Dustin Pavelek, P.E. lectures/2019 01 31 Pavelek... · • Vibration spectra show high 1X and gear mesh vibration on the high speed gearbox. 1/30/2019 3 Case Study 1: Alignment and

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Adventures in Field Vibration TestingDustin Pavelek, P.E.

Sr. Consultant

Kelm Engineering, LLC

MEEN 459/659 – Spring 2019

Dustin Pavelek, P.E.

Dustin Pavelek is a Sr. Consultant with Kelm Engineering,LLC where he is responsible for conducting analyticalstudies and field vibration testing for rotating andreciprocating machinery.

He previously served as a member of corporateMachinery Engineering and Predictive Maintenancegroups in the petrochemical and power generationindustries. He is a proud graduate of Texas A&MUniversity and holds a B.S. (2004) and an M.S. (2006) inMechanical Engineering.

Pavelek is a registered professional engineer in the Statesof Texas and Louisiana and is a Certified ISO Category IVVibration Analyst through the Vibration Institute.

What to Expect Today

• A handful of case studies from actual field

or shop vibration tests

• An honest description of how some things

have (or could have) gone wrong

• A few tips to keep in your tool box for the

future

• Some discussion on choosing a career

path

Case Study 1: Alignment and Field Balancing

• Machine Type: Multistage Centrifugal Compressor

• Plant Type: Coal-fired Power Plant

• Application: Soot Blowing Air Compressor

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• Instrumentation:o Plant proximity probes

and monitoring system

o Temporary magnet-mounted accelerometers

o Laser tachometer

• Test Plan:o Visual Inspection

o Alignment

o Operating Test

o Balancing

o Mechanical Verification


• Challenges

o The plant personnel installed the machines

o A gearbox OEM representative provided oversight for

the onsite gearbox overhaul

o A machine with a history of things going very, very bad

• Results

o The machine tripped on high vibration on multiple start

attempts

o Vibration data showed high speed gearbox was the

culprit


• Vibration trends from prox probes show high

speed gearbox vibration was excessive


• Vibration spectra show high 1X and gear mesh

vibration on the high speed gearbox

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• Gearbox bearings were suspected

• HSGB has an “upmesh”


• Gearbox output shaft bearings were installed

upside down

Case Study 2: Structural Modal Test

• Fall protection harness

manufacturer

• Drop test rig

certification testing

• Lower limit of 200 Hz

for fixture structural

natural frequencies

• Static deflection limits

for structure


• Test Plano Pre-test

o Where do we hit?

o Response measurement locations?

o Conduct modal testo Triaxial Accels

o Instrumented Hammer

o Multi-channel DAQ

o Conduct static deflection testo Calibrated load cell

o Dial indicator

o Proximity probe

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• So… how’d it go?


• So… how’d it go?


• What about the static test?


• What went wrong?

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Case Study 3: Multiplane Balancing and Testing

• Machine Type: Steam Turbine-Generator

• Plant Type: Combined Cycle Power Plant

• Problem: High vibration during startup


• Test Plan:

o Startup/coast down vibration

o Permanent/temporary proximity probes

o Temporary accelerometers

o Tach/Phase reference

o Bearing housing impact testing

o Rotordynamic study

Case Study 3: Multiplane Balancing and Testing Case Study 3: Multiplane Balancing and Testing

• Startup/Coast Down Vibration

30372337

1760

1126

946

778.6

369.1

0

500

1000

1500

2000

2500

3000

3500

4000

0

1

2

3

4

5

6

7

8

9

10

0:00:00 0:02:53 0:05:46 0:08:38 0:11:31 0:14:24 0:17:17

Ro

tor

Sp

ee

d (

RP

M)

Ove

rall

Vib

rati

on

Am

pli

tud

e (

mil

s p

k-p

k)

Time (h:mm:ss)

Coastdown Data: Unit 1 Overall Vibration and Speed Trends

1X 1Y 2X 2Y 3X 3Y 4X 4Y 5X 5Y 6X 6Y RPM

2340

1127

945.5

786.7

0

500

1000

1500

2000

2500

3000

3500

4000

0

1

2

3

4

5

6

7

8

9

10

0:00:00 0:00:43 0:01:26 0:02:10 0:02:53 0:03:36 0:04:19 0:05:02 0:05:46

Ro

tor

Sp

ee

d (

RP

M)

Ov

era

ll V

ibra

tio

n A

mp

litu

de

(m

ils

pk-

pk

)

