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  1. jmack

    Additive frequencies

    Is it possible to have a gearbox with a 30Hz input and 35Hz output shaft speed cause a 65Hz vibration frequency response? We have a machine with repeat bearing failures which has a dominant frequency of vibration at 65Hz which lines up to nothing else except the addition of the input and output...
  2. jmack

    Gear Assembly Phase Frequency????

    We have had a vibration in the third section of the paper machine which has the following characteristics. In velocity: 13650cpm - 0.067ips, 18225cpm - 0.082ips, 22725cpm - 0.0525ips, 27075cpm - 0.069ips. In acceleration: distinct peak at 4560cpm at around 0.02 g's with a gradual decrease in...
  3. jmack

    On the run misalignment adjustment

    Just as a sideline. Check where this pump is operating in comparison to the best efficiency point. More than once I have seen overhung centrifugal pumps showing high 1 X because they were operating well off the BEP. If you are operating significantly (I hate these subjective adjectives) off the...
  4. jmack

    Automobile Vibration

    Tom, I believe I did read a similar paper many years ago, but this one was comparing the natural frequencies of japanese made cars to north american made cars and highlighted a trend of the north american car makers in following the japanese trend, in producing cars with increasingly higher...
  5. jmack

    Want to lower HIGH horiz vibe readings !

    Nisqually, My suggestion would be to take phase readings. This will help to eliminate extensive time associated with the trial and error approach. J MacK
  6. jmack

    Shaft unbalance caused by oversize key

    Nisqually, Managers read eng-tips as well. Just for future reference, you might want to use words such as sub-optimal, instead of top heavy and dumb. Being right does not gaurantee success,... skilled negotiation will. 15% technical,... 110% interpersonal. J MacK
  7. jmack

    Shaft unbalance caused by oversize key

    Ralph2, It would seem that some of the more recent issues to you are insignificant, or should be "ignored". I can see why we have petrochemical plants having major disasters with this type of attitude towards precision. My advice would be to read some of the advice that Locock is...
  8. jmack

    shaft Alignment of rotating mach..

    fbjavier, First and foremost you would not treat an induction motor alignment the same as a turbine or a gearset. You also would not treat an 1800 or 3600 rpm motor the same as 4000 - 12000 output gearset, so i would ignore the advice of some who may think that this is a similar situation...
  9. jmack

    shaft Alignment of rotating mach..

    fbjavier, Ignoring babbit clearance is not standard practice by millwrights. These lift numbers are usually given by the manufacturer and are compensated for as such. Also, I have yet to see a pinion ride up a bull gear under load. Pinion and bull gears are designed so that the radial...
  10. jmack

    Shaft unbalance caused by oversize key

    nisqually, Yes a picture is worth a thousand words, and you will have to dynamically balance this type of overhung setup if you want to be effective in reducing vibration due to imbalance, it is basically the same for overhung pumps as well. Is it possible to cut the shaft off to eliminate...
  11. jmack

    Shaft unbalance caused by oversize key

    Nisqually, First and foremost with 3600 rpm equipment, alignment is always a big issue even with belt drive.You MUST align the sheaves properly first before you undertake any kind of bqalancing operation. Misalignment on belt drives can produce peaks predominately at 1X, so it is especially...
  12. jmack

    shaft Alignment of rotating mach..

    fbjavier, You are correct in thinking this float has an effect. You are actually talking about the hydrodynamic oil film that causes the shaft to lift under rotation. This oil film separates the two parts (shaft and bearing surface) with this oil film and prevents metal to metal contact...
  13. jmack

    Shaft unbalance caused by oversize key

    nisqually, A couple of things here. The first is an easy one...profile the key to match the shaft and the coupling symmetry. This is much easier than trying to compensate for a key that is not profiled. The second thing is that these type of balances are largely dependent upon the...
  14. jmack

    Looking for info on pdm programs

    Micjk, There are many "intangible" benefits to implementing a proactive/predictive program. One such benefit I have seen is that there is an added cohesiveness to the group involved in RCA, predictive and proactive maintenance regimes. It brings you closer to the reality of what is...
  15. jmack

    Transient Refiner Vibration

    I presently am working on a refiner vibration (Two 5000hp synchronous motors facing each other 1200 rpm), that has a vibration under load with the following FFT characteristics: 1200 cpm - 0.0168 ips 2400 cpm - 0.0372 ips 3600 cpm - 0.0116 ips 2138 cpm - 0.3524 ips 4276 cpm - 0.0434 ips 6414...
  16. jmack

    Strange Spectral Peaks around 0 hz?

    We also use the IRD Datapak as well as the Enwatch system and I personally see "Ski Slopes" on a regular basis. We see them in flooded dryer situations where the saturation effect is prominant, we in fact use this as an indicator of flooding! This can be saturation where you are...
  17. jmack

    Vibration Alarm Setpoints

    Setting common alarm limits, based upon mere operating speed,is clearly not the be all and end all to raising concern over machine operating condition. I have personally seen paper machine dryer bearing failures where overall magnitude readings were less than 0.05 ips (@190 rpm), and output...

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