electrical signature analysis (esa) as a diagnostic

1

OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY

Electrical Signature Analysis (ESA) as a Diagnostic Maintenance Technique for

Detecting the High Consequence Fuel Pump Failure Modes

D. E. Welch, H. D. Haynes, D. F. Cox, and R. J. MosesOak Ridge National Laboratory

Oak Ridge, Tennessee

Presented to Mr. Richard HealingDirector of Transportation Safety and Security

Battelle Memorial InstituteOct. 23, 2002

2


This presentation will show how electrical signature analysis (ESA)methods can be used to monitor the condition of fuel pumps and other electromechanical devices

• BACKGROUND– Basic Principle– General Benefits– Application Examples– Acceptance of ESA Technology

• CONDITION MONITORING OF C-141 FUEL PUMPS– General Information– Portable System– Test Locations– Data Analysis (time waveforms, frequency spectra, key parameters)– Detecting Fuel Pump Degradation with ESA (bearing wear)

• ONGOING WORK

• SUMMARY

3


ELECTRICMOTOR

TRANSMISSION(GEARS, BELT)

ACPOWERSOURCE

Current andVoltageSensors

MECHANICALLOAD

PRIMEMOVER

TRANSMISSION(GEARS, BELT)

GENERATOR ELECTRICALLOAD

Generator Systems

Motor Systems

ESA SYSTEMSIGNAL CONDITIONING

COMPUTER VIRTUAL INSTRUMENT

ESA capitalizes on the intrinsic abilities of conventional electricmotors and generators to act as transducers and only requires access to the equipment electrical lines

4


ESA is an attractive technology for a wide variety of applications

BENEFITS

WHENTO USE

ESA

• Non-intrusive and remote monitoring capability • No equipment-mounted sensors required• Applicable to high and low power equipment• Large range of applicable analysis methods• High sensitivity to a variety of disorders

– degraded and misaligned motors and generators– worn bearings, gears, and belts– unstable process conditions– power system degradation

• On-line performance monitoring• Catastrophic failure prevention• Improved safety, reliability, and operational readiness• Quality assurance and evaluation• Energy conservation• Predictive maintenance (prognostics)• Field diagnostic testing• Remaining life assessments

5


ESA has been used on a large number of components and systems

² Vacuum Pumps

• Nylon Spinning Machines

² Peristaltic Pumps

• Diesel Engine Starter Motors

² Motor-Operated Valves

• Large Blowers and Fans

² Aircraft Fuel Pumps

• Coal Pulverizers

² Large Compressors

• Variable Speed Motors

² Helicopters

² examples provided in this presentation

² Fuel Injectors and Solenoid Valves

• Army Portable Power Generator-Sets

• Heat Pump and Air Conditioning Systems

• NASA Propellant Control Valve

² Consumer Power Tools and Appliances

• Army Ammunition Delivery Systems

• Multi-Axis Industrial Cutting Machines

• Electric Vehicle Motors and Alternators

² Aircraft Integrated Drive Generators

• Navy Fire and Seawater Pumps

• Other Centrifugal Water Pumps

• Reproduction Machine Motors

6


0.0E+00

2.0E+01

4.0E+01

6.0E+01

8.0E+01

1.0E+02

1.2E+02

1.4E+02

1.6E+02

1.8E+02

0 5 10 15 20 25 30 35 40 45 50

Frequency (Hz)

Dem

od

Cu

rren

t S

ign

al

0.0E+00

1.0E+00

2.0E+00

3.0E+00

4.0E+00

5.0E+00

6.0E+00

7.0E+00

8.0E+00

0 5 10 15 20 25 30 35 40 45 50

Vib

rati

on

Sig

nal

BP

3B

2P

4B 5B

MS

7B8B

9B

2B

SPF

3P 6P

6B

B = Belt RotationP = Pump RotationMS = Motor SpeedSPF = Slip-Poles

Using ESA, motors and generators act like accelerometers thatare already installed and sending signals along the power line

(Example: Vacuum Pump)

B

P 3B

2P

4B

5B

MS7B

8B

9B

2B 3P6P

6B

• Periodic mechanical events associated with the motor, belt, and pump produce periodic vibrations and periodic variations in running current.

