I created this presentation for Mobius about 6 years ago and I recently rediscovered it and posted it on LinkedIN. I got a lot of positive feedback so I thought I would share it here as well. It is intended for people just getting into vibration. It describes how to detect an outer race bearing defect in the time waveform,, the spectrum and using demodulation. It explains the relationship between these three data types. http://www.zencovibrations.com...tion-analysis-video/ En Espanol:...
So, it's ok now to post links to a commercial site, where you are selling goods and services, as long as you provide a little useful information, and to load up your "signature" with links to your stuff? Or is that just for certain folks? Back in the old days, folks would be howling about something like this. I guess times have changed. "A lot is possible. But most of the time a little is sufficient."
Hi All, Anyone know or have information on how to convert the minimum value that FLIR GF320 camera detect the gases to ppm? Appreciate anyone can help. Butane -0.4g/hr =___ppm· Ethane - 0.6g/hr=___ppm Ethanol - 0.7g/hr=___ppm Methane - 0.8g/hr=___ppm Thank you.
There is no direct conversion for this. PPM is a dimensionless quantity while g/hr has dimensions of mass/time. You're going to have to multiply it by a period of time and divide it by some mass to achieve the correct dimensions, and to do this you would be making some pretty large guesses.
Good evening: We are monitoring equipment that rotates at low speed (below 20 RPM) and our concern is how to detect that the equipment is unbalanced or misaligned, is there any method in this regard for detection?. We have disassembled a equipment and found it misaligned and could not be detected in the vibrational monitoring. Regards.
Misalignment can occur at low speeds like 20 RPM but unbalance is a bit unlikely since the forces created vary as the speed squared. So at low speed, usually low forces exist, at least due to unbalance. There are exceptions, a bent shaft or a missing component for instance. From an instrumentation standpoint, at low speeds like 20 RPM, specialized instrumentation will likely be required. A velocity transducer for instance may have very little response, if any, below 240 CPM. What type...
Goodnight: The equipment operates at a speed of 12 RPM and the accelerometer that is being used is the SKF_CMSS2200 of 100 mV/g (attached data sheet). The bearing type is a double row spherical roller bearing. I also attach a file of the misalignment that was found on the equipment.
In your case, at such low speed, vibration measurement won't give you reliable unbalance and misalignment diagnose. I would send the rotor to workshop balancing, bring it back and do precise alignment. Normaly, rotor at such low speed doesn't need to be balanced at all.
From your specification sheet...Frequency range: – ±10%: 1,0 to 5 000 Hz – ±3 dB: 0,7 to 10 000 Hz. This more or less says it all. The transducer you are using has very little value at 12 RPM. The portion of the specification reading ±3 dB: 0,7 to 10 000 Hz is the key part as is the curve titled Typical Frequency Response. +3 dB is a 41% error (reading high) and -3 dB is a 30% error (reading low). At the low end, the 0.7 Hz or 42 CPM, the device could exhibit these errors. The device...
At such low speeds, vibration will not be an issue. Torsional distortion issues at the couplings and shaft could be a factor. Since the misalignment is clearly visible, the easiest solution would be to realign it properly.
Esta placa típicamente usa inglés. Debe tomarse el tiempo para traducir al inglés en lugar de esperar que nosotros traduzcamos sus respuestas en español. This board typically uses English. You should take the time to translate to English rather than expect us to translate your replies that are in Spanish.
Depends on the pressure, type of leak (tear, crack, piping, distance) at the leak site. Typically, ultrasound is rated at finding a leak at 1x10-3 to 1x10-4 std/cc/sec.(ASNT E-1002-96). Of course helium & specific gas detectors and mass spectrometers such as those typically used for helium as well detectors that read difference in thermoconductivity, are more sensitive than the UT. At one time, UE Systems sold a liquid known as LLA or Liquid Leak Amplifier. This was a low surface tension...
Anyone have experience using Ultrasound for Helium Leak detection. One of my guys just completed the level 1 with SDT and the instructor was saying it difficult to detect. Any thoughts would be appreciated.
Measure the amplitude at the top and bottom part of the vibration mount and it should be same across all vibration mounts of the machine, so any deviation will give u the hint of a faulty mount Measure the overall height of all vibration mounts (ideally loaded ) any major difference is a telltale sign of spring or material deformation Look for the signs of high 1x peak in horizontal direction with comparatively thicker base (however this is not always a sign of bad vibration mount)
It is common for a bad selection and placement of these feet if you as normally are select them from the machine weight and in the chart of the supplier of the feet. This is then for a vertical load normally and if you have a vibrating fan in one end and it makes the frame wiggle-waggle (see-saw?) it may be due to a resonance made up by the feet... so if you gave hi vibration in one end and not the other plug in a pine wedge to short those feet in the vibrating end to verify the problem. In...
