Your question seems to be of a general nature so I can't be very specific in my reply. If you want to be more specific about a particular machine, perhaps some better guidance can be offered. It would be my recommendation that gear mesh in virtually any machine be monitored. Most specifications today place limits at about 10 g's peak, or less. High speed gearboxes tend toward the lower end, perhaps the 4 g's peak area, where relatively slow gearboxes may have specifications up near the 6 to...
I'm talking about the high speed gearbox at speed of 88hzs. And the gear mash on 5902hzs is the previous frequency of this gearbox was (.2g)it has now gone up to 2.1g. The vibration in the gearbox 2.8mm / sec. and acceleration increased from .2g to 2.1g, sometimes even up to 4g. That is why I had asked this question that if there is acceleration with the mashing, then how worried it is. thanks's for given the feedback.
Some questions: What was the period of time from 0.2 g to 2.1 g? Is this a double helical or single helical gearbox? What type couplings are used? Are you doing lubricant analysis? Is the machine equipped with proximity probes and if so, are you monitoring the gap voltage?
The amplitude of gear mesh directly related to the load of the machine . have you check the load of the gearbox at this period? Have you seen sideband around the gear mesh? And be sure about the alignment
This statement can be true in a high speed gear set that is under distress. In a "healthy" gear set the statement may very well be incorrect. Many geometric modifications to the gear profiles, lead, etc. may exist in high speed gearing that can influence mesh frequency exactly opposite to the statement. In other words, at light load the mesh frequency component may be higher than that obtained at design load. Another question for the OP, how is this accelerometer mounted?
I guess I have never noticed this on my 2130 or 2140, but when i'm taking a point reading my live data shows the waveform in in/sec. But saved waveforms are in acceleration/G's? I have combed through every setting and don't see an option to change this, or maybe i'm just missing something and it's supposed to integrate for averaging? I just cant understand why when taking data I cant view it in its saved form of acceleration.
I would like to ask you for a recommendation regarding the existing problem of high acceleration of the gearbox casing. The gearbox is single-stage with cylindrical helical gears. It is installed between LP and HP centrifugal air compressors. Available gear unit data: rated power: 6491 kW bull gear speed range: 5280 rpm – 6480 rpm pinion speed range: 9000 rpm – 11040 rpm number of teeth on the bull gear: 99 number of teeth on the pinion: 58 The gearbox accelerations are measured with two...
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.
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...
Typically acceleration enveloping, spike energy, peakvue etc... is used in order to see the initial indication of bearing or gearmesh defects which are then tracked for changes. We usually use straight acceleration peak to peak time waveform readings and not the algorithm (enveloping) to determine severity and generally look for physical movement (defects showing up in velocity) before calling for a change out. Of course this depends upon the ramp up (rate of change) of acceleration as well.
It depends on customer decision. The analyser will give a recommendation based on data. Also, follows up the trend of acceleration envelop. If found bearing frequency in the spectrum, first he will ask to relubricate the bearing. If the trend follows up, He may recommend changing bearings. Bearing frequency will go up very fast damage the bearing (maximum 2 months, based on my experience )
It is an extraordinary privilege to communicate with a man who worked for BN. At the moment I am not able to answer your questions. I need some time to check the details. I believe that I will be able to inform you regarding this on Tuesday, so I'll get back to you. Just one more information. Unfortunately, System 1 is not installed yet, but Data Manager 2000 is intalled. However I believe that the same verification test for accelerometers is needed.
Ah...data manager 2000. Great package in its day and yes th verification needs to be done. By the way I failed to answer your previous question about soft foot and the effect on casing levels. I would suggest care in this regard. It is possible to purposely rack the housing, distort it in other words, to shift the tooth contact. This is done in single helical gearing and not double helical gearing and more often on a fabricated steel housing as opposed to a cast housing. This is accomplished...
