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 Members , We have a H.T.Feed Pump failure in our Customer site H.T.Feed Pump running at 3000 r.p.m and Pump has Journal Bearings and it has 12 stages .We have found Rubbing in spectrum after the physical examination , we found uneven clearances . We have found increased Vibration on 21 st and New Bearings are installed on 22 nd Sep 2018 .Again Vibration trend increasing .Please share your opinions .
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...
e have a large capacity (2 No's) Induced draft fans. One of the fan motor is showing high vibration in vertical direction at Motor DE side.Max. vibration is 3.7 to 4 mm/sec. Alarm value recommended by OEM 3.5 for motor vibration.Also abnormal sound from fan to motor coupling noticed.Kindly suggest possible cause. Also can anybody tell possible reason for 6th order dominant frequency in journal bearings?I have seen in many journal bearings such spectrum. Only 6th order is dominant in...
we had 3 lobe journal bearing in a machine with 45000 rpm. after many years bearing change with new one but second bearing was not 3 lobe like another one and it change wrongly. actually it was simple journal bearing just with 3 oil grooves and it was just look like 3lobe bearing!!! but machine started and it seem no problem on vibration, temperature and etc. i must add 45000 rpm is vendor critical speed and over speed is 35000 rpm actually. now this is my question: we did mistake but why...
does collector rotor that couples with a flexible rotor 50Hz, is rigid or flexible? and balance process do only mass residual balancing?(iso1940) Keep in mind that collector from one side couple to the main rotor and another side-mounted on journal bearing.
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.
have you checked bore alignment of bearing housing with datum point at seal location? I agree with John that have you checked the oil quality? I have ever seen a similar case with the water entered into oil.
Your graphs all show highest peak @6.133 Orders (not 6.0 Orders). Not sure how your software order normalized the spectrum but can you confirm you actually have 6 times running speed. Let's assume for a moment the spectrum truly is exactly 6 times running speed. How many blades are in the fan? 6? What type of coupling? Does the coupling contain 6 of something? Also, suggest you give us more background about the problem. Has this existed since startup or gradually increased to these levels?
What's the software you are using? Try a high resolution FFT and post it here in terms of HZ. Since you have mentioned it as an ID Fan. Make sure it is running at your mentioned orders as configured in the software. If possible change the speed of the Fan and check if the peak is shifting
@ IVIBR8 Thanks for your reply.The problem started after maintenance team adjusted blade pitch as per DCS command.Example For 20% opening they adjusted Blade pitch at 20% in local. Before this job vibration was around 0.8 mm/sec at motor DE(V) As per your Queries ID fan has 20 blades & coupling bolts is around 9 (Allen key bolts) Its Rigiflex Coupling.Complete spectrum(with Fan data) is attached. We didn't perform any alignment till date.With blade pitch operation vibration doesn't...
You should go back to the OEM. There just isn't any way we can answer your questions except to deal in generalities. My 1st question would be why was the 3-lobe there to begin with? Was it a true 3-lobe with a defined profile, or was it just 3 axial oil grooves like what you put in as a replacement?
thanks JOHN. you know works will be done with lower cost out of OEM but as i sad this replacement was wrong and for your question yes. original bearing has 3 none center lone (0.1mm off center) but second one as you said just has 3 axial oil grooves and it seem simple journal bearing. The thing that surprised me the most is that machine speed is 35000rpm.
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).
It is another mass on a flexible rotor. Balancing it may or may not affect vibrations at other bearings. Have you contacted a knowledgeable person with OEM? If vibration is considered high on the bearings, then look for mounting eccentricity and resonant bearing housing before considering trim balancing. Walt
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