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  1. vgarzani

    Predicting chattering

    Thank you all for your posts. In response to the question what would we do if chattering would have been predicted: Well, we avoided the issue by making a procedure change which precluded having to wade into the what-if's that resulted in conditions that may have resulted in chattering or...
  2. vgarzani

    Predicting chattering

    We are analyzing a system at a plant for a postulated accident and are predicting transient conditions. This is a water system and in the transient two phase conditions are predicted. Predicted seal leakage is an input to the system and the transients show peaks of high leakage flow into the...
  3. vgarzani

    Large Machine Resonance base Repair

    If a quick and dirty model of stiffness is AE/L, then for grout, even if 'E' is quite small, 'A' surely is huge compared to the anchorage. At my plant we have made big improvements reducing base motion by carefully applying an epoxy grout under existing base plates and skid frames, where ODS...
  4. vgarzani

    Azimuth Slew Bearing Vibration/Frequency Response

    I assume some sort of lubrication is involved. So, you are going to do some testing for validation if it really is important - right? My thinking is that with a test payload and a well defined mounting some preliminary tests could be quickly done to get your model of the bearing tuned in. But...
  5. vgarzani

    Can Pumps Operate Below Shutoff Head?

    Your pump sounds like the 900 hp big brother of the 600 hp variety that we have. Q: Is the miniflow routed directly back to the pump suction? Also, how sensitive do you think vibration is as an indicator of poor hydraulic conditions in this pump? I'm not really sure, even though our pumps are...
  6. vgarzani

    flywheel interference fit to shaft.... allowance for ID expansion?

    Are you having step changes in 1X response even after using the 3 tangential key design? I have 8 of these things in service, but haven't installed the 3rd T key yet. When lightening strikes our switchyard, it is not unusual to see a number of step changes in 1X. The first time it happened...
  7. vgarzani

    Why is stiffer better?

    A couple of basic considerations: 1) The example of many belt driven fan units is to float the whole machine, but to ensure what is isolated is of itself stiff for general reliability - for example there is bracing to limit deflections due to belt pull. Kind of the best of both worlds -...
  8. vgarzani

    shaft Alignment of rotating mach..

    You may consider making an effort to quantify thermal growth. Acculign (not sure of spelling) is a simple system where benchmarks are mounted on the bearing casings and on the foundation (or whatever your interested in really) and precise distance measurements are made in three dimensions at...
  9. vgarzani

    time frequency views of machinery vibration

    Have to admit - no new insights or catches yet. Some interesting structure apparent in geardrive data - but you guessed it, we had it called anyway. I do have a situation that seems to be pretty well depicted with time-freq view, I think involving unsteady flow in a single stage vertical...
  10. vgarzani

    time frequency views of machinery vibration

    Used to be PdM person at NucPowerStation, now am pump Eng. but still dabble. I was intrigued by Gaberson's recent article in S&V on Wavelets. Found an excellent time freq. toolbox for Matlab at: http://crttsn.univ-nantes.fr/~auger/tftb.html - skip to the chase, the Choi-Williams distribution...
  11. vgarzani

    Age Effects On Performance Curve

    May be too late in this thread, but the thrust curves mentioned by vanstoja were most interesting. Where do these come from? Force transducers in the mounting structure during performance testing? I have always thought that a step change improvement in condition assessment (either at the...
  12. vgarzani

    Velocity & Displacement

    This may not be specifically practical to your objectives, but with regard to the transient nature of what you will be looking at, consider browsing discussions and examples of time-frequency analysis. Look at UMich and Rice electrical and computational science schools. I think the academic...
  13. vgarzani

    BASIC MODELING

    Correction, I-xx and I-zz were the interresting terms. Doesn't change the message - just wanted to correct the mistake.
  14. vgarzani

    BASIC MODELING

    Validating FE is fun, but be ready (and open) to learn stuff. Regarding the mass, clearly the closer to a sphere it is the less it will matter. I used a lumped mass to represent a cooling tower gear box and fan - I clearly had to iterate with the I-yy (y being up). Be able to develop a matrix...

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