Re: Piping Load and Machine vibrations

ive worked with the vibration and piping guys for quite a long time (this was during the days when ird and simplex rule). i have not observed a turf war between the rotating and fixed equipment honchos. matter of fact, if something new came up related to the vibration of equipment in which the piping is suspected as the culprit - there was a mad scramble for the data.

if the equipment has already been succesfully commissioned before the spike in the velocity has been noticed then the piping then do it. why? if the nozzle joint has been forced, then the vibraton signature when the baseline was being taken should have caught it.

• In PipingDesign@y..., RaviRaj_Rastogi@r... wrote:
  >
  > The question below may not be directly related to the Pure Piping
  design
  > nevertheless of great importance in an operating plant.
  >
  > In an operating plant a conflict between Rotary and Piping often
  arises
  > whenever the rotary machine developes malfunction, attributing the
  cause to
  > each other.
  >
  > On Line Machine Monitoring System for a high speed Rotary machine
  say a
  > Centrifugal compressor, gives data like Shaft locus plots, Online
  > vibrations characteristics seen at the DE (Drive end) and NDE (Non
  drive
  > end) bearings of the machine, including the similar data for the
  driver
  > shaft /Gear Box (if required) etc. This data when interpreted
  properly can
  > give information about any malfunction serious enough to cause any
  > unplanned Plant outage.
  >
  > However, in a particular case, where a sudden increase of
  vibration level
  > after a satisfactory operation run for several months were
  recorded at the
  > DE of a centrifugal machine, it was inferred from the locus plot
  of the
  > shaft , that external pre-load exists on the machine. The bearing
  oil
  > temperature / pressure recorded normal.
  >
  > Here my question to the forum is that ,in what manner does the
  external
  > preload ( which is static Force, due to piping on nozzles) can
  cause high
  > vibrations seen by the shaft bearings. Can there be any correlation
  > established between the Shaft locus or any other parameter of the
  machine
  > to the external pre-load seen by the machine. Request your views
  far and
  > wide.
  >
  > Regds