Part 3 condition monitoring 02 2004

The test process developed: Develop a rotor model to calculate the natural frequencies, mode shapes, rotor deflection and bearing loading.. Perform free-free and installed experimental m

At the beginning of the project there was a need to identify the

rolls with loose or failed bolts A non-intrusive testing method

was desired

Monitor for changes in the natural frequency of the shaft-roll assembly

to detect changes in the bolted joint stiffness, i.e., an indicator of loose

or failed bolting.

Use vibration data measured at the end of the roll to detect faulty

bearings (This had been used in an aborted program).

The test process developed:

Develop a rotor model to calculate the natural frequencies, mode

shapes, rotor deflection and bearing loading.

Perform free-free and installed experimental modal testing of a shaft-roll assembly

Use bump testing to determine if this test could be used to identify

defective shaft-roll bolted joints.

Measure roll run out using a contact slider block or shaft rider

instrumented with a low frequency accelerometer Establish run out limits to indicate when to pull a roll.

At the beginning of the project there was a need to identify the

rolls with loose or failed bolts A non-intrusive testing method was desired

The test process developed:

Although not considered the preferred method, access to the bearing

housings was limited so a long stinger was used at the end of the rolls (This method had been used previously in a now aborted program.)

The data from the end of the roll could be used to identify the stage of bearing failure Ref TA Vibration Chart.

!

" "

Roll End Brg

Outer race damage Spalling and fatigue failure evident Roller impressions occurred during pressing the bearing off the shaft Most load carried by the outer set of rollers.

Roll End Brg

Vibration data indicated outer race bearing flaw frequencies.

ROUTE WAVEFORM 24-Oct-01 10:36:45 RMS = 1472 PK(+) = 6766 PK(-) = 6234 CRESTF= 4.60

-0.8

-0.4

0

0.4

0.8

Time in Seconds

DRol - J12 Drawrolls J12 DRolls-R19 Drawroll 19_OB Axial

ROUTE SPECTRUM 24-Oct-01 10:36:45 (SST-Corrected) OVERALL= 2838 V-DG

PK = 2821 LOAD = 100.0 RPM = 90

RPS = 1.50

0

0.05

0.10

0.15

0.20

0.25

Frequency in CPM

Roll End Brg

One large flaw was found in the outer race The load zone track is clearly visible

The shape of the flaw indicated either corrosion or impact damage as the initiator Since evidence of corrosion was not present, impact damage during installation was the most likely initiator of the flaw.

Load Zone Track

Roll End Brg, SKF 222348 CC Spherical Roller

Typical bearing failure indication in the data - Outer Race Defects with

modulation by run speed (sidebands) (Vibration levels are low)

Step One

Step Two

Develop Rotor Models

Calculate Free-Free and Installed In Gearbox Natural Frequencies

(Critical Speeds) and Mode Shapes.

Conduct Modal Testing

Free-Free Modal Test of Suspended Shaft-Roll

Curve Fit Data to Find Natural Frequencies and Mode Shapes

Compare to Rotor Models

Installed Shaft-Roll Modal Test

Curve Fit Data to Find Natural Frequencies and Mode Shapes

Compare to Rotor Models & Correct Models If Required

Step Three

Bump Test of Installed Shaft-Roll Assembly To Identify Defective

Rotors

Compare Peak Hold or Triggered Spectrum To Modal Data &

Model

Use This Test Method To Test all Suspect Rolls if It Proved

Successful

Follow-up With Modal Testing On As Needed Basis

Roll-Shaft Natural Frequency & Mode Shape Test Process

Step One

Develop Rotor Models

Free-Free Impact Modal Test of Shaft & Roll.

- The assembly is supported by Nylon Slings

- An instrumented hammer is used to impact the assembly

- An Accelerometer is used to measure the response at each point along

the shaft as indicated by the dots.

Step Two

Page 4

Free-Free Impact Modal Test of Shaft & Roll.

- The assembly is supported by Nylon Slings

- An instrumented hammer is used to impact the assembly in the horizontal

direction

- An Accelerometer is used to measure the response at each point along

the shaft as indicated by the dots.

Free-Free Impact Modal Test of Shaft & Roll.

- The assembly is supported by Nylon Slings

- An instrumented hammer is used to impact the assembly in the horizontal

direction.

- An Accelerometer is used to measure the response at each point along

the shaft as indicated by the dots.

Free-Free Impact Modal Test of Shaft & Roll.

- The assembly is supported by Nylon Slings

- An instrumented hammer is used to impact the assembly in the horizontal

direction.

- An Accelerometer is used to measure the response at each point along

the shaft as indicated by the dots.