One of the accelerometers is old and never calibrated. The second one is new, installed a few months ago. The accelerometers are firmly installed in the machine casing using the mounting studs. The inteface modules have a sensitivity of 10,2 mV/m/s 2 . The Data Manager sensitivity was configured to 9,75 mV/m/s 2 because elecrtical safety barriers. Nobady has ever felt any strange noise in the gearbox. We shall do the impact test of the casing when the machine will not be in operation. Do we...
Spectrums seem much cleaner but still show excessive levels, especially the first one with the mesh frequency level of about 143 m/sec^2. Lacking any historical data to prove the machine ever ran lower would make me concentrate on the casing being a source of resonance. Walt raised a good question about the housing around the accelerometer. Is the accelerometer mounted to the casing and the housing only affords protection, or is the housing mounted to the casing and the accelerometer is...
Acceleration and vibration velocites wiil be measured by the portabe at the beginning of next week. DM2000 shows the overall values as well. It can be seen in the attachment of my first post. Anyway I'll provide new data.
Nothing magic about the Hanning window and I'm not sure that Data Manager had the capability. With a sine wave exactly at a spectral line the error is 0%. If the sine wave is midway between the two frequency lines, a case for a maximum error, it is 15% (1.4 dB). I'm also not sure if the Data Manager had resolution beyond 400 lines.
Measured vibration values at bearing locations of the gearbox are attached. DM2000 has a resolution of up to 400 lines. Accelerations are measured in rms values. Therefore, there is no overall amplitude values in the spectrum plots. If we change the measurement in pk values, the previous data will be lost.
Riro, what is the date format? Is 04.03.2019 March 4th as would be typical in Croatia according to the web? Based on your prior response I was expecting data from early May. Can you provide details on the transducer and how it was mounted? Do you have any insight as to what the frequency is at 2537 Hz? Mesh, based on your previous tooth combination is around 8712 Hz, which I don't see but I do see something at 9661 Hz labeled as "gear damage" in the Symptom portion of the plots.
There's a possibility that a structural resonance was introduced by the process of replacing the damaged gear a few months ago. You may conduct a transient test to confirm if there is a resonance at around 9650 Hz. The suggested procedure is below: 1) run-up the machine in its speed range, i.e. 5280 ~ 6480 rpm 2) record the acceleration level of gear mesh frequency at each speed in the range with an interval of say 5~10 rpm 3) plot the gear mesh vibration level against gear mesh frequency in...
Transducer saturation is a likely situation. There are some accelerometers that are 25 mV/g in the market place that are less likely to saturate. But look at your data and the practicality of the situation. 100 g's peak at 60 Hz is slightly over 1/2 inch pk-pk displacement. 100 g's peak at 6000 Hz is slightly over 0.05 mil. Is that your transducer at about the 12 o'clock position in the picture? How is it mounted? Can you post a representative spectrum?
Data is collected in the vertical orientation with a magnet mount using a high frequency accel. and is being collected on the center of the case. We found some cracks in the piping which lead us to investigate further and is why we are collecting casing data. Here is a spectrum of the point.
Magnet mount is a major contributor to what I see in that spectrum. I suggest you review the paper at https://www.ctconline.com/pdf/...nted%20Resonance.pdf and specifically Figure 2 that indicates that the upper limit of measurements with a "curved surface magnet" is about 2 kHz or 120,000 cpm. That may not be the magnet you are using. An accelerometer has a mounted resonance based on a stud mount into a very specific machined surface. Anything you do other than that lowers that mounted...
Sorry for miss information. I collected vibration signal from reduction gear box. The input pinion speed 22124 rpm, and output 1800 rpm Generator. Dear John, the unit is the topic "High Vibration Gen during No-load" I wonder about 500 Hz and Harmonic, why have many harmonic of 500 Hz and the amplitude is the same level. I suspected it come from ground loop or error signal, not mechanical problem. Ref. to frequency chart of gear not have 500 Hz. Thank & regards,
Costa, Is the vibration highest at a specific speed or is it high no matter the speed? Startup/coastdown test? Bump tests? Is this a new machine design? Are you in the beta testing stage of design? I see multiple bearing stands, can you provide a plot that shows all data that you have collected in radial and axial direction? Are you trying to compete with the Solmaz unit? Looking at your machine (yellow) the looseness is most likely coming from the machine base as previously posted. The...
