Basic Engine and Compressor Analysis

Basic Reciprocating Engine & Compressor Analysis Techniques

Azonix-Dynalco Kathy Boutin, B.Sc. Ben Boutin, P.Eng.

© 2003 DYNALCO CONTROLS

GMRC 2003 GAS MACHINERY CONFERENCE BASIC ENGINE & COMPRESSOR ANALYSIS TECHNIQUES

1

Focus of this course

In this course, we illustrate engine and compressor behavior using data taken from running machinery  The data were recorded by analysts running their own predictive maintenance programs  We show faults that are seen in recip equipment and present techniques to detect them 

© 2003 DYNALCO CONT ROLS

GMRC 2003 GAS MACHINERY CONFERENCE SHORT COURSE: BASIC ENGINE & COMPRESSOR ANALYSIS TECHNIQUES

2

1

Short Course Outline Analysis Programs  Characterizing engines and compressors 

Data types  Testpoint Locations 



Sequence of events 2-stroke engines  4-stroke engines  Compressors 

Analyzing engine faults  Analyzing compressor faults  Analyzing auxiliary equipment faults 



3

Analysis Programs

Objectives  Types of analysis  Analysis process 



4

2

Analysis Programs Objectives of analysis programs

Eliminate expensive, unnecessary maintenance  Decrease maintenance costs  Increase machine availability  Decrease down time  Improve performance  Reduce emissions 

“You can’t improve what you don’t measure”



5

Analysis Programs Types of machinery machinery analysis 

Maintenance Analysis Identifies incipient failure so that you can turn unscheduled maintenance into scheduled maintenance  Helps avoid in-service failures maintenance e cost  Goal is to reduce maintenanc 



Performance Analysis Characterizes the engine/compressor operating potential  Efficiency  Fuel consumption  Horsepower  Throughput 



6

3

Analysis Programs The analysis process

Gather data from the machine  Reduce the data to measures of performance and condition  Organize and present the reduced data  Infer performance and condition  Report findings  Take action  Follow up 



7

Characterizing Engines and Compressors

Data Types  Testpoint Locations 



8

4

Characterizing Engines and Compressors Special data types 

Process data Tell about the process  Examples: suction temperature and pressure 



Phase-marked data Data is referenced to the flywheel  Example: pressure versus time data 



Non-phased data Sampling is a function of time only  Example: acceleration data from a turbocharger bearing 



9

Characterizing Engines and Compressors Measuring flywheel position 

Once-per-degree Shaft encoder  360 pulses per revolution  Better accuracy 



Once-per-turn Magnetic, active or optical pickups are common  1 pulse per revolution  Usually permanently mounted 



10

5

Characterizing Engines and Compressors Example of phase-marked pressure (PT) C402 - C cylinder 2 09/09/1998 12:02:53 PM HE Period 5, CE Period 5 1700 1600 1500

Head and crank end pressure traces on a compressor cylinder

1400 1300

) g i s1200 p ( e r1100 u s s e1000 r P

900 800 700 600 500

0

45


90

135 180 225 Crank Angle (deg)

270

315

360


11

Characterizing Engines and Compressors Free-running, non-phased data

Data is recorded independent of crankshaft position  Returns 

Overall vibration level  Spectrum showing frequency components 



Common applications: Structural vibration  Supports, foundations  Turbochargers  Oil and water pumps  Pressure pulsation 



12

6

Characterizing Engines and Compressors Example of free-running, non-phased, spectrum data UNIT #4-E Testpoint OPEH 7/17/2002 10:51:55 AM 1.0 Testpoint : OPEH VIB No. Of Lines : 400 No. Of Averages : 5 Calc Overall : N/A Trap Overall : 1.325

1 times run speed

0.9 0.8

Peak At Frequency 1.020 at 322.5 0.507 at 1305.0 0.122 at 652.5 0.110 at 487.5 0.098 at 1627.5 0.079 at 2932.5 0.073 at 1357.5 0.061 at 1140.0 0.061 at 1020.0 0.061 at 975.0

2 times run speed

)0.7 k p k 0.6 p o d u e 0.5 s p ( l i 0.4 m

4 times run speed

0.3

Spectrum from engine frame near anchor bolts. Mils peakpeak, oil pump end, horizontal direction. Engine speed 323 RPM

0.2 0.1 0.0 0

500


1000

1500 cpm

2000

2500

3000


13

Engine Data Cylinder exhaust temperatures  Infrared temperature wand • pyrometer

Turbocharger/blower • Standard accelerometer mounted on bearings and near turbine and compressor wheels • Frequency domain vibration Ignition secondary • Inductive connection to unshielded spark plug cable • Multi-period sampling statistics • Ignition secondary patterns Ignition primary (not shown) • Connection to primary box • Ignition primary firing patterns TDC Reference • Shaft encoder • Magnetic pickup • Phased data • RPM

Cylinder, valve, wrist pin and bearing vibration • Ultrasonic microphone • Standard accelerometer • Time domain data phased to crankshaft position

Cylinder pressure • Pressure transducer • Time domain data phased to crankshaft position • Peak pressure statistics

Frame vibration (displacement) • Tri-axial accelerometer (H, V, A) taken at opposite corners of engine frame • Frequency domain data


7

Characterizing Engines and Compressors Typical 2-stroke engine PT/VT 20905-E Cylinder P5 3/27/2002 8:57:46 AM Period 0 600

118

137

PT

550

223 Intake 242 Exhaust 273

Fuel 213

--------------

500

VT

-

450 - P5 VT4

) 400 g i s p350 ( e r u300 s s e r 250 P

- Scale 2.4 -

200

-

150 -

100

-

50

--------------

0 0

45

90


135

180 Angle (deg)

225

270

315

360


15

Characterizing Engines and Compressors Typical 4-stroke engine PT/VT 5302-E Cylinder 2L 12/3/2001 9:15:58 AM Period 1 1100

Intake 281

140

Fuel 315

620

391 Exhaust

--------------

583

1000

-

900

VT

-

800

- 2L VT4

) g 700 i s p ( 600 e r u s s 500 e r P

- Scale 5.0 -

400

-

300

-

200

PT

-

100

--------------

0 0

45

90

135


180

225

270

315 360 405 Angle (deg)

450

495

540

585

630


675

720

16

8

Compressor Data

Crosshead Vibration • Standard accelerometer • Time domain data phased to crankshaft position • Relate to rod load

Valve cap temperatures • Infrared temperature wand • thermocouples, RTDs

TDC Reference • Shaft encoder • Magnetic pickup • Phased data • RPM

Suction/discharge temperatures • Infrared temperature wand • thermocouples, RTDs Suction/discharge valve vibration Compressor ring leak vibration Liner scoring • Ultrasonic microphone • Standard accelerometer • Time domain data phased to crankshaft position Head/crank end pressure • Pressure transducer • Time domain data phased to crankshaft position • Multi-period sampling statistics

Rod Motion • Proximity probes • Time-domain data phased to crankshaft position • Rod displacement trends

Suction/discharge nozzle pressure • Pressure transducer • Time domain data phased to crankshaft position (valve/passage loss calculations) • Frequency domain (pulsation spectrum) • Multi-period sampling statistics

Frame vibration (displacement) • Tri-axial accelerometer (H, V, A) taken at opposite corners of engine frame • Frequency domain data


Characterizing Engines and Compressors Typical HE compressor pattern K200 - C cylinder 4 9/23/1998 9:52:15 AM HE Period 5, CE Period 7 -------------- 4HD1 VT1 - Scale 3.0 - 145 DGF ---------------- 4HD2 VT1 - Scale 3.0 - 146 DGF --------------- 4HS1 VT1 - Scale 3.0 - 84 DGF --------------- 4HS2 VT1 - Scale 3.0 - 84 DGF ---------------

CE PT

600 550 HE PT

) g 500 i s p ( e r 450 u s s e r P 400

HE VT

350 300 250 0

45

90

135

180

225

270

315

360

Crank Angle (deg) © 2003 DYNALCO CONT ROLS


18

9

Sequence of events

2-stroke, spark-ignited engine  4-stroke, spark-ignited engine  Double-acting, reciprocating compressor 



19

Understanding Machine Faults 

To recognize faults in compressors and engines, we must understand how they behave in normal operation Do the mechanical events you expect to see actually happen?  Do the events appear to be normal? 