• All key mechanical events are sensed by both the accelerometer and motor.

MotorPump

7


ESA can reveal detailed information at the subcomponent level(Example: Motor-Operated Valve)

0

1

2

3

4

5

6

7

8

9

10

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5TIME (s)

RM

S M

OT

OR

CU

RR

EN

T (

A)

0.00

0.05

0.10

0.15

0.20

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0

FREQUENCY (HZ)

DE

MO

DU

LA

TE

D M

OT

OR

CU

RR

EN

T

A

B D

CE

F

G

Motor Current Time Waveform(Transient Information)

I

J

K

L

M

N

Demodulated Motor Current Frequency Spectrum(Periodic Information)

Motor inrush current

No - load current Hammerblow current

Stem nut clearance time Packing drag current

Stem coupling timeUnseating current

Worm gear rotation

Motor slip Worm gear rotation sidebands

Worm gear tooth meshing Motor speed

Worm gear mesh harmonic

K

AB

CD

EF

G

IJ

KL

MN

Total running currentH

H

Motor-Operated Valve

A

B

C

D

E

F

G

I

JK

L

M

N

H

8


-0.01

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.000 0.001 0.002 0.003 0.004Time (s)

Co

nd

itio

ned

Cu

rren

t Sig

nal

• ESA methods can differentiate between effects due to changes in injector temperature, voltage, and supply pressure.

• ESA methods have been successful at detecting injector outlet port plugging.

Plungermoves

only3 mils

~ 2 ms

Multiple bouncesare evident in the

current signal

The feasibility of using ESA to monitor the performance and condition of fuel injectors has been demonstrated

• ESA offers a quick, inexpensive method for checking the quality of newly-manufactured injectors.

• ESA can be the basis for new, non-intrusive test equipment for engine maintenance shops.

TIME --->

CU

RR

EN

T --

->

InjectorControlVoltage

Raw Current Signal

Fuel Injector

CURRENTSENSOR

Conditioned Current Signal

Injectorstarts

to open

9


1000800600400 1200 1400 1600 1800 20002000

Frequency (Hz)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

Dem

odul

ated

Mot

or C

urre

nt

Several consumer tools and appliances were also examined to show the versatility of ESA

(Example: Power Drill)

Power Drill

• Drill frequency components were observed with ESA.

• Relationships were established between vibration magnitudes and ESA parameters for different levels of motor unbalance.

Motor Speed429 Hz

Chuck Speed38.2 Hz

Gear Mesh1717 Hz

10


0.0E+00

5.0E-08

1.0E-07

1.5E-07

2.0E-07

2.5E-07

3.0E-07

3.5E-07

6300 6320 6340 6360 6380 6400

Frequency (Hz)

Co

nd

itio

ned

IDG

Vo

ltag

e S

ign

al

ESA was used to detect mechanical degradation on a commercial aircraft integrated drive generator (IDG)

• IDGs provide power for devices in the passenger cabin such as reading lights and microwave ovens.

• On certain aircraft, IDGs fail at the rate of four per year. Each IDG costs $250K to replace.

Scavenge pump gear mesh with new gear set

Scavenge pump gear mesh with bad gear set

• The primary failure mode is seizure and destruction of scavenge, drive pump, and axial gears on the IDG’s main shaft.

• Even at very low generator electrical loads, ESA can detect gear problems before they fail.

Integrated DriveGenerator (IDG)

11


Damaging aerodynamic conditions, such as rotating stall, can be detected using ESA

• 1700-hp axial flow compressors are used in large numbers in U.S. uranium enrichment plants.

• Certain process flow configurations can induce rotating stall, which quickly accelerates blade fatigue damage.