Hi, I am bit confused with the acceleration severity limits( 'g ' values ) for high speed and low speed machinery. so, kindly let me know what are the standard limits.I will be very thankful if you send me a copy of that. firstname.lastname@example.org Thanks in advance, Regards, NAG.
dear all Have a electro motor with bearing noise NDE Bearing is NU 1044 M out put:3700 kw speed:750 rpm (Shaft speed frequency 12.5 Hz) Frequency drive controlled. Electro motor has increasing Acceleration RMS value (5 g today) and peaks at lower frequency on Velocity FFT. Peak of 7.17 mm/s (0-P) at 8.75 Hz. Acceleration FFT is showing peak of 3.2 g (RMS) at 2950 Hz. Any suggestion what can be the cause and how severe is this numbers..
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
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 ...
Dear All, I would like to know below points please anyone can give your valuable answer for below . Why we are measuring vibration readings in three directions ? and what is the reason for measuring vibration in these three directions ? and why we are measuring Acceleration or peak or in Horizontal direction only?
Hi I thought of worth sharing this. I found some weird vibration pattern (see attached images) on one of the Dry felt roll bearing. The peakvue waveform has lot of impacting. Outer race frequency was there with 0.2 order side bands. Nothing severe appeared in normal acceleration spectra. I have asked to inspect for severe looseness ASAP. So maintenance crew opened the bearing next day, with surprise they found 2 rollers out of bearing rattling inside the housing. Has anyone come across...
Dear All, How can I measure displacement using accelerators in VibXpert II using route (double integration). I have tried to make a new task template but it required displacement sensor to measure displacement. Can anybody guide me how to do that?
The 3 directions are used to evaluate the motion (vibration) in the space. Usually the largest motion will be the most important and they are almost always unequal. One can record the (translation) motion of the bearing housing in all possible directions which are 3 per basic physics. Recall 3D. This approach is oversimplifying the real physics of the machine but it serves the practical applications. An important assumption is that the bearing housing acts as a rigid object or like a point.
I am picturing, without the benefit of pictures, that the cages/retainers are in mighty tough shape to have allowed the rollers to escape. Sounds like the tail end of the failure process. Timken calls it "total lock up" http://www.timken.com/en-us/pr...-Reference-Guide.pdf
Hi Rookie, I see same patterns in the TWF in 1/19/2015 and 12/2014 waveform too. what was the faliure mode at that time during that period Regarding your failure I have several experiences Rollers may come out of spherical roller bearings in Prong type brass metal cages. ( Reason - insufficient lubrication and brass is a self lubricator/sacrificer ending up in increased cage pocket clearance) The rollers coming out is also possible when there is sudden acceleration and deceleration of the...
Can hear the noise when close to the bearing (airborn) , attached wav file is from a electronic stethoscope and recording is 10 sec from bearing with noise and 10 second from similar motor without issue. attached is the velocity time sheet from vibration tool.
On the audio file, has the power to the motor been cut at about 9 seconds, or does the noise suddenly cease? I also note that the bearing you mention is a cylindrical roller bearing which can exhibit signs of skidding motors. A good thread that discusses this is at https://www.maintenance.org/to...g-skidding#131103501
The recording was 10 second from the noise bearing, then 10 second from another motor with same bearing operating at same condition. In the Velocity FFT sheet is it peaks (10mm/s O-P)on FTF frequency of 5.58 Hz (motor is operated at 750 rpm. Will have a look at this thread.
Removed the bearing and attached picture is how it looked like. looks like false brinelling. damage to outer race was on lower part. also looks like contamination in the bearing or skidding damage to outer race. vibration measurement had high peak in FTF frequency range on the Velocity FFT. What i think is strange is that temperature was normal!
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