type of final analysis, etc. Do they not collect conventional data using velocity units rather than using a possible filtering system of analysis with a high...
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Re: When to change a bearing?

Akhil Rathore ·
Acceleration Envelope is a good tool to identify bearing issues..but sticking only to that is not wise. there are so many other things to look at. I would say replacing the bearing is the sole discretion of the analyst who has been monitoring them continuously as many things are to be kept in mind while taking the call. depends from machine to machine, bearing to bearing, next shutdown....and so on.. many of us want that the removed bearing should have some visible faults, but is not...
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