 

 



when do they occur? what is the relative magnitude? do they look the same as they did last time? do they look the same as the next machine?

What is the performance of the machine?



20

10

Sequence of events for a 2 stroke engine

Pressure versus crank angle (PT)  Pressure-Volume (PV)  Vibration versus crank angle (VT) 



21

Sequence of events for a 2-stroke engine PT: start of cycle

• Ignition has occurred • Flame front travel has begun • Mixture is superheated air and fuel e r u s s e r P

0 90


180 Crank Angle (Deg)


270

360

22

11

Sequence of events for a 2-stroke engine PT: combustion

• Flame travels through chamber • Heat is released, pressure rises • Temperature at flame front is about 3500°F • Peak occurs 10-15 deg ATDC

e r u s s e r P

• Speed of propagation is critical •Too fast, detonation •Too slow, soft fire

0 0

90

180

360

270

Crank Angle (deg)



23

Sequence of events for a 2-stroke engine PT: power

• Combustion is complete • Pressure drives piston down • As volume increases, pressure decreases e r u s s e r P

0 0

90

180

270

360

Crank Angle (deg)



24

12

Sequence of events for a 2-stroke engine PT: exhaust blowdown

• Piston uncovers exhaust port • Pressure drops more rapidly (blowdown) • Temperature is now about 800°F e r u s s e r P

0 0

90

180

360

270

Crank Angle (deg)



25

Sequence of events for a 2-stroke engine PT: air intake

• Intake port is uncovered • Cylinder pressure ≤ intake pressure • Fresh air under pressure sweeps and cools e r u s s e r P

0 90


180 Crank Angle (Deg)


27 270

360

26

13

Sequence of events for a 2-stroke engine PT: scavenging

• Scavenging continues until intake closes • Cylinder cooling continues

e r u s s e r P

0 0

90

180

360

270

Crank Angle (deg)



27

Sequence of events for a 2-stroke engine PT: fuel intake

• Scavenging continues until intake closes • This is the lowest pressure in the cylinder • Fuel is injected just prior to exhaust closure • Open exhaust port drags fuel down e r u s s e r P

• Port closes before any fuel escapes

0 0

90

180

270

360

Crank Angle (deg)



28

14

Sequence of events for a 2-stroke engine PT: compression

• Fuel injection ceases, ports are closed • Pressure begins to rise • Air-fuel charge is turbulent • Turbulence mixes the air-fuel charge e r u s s e r P

• Temperature rises

0 0

90

180

360

270

Crank Angle (deg)



29

Sequence of events for a 2-stroke engine PT: ignition

• Ignition occurs 5-10 degrees BTDC • Advance gives time to initiate combustion and for flame front travel • Air-fuel charge is superheated e r u s s e r P

0 0

90

180

270

360

Crank Angle (deg)



30

15

Sequence of events for a 2-stroke engine PT: end of cycle

• Flame front begins propagating through chamber

e r u s s e r P

0 0

90

180

360

270

Crank Angle (deg)



31

Sequence of events for a 2-stroke engine PV: start of cycle (TDC)

• Ignition has occurred • Flame front travel has begun • Mixture is superheated air and fuel e r u s s e r P

0 0

25

50

75

100

Swept Volume (%)



32

16

Sequence of events for a 2-stroke engine PV: combustion

• Flame travels through chamber • Heat is released, pressure rises • Temperature at flame front is about 3500°F • Peak occurs 10-15 deg ATDC

e r u s s e r P

• Speed of propagation is critical •Too fast, detonation •Too slow, soft fire

0 0

25

50

100

75

Swept Volume (%)



33

Sequence of events for a 2-stroke engine PV: power

• Combustion is complete • Pressure drives piston down • As volume increases, pressure decreases e r u s s e r P

0 0

25

50

75

100

Swept Volume (%)



34

17

Sequence of events for a 2-stroke engine PV: exhaust blowdown

• Piston uncovers exhaust port • Pressure drops more rapidly (blowdown) • Temperature is now about 800°F e r u s s e r P

0 0

25

50

100

75

Swept Volume (%)



35

Sequence of events for a 2-stroke engine PV: air intake

• Intake port is uncovered • Cylinder pressure ≤ intake pressure • Fresh air under pressure sweeps and cools e r u s s e r P

0 0

25

50

75

100

Swept Volume (%)



36

18

Sequence of events for a 2-stroke engine PV: scavenging

• Scavenging continues until intake closes • Cylinder cooling continues

e r u s s e r P

0 0

25

50

100

75

Swept Volume (%)



37

Sequence of events for a 2-stroke engine PV: fuel intake

• Scavenging continues until intake closes • This is the lowest pressure in the cylinder • Fuel is injected just prior to exhaust closure • Open exhaust port drags fuel down e r u s s e r P

0 0

25

50

75

100

Swept Volume (%)



38

19

Sequence of events for a 2-stroke engine PV: compression

• Fuel injection ceases, ports are closed • Pressure begins to rise • Air-fuel charge is turbulent • Turbulence mixes the air-fuel charge e r u s s e r P

• Temperature rises

0 0

25

50

100

75

Swept Volume (%)



39

Sequence of events for a 2-stroke engine PV: ignition

• Ignition occurs 5-10 degrees BTDC • Advance gives time to initiate combustion and for flame front travel • Air-fuel charge is superheated e r u s s e r P

0 0

25

50

75

100

Swept Volume (%)



40

20

Sequence of events for a 2-stroke engine PV: end of cycle

• Flame front begins propagating through chamber

e r u s s e r P

0 25

0

50

100

75

Swept Volume (%)



41

Sequence of events for a 2-stroke engine Cylinder vibration: start of cycle 137

223 Intake 242 Exhaust

118 Fuel 213

273

e r u s s e r P

0


45

90

135

180 Angle (deg)

2 25

270


315

360

42

21

Sequence of events for a 2-stroke engine Cylinder vibration: combustion 137


118 Fuel 213

273

• Rings become fully loaded by gas pressure • May see some vibration resulting from combustion e r u s s e r P

0


45

90

135

180 Angle (deg)

2 25

270

315


360

43

Sequence of events for a 2-stroke engine Cylinder vibration: power 137


118 Fuel 213

273

Ring noise

e r u s s e r P

0


45

90

135

180 Angle (deg)

2 25

270


315

360

44

22

Sequence of events for a 2-stroke engine VT Cylinder vibration: exhaust blowdown 137


118 Fuel 213

273

Exhaust Blowdown

e r u s s e r P

0


45

90

135

180 Angle (deg)

2 25

270

315


360

45

Sequence of events for a 2-stroke engine VT Cylinder vibration: air intake and scavenging 137


118 Fuel 213

273

e r u s s e r P

0


45

90

135

180 Angle (deg)

2 25

270


315

360

46

23

Sequence of events for a 2-stroke engine VT Cylinder vibration: fuel intake 137


118 Fuel 213

273

e r u s s e r P

0


45

90

135

180 Angle (deg)

2 25

270

315


360

47

Sequence of events for a 2-stroke engine VT Cylinder vibration: compression 137


118 Fuel 213

273

Fuel Valve Closure

e r u s s e r P

0


45

90

135

180 Angle (deg)

2 25

270


315

360

48

24

Sequence of events for a 2-stroke engine VT Cylinder vibration: ignition 137


118 Fuel 213

273

Ignition 5-10 degrees BTDC

e r u s s e r P

0


45

90

135

180 Angle (deg)

2 25

270

315


360

49

Sequence of events for a 2-stroke engine VT Cylinder vibration: end of cycle 137


118 Fuel 213

273

e r u s s e r P

0


45

90

135

180 Angle (deg)

2 25

270


315

360

50

25

Sequence of events for a 4 stroke engine

Pressure and vibration (PT/VT)  Pressure-Volume (PV) 



