ODS is a process of diagnosing rotating machinery, it may become unavoidable to do some structural vibration analysis as well. Most often this is done by performing ODS (Operating Deflection Shape Analysis) or Modal Analysis. An operating deflection shape shows the deformation of a structure at a specific frequency or during a time waveform playback. ODS shows the response of a structure to both resonant and forced vibration, and is generally very representative of the real world data. Once the model is complete, test data is collected at various points on the assembly using a dual channel analyzer. One probe (or an optical/laser tachometer) remains in place at all times while the other probe is moved from point to point. During the data collection process, care must be taken to ensure all data is collected on the right point and in the right direction. After all data has been collected, the software merges the data with the model and the resulting animation shows how the item moves. Animations can show abnormal movement caused by looseness, weak and flexible structures, resonance, vane pass, excessive forces, operating loads and more. Animations will also show how components move with respect to each other, such as with misalignment. They also show how components move with respect to the structure to which they are attached (soft-foot, looseness, etc.).

1. Operational Deflection Shape
(ODS) Analysis
Taqi-Ud-Din Haider
Vibration Analyst Level – III

2. What is Operational Deflection Shape (ODS) Analysis
• ODS models is a technique for observing the real behavior of
system vibration against any forcing function.
• ODS is the actual machine response, and contains the overall
vibration of components of any system, of both the forced
and resonant (natural frequency) vibration.

3. • Model of the system is created, and then its motion is driven by
sensor measurements (phase and amplitude) called as relative
motion/vibration.
• The relative vibration is measured at various points across the system,
that vibration/motion is known as degrees of freedom (DOF).
What is Operational Deflection Shape (ODS) Analysis

4. Difference between ODS and Modal Analysis
• ODS is performed when machine is in running mode and Modal
Analysis is performed when machine is in stop condition.
• An operating deflection shape shows the deformation of a structure
at a specific frequency or during a time waveform playback.
• The method of modal analysis is similar to ODS, in that, system is
excited by external known force (With Modal Hammer) and response
is measured at various locations of system.
• The primarily concern of modal analysis is to deal with resonance
frequencies (natural frequencies) of a structure, to visualize the
deformation in shape when excited by force.

5. Why ODS Analysis?
• When failed to analyze the problem in routine vibration analysis .
• To locate the origin of forcing function in the system.
• When resonance is suspected and source to identify .
• When the vibration transmission path to identify.
• To study the mode shapes of system.
• To identify non linearity in the system.

6. Resource for ODS Analysis
• Tools
• 2-Channel vibration analyzer with cross channel measurement option.
OR
• Single channel analyzer with tech option for peak and phase measurement.
• Software
• ODS analysis software.
• Skills
• Knowledge of phases analysis.
• Knowledge of coherence analysis.
• Knowledge of mode shapes and resonance
• 3D object modeling skill (CAD) for ODS software

7. Testing Resonance
Cascade Plot Bump Test

8. Measuring Phase Analysis
• Phase is the time difference between two measurements points
of a same cycle of frequency, from a fixed reference point
(Presented in Angle)
10 Time in Sec
``
Heavy
Spot

9. ODS Data Collection Procedure
• Make a sketch of machine with dimension in MM or Inch.
• Marks the points on machine according to sketch.
• Mark No. of point on sketch and machine, points depends upon the
machine size. (don’t mark too close or too far).
• Consider concrete base, foundation, sole/base plate, motor/pump foot,
and associated piping (suction and discharge line) a part of the machine.

10. ODS Data Collection Procedure Cont…
• Identify the nods and antinode points of machine.
• Measure the vibration at different location to point the reference sensor.
• Vibration at reference point should be strong and comparable with other
points for good data and stable phase reading.
• Collect the data from all points if possible e.g. Point 1XYZ, Point 2XYZ …..

11. Example of Machine Sketch
1
8
23
9
4567
1011121314
15
16
17
18192021

12. Example of Marking on Machine
27
6
10
11
14
15
16
17
18
19
20
21
22
23
24
25 26
28

13. ODS Data Collection Procedure Cont…
• Make a worksheet to note down the vibration amplitude and phase.
• In the case of opposite direction of sensor mark (-) negative in sheet.
• Phase reading should be stable.
• Coherence should be stable and > .8,
• In the case of low coherence following point should be consider.
• Sensor location and mounting.
• Change in reference or operating frequency.
• Problem with cable/sensor.
• Non linearity in structure (e.g. loose bolt, and welding cracks, etc.)

14. Datasheet
Point Axis
Sen.
Dir.
Amp. Ph. Coh.
1
X + 5.3 0 .99
Y + 5.2 90 .99
Z + 1.7 235 .99
2
X + 4.3 10 .81
Y + 3.9 110 .70
Z + 5.7 190 .82
3
X - 8.2 180 .92
Y - 6.5 270 .99
Z + 1.6 75 .75
Point Axis
Sen.
Dir.
Amp. Ph. Coh.
4
X - 5.3 100 .81
Y + 5.2 190 .70
Z + 1.7 35 .82
5
X - 4.3 170 .92
Y + 3.9 130 .99
Z + 5.7 160 .99
6
X + 8.2 80 .79
Y + 6.5 27 .78
Z + 1.6 17 .71
Machine ID: RAW Water Pump No. 1. Running RPM: 2450 Frequency: 42 Hz

15. Assigning the Data (Vibration And Phase) to Node Points
• Draw machine model with
same dimension.
• Data to be assign to the
nodes, marked on machine
and raw sketch.
• Good model help to analyze
the problem.
• More data to model,
animation/Mode Shape will
more clear.

16. ODS Animation

17. ODS Frame Sequence

18. Thank You
For any query please contact
Taqi Ud Din Haider
Email: taqi.haider@live.com