ODS stands for operating deflection shape.
ODS analysis generates a computer model of your machinery that depicts its
motion while running at operating speed & load. You literally “see” how
your machine is moving as it operates. This modeling can be extremely
useful to illuminate an otherwise elusive solution to machinery vibration
First, a CAD model of the machine or mechanical system is created (structure
Second, detailed & meticulous vibration measurements are made on the
machine typically during normal operation. These measurements consist of
both the amplitude & phase of vibration at one or multiple frequencies of
interest all referenced to a common point.
Finally, these field measurements are imposed on the model to generate
visible animations of the model/machine at the distinct vibration frequencies
of interest (typically the “offending frequencies”).
When standard vibration analysis techniques
have failed to determine the exact problem.
When resonance is suspected.
An ODS or Modal job begins best with a
determination of the “offending frequencies of
vibration” usually made using standard, route
The Le Tourneau Crane should operate at max running speed 0.025
CPS or 1.5 Rpm, it is observed high vibration levels during
operation (jerking) and structure looseness problem which has
destructive effect on the long run operation.
Vibration measurement and ODS analysis were carried out by in
order to detect the main source of that high vibration, also in
order to shows the crane motion while operating & the crane
deflection shape due to that vibration.
The crane rotates by large swing gear with 82 teeth which showed
by the black arrow in the next image & driven by pinion gear
connected to the gear box
The whole structure shows high vibration levels 42 mm/s rms on
the column, swing table & Control room base.
The Machine exhibits unacceptable vibration levels.
The main vibration at the machine bearings spectra is at the high
amplitude gear meshing frequency 2 Hz or (82 X) which indicates
gear eccentricity and/or improper backlash problem.
Bump test was carried out to the structure and it is found that the
column natural frequency is matching the gear meshing
frequency which causing resonance in the structure.
It is recommended to make ODS analysis to locate the max
deviation point, as the problem should be solved either by
adjusting gear backlash and adding stiffen supports to the crane
Point Location Amplitude Units Phase Angle Readings
Ref. Point 15 mm/s 0.00°
Point No.1 15 mm/s 230
Point No.2 7 mm/s 220
Point No.3 12 mm/s 240
Point No.4 11 mm/s 220
Point No.5 10 mm/s 210
Point No.6 4 mm/s 169
Point No.7 15 mm/s 160
Point No.8 14 mm/s 160
Point No.9 4 mm/s 240
Point No.10 12 mm/s 230
Point No.11 14 mm/s 220
Point No.12 2 mm/s 110
Point No.13 4 mm/s 130
Point No.14 5 mm/s 98
Point No.15 8 mm/s 140
Point No.16 12 mm/s 160
Point No.17 15 mm/s 230
Point No.18 16 mm/s 230
Point No.19 22 mm/s 230
Point No.20 23 mm/s 230
Point No.21 25 mm/s 230
Point No.22 12 mm/s 230
Point No.23 17 mm/s 230
Point No.24 18 mm/s 230
Point No.25 19 mm/s 230
Point No.26 20 mm/s 230
Point No.27 22 mm/s 240
Point No.28 15 mm/s 240
Point No.29 17 mm/s 240
Point No.30 18 mm/s 240
It recommended that we should use 3rd party to check the swing
gear teeth profiling and how much back lash between the pinion
gear and swing gear.
In addition we should add stiffen supports to the column base at
the same arrows locations in the pervious image.
After gear teeth profiling checking we found that we got 19 mm
back lash between the two gears so, we changed the pinion gear
with different one ( same number of teeth but larger size)
Also after adding the stiffen supports to the column base the
vibration levels shows significant decrease.