1700-hp Axial-Flow Compressor

0 5 10 15 20 25 30 35 40

Frequency (Hz)

Dem

od

ula

ted

Mo

tor

Cu

rren

t

Demodulated Motor Current Spectra Obtained From the Control Room

Normal Operation

Rotating Stallrotating stall

frequency(RSF)

2X RSF

12


A relationship was identified between helicopter rotor unbalance and the harmonic content of the rotor tachometer generator (RTG) output voltage

1

1.05

1.1

1.15

1.2

RT

G H

arm

on

ic C

on

ten

t

No Added Mass 5.9 g 11.6 g

Unbalance on End of Rotor Blade

-1.2

-0.8

-0.4

0

0.4

0.8

1.2

0 0.05 0.1 0.15 0.2

Time (s)

RTG

Sig

nal M

agni

tude

1E-04

1E-03

1E-02

1E-01

1E+00

1E+01

0 1 2 3 4 5 6 7 8 9 10 11 12Frequency (harmonic orders)

RTG

sig

nal m

agni

tude

Bell Jet Ranger Helicopter

1X

5X 7X 11X

9X3X

13


1E-01

1E+00

1E+01

1E+02

1E+03

0 5 10 15 20 25 30

Frequency (Hz)

Dem

od

ula

ted

Cu

rren

t

0

20

40

60

80

100

120

140

0 10 20 30 40 50

Time from start of test (hr)

RP

F A

mp

litu

de

ESA can detect changes in component condition before failure(Example: Peristaltic Pump)

1 XMotorSpeed

3 X Motor Speed(roller-pass freq. RPF)

2 X RPF

pump uses3 rollers

DegradationCurve

Pump Failure (ruptured tube)

14


0

5

10

15

20

25

30

35

40

45

1/1/93 1/1/94 1/1/95 1/1/96 1/1/97 1/1/98 1/1/99 1/2/00 1/1/01 1/1/02

Time

Nu

mb

er o

f P

aten

ts

Oak Ridge Patents

Licensee Patents

Other Company Patents

Cumulative Number of U.S. Patents Referencing The First Oak Ridge ESA Patent

ESA is now recognized as a viable diagnostic method

Commercially Available ESA System

15


Auxiliary Fuel Pump

Main Fuel Pump

ORNL is presently developing an ESA-based instrument for monitoring the condition of C-141 fuel booster pumps

C-141 Starlifter

• Each C-141 has 20 fuel booster pumps (5 fuel tanks per wing, 2 pumps per tank)

• Fuel pumps are centrifugal and driven by 3-phase electric motors

• Two designs are used: Main (~ 4A), Auxiliary (~ 10A)

• Work to date has focused on the aux fuel pump

16


The development is progressing well and is being accomplished through a series of tasks

Develop / ModifyESA Tools

HardwareSignal Conditioning Box

SoftwareData Acquisition VIData Analysis VI

Noise Floor Extraction VIFix Data Fields VI

Parameter Analysis VI

Acquire Fuel PumpMotor Current Data

AMARC "As -Received" ConditionImplanted DegradationCondition "F” Pumps

OCALC and WPAFB Field Testing

Obtain Pump Forensic DataBearing and Journal DiametersThrust Washer Axial Thickness

Motor Electrical Parameters

Discoverand Verify

RelationshipsBetween ESAResults and

Pump ForensicData

Consolidate Tools,Knowledge, and

User Requirementsinto a Field-Ready

Prototype Instrument

Perform Field VerificationTests of Prototype

Instrument

Modify and Improve Prototype Instrument

Define Final InstrumentSpecifications

Construct FinalInstrument(s)

TOOLS KNOWLEDGE PROTOTYPE

FIELD

Define User Requirements

Database

17


Fuel pump motor current signals have been obtained using a portable system

Fuel pump data acquisition system developedas a research and development tool

Concept of a "suitcase-style"ESA-based diagnostic system

CURRENT PROBES

PORTABLECOMPUTER

SIGNALCONDITIONING

Present System System Under Development

The suitcase-style ESA system can serve as the platform for other potential aircraft diagnostic applications such as flight control surface drive actuators,

landing gear bay door actuators, integrated drive generators, etc.