Are those measurements on the photo in horizontal or vertical direction? What kind of machine and size and speed? Your OP question needs to specify the type of vibration mount/pad and the direction of vibration. Why do you suspect there is a vibration mount problem? Walt
Dear Walt, thanks for your comment, the motor is about 14kW (50Hz, 1500 rpm), I have checked the severity chart ISO 10816, and maximum permissible for normal operation condition is about 4,5 mm/sec for low power machine. based on this standard we consider to do some actions.. RRR
My advice: don't stick with the ISO10816 table. A 14 kW fan with vibration pads can be easily regarded as one ISO grade higher sometimes even two. The standard itself allows you to do it with some arguments.
I'll ask again " Why do you suspect there is a vibration mount problem? " What indications do you have (observations or measurements) that the vibration mounts are defective or suspect? Rotary lobe blowers produce pulsation frequency and harmonics that can change with load (pressure differential) and may excite structural resonant frequencies. There are many indications of defective or failed vibration mounts depending upon type and if correctly selected and sized such as: loose/broken bolts...
If you follow ISO recommendations, collect data as the ISO describe, Hor, Vert, Axial on the bearings. In my book I follow ISO 10816-1 as it been mu follower for 40 years and the 2.8 is acceptance and 7.1 where you at least should do something. So verify the readings, H,V,A at both bearings and tell us the result. Next check if it is 1xRPM same both H and V, clean the fan and if it doesn't help, balance it if that is not feasible actually don't want to be balanced, look at the foundation.
Mr Ramon, where is your statement about the looseness coming from? Also at 5,7 mm/s I would not talk about any vibration excitation. Have I overlooked any bearings spectrum data? What are your motor and fan bearing values? Please send us all of your recorded spectrums otherwise you can't expect a quality answer. Your post started with isolation pads, now continues with bump tests..... I think you began to start solving your machine problem from the wrong side. Let's start from the beginning.
Dear All, Today I did Dump Test in base of blower & motor, please check that we found two natural frequencies at 12.5Hz and 25 Hz, with motor in OFF position . may for that reason the system response at 1x rpm force excitation? now we can say the system has looseness with resonant vibration? RRR
I don't see any critical issues from your data sent. No obvious mechanical looseness, no critical vibration level. 1st peak amplitude is a little higher in horizontal and could indicate some residual unbalance on the motor-coupling-blower shaft line. I wouldn't say this machine needs some actions. It would be good to have some envelope/peakvue data for bearing evaluation. However if the vibration level still bothers you, you could try field balancing on the motor fan and on the coupling. I...
" Today I did Dump Test in base of blower & motor, please check that we found two natural frequencies at 12.5Hz and 25 Hz, with motor in OFF position . may for that reason the system response at 1x rpm force excitation? now we can say the system has looseness with resonant vibration? " You did not indicate what direction and locations you did "Dump Test" (impact test), but I assume it was in horizontal direction. You have a curious choice of mixed vibration units mm/sec RMS velocity...
Well, if you answer some questions it is easier to reply. So how old are the pads? OEM normally state 10 years op time and shorter in sun and chemical environ then they get stiff "change properties". So maybe the customer don't like beams in the machine and if the machine previously was ok, so change pads to new, correctly selected pads? Or make your own but blower foundations are tricky, not funny. Have you checked the bearing condition, greasing? Just asking.
Thanks for your comments: Mr Walt , Mr Oli and Mr Becar. for continues supporting in this case, I asked to Operational people they told me that this pads have not been replaced since the plant started (more than 30 years). and I checked vibration in foundation and I found 0.39 mm/sec at down side of Vib pad. to replace all vibration pads will be good recommendation for our customer. RRR
You have some cracks in the foundation also. are they serious, if you measure vibration each side of the cracks is it the same vibration or do the cracks separate parts of the concrete? Isolation pads "seismic mount" are defined to have one side mounted on a reasonably stiff foundation, if that is not the case anymore they may not work as intended. Inject something if needed maybe?
Ramon, Your "temporary" structural modifications was surprisingly effective! You demonstrated significant vibration reduction by adding mass to lower the natural frequency. I don't know if you thought the wood beam would add stiffness or not, but at least it worked quite well. I could make a suggestion for a more permanent modification, but I would like to see what you do. The blower spectrum now looks more "normal" with pulsation peaks higher than 1xSS. Good job! Walt
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