51

Sequence of events for a 4-stroke engine PT/VT: top dead center 137

417 Exhaust 565 611 Fuel 502

Intake 300

• Ignition has occurred • Flame front propagation has begun • Mixture is superheated air and fuel e r u s s e r P

2

1

0 180

0 1 © 2003 DYNALCO CONT ROLS

Combustion

2

360 Crank Angle (deg) Exhaust

3

Intake

720

540 4

Compression


52

26

Sequence of events for a 4-stroke engine PT/VT: peak firing pressure 137

417 Exhaust 565 611 Fuel 502

Intake 300

• Flame front propagation through cylinder • Pressure and temperature rise •Too fast, detonation •Too slow, soft fire

e r u s s e r P P re s u

2

1

0 180


Combustion

2


3

Intake

720

540 4

Compression


53

Sequence of events for a 4-stroke engine PT/VT: power stroke 137

417 Exhaust 565 611 Fuel 502

Intake 300


2

1

0 180


Combustion

2


3

Intake

720

540 4

Compression


54

27

Sequence of events for a 4-stroke engine PT/VT: exhaust blowdown 137

417 Exhaust 565 611 Fuel 502

Intake 300

• Exhaust gases leave through exhaust valve port to exhaust header and then to the turbocharger

Blowdown

e r u s s e r P

2

1

0 180


Combustion

2


3

Intake

720

540 4

Compression


55

Sequence of events for a 4-stroke engine PT/VT: air intake 137

417 Exhaust 565 611 Fuel 502

Intake 300

Exhaust valve closure

e r u s s e r P

4

3

0 180


Combustion

2


3

Intake

720

540 4

Compression


56

28

Sequence of events for a 4-stroke engine PT/VT: fuel intake 137

417 Exhaust 565 611 Fuel 502

Intake 300

Intake valve closure

e r u s s e r P

4

3

0 180


Combustion

2


3

Intake

720

540 4

Compression


57

Sequence of events for a 4-stroke engine PT/VT: compression and ignition 137

417 Exhaust 565 611 Fuel 502

Intake 300

Fuel valve closure

e r u s s e r P

4

3

0 180


Combustion

2


3

Intake

720

540 4

Compression


58

29

Sequence of events for a 4-stroke engine PT/VT: end of cycle 137

417 Exhaust 565 611 Fuel 502

Intake 300

What’s this?


1

2

0 180


2

Combustion


3

Intake

720

540 4

Compression


59

Sequence of events for a 4-stroke engine VT: crosstalk (KVS 412) K200 - E 9/10/1995 6:51:46 AM Engine Cylinders: Phased Vibration VT4:

2

P1

0

672

-2 2

P2

0

192

-2 2

P3

0

432

-2 2

P4

0

72

-2 2

P5

0

552

-2 2

P6

0

312

This engine -2 has solid lifters 0


90

180

270

360

450

540


630

720

60

30

Sequence of events for a 4-stroke engine PV: top dead center

2

1 0 0 3


25 COMBUSTION

50 4

EXHAUST

75 1

INTAKE

2

100 COMPRESSION


61

Sequence of events for a 4-stroke engine PV: air intake

• Fresh air enters cylinder

2

1 0

3


COMBUSTION

4

EXHAUST

1

INTAKE

2

COMPRESSION


62

31

Sequence of events for a 4-stroke engine PV: fuel intake & compression

• Fuel intake starts BBDC • Turbulence stirs mixture

2

1 0 0 3


25 COMBUSTION

50 4

EXHAUST

75 1

INTAKE

2

100 COMPRESSION


63

Sequence of events for a 4-stroke engine PV: ignition

• Mixture is compressed and superheated • Ignition occurs 10-20 deg BTDC

2

1 0

3


COMBUSTION

4

EXHAUST

1

INTAKE

2

COMPRESSION


64

32

Sequence of events for a 4-stroke engine PV: top dead center

• Ignition has occurred • Flame front travel has begun

4

3 0

3


COMBUSTION

4

EXHAUST

1

INTAKE

2

COMPRESSION


65

Sequence of events for a 4-stroke engine PV: peak firing pressure

• Flame travels through chamber • Heat is released, pressure rises • Peak occurs 15-20 deg ATDC • If pressure increase is … •Too fast, detonation •Too slow, soft fire

4

3 0

3


COMBUSTION

4

EXHAUST

1

INTAKE

2

COMPRESSION


66

33

Sequence of events for a 4-stroke engine PV: power stroke

• Combustion is complete • Pressure drives piston down • As volume increases, pressure decreases

4

3 0

3


COMBUSTION

4

EXHAUST

1

INTAKE

2

COMPRESSION


67

Sequence of events for a 4-stroke engine PV: bottom dead center

• Exhaust valve opens just before BDC

4

3 0

3


COMBUSTION

4

EXHAUST

1

INTAKE

2

COMPRESSION


68

34

Sequence of events for a 4-stroke engine PV: exhaust

• Pressure drops rapidly (blowdown)

4

3 0

3


COMBUSTION

4

EXHAUST

1

INTAKE

2

COMPRESSION


69

Sequence of events for a 4-stroke engine PV: end of cycle

4

3 0 0 3


25

COMBUSTION

50 4

EXHAUST

75 1

INTAKE

2

100 COMPRESSION


70

35

Sequence of events for a double acting reciprocating compressor     

Head End (HE) compression cycle (PV) Crank End (CE) compression cycle (PV) HE valve events HE and CE pressure-time (PT) HE and CE vibration-time (VT)



71

Sequence of events in a reciprocating compressor HE compression cycle HE Compression Discharge

3

Pd

e r u s s e r P

1-2

2

HE Discharge e m u l o V e c n a r a e l C

2-3

Compression Expansion

HE Expansion

P ru s e

3-4

ra e lC V c n m u o

1

Ps

Suction

4

Swept Volume

Volume © 2003 DYNALCO CONTROLS

HE Suction

4-1


72

36

Sequence Sequence of events in a reciprocatin reciprocating g compressor compressor CE compression cycle CE Compression

1-2

Discharge

2

3

Pd

e r u Compression s s e r P

Expansion

e m u l o V e c n a r a e l C

CE Discharge

2-3

CE Expansion

3-4

1 Ps

Suction

4

Swept Volume

CE Suction

Volume © 2003 DYNALCO CONTROLS

4-1


73

Sequence Sequence of events in a reciprocatin reciprocating g compressor compressor PV: HE compression compression event Suction Line Pressure (Ps)

2

Pd

Suction closed

e r u s s e r P


Compression Cylinder Pressure (Pcyl) is above Ps and increasing to Pd. Discharge valve opens when Pcyl is greater than Pd (2).

1 Discharge

Ps

AP

closed

Volume


AS AP

AD

Discharge Line Pressure (Pd)


74

37

Sequence Sequence of events in a reciprocatin reciprocating g compressor compressor PV: HE discharge event Suction Line Pressure (Ps)

3 Discharge

Pd

2 Suction closed

e r u s s e r P


AS AP

Compression Cylinder Pressure (Pcyl) is above Pd and decreasing to Pd. Discharge valves closes when Pcyl equals Pd (3) at TDC.

1 Discharge

Ps

open

AP

Piston Stroke Volume Discharge Line Pressure (Pd)

Volume



75

Sequence Sequence of events in a reciprocatin reciprocating g compressor compressor PV: HE expansion event Suction Line Pressure (Ps)

3 Discharge

Pd

2 Suction closed

e r u s s e r P


AS AP

Compression Cylinder Pressure (Pcyl) is below Pd and decreasing to Ps. Suction valve opens when Pcyl is less than Ps (4).