18


Fuel pumps have been tested at two test facilities

ORNL Fuel Pump Test FacilityOklahoma City Air Logistics Center(OC-ALC) Fuel Pump Test Facility

19


Fuel pumps have also been tested on four C-141 aircraft at Wright-Patterson Air Force Base

( Tail Numbers: 67959, 50249, 60132, 67957)

20


Fuel pump motor current leads are accessible at several locations on the C-141

Inside Fuselage Under Wing

21


Software was developed to acquire and save fuel pump current waveforms for off-line analysis

Portable Computer and Data Acquisition Virtual Instrument (VI)

Typical Single PhaseCurrent Waveform

-12

-8

-4

0

4

8

12

0.000 0.010 0.020 0.030 0.040 0.050

Time (s)

Ph

ase

T1

Cu

rren

t (A

)

22


1E-12

1E-10

1E-08

1E-06

1E-04

1E-02

1E+00

0 2000 4000 6000 8000 10000

Frequency (Hz)

Avg

Ph

ase

Cu

rren

t (r

aw)

1E-12

1E-10

1E-08

1E-06

1E-04

1E-02

1E+00

Avg

Ph

ase

Cu

rren

t (r

aw)

1E-12

1E-10

1E-08

1E-06

1E-04

1E-02

1E+00

Avg

Ph

ase

Cu

rren

t (r

aw)

1E-12

1E-10

1E-08

1E-06

1E-04

1E-02

1E+00

2600 2800 3000 3200 3400

Frequency (Hz)

Avg

Ph

ase

Cu

rren

t (r

aw)

1E-12

1E-10

1E-08

1E-06

1E-04

1E-02

1E+00

Avg

Ph

ase

Cu

rren

t (r

aw)

1E-12

1E-10

1E-08

1E-06

1E-04

1E-02

1E+00

Avg

Ph

ase

Cu

rren

t (r

aw)

Auxiliary fuel pump motor current spectra are complex and difficult to analyze in their “raw” state

Pump A3926 (flow rate ~ 35000 lb/hr)


Pump A3926 (flow rate = 0 lb/hr)



Pump A3926 (flow rate = 0 lb/hr)

Many Frequency Components Are Present Most Peaks Move As Flow Rate Changes

23


1E-18

1E-17

1E-16

1E-15

1E-14

1E-13

1E-12

1E-11

60 70 80 90 100 110 120 130 140 150

Frequency (Hz)

Dem

odul

ated

Cur

rent

Sig

nal

A3926, 0 lb/hrA3926, ~ 17000 lb/hrA3926, ~ 35000 lb/hr

By demodulating the raw current signals, the motor speed peaks can be identified and the rest of the spectrum more easily interpreted

SS = 2 (LF) / NP

SPF = NP (SS - MS)

78.36 120.27

97.02

117.16

132.66

111.22

MS = motor speed (Hz)LF = line frequency (Hz)NP = number of motor polesSS = synchronous speed (Hz)SPF = slip pole frequency (Hz)

For An Auxiliary Fuel Pump

NP = 6; LF = 400 HzSS = 2 (400 Hz) / 6 = 133.33 Hz

at 0 lb/hr:MS = 120.27 Hz (7216.2 RPM)SPF = 78.36 Hz



24


Demodulated motor current spectra can then be analyzed on a relative frequency scale (orders of motor speed)

Relationship With Auxiliary Pump And Motor DesignESA ParameterFundamental and second harmonic of motor speed.1xMS, 2xMS

The magnitude of the slip-poles peak increases with motor rotor bar degradation. motor slip-poles

The pump has 4 impeller vanes.4xMS

These harmonics represent multiples of 6x (the motor has 6 poles) or possibly a center frequency at 18x (the motor has 18 stator slots) that is modulated by 6x.

