Vibration measurements

Stork Optimization Services has two systems to perform vibration measurements, viz.: CSI portable spectrum analysers or the multi-channel real-time analysers of Bently Nevada. Stork Optimization Services is able to carry out the measurements below at short notice anywhere in the world in order to demonstrate the dynamic behaviour of your installation.

Portable Spectrum analyser

This data collector performs and records vibration measurements on various sorts of rotating equipment. The measurements can be sub-divided into 3 categories on the basis of the customer’s wishes:

Zero measurements
A one-time only measurement is performed shortly after an overhaul or new construction.

Trend measurements
These measurements are performed periodically, in which slight rises can be noticed at an early stage.

Troubleshooting
These measurements are performed in the event of deviating behaviour of the installation in order to identify the cause within a short time.

Considering the short time needed to prepare this equipment, we are adequately able to perform vibration measurements at our clients’ premises. This spectrum analyser can detect the errors/ defects below:

Gear damage
Bearing defects, sub-divided into:
- inner ring damage
- outer ring damage
- roller elements damage
- cage fractures
Alignment errors
Looseness and play
Imbalance (including on-site balancing)
Resonance areas (using impact test)

A possible cause determined during the measurements is discussed with the client, and Stork Gears & Services may take direct action. Any further analysis needed can be carried out at short notice and recorded in a report.

Multi-channel real-time analyser

The multi-channel real time analyser is used to determine the dynamic behaviour of your turbo machinery simultaneously with several housing vibration, axle displacement recorders and key phasers.

Several of the data presentation techniques, which can be used to give a correct analysis, are briefly described below:

Orbit or time-based graphs
Give the actual vibration signal in time. These plots give information about the phase, unfiltered amplitude, frequency and form of the dynamic movement of the axis.

Trend graphs
Used to plot variables such as vibrations, pressure and temperature against time. Parameter change can be an early indication of possible defects in your installation.

Radial axis position graphs
Show the average radial axis displacement in the two dimensional plane. Changes in axis position indicate possible changing forces on the axis, e.g. as a result of alignment errors or process forces or indicate wear of the white metal.

Bode and polar graphs
Can show amplitude and phase of the filtered signal combined. These graphs are used to visualise lateral resonance frequencies. The results can indicate how good a system is suppressed by the passing of lateral resonance.

Full-cascade graphs
Several frequency spectra are plotted against speed in these graphs. These 3-dimensional presentations are used to observe changes in the frequency spectrum during a start-up and/or run-out.