Soft Foot

Soft foot is a term used for machine frame distortion. The distortion is caused when one or more foot of a machine differ in height from the others.[1] This in turn may be due to differences when the machine was manufactured, a squishy footage with oil film etc. between foot and base, a bent foot, or it may be induced by a pipe to which the machine is attached (e.g. a pipe on top of a pump), which prevents the machine from touching all its feet to its base.

Soft foot usually gives rise to a 1x harmonic of the rotation frequency in the spectrum when radial (horizontal or vertical) vibration measurements are taken. It can be detected in this way.

Similar harmonic 1x is caused by misalignment and looseness. Usually not only will it resemble them, but it also causes misalignment, imbalance and other problems. In fact, it may be loose, not strictly a soft foot. Therefore, a way to tell the difference is needed.

To differentiate soft foot from misalignment and looseness, even if it causes misalignment when present, one way is to loosen each foot bolt at a time, while the other three are tight. If loosening one of them reduces vibration amplitude (which would be opposite to what one would expect if the machine was all right and we caused looseness by unscrewing of the bolt), then soft foot was present.

Another way to differentiate soft foot from looseness are phase measurements between the machine foot and the base/ground. 180 degrees difference indicates looseness.

Soft foot can be detected by using a variety of methods, including:

Once soft foot has been detected, it can be corrected by shimming the machine feet until all four feet are in solid contact with the foundation or baseplate.

References

  1. ^ Case, Brad (2010-06-04). "Soft Foot–What It Is and How to Minimize It". acoem.us. Retrieved 2025-08-04.

Content Disclaimer

Informasi ini disarikan dari Wikipedia dan disajikan kembali untuk tujuan edukasi. Konten tersedia di bawah lisensi CC BY-SA 3.0. Kami tidak bertanggung jawab atas ketidakakuratan data yang bersumber dari kontribusi publik tersebut.

  1. The information displayed on this website is sourced in part or in whole from Wikipedia and has been adapted for the purpose of restating it. We strive to provide accurate and relevant information, however:
  2. There is no guarantee of absolute accuracy. Wikipedia is an open, collaborative project that can be edited by anyone, so information is subject to change.
  3. It is not intended to constitute professional advice. The content displayed is for informational and educational purposes only. For important decisions (e.g., medical, legal, or financial), please consult a professional.
  4. Content copyright. Wikipedia is licensed under the Creative Commons Attribution-ShareAlike License (CC BY-SA). This means that content may be reused with appropriate attribution and shared under a similar license.
  5. Responsible use. Any risk arising from the use of information from this website is entirely the responsibility of the user.