6xMS, 12xMS, 18xMS,24xMS, 30xMS, 36xMS

The motor has 28 rotor bars. 56 = 2 x 2828xMS, 56xMS

54 = 3 x 18, where 3 = number of motor phases, 18 = number of motor stator slots.54xMS

84 = 3 x 28, where 3 = number of motor phases, 28 = number of motor rotor bars.84xMS

1E-24

1E-22

1E-20

1E-18

1E-16

1E-14

1E-12

1E-10

1E-08

22 23 24 25 26 27 28 29 30 31 32 33 34

Frequency (Orders of Motor Speed)

Dem

od

ula

ted

Cu

rren

t Sig

nal

A3926, 0 lb/hr

A3926, ~ 17000 lb/hrA3926, ~ 35000 lb/hr

Many motor speed harmonics are present, as illustrated in this partial spectrum

29X 30X28X

24X

25


Current waveforms were analyzed to extract motor speed harmonicsand other important parameters believed to be related to fuel pump condition and performance

Portable Computer and Data AnalysisVirtual Instrument (VI)

Fuel Pump ESA Parameters

ν Motor speed (MS) in Hzν 1 x MS magnitude ν 4 x MS magnitude ν 6 x MS magnitude ν 12 x MS magnitude ν 18 x MS magnitude ν 24 x MS magnitude ν 26 x MS magnitude ν 27 x MS magnitude ν 28 x MS magnitude ν 29 x MS magnitude ν 30 x MS magnitude ν 36 x MS magnitude ν 42 x MS magnitude ν 48 x MS magnitude ν 54 x MS magnitudeν 56 x MS magnitude ν 66 x MS magnitude ν 72 x MS magnitude ν 84 x MS magnitude ν Slip-poles magnitudeν P1 = avg of all peaks from 27.4x to 27.6xν P2 = avg of all peaks from 28.4x to 28.6x

ν P3 = avg of all peaks from 28.9x to 29.1xν P4 = avg of all peaks from 29.4x to 29.6xν P5 = avg of all peaks from 30.4x to 30.6xν P6* = avg of lowest 50% of peaks from 27.4x to 27.6xν P7* = avg of lowest 50% of peaks from 28.4x to 28.6xν P8* = avg of lowest 50% of peaks from 28.9x to 29.1xν P9* = avg of lowest 50% of peaks from 29.4x to 29.6xν P10* = avg of lowest 50% of peaks from 30.4x to 30.6xν P11 = avg of all peaks from 28x to 30xν P12* = avg of lowest 50% of peaks from 28x to 30xν P13 = avg of all peaks from 35x to 38xν P14* = avg of lowest 50% of peaks from 35x to 38xν P15 = avg of all peaks from 42x to 44xν P16* = avg of lowest 50% of peaks from 42x to 44xν 2 x MS magnitudeν (2 x MS magnitude) / (1 x MS magnitude)ν (((83 x MS) + (85 x MS)) / 2) / (84 x MS) = 1x mod of 84xν T1 phase current RMS magnitude in ampsν T2 phase current RMS magnitude in ampsν T3 phase current RMS magnitude in ampsν neutral current RMS magnitude in ampsν current unbalance in percentν slip-poles based detected motor speed in Hzν harmonic based detected motor speed in Hz

TEST PARAMETERS

MOTOR CURRENT PARAMETERS

* =These parameters measure the base of the spectrum. This is re ferred to as the “noise floor”.

ν Monthν Dayν Yearν Pump type (code)ν Pump prefix (code)

ν T1, T2, T3 (mv/A)ν Neutral (mv/A)ν Test location codeν Pump position codeν DAQ VI version

ν Pump numberν Flow rate (pph)ν Pressure (psi)ν Sample rateν Number of samples

26


Fuel pump speed and current vary according to flow conditionsas illustrated by this C-141 fuel transfer test

Motor Speed vs. Motor Currentfor 50249 RW, E3, Aux, Pri

4

5

6

7

8

9

10

11

12

100 105 110 115 120 125 130

Motor Speed (Hz)

Mo

tor

Cu

rren

t (A

mp

s)

Aux Pump Test During Zero Flow and Fuel Transfer Conditions(Tail Number 050249: RW, E3, Aux, Pri)

0

2

4

6

8

10

12

14

0 100 200 300 400 500 600 700

Time (s)

Ph

ase

A R

MS

Mo

tor

Cu

ren

t (A

)

Phase A RMS Motor CurrentDuring Zero Flow Test (A)Phase A RMS Motor CurrentDuring Fuel Transfer Test (A)

zeroflow

pump is shut off

flow controlvalve was apparently

closedmomentarily(zero flow)

high flow rate(fuel transfer toRW ER tank)

running current suddenly dropsbelow deadhead flow level

(fuel pump running dry)

stoppedrecording

started recording(pump is running)

1

2

3

4

1

2

3

4

With increasing flowrate, the motor works harder, which resultsin the motor slowingdown and drawing

more current.