Expansion

1 Discharge

Ps

AP

closed

4

AD

Piston Stroke Volume

Volume


Discharge Line Pressure (Pd)


76

38

Sequence Sequence of events in a reciprocatin reciprocating g compressor compressor PV: HE suction event Suction Line Pressure (Ps)

3 Discharge

Pd

2 Suction open

e r u s s e r P


AS

Compression Cylinder Pressure (Pcyl) is below Ps and increasing to Ps. Suction valve closes when Pcyl is equal to Ps (1) at BDC.

Expansion

1 Discharge

Ps

Suction

4

AP

closed

AD

Piston Stroke Volume Discharge Line Pressure (Pd)

Volume



77

Sequence Sequence of events in a reciprocatin reciprocating g compressor compressor Example: HE and CE PV K200 - C cylinder 4 9/23/1998 9/23/1998 9:52:15 AM HE Period 5, CE Period Period 7 600 550

) g i s p ( e r u s s e r P

500 450 400 350 300 250 0


25

50 75 Percent swept volume


100

78

39

Sequence of events in a reciprocating compressor PT: HE and CE Discharge Pressure

D

2 3

A

A

CE PT HE PT

Suction Pressure 1

C

B

0

1

4

180

360

Crank Angle (Deg)

Head End: Expansion (A-B) Crank End: Compression (1-2)

Suction (B-C)

Compression (C-D)

Discharge (D-A)

Discharge (2-3)

Expansion (3-4)

Suction (4-1)



79

Sequence of events in a reciprocating compressor HE valve vibration

4

HE Discharge

1

0

6

1 Suction valve opens (depends on clearance volume)

4 Discharge valve opens (typically the loudest)

2 Suction gas fills the cylinder.

5 High pressure gas is discharged into discharge line.

3 Suction valve is lowered gently onto the seat at BDC – closing event is not always visible. HE Suction

5

2

3

180

6 Discharge valve is gently lowered onto the seat at TDC – not always visible.

360

Gas blowing noise is loudest at valve opening and gradually diminishes as gas velocity through the valve decreases. © 2003 DYNALCO CONTROLS


80

40

Sequence of events in a reciprocating compressor CE valve vibration

CE Discharge

CE Suction

0


180


360

81

Sequence of events in a reciprocating compressor HE and CE valve crosstalk

HE Discharge

CE Discharge

CE Suction

HE Suction

0


180


360

82

41

Sequence of events in a reciprocating compressor Typical HE PT/VT signature K200 - C cylinder 4 9/23/1998 9:52:15 AM HE Period 5, CE Period 7 -------------- 4HD1 VT1 - Scale 3.0 - 145 DGF --------------- 4HD2 VT1 - Scale 3.0 - 146 DGF --------------- 4HS1 VT1 - Scale 3.0 - 84 DGF --------------- 4HS2 VT1 - Scale 3.0 - 84 DGF --------------

600 550 ) g 500 i s p ( e r u 450 s s e r P 400

350 300 250 0

45

90

135

180

225

270

315

360

Crank Angle (deg) GMRC 2003 GAS MACHINERY CONFERENCE BASIC ENGINE & COMPRESSOR ANALYSIS TECHNIQUES


83

Quick Recap 

So far, we’ve talked about the normal behavior of: 2-stroke, spark-ignited recip engine  4-stroke, spark-ignited recip engine  double-acting, reciprocating compressor 



Now we know what they are supposed to look like, we can look at faults



84

42

Analyzing Engine Faults

Combustion  Mechanical 



85

Engine faults we can monitor Combustion Quality

Mechanical Condition

•Unbalance

•Leaking valves

•Detonation

•Leaking rings

•Misfire

•Valve train (cam, guides, lifters, linkage)

•Pre-ignition

•Worn,

•Excessive Emissions

•Port/bridge wear

Operating Performance

•Carbon

•Indicated horsepower

•Wrist

•Torque

•Main bearings, crank pins

•Efficiency

•Ignition problems

Economic Performance

•Turbocharger faults

•Fuel cost

•Oil Pump, water pump problems

•Fuel consumption

•Frame, foundation vibration


scored liner and piston in ports

pin


86

43

Combustion

Many of the problems we face with engines are due to variable combustion  Engines do not fire the same way each cycle 



87

Combustion Chemical equation of combustion

Engines convert chemical energy to heat  Take a simple gas such as Methane (CH 4)  Combine it with oxygen and start the reaction 

CH

4



+ 2O 2 → CO 2 + 2H2O

Produces carbon dioxide plus water vapor and releases heat of about 1000 BTU/ft 3 of methane consumed



88

44

Combustion If only it was that simple…

Air is primarily O 2 (23%) and N 2 (77%)  Both are involved in the chemical reaction  The combustion process is neither complete nor instantaneous  Many intermediate steps and reactions occur  This leads to other exhaust products such as NOx, HC, CO and particulates (smoke) 



89

Combustion Why is combustion so variable?

incomplete mixing in the cylinder  difficulty burning lean air/fuel mixtures  inconsistent air/fuel charge in each cycle  poor fuel quality  ignition faults  incorrect valve timing  varying ambient conditions 



90

45

Combustion Results of poor combustion

Firing in each becomes inconsistent, high fires followed by low fires  Stress the engine thermally and mechanically  Reduce the life of engine components  Waste fuel  Increase emissions  This costs a great deal of money 



91

Combustion Typical faults

Unbalance  Dead cylinders  Early firing  Soft firing  Detonation  Pre-ignition 



92

46

Engine balance

The manufacturer designed the engine to handle specific cylinder pressures and temperatures  Cylinders with high peak pressures develop much greater mechanical and thermal stress  Engine balancing distributes this mechanical and thermal stress across the engine to maximize component life 



93

Engine Balance Cylinder pressures (balanced HBA) Unit2 4/15/2002 9:21:55 AM All cylinders - In Bank Order

800 700 P2

600

P1

P3

) g i s 500 p ( e r u 400 s s e r P

P4

P8

P5 P6

+10%

P7

+2% -2% -10%

300 200 100 0 0

45


90

135

180 225 Crank Angle (deg)

270


315

360

94

47

Engine Balance Pressure rise rate (balanced HBA) Unit2 4/15/2002 9:21:55 AM All cylinders - In Bank Order 35 ) θ d / p d ( e t a R e s i R e r u s s e r P

P2

P4

P8

P5

30 P3

25

P6

P1

20

P7

15 10 5 0 -5 -10 -15 0

45


90

135


270

315


360

95

Engine Balance Cylinder pressures (unbalanced HLA) C2B-E 6/6/2001 7:22:02 AM All cylinders - In Bank Order

700 2

600 ) g i s p ( e r u s s e r P

7 8

3

500

4

+10% +2% -2% -10%

5

1 400

6

300 200 100 0 0

45


90

135


270


315

360

96

48

Engine Balance Pressure rise rate (unbalanced HLA) C2B-E 6/6/2001 7:22:02 AM All cylinders - In Bank Order

2

20

) θ d / p 15 d ( e t a R 10 e s i R e 5 r u s s e r P 0

Highly variable

7

3 8 4

1

5 6

-5 -10

0

45


90

135


270


315

360

97

Detonation Detonation is rapid and uncontrolled combustion. Detonation can lead to rapid failure due to high thermal and mechanical stress. Causes of detonation:  Mixture too rich  Clogged/dirty air intake (air inlet filters, aftercoolers or blowers)  Incomplete scavenging  inconsistent fuel composition  Overloaded engine  Ignition timing too advanced  Highly loaded cylinders in an unbalanced engine are more susceptible to detonation. © 2003 DYNALCO CONT ROLS


98

49

Detonation Engine PT parade (Ajax DPC-720-LE-H-2) K203 - E 11/21/1996 2:13:03 PM All cylinders - In Bank Order