Time (h:mm:ss)

Startup Data: Unit 1 Overall Vibration and Speed Trends

1X 1Y 2X 2Y 3X 3Y 4X 4Y 5X 5Y 6X 6Y RPM

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• Impact Data


• Rotordynamic Modeling


• Balancing Results

-360

-270

-180

-90

0

90

180

270

360

0

2

4

6

8

10

12

14

16

0 500 1000 1500 2000 2500 3000 3500 4000

Phase (degrees)

Vibration Amplitude (mils pk-pk)

Speed (RPM)

Bearing 5Y Measured Response - After Balancing

Bearing 5Y Amplitude Bearing 5Y Phase

Case Study 4: Vertical Pump

• Machine Type: VFD

Motor Driven Vertical

Pump-2000HP

• Plant Type: Sewage

Treatment

• Problem: Acceptance

Testing

• Speed Range:270-395

RPM

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• Test Plan:

o Impact Tests

o Operating vibration measurement


• Test Plan:

o Impact Tests – No impact hammer!

o Operating vibration measurement


Vibration Spectra

Uncoupled

400 RPM


Vibration Spectra

Uncoupled

300 RPM

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Vibration Spectra

Uncoupled

273 RPM


Vibration Spectra

Uncoupled

273 RPM

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

50 100 150 200 250 300 350 400 450

Ov

era

ll A

mp

litu

de

(in

/s-

pk

)

Speed (RPM)

VFD Coastdown

Overall Vibration Amplitude

1XPosition-Overall 1YPosition-Overall 2XPosition-Overall 2YPosition-Overall

• VFD Controlled Coast Down Vibration


Vibration Spectra

Uncoupled

273 RPM

• E-Stop Coast Down Vibration

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

50 100 150 200 250 300 350 400 450

Ov

era

ll A

mp

litu

de

(in

/s-

pk

)

Speed (RPM)

Emergency Stop Coastdown

Overall Vibration Amplitude

1XPosition-Overall 1YPosition-Overall 2XPosition-Overall 2YPosition-Overall


Vibration Spectra

Uncoupled

273 RPM

• Vibration Spectra before/after E-stop

pressed by operator

o Electrical/magnetic forces excited resonance

o Poor motor thrust collar fit caused the excitation

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Case Study 5: Paper Mill Debarker

• Extensive foundation work done to reduce

vibration. Test to document results.

• Challenge: Transient vibration.

• Solution: Time-based ODS


Case Study 5: Paper Mill Debarker Case Study 5: Paper Mill Debarker

• Feb 28,2012

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• Feb 28,2012


• Transient ODS Results


• Final Solution: More Steel!

Case Study 6: Industrial Noise Measurement

• Sound measurement:

o Useful for machinery troubleshooting

o Also useful for keeping the neighbors happy!

o IIoT Solution for Remote Monitoring

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Case Study 6: Industrial Noise Measurement

• Overall levels, Octave band filtering,

attenuation from weather conditions

Case Study 7: Wind Tunnel Torsional Test

• Application: Wind Tunnel Synchronous Motor

• Scope:

o Document Static/Dynamic Torque

o Document Power

o Document TNF’s

o Measure Vibration

• Test Plan:

o Strain Gages

o Radio Telemetry

o Laser Tachometer

o Accelerometers


• Careful surface preparation and calibration

procedure required for strain gage application


0

200

400

600

800

1000

1200

1400

1600

1800

2000

0

10000

20000

30000

40000

50000

60000

0 20 40 60 80 100 120 140 160 180

Po

we

r (H

P)

Me

asu

red

To

rqu

e (

ft-l

bs)

Speed (RPM)

Measured Torque and Horsepower

Measured Torque (ft-lbs) Power (HP)

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Case Study 7: Wind Tunnel Torsional Test Case Study 7: Wind Tunnel Torsional Test

6’-1” (w/ hard hat)

Case Study 8: ID Fan Torque Measurement

• ID Fan in an air separation facility

o Document static/dynamic torque during startup and

operation

o Identify torsional natural frequencies using strain gages

o Validate analytical model of torsional system

• Test Plan:

o Strain Gages

o Radio Telemetry

o Laser Tachometer


• Static/Dynamic Torque Data Looks Great!

0

200

400

600

800

1000

1200

0

5000

10000

15000

20000

25000

30000

12:24:29 12:38:53 12:53:17 13:07:41 13:22:05

Sp

ee

d (

RP

M)

Torq

ue

(in

-lb

)

Time

Static Torque

Dynamic Torque

Speed

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• TNF matches prediction very well!