27


20

25

30

35

40

0 10000 20000 30000 40000 50000

Flow Rate (lb/hr)

Pre

ssu

re (

psi

)

6.7

7.1

7.5

7.9

8.3

8.7

9.1

9.5

9.9

10.3

10.7

6500 6600 6700 6800 6900 7000 7100 7200 7300

Motor Speed (RPM)

RM

S M

oto

r C

urr

ent

(A)

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

Flo

w R

ate

(lb/h

r)

Using an instrumented flow test loop, fuel pump performancecurves can be fully developed and studied

(Example: Auxiliary Pump, A3926, As-Received Condition)

Motor Current

Flow Rate

28


A flow test loop also provides a means to develop diagnostic methods for detecting degradation that can adversely affect fuelpump operational readiness

• Foreign object damage (FOD)• Axial thrust washer wear• Impeller / shroud blow by• Motor electrical degradation

• Impeller imbalance due to nicks / abrasion²Front carbon bearing or journal wear• Rear carbon bearing or journal wear

The C-141 fuel pump can suffer from a variety of problems

To determine if ESA methods can detect front bearing wear, five auxiliary pumps obtained from AMARC were tested in “as-received” condition and after machining an additional ~ 10 mils (0.010 inches) wear in the front carbon bearings of each pump.

Aerospace Maintenance and Regeneration Center (AMARC) at Davis-Monthan AFB, AZ

²

29


Hydrodynamic performance curves do not provide a reliablemeans of detecting the additional bearing wear

(Examples: A3493 and A3852)

15

20

25

30

35

40

45

0 10000 20000 30000 40000 50000

Flow Rate (pounds per hour)

Pum

p D

isch

arge

Pre

ssur

e (p

si)

A3493 (as received)

A3493 (with additional front bearing wear)

15

20

25

30

35

40

45

0 10000 20000 30000 40000 50000

Flow Rate (pounds per hour)

Pum

p D

isch

arge

Pre

ssur

e (p

si)

A3852 (as received)


30


Efforts were focused on developing a new method that can quicklydetect bearing wear in fuel pumps that are installed in flow test loops and in C-141 aircraft

• An ESA-based method would only require access to the motor power leads.

• Zero-flow conditions are easy to establish on an aircraft while on the ground.

• Although a significant fuel pump flow rate can be established (from tank to tank transfers), zero-flow testing is less intrusive.

• An ESA diagnostic method that can be used at zero flow is more “robust” than a method that is sensitive to flow-rate variations.

An ESA-based method that can detect fuel pump bearing wear atdeadhead (zero flow) conditions would be particularly beneficial

31


1E-26

1E-24

1E-22

1E-20

1E-18

1E-16

1E-14

1E-12

1E-10

1E-08

1E-06

1E-04

1E-02

1E+00

0 10 20 30 40 50 60 70 80 90 100

Frequency (orders of motor speed)

Mot

or C

urre

nt S

BD

Mag

nitu

de

A2188 (as-received)


It was discovered that the noise floor of the demodulated motorcurrent spectrum at deadhead conditions increased in all fivepumps after the front bearings were degraded

Increases in the noise floor can be seen where the red spectrum rises

above the blue spectrum

1

10

100

1000

10000

0 10 20 30 40 50 60 70 80 90 100

Frequency (orders of motor speed)

SB

D N

ois

e F

loo

r M

agn

itu

de

Rat

io (

aft

er w

ear

/ bef

ore

wea

r)

A2188A3095A3493A3852A3926Average

Within the 20x to 40x range, the average

noise floor increased over two orders of magnitude (greater than 100 times) as a direct result of the

additional front bearing wear

32


1E-23

1E-22

1E-21

1E-20

1E-19

1E-18

A13

25(a

r,fb

c=1.