600 550 500 ) g i s p ( e r u s s e r P

P3 – Detonating Cylinder

450 400 P1 350 300

P2

P4

+10% +2% -2% -10%

250 200 150 100 50 0 0


45

90

135 180 225 270 Crank Angle (deg)

315

360


99

Detonation Multiple PT cycles for a power cylinder (P3) K203 - E - P3 PT3 11/21/1996 2:13:03 PM

550 500

Detonation

Detonation

Detonation

450 400 350

Misfire

300

Misfire

250 200 150 100 50 0 500

1000

1500

2000

2500

3000

3500

Samples



100

50

Soft Firing Soft Firing occurs when the pressure in the cylinder rises too late (also called late firing). The PFP is usually low and late. Causes of soft fires:  incomplete scavenging  air/fuel ratio too lean causing slow flame front  air/fuel ratio too rich for proper combustion  late ignition timing  poor fuel composition



101

Soft Firing Engine pressure signature comparisons 1A - E 5/22/1997 10:34:26 AM All cylinders - In Bank Order

800 700

P1R

600 ) g i s500 p ( e r u400 s s e r P300

P3R

P5R

P4R

P3L

P1L

P2R

P4L P5L

P2L

200 100 0 0

45


90

135


270


315

360

102

51

Soft Firing PT: comparison to normal (HBA) 20905-E Cylinder P8 7/14/1999 6:46:53 AM Period 3

550

137

500

223 Intake

118

242 Exhaust Fuel 213

450

273

400 ) g i s p ( e r u s s e r P

Normal

350 300 250 200

Soft (Late) Fire

150 100 50 0 0 © 2003 DYNALCO CONT ROLS

45

90

135


315

360


103

Soft Firing PV: comparison to normal (HBA) 20905-E cylinder P8 7/14/1999 6:46:53 AM Period 3

550 500 450 400 ) g i s p (

350 300

Normal

e r 250 u s s e r 200 P

150 100 50 0

Soft (Late) Fire 0


25

50 % swept volume

75

100


104

52

Soft Firing Another example comparing engine PTs (CB QUAD) C402 - E 9/9/1998 12:02:53 PM All cylinders - In Bank Order - CRC is corrected

1000 900 P3L

800

) g i s p 700 ( e r 600 u s s e r 500 P

P4L P1R P5L

P2R

P3R

P4R P5R

P6L

P6R

+10% +2% -2% -10%

P2L

400 300 200 100 0 0

45


90


270

315


360

105

Early Firing Early firing occurs when the pressure in the cylinder rises too early. The PFP is usually high and close to TDC. Causes of early firing:  air/fuel ratio too rich  early ignition timing  warm air temperature



106

53

Early Firing engine pressure comparison 1A - E 5/22/1997 10:34:26 AM All cylinders - In Bank Order

800 700 P1R P3R

600 ) g i s 500 p ( e r u400 s s e r P300

P5R

P4R

P1L

P3L

P4L

P2R

P5L

P2L

200 100 0 0

45


90

135


270


315

360

107

Dead Cylinders

Dead cylinders have no discernable combustion. Causes of dead cylinders:  ignition problem  improper air/fuel charge



108

54

Dead Cylinders Cylinder comparisons of peak pressures (QUAD) C402 - E 9/9/1998 12:02:53 PM All cylinders - In Bank Order - CRC is corrected

1000 900

P4L

P3L

800

) g i s p 700 ( e r 600 u s s e r 500 P

P1R P5L

P2R

P4R

P3R

P5R

P6L

P6R

+10% +2% -2% -10%

P2L

400

P1L

300 200 100 0 0

45


90


270

315


360

109

Dead Cylinders Cylinder comparisons of pressure shape & timing C402 - E 9/9/1998 12:02:53 PM All cylinders - To Center of Plot - CRC is corrected

1000 900 800 ) g i s p ( e r u s s e r P

700 600 500

P2L soft fire

400 300

P1L Dead Cylinder

200 100 0 -180


-135

-90

-45 0 45 Crank Angle (deg)

90

135

180


110

55

Dead Cylinders Cylinder comparisons of pressure rise rate C402 - E 9/9/1998 12:02:53 PM All cylinders - To Center of Plot - CRC is corrected

35 30 Normal

25 ) θ d / P d ( e t a R e s i R e r u s s e r P

20

Other cylinders

15 10

P2L Soft Fire

5 0 -5 -10

P1L – Dead Cylinder

-15 -20 -180

-135


-90

-45 0 45 90 Crank Angle (deg)

135

180


111

Dead Cylinders Pressure and pressure rise rate relationship C402 - E Cylinder P1L 9/9/1998 12:02:53 PM Period 4 CRC is corrected

- 103 EXH AU ST POR T -123 INTAKE PORT

1000 900

-125

1 00 119

-65 FUEL VALVE

800 ) g i s p ( e r u s s e r P

Normal PT

700 600 500 400

∂P ∂θ

PT

300 200 100 0 -180 © 2003 DYNALCO CONT ROLS

-135

-90

-45 0 45 Crank Angle (deg)

90

135

180


112

56

Dead Cylinders PV comparison to normal C402 - E cylinder P1L 9/9/1998 12:02:53 PM Period 4 CRC is corrected

1000 900 800 700 600 Normal

500 400 300 200

Dead Cylinder

100 0 0 © 2003 DYNALCO CONT ROLS

25

50 75 % swept volume

100


113

Pre-ignition Pre-ignition is the premature combustion of the air/fuel mixture before the normal ignition event (autocombustion). PFP may occur before TDC causing excessive force on the piston, wrist pin, connecting rod and bearings. The mechanical and thermal stress resulting from preignition can cause cracked heads, torched or seized pistons. Causes of pre-ignition  hot spots in the cylinder caused by ash or carbon build up  hot spots created by detonation  early ignition timing is not normally considered preignition. © 2003 DYNALCO CONT ROLS


114

57

Pre-ignition PT comparison to normal 1000 900

-145

5E Cylinder P4 8/15/2002 4:39:48 PM Period 5 -130 Intake 130 -110 Exhaust 110 -77 Fuel

800 700 ) g i s 600 p ( e r 500 u s s e 400 r P

300 200 100 Normal

0 -180

-135


-90

-45

0 Angle (deg)

45

90

135

180


115

Pre-ignition PV showing 2 crank revolutions

Negative work

Positive work Positive work



116

58

Combustion Analysis summary Observation

Characteristics

Normal



Unbalanced



Detonation



All cylinder average PFPs fall within 10-15% of the engine average PFP  Low cycle-to-cycle deviation in cylinder PFP  PFP angle consistent and at expected location  Similar exhaust temperatures among power cylinders Uneven average peak firing pressures  High deviation in PFP for cylinder  Uneven exhaust temperatures  Usually accompanied by higher NOx and HC Often audible High PFP with early PFP angle  Very high pressure rise rate compared to other cylinders  Often develops a shock wave that is seen in the PT  Combustion may make more noise than normal 



117

Combustion Analysis summary (cont.) Observation

Characteristics

Soft Firing



Type of misfire Average PFP lower than normal  PFP angle later than normal  Low pressure rise rate when compared to other cylinders (or history)  May be followed by detonation  Increased exhaust temperature 

Early Firing


PFP angle earlier than normal  Average PFP higher than normal  Higher pressure rise rate when compared to other cylinders (or history)  Lower exhaust temperature 


118

59

Combustion Analysis summary (cont.) Observation

Characteristics

Dead Cylinder



Pre-ignition



Average PFP at running compression – exhibits no cycle variation, low PFP deviation  Maximum pressure = running compression pressure  Low pressure rise rate when compared to other cylinders (or history)  Consumes horsepower  Wastes fuel ($100-$200/day/cyl)  Fuel in exhaust manifold is a backfire risk  Low exhaust temperature Auto-combustion occurring before normal ignition  PFP angle may occur before TDC  Causes mechanical and thermal stress on piston, wrist pin, connecting rod and bearings