0.08, 1649.65

0.25, 943.52

-3000.00

-2000.00

-1000.00

0.00

1000.00

2000.00

3000.00

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70

Torq

ue

(in

-lb

)

Time (seconds)

Measured Torque After Motor Trip


• Dynamic Torque below acceptable limit!

1463, 3925

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 2500 5000 7500 10000 12500 15000 17500 20000

Torq

ue

(in

-lb

, P

K)

Frequency (CPM)

Dynamic Torque Spectrum at 999 RPM


• Uh-oh…


• Lesson Learned:

o Regardless of any real or perceived schedule

pressure, SAFETY must be your #1 priority during a

test

o Rotating machinery CAN BE hazardous

o Broken rotating machinery IS hazardous!

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Case Study 9: Online Torque Monitoring

• Problem:

o Integrally Geared Air Compressor Driven by a Synchronous Motor

o Multiple coupling failures had previously occurred

o Client wanted an online monitoring device to measure static and dynamic torque

• Solution:

o Off-the-shelf strain gages/transmitter/reciever

o Custom Labview software

o Verify instrumentation/data with known hardware


• Hardware:


• How did the online system compare to known

temporary instrumentation… GREAT!


• Uh-oh…

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• Solution:

o Parts shipped to

manufacturer for

repair

o Collar re-installed

with adhesive on

the ID to maintain

axial position

Case Study 10: Urea Conveyor Vibration

• Application: Granular urea conveyor in a

fertilizer production facility

• Problem: Belt-driven conveyor experienced

drive belt slipping from pulley

o Plant attributed belt slippage to resonance

problem

• Test Plan:

o Impact Testing

o Vibration Amplitude/Frequency Measurement

o Try not to get too filthy!

Case Study 10: Urea Conveyor Vibration Case Study 10: Urea Conveyor Vibration

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Case Study 10: Urea Conveyor Vibration Case Study 10: Urea Conveyor Vibration

• Very low first natural frequency (<4 Hz)

Case Study 10: Urea Conveyor Vibration

• Final Solution: Don’t forget to tighten

fasteners!

Case Study 11: Chilled Water Pumps

• Application: Chilled water pumps at a prominent university

• Problem: High 1x vibration

• Test Plan:

o Impact Testing

o Vibration Amplitude/Frequency Measurement

o Field Balancing

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• Highest vibration at 1X running speed

• Indication of excessive imbalance

• Maybe resonance… Let’s Check!


• Source of imbalance was the improperly sized

keys on the coupling

• The keys were too short to fill the void in the

keyway

• Balance correction weights were installed at the

same angle as the key to correct

Case Study 12: Condensate Pumps

• Application: A/B/C Condensate Pumps at a Combined Cycle Plant

• Problem: A-Pump keeps tripping on high vibration

• Test Plan:

o Impact Testing – 3 pumps

o Vibration Amplitude/Frequency Measurement on A Pump


• Measurement Setup:

o Accelerometers on motor bearings and pump upper

bearing

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• Test Data – Overall Vibration Amplitude Trend

Step Change


• Test Data – 1X Vibration Amplitude Trend

Step Change


• Test Data – 1X Vibration Amplitude Trend

Step Change


• Test Data – 1X Vibration Phase Trend

Step Change

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• Test Data – Subsynchronous Vibration

Amplitude Trend

Step Change

OH NO!!


• Why is only A Pump bad? Structural?

• Impact testing on all 3 pumps…

0.000001

0.00001

0.0001

0.001

0.01

0 20 40 60 80 100 120 140 160 180 200

IPS/l

b

Frequency (Hz)

FRF Comparison - Vertical Direction

A_Vert B_Vert C_Vert


• Q: So… is it the pump or the motor??

Coupled

Operation

Uncoupled

(motor solo)

A: Both!


• So… What was wrong?

• Pump ingested foreign material

o Caused pump impeller damage and excessive

imbalance (High 1X) leading to excessive pump

bearing clearance (High Subsynchronous)

o Subsynchronous pump vibration excited structural

natural frequencies

• What about the motor solo?

o Motor was supplied with excessive imbalance

Documents

Dustin Pavelek, P.E. lectures/2019 01 31 Pavelek... · • Vibration spectra show high 1X and gear mesh vibration on the high speed gearbox. 1/30/2019 3 Case Study 1: Alignment and