Hi we have 3 stage integrally geared compressor. after unbalance 3th stage it change with new one and 3th bearings change too but it trip after start because of high vibration on 3th stage. 3th stage rpm: 40000 1th and 2th critical speed: 11000 - 34000 bearing: tilting pad with 5 pads. load between pads. condition monitoring dose not observed 1X and 90 degree phase + or - 30 degree. (usual unbalance sign)
I guess you have looked at the data leading up to the trip enough to observe the lack of 1X. Can you tell us what frequencies were present? Supply some plots. This and you other questions are shaping up to be a guessing game. If you want good suggestions we need to see some data for this and all your other questions.
Hi friends As we know there are instructions and limits in tilting pad journal bearing. I know it's for Babbitt side (or side of rotating shaft) but I don't know anything about bottom side the side lead on cover or housing bearing. Do you know any information about it's design law's.
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Dear All, can any one support me in this problem: we have one Siemens compressor centrifugal single stage integrally geared observed a high vibration in radial tilting pad bearing in pinion shaft compressor side without any changes in axial displacements? ----------------------- Actions for inspection: *IGV & Impeller are ok but found amount of water insuction spool passing from the demister. *Gears teeth & backlash are ok. *Clearances are checked for Radial tilting pad bearings of...
I think that: Q1. What is the clear effect of water to the comp performance?and how can be observed thru vibration monitoring? The water in air/gas will effect to comp performance (changing density of gas/air) and it depends on how many water in. In my experience, one of effect you can see when you inspect impeller is erosion/corrosion on surface of impeller. I have no experience with much water in gas so I do not know how it is. However, I think that if the water in gas too much, it will...
Hi guys i am a little confused in tilting pad journal bearing curves. i know concept of preload and design factors in pads curve in Babbitt side (shaft side actually) but what is radius of back of pads? (in attached file is named R out) as we know in pivot type, back of pads contact with bearing shell (named R bearing) and i think if R out = R bearing it dose not happened any tilt. so i guess R out must be different with R Bearing. is my logic true? and how can obtain R out? if we assumed it...
If there is a mechanical pivot in (or near) the center of the pad, then the curvature of the back of the pad is irrelevant (other than that you don't want it to contact anything through the full possible range of pad tilt). It would be whatever is easiest to manufacture. I've heard of fluid pivots, which would be different. I don't know anything about those. Sorry if I have misunderstood your question.
We have Siemens SGT 300 ( 7.5 MW) Gas turbine Generator. During starting of this machine heavy vibration observed and machine tripped at 9000 RPM on high vibration ( Vibration tripping set at 90 Microns). More than 15 trial taken in this machine neglecting vibration. On opening this machine cold end bearing found damage. Photographs attached. What is probable reason for this bearing failure??
Dear sir , its clear that the bearing has continuous rub , primary suspect on Lubrication .But we could find the root cause , if we have Vibration Spectrum ,Orbit plots or Shaft center lone data ,Please post if you have any .
Hi Pawannlng, Why it need to neglect the vibration? could you share plot if any like shaft centerline, sequence of orbit and time signal, bode and polar possible. When is the last time taken oil analysis prior this incident? regards, RG
Dear Pawan, Without referring the diagnostic plots i think its very difficult to pin point the root causes of the failure. For fluid film tilting pad bearings, we need to refer more plots and one plot may not give clear conclusion. My opinion, since i am practicing vibration analyst more into this type of bearings. For hydro machines this type bearings are commonly used. Sherub
Dear Pawannlng, the possibles causes are: 1.- misalignment (external misalignment) 2.- bearing housing excentricity (internal misalignment) 3.- low lub oil pressure in bearing or any restriction in lub line. 4.- over radial load. 5.- Preload in bearing (internal or external) we can rule out the last possibles causes using technologies that Rotating Guy said (Shaft centerline, sequence of orbit and time signal, bode and polar possible, spectrum, etc).
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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