119

Combustion PT for a dead cylinder, soft fire, and detonation K203 - E Cylinder Cylinder P3 11/21/1996 11/21/1996 2:13:03 2:13:03 PM PM Period Period 1 109

600

126 FUEL VALVE 206

251 EXHAUST VALVE 234 INTAKE VALVE 307

550 500 450 ) g i s p ( e r u s s e r P

400 Detonation

350 300 250 200 150

Soft (Late) Fire

100 50

Dead Cylinder

0 0

45


90

135


315

360


120

60

Combustion PV for a dead cylinder, soft fire, and detonation K203 - E cylinder P3 11/21/1996 2:13:03 PM PM Period 1

550 500 450 400 ) g i s p ( e r u s s e r P

350 300

Detonation

250 200 Soft (Late) Fire

150 100

Dead Cylinder

50 0 0

25


50 % swept volume

75

100


121

Analyzing the mechanical condition of engines

Valves  Liners wrist pins  Rods and wrist  Rings  Ignition systems 



122

61

Valve Train Rocker Arm

Valve Lifter

Push Rod

Valve Springs

Valve Stem

Exhaust Port

Valve Seat Cam Follower Cam Lobe



123

Valve Train Common problems Mechanical  Loose/worn rocker arm  Improper lifter clearance  Broken springs  Incorrect spring tension  Worn valve guide  Worn or mis-timed cam  Excessive cam gear lash


Leakage  Burnt valves  Deposits on valve seat  Damaged seat  Bent valve stem


124

62

Valve Train Incorrect clearance

May cause the valve to open and close at the wrong time  Valve opening event can be noisy – the clearance is taken up on the leading edge of the cam lobe  Can cause noisy valve closure if the valve is dropped onto the seat 

t f i L

Crank Angle

n o i t a r b i V

Valve opens late & sharp


Normal Lift

Excessive Lash

Valve closes early & drops on seat


125

Valve Train Hydraulic lifters

Hydraulic lifters maintain correct valve timing and minimize valve train wear over a wide range of operating conditions  Oil pressure within the lifter maintains correct clearances in the valve train If the lifter collapses…  The valve may open late and close early  The vibration pattern shows impacts at opening and closure 



126

63

Valve Train Excessive EV clearance (KVGR with solid lifters) K1F - E 12/13/1994 11:19:43 AM Engine Cylinders: Phased Vibration VT4: 2.5

2.5 P

P1

1

0.0

0.0

-2.5

-2.5

2.5

P2

2.5

0.0 P

0.0

2

-2.5

2.5 0.0

0.0 P

P9

3

-2.5

-2.5

2.5

P4

P8

-2.5

2.5

P3

P7

2.5

0.0

0.0

P10

4

-2.5

-2.5

2.5

2.5

P

P5

0.0

0.0

-2.5

5

2.5

2.5

P6

P11

-2.5

P

0.0

0.0 -2.5

P12

-2.5 P

0

90

180

6

270

360

450

540

630

720

90

180

270

360

450

540



630

720

127

Valve Train Vibration comparison for a leaking EV (KVGR) P1

P2

P3

P4

P5

P6

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5 0

90

180


270

360

450

540

630

720 0

90

180

270

360

450

540


630

P7

P8

P9

P10

P11

P12

720

128

64

Valve Train PT and PV: leaking exhaust valves (KVGR) Intake 294

500

580

150

390 Exhaust

500

450

450

400

400

Normal

350

350

) g i s 300 p (

300

2

e r u 250 s s e r P 200

150

1 low compression 2 low PFP Normal

3 low expansion High exhaust temp

2

250 200

1

150

100

100

50

1

50

3

0

3

0 0

45 90 135 180 225 270 315 360 405 450 495 540 585 630 675 720

0

Angle (deg)


25

50 % swept volume


75

100

129

Valve Train Worn rocker arms (KVGR) K1D - E 2/3/1997 10:52:37 AM Engine Cylinders: Phased Vibration VT4:

P1

P2

P3

P4

P5

P6

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5

2.5

2.5

0.0

0.0

-2.5

-2.5 0

90

180

270


360

450

540

630

720

0

90

180

270

360

450


540

630

P7

P8

P9

P10

P11

P12

720

130

65

Valve Train Worn cam gear (KVS) NO-4 - E 2/28/1995 1:38:59 PM Engine Cylinders: Phased Vibration VT4: 2

2

P1

P2

P3

P4

P5

P6

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2

-2

0

90

180

270


360

450

540

630

720 0

90

180

270

360

450

540


630

P7

P8

P9

P10

P11

P12

720

131

Valve Train Worn cam gear (KVS) NO-4 - E Cylinder P12 2/28/1995 1:38:59 PM 161 INTAKE VALVE 325

1000

410 EXHAUST VALVE 575 FUEL VALVE 536 621

NO-4 - E Cylinder P6 2/28/1995 1:38:59 PM 161 INTAKE VALVE 325

1000

410 EXHAUST VALVE 575 621

FUEL VALVE 536

900

900

-

800

800

-

700

- P6 VT4

600

-

700 ) g i s p (

) g i s p600 (

e r u s s 500 e r P

e r u s s e r 500 P

400

400

-

300

300

-

200

200

-

100

100

-

0

- Scale 2.0

0 0

45

90 135 180 225 270 315 360 405 450 495 540 585 630 675 720 Angle (deg)


0

45 90 135 180 225 270 315 360 405 450 495 540 585 630 675 720 Angle (deg)


132

66

Valve Train Leaking fuel valve (HLA) C2A-E 10/10/2001 6:28:53 AM Engine Cylinders: Phased Ultrasonic ULT:

1F

5

5

0

0

-5

-5

5

5

Hard closures

2F 0

0

-5

-5

5

5

3F 0

5F

Leakage

0

-5

-5

5

5

4F 0

0

-5

6F

7F

8F

-5

0

45

90

1 35


18 0

22 5

270

315

3600

45

90

135

180

225

270


315

360

133

Valve Train Leaking fuel valve (HLA) C2A-E Cylinder 8 10/10/2001 6:28:53 AM Period 9 130 110

700


Fuel 213

--------------

-

- 8FV ULT

-

600

-- Scale 4.0

-

500

-

---------------

-

Leak as P rises

- 8 ULT -- Scale 4.0

) 400 g i s p ( e r u s 300 s e r P

-

-

---------------

200

-

- 8 VT4 -- Scale 2.0 -

100

-

--------------

0 0

45

90

135

180

225

270

315

360

Angle (deg)



134

67

Valve Train Analysis summary

Fault

Characteristics Valve opening events are quiet or absent  Valve events are similar across the entire engine  Closing events are at expected crank angle, single impact of short duration  No leakage occurs after valve closure

Normal



Worn rocker bushing Excessive lifter clearance




Multiple impact following normal valve closure  Excessive noise on opening or closure Valve opens late and closes early  Impact noises on valve closure  Sometimes see impact on opening  Early closing exhaust valves may raise the PV toe 


135

Valve Train Analysis summary (cont.)

Fault Characteristics Impact noises on opening and closure Broken Valve may close late valve spring Roughness seen in vibration pattern as valve opens Worn valve and closes guide  



Valve may hang up in the guide and not close at the correct time  May see gas leakage if valve does not seat properly 

Cam gear faults


Impacts in the vibration as gear teeth pass each other  May cause excessive wear on the cam lobe leading to rough vibration pattern  When troubleshooting, be prepared to move the vibration transducer around 


136

68

Valve Train Analysis summary (cont.)