3)

A30

95(a

r,fb

c=1.

3)

A35

05(a

r,fb

c=1.

4)

A31

17(a

r,fb

c=1.

8)

A37

48(a

r,fb

c=1.

3)

A16

33(a

r,fb

c=1.

9)

A24

75(a

r,fb

c=1.

4)

A34

0(ar

,fbc=

1.1)

A10

74(a

r,fb

c=1.

9)

A37

49(a

r,fb

c=1.

9)

A32

98(a

r,fb

c=1.

8)

A39

26(a

r,fb

c=1.

1)

A33

70(a

r,fb

c=4.

2)

A47

0(ar

,fbc=

2.5)

A11

4(ar

,fbc=

0.9)

A68

0(ar

,fbc=

1.8)

A25

18(a

r,fb

c=1.

4)

A37

80(a

r,fb

c=2.

2)

A24

24(a

r,fb

c=1.

6)

A21

88(a

r,fb

c=1.

3)

A33

43(a

r,fb

c=1.

9)

A12

21(a

r,fb

c=1.

3)

A34

93(a

r,fb

c=2.

3)

A38

52(a

r,fb

c=3.

3)

A97

5(ar

,fbc=

4.5)

A32

05(a

r,fb

c=4.

5)

A17

00(d

,fbc=

8.0)

A30

95(d

,fbc=

11.7

)

A38

52(d

,fbc=

11.9

)

A21

88(d

,fbc=

11.6

)

A34

93(d

,fbc=

12.5

)

A34

95(d

,fbc=

22.8

)

A39

26(d

,fbc=

11.3

)

No

ise

Flo

or

(20X

- 40

X) A

vera

ge

Mag

nit

ud

eWhen the 20x–40x noise floor magnitudes were plotted for allauxiliary pumps where the bearing dimensions were known,a strong relationship was revealed

front bearing clearance (mils) > 20

10 < front bearing clearance (mils) < 20

3 < front bearing clearance (mils) < 10

front bearing clearance (mils) < 3

ar = as received; d = with implanted defect

fbc = front bearing clearance (mils)

1E-23

1E-22

1E-21

1E-20

1E-19

1E-18

FBC<3 (22 pumps)

3<FBC<10(5 pumps)

10<FBC<20(5 pumps)

FBC>20 (1 pump)

No

ise

Flo

or

(20X

- 4

0X)

Ave

rag

e M

agn

itud

eFBC = front bearing clearance in mils

33


Several activities are ongoing or planned for the near future

• Additional testing of auxiliary fuel pumps is ongoing. Methods for detecting other pump degradations using ESA will be explored.

• A comprehensive test plan will be carried out on main fuel pumps for the purpose of identifying ESA diagnostic methods for these pumps.

• A suitcase-style ESA instrument is under development. Two prototypes will be constructed and delivered to the Air Force at the conclusion of the project.

• Additional opportunities for developing ESA diagnostic systems for additional components and systems (e.g., generators, aircraft engines, electric motors, active synchrophasers, and motor-driven actuators for control surfaces) will be explored with the Air Force and other interested organizations.

34


Summary

• Electrical signature analysis (ESA) can be a powerful addition to condition-based maintenance programs.

• ESA is a non-intrusive technology that exploits the abilities of electric motors and generators to act as transducers.

• ESA can enhance equipment safety, reliability, and operational readiness by providing improved diagnostics and prognostics.

• The Oak Ridge National Laboratory (ORNL) is presently developing a portable ESA-based instrument for monitoring the condition of C-141 fuel pumps.

• Fuel pump electric current data have been acquired from many pumps that were tested at Wright-Patterson Air Force Base, Oklahoma City Air Logistics Center, and ORNL.

• A new capability to detect front bearing wear in C-141 auxiliary fuel pumps has been developed using ESA. Additional capabilities are anticipated through continued testing of auxiliary and main fuel pumps in the field and at instrumented test facilities.

electrical signature analysis (esa) as a diagnostic

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