Fault

Characteristics

Leaking valves Improper valve seating



Blowby pattern appears when pressure rises in the cylinder

Multiple impacts on valve closure as valve finds the seat  Look for differences in valve closure across the engine  Can be caused by beat-out seat, worn/broken/incorrect spring, worn guide, loose rocker arm, bent valve stem  May see blowby pattern when pressure is high in the cylinder 



137

Pistons, Rods, Rings and Liners

SOURCE: navsci.berkeley.edu/ ns10/piston.htm © 2003 DYNALCO CONT ROLS


138

69

Piston slap

Piston slap occurs when the piston skirt impacts the liner  Tends to occur after peak pressure when the pressure is high and there are side forces on the piston  Becomes more pronounced when the clearance in the upper cylinder increases due to ring wear 



139

Piston Slap Low frequency vibration showing piston slap (HLA) C2A-E 6/5/2001 8:23:09 AM Engine Cylinders: Phased Acceleration VTL:

1

2

3

4

5

5

0

0 5

-5

-5

5

5

0

0 6

-5

-5

5

5

0

0 7

-5

-5

5

5

0

0

-5

-5

0

45

90


135 180 2 25 2 70 3 15 3 60 0

45

90

8

135 180 2 25 2 70 315 360


140

70

Piston Slap Low frequency vibration showing piston slap (HLA) C2A-E Cylinder 3 6/5/2001 8:23:09 AM Period 6 130 110

700 Not always visible in ultrasonic 600 ) g i s p ( e r u s s e r P

Fuel 213


500 400 300 200 100 0 0


45

90

135 180 225 Angle (deg)

270

315

-------------- 3FV ULT -- Scale 20.0 ----------------- 3 ULT -- Scale 4.0 --------------- 3 VTL -- Scale 6.0 --------------- 3 VT4 - Scale 2.0 --------------360


141

Piston Rods 

Excessive wrist pin and connecting rod bearing clearances produce “impacts” at load reversal in the piston pin bushing in 4-stroke engines, vibration spikes occur near TDC  in 2-stroke engines, vibration spikes occur near BDC 



There is usually cycle-to-cycle variability in the location of the vibration



142

71

Piston Rods Wrist pin load for a 2-stroke engine Wrist pin load in a 2 stroke engine 250000

Gas force

Vibration occurs around BDC where load is minimal

200000

Total force

150000 ) s b l ( e c r o F

Inertia

100000

50000

0

-50000 0

45

90

135

180

225

270

315

360

405

450

495

540

585

630

675

720

Degrees



143

Piston Rods Wrist pin load for a 4-stroke engine Wrist pin load in a 4 stroke engine 250000

Gas force 200000

Total force 150000 ) s b l ( e c r o F

Vibration occurs around TDC where load reverses

Inertia

100000

50000

0

-50000 0

45

90

135

180

225

270

315

360

405

450

495

540

585

630

675

720

Degrees



144

72

Piston Rods Excessive wrist pin clearance (KVS) K200 - E Cylinder P6 1/16/1996 9:39:11 AM Period 6 137 INTAKE VALVE 300 700

417 EXHAUST VALVE 565 FUEL VALVE 502 611

--------------

600


-

500

P6 VT4

400 - - Scale 2.0 300

-

200

100 0

-------------0

45

90


135 1 80

225

270 3 15 360 405 450 Angle (deg)

495

540 585

630


675 7 20

145

Piston Rings Worn or improperly loaded rings

The presence of gas passing noise when cylinder pressures are high indicates blowby  Be careful though, it could be leakage around rings or valves  A damaged liner will prevent rings from sealing properly  Even moderate blowby may be sufficient to cause a significant rise in the engine crankcase pressure  Ring fouling prevents pressure from getting behind the rings to load them properly 



146

73

Liners Scuffing and scoring 

Liner scuffing or scoring is often seen as symmetric vibration spikes around TDC 









For a 2-stroke engine, piston rings pass the same point twice in one cycle For a 4-stroke engine, piston rings pass the same point 4 times in one cycle Ring loading affects the degree that each event is seen

Wear is usually faster in the upper liner due to high PFP Crankcase pressure may increase due to blowby resulting from the liner wear GMRC 2003 GAS MACHINERY CONFERENCE SHORT COURSE: BASIC ENGINE & COMPRESSOR ANALYSIS TECHNIQUES


147

Liners Liner groove (KVS, P2, 10 rotations) NO-6 - E 12/21/1995 8:14:16 AM Engine Cylinders: Phased Vibration VT4:

P2 (MMM)

P2 (1)

P2 (Med 2)

P2 (3)

P2 (4)

P2 (5)

2

2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

P2 (6)

P2 (7)

P2 (8)

P2 (9)

P2 (10)

-2

-2 0

90

180


270

360

450

540

630

720

0

90

180

270

360

450


540

630

720

148

74

Liners Liner groove (KVS) NO-6 - E Cylinder P2 12/21/1995 8:14:16 AM Period 2 151

1000 900

FUEL VALVE 504

--------------

610 -

Symmetric angle cursors reveal liner groove

800


403 EXHAUST VALVE 560

INTAKE VALVE 345

-

700

-

600

-

500

- - Scale 2.0

400

-

300

-

200

-

100

-

0

20 0

340

45

90

135

180

225

270

380

--------------

700

315 360 405 Angle (deg)

450

495

540

585

630

675

720



P2 VT4

149

Liners Liner groove (KVS) NO-6 - E 12/21/1995 8:14:16 AM Engine Cylinders: Phased Vibration VT4:

Crosstalk from P1 exhaust blowdown

Crosstalk from P3 exhaust blowdown

P2 (MMM)

P2 (1)

P2 (Med 2)

P2 (3)

P2 (4)

P2 (5)

2

2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

P2 (6)

P2 (7)

P2 (8)

P2 (9)

P2 (10)

-2

-2 0

90

180


270

360

450

540

630

720

0

90

180

270

360

450


540

630

720

150

75

Liners Crosstalk from exhaust event on P3 (KVS) NO-6 - E 12/21/1995 8:14:16 AM Engine Cylinders: Phased Vibration VT4: 2

2

P1 0

0 P7 422

-2 2

17

-2 2

P2 0

0 P8 662

-2 2

257

-2 2

P3 0

0 P9 182

-2 2

497

-2 2

P4 0

0P10 542

-2 2

137

-2 2

P5 0

0P11

Unphased cursor indicates crosstalk from other cylinders

302

-2 2

617

-2 2

P6 0 -2

0P12 377

62

0

90

180

270


360

450

540

630

720 0

90

180

270

360

450

540


630

-2 720

151

Liners Liner wear (KVS) NO-6 - E 3/19/1996 1:28:36 PM Engine Cylinders: Phased Vibration VT4: P1

P2

NO-6 - E 3/19/1996 1:28:36 PM Engine Cylinders: Phased Vibration VT4:

2

2

0

0

-2 2

-2 2

0

0

P4

P5

P6

P8

-2 2

-2 2

P3

P7

Chatter as loaded rings pass over wear

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

-2 2

-2 2

0

0

P9

P10

P11

P12

-2

-2

0

90

180

270


360

450

540

630 720 0

90

180

270

360

450


540

630

720

152

76

Liners Liner wear (KVS) NO-6 - E Cylinder P7 3/19/1996 1:28:36 PM Period 2 151

1000

INTAKE VALVE 345


FUEL VALVE 504

--------------

610

900

-

800

-

700

-

) g i s 600 p (

-

e r 500 u s s e400 r P

P7 VT4

- - Scale 2.0 -

300

-

200

-

100

-

0

-------------0

45

90

135

180 225

270

315

360

405

450

495

540

585

630 6 75 7 20

Angle (deg) © 2003 DYNALCO CONT ROLS


153

Liners Liner wear confirmed by symmetric cursor (KVS) NO-3 - E Cylinder P5 5/1/1995 8:06:19 AM Period 2 161 INTAKE VALVE 325

1000


FUEL VALVE 536

--------------

621

900

-

800

-

) 700 g i s p (

- P5 VT4

600

-

e r u s500 s e r P

- - Scale 2.0

400

-

300

-

Symmetric cursor indicates the liner is worn.

200 100

-

0

128

0

45

232

488

592

--------------

90 135 180 225 270 315 360 405 450 495 540 585 630 675 720 Angle (deg)



154

77

Liners Liner wear (KVS) NO-3 - E 5/1/1995 8:06:19 AM Engine Cylinders: Phased Vibration VT4: 1

P1

1

0

0

-1

-1

1

1

P2

0

0

-1

-1

1

1

P3

0

0

-1

-1

1

1

P4

-1

-1

1

1

P9

0 P11

0 -1

-1

1

1

P6

P8

0 P10

0

P5

P7

0 P12

0

-1

-1

0

90

180

270


360

450

540

630

720 0

90

180

270

360

450

540


630

720

155

Liners Port bridge wear (HLA) C2A-E 10/10/2001 6:28:53 AM Engine Cylinders: Phased Ultrasonic ULT: 10

10

1

5 0

0

-10 10

-10 10

2

0

0

-10 10

-10 10

3

0

0

7

-10 10

-10 10

4

6

0

0

8

-10

-10

0

45

90

135


180

225

270

315 360 0

45

90

135

180

225


270

315

360

156

78

Liners Port bridge (HLA) C2A-E Cylinder 4 10/10/2001 6:28:53 AM Period 6 130 110

700

Fuel 213


Excessive ring noise 600 500 ) g i s 400 p ( e r u s s 300 e r P

200

100

0 0

45


90

135

180 225 Angle (deg)

270

315

-------------- 4FV ULT - - Scale 10.0 --------------- 4 ULT - - Scale 10.0 --------------- 4 VT4 - - Scale 2.0 --------------

360


157

Ignition Systems 

Provide the energy to begin the chain reaction in the air/fuel mixture and consists of… Power supply  Timing circuit  Distribution mechanism  Transformer  Spark plug 



158

79

Ignition Systems Ignition Primaries Zener Gates

C402 - E Cylinder P1L 07/03/1997 8:07:43 AM 5.5 5.0

P4L P1R

P5L P4R

P2L P5R

P3L P2R

P6L P3R

P1L P6R

4.5 4.0 ) 3.5 V ( e 3.0 g a t l o 2.5 V

TDC Voltages should be similar

2.0 1.5 1.0 0.5 0.0 0

45

90

135

180

225

270

315

360



159

Ignition Systems Ignition secondaries Capacitor Discharges

Coil ring down

e g a t l o V y r a d n o c e S

Plug Stops Firing Arc Duration

Indication of ionization voltage

0


1

2

3

Time (ms)

4


5

160

80

Ignition Systems Typical ignition secondary patterns C402 - E 09/09/1998 12:02:53 PM

0

0

P5LR (Med 1)

P4LL (Med 1) Ignition timing angle = 5.9

Ignition timing angle = 5.7

0

0

P6LL (Med 1)

P4LR (Med 1) Ignition timing angle = 5.9


0

0

P6LR (Med 1)

P5LL (Med 1) Ignition timing angle = 6.1

Ignition timing angle = 6.3 0 © 2003 DYNALCO CONT ROLS

1

2

3

4

5 0

1

2

3


4

5

161

Ignition Faults Timing 

Advanced timing can cause… early combustion  early and increased PFP  detonation  lower exhaust temps 



Retarded timing can cause… delayed combustion  late and low PFP  misfires/soft fires  higher exhaust temperatures 



162

81

Ignition Faults Typical spark plug problems

Excessive gap – ionization voltage increases, strong spark  Insufficient gap – ionization voltage decreases, weak spark  Fouling – build up of contaminants decreases gap and causes ionization voltage to decrease  Plug wear or metal flaking – increases gap therefore increases ionization voltage 



163

Ignition Faults Cables

Corrosion build up reduces ionization voltage  Damaged or loose cables can cause ground faults and arcing to cylinder head 



164

82

Ignition Faults Coils

Check for correct polarity  Look at coil ring down to assess coil winding condition 



165

Ignition Faults Two bad coils – plug did not fire C402 - E 9/9/1998 12:02:53 PM Secondary Ignition (Y Axis: mV -- X Axis: ms) 0

P1LL

0

P1RL


-250 0

P1LR

0

P1RR


-250 0

P2LL


-250 0

P2RL


-250 0


-250 0

P2LR -250

P2RR


0

P3LL


-250


-250 0

P3RL


-250 0


-250 0

P3LR -250 0

P3RR

Ignition timing angle = 5.9 1


2

3

4

5


-250

0

1

2


3

4

5

166

83

Ignition Faults Reversed coil 10JVGE-E 4/24/2001 7:34:26 AM

10JVGW-E 4/24/2001 10:55:35 AM

Secondary Ignition (Y Axis: mV -- X Axis: ms)

Secondary Ignition (Y Axis: mV -- X Axis: ms)

200 200 100

P1C 0

P1C -0

-100 -200

200

200 100

P2C 0

P2C -0

-100 -200

200

200 100

P3C 0

P3C -0

-100 -200

200

200 100

P4C 0

P4C -0

-100 -200 0

1

2


3

4

5

0

1

2

3


4

5

167

Analyzing Compressor Faults

What faults can we detect?  Characterizing the normal compressor  Identifying faults 



168

84

Compressor faults we can detect Valve condition

Cylinder and rod condition

• suction valve leaks

• ring

• discharge

• liner or piston wear

valve leaks

• slamming • excessive • valve

leaks

• rider

lift

band wear

• crosshead

flutter

• cylinder

knocks

stretch

• broken springs

• main

bearings

Performance

Auxiliary equipment

• capacity

• piping

• horsepower

• foundation

and vessels and grout

• excess rod load and lack of

reversal © 2003 DYNALCO CONT ROLS


169

Characterizing the machine 

Analysts use all of these: Operating data  Pressure and vibration versus time (PT/VT)  Pressure versus volume (PV)  Log P versus Log V  Historical data, maintenance logs  Population comparison  Calculation results  Normalized parameters 



170

85

Characterizing the compressor Normal PT/VT K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800

-------------- 4HD1 VT1 - Scale 7.0 - 150 DGF --------------- 4HD2 VT1 - Scale 8.3 - 152 DGF --------------- 4HS1 VT1 - Scale 7.9 - 91 DGF --------------- 4HS2 VT1 - Scale 8.7 - 91 DGF --------------

750 700 650

) g i s p600 ( e r u s550 s e r P

500 450 400 350 0

45


90

135


270

315


360

171

Characterizing the compressor Leaking HE discharge valve: PT/VT K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800


750 700 650

) g i s p600 ( e r u s550 s e r P

500 450 400 350 0

45


90

135


270

315


360

172

86

Characterizing the compressor Leaking HE suction valve: PT/VT K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800


750 700 650

) g i s p600 ( e r u s550 s e r P

500 450 400 350 0

45


90

135


270

315


360

173

Characterizing the compressor Leaking Rings: PT/VT K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800


750 700 650

) g i s p600 ( e r u s550 s e r P

500 450 400 350 0

45


90

135


270

315


360

174

87

Characterizing the compressor Normal PV K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800

Actual PV

750 700

VEd

650

) g i s p600 ( e r u s550 s e r P

Theoretical PV

500 450 VEs 400 350 0

25


50 Percent swept volume

75


100

175

Characterizing the compressor Leaking HE suction valve: PV K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800 750 700

VEd

650

) g i s p600 ( e r u s s550 e r P

500 450 VEs 400 350 0


25


75


100

176

88

Characterizing the compressor Leaking HE discharge valve: PV K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800 750 700

VEd

650

) g i s p600 ( e r u s550 s e r P

500 450 VEs 400 350 0

25



75


100

177

Characterizing the compressor Leaking rings K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800 750 700 650

) g i s p600 ( e r u s550 s e r P

500 450 400 350 0


25


75


100

178

89

Characterizing the compressor Normal LogP-LogV K200 - C cylinder 4 8/29/1996 10:52:08 AM HE ratios calculated using geometry. CE ratios calculated using geometry.

d n E d a e H

ne = 1.26

nc = 1.26

End 4H Step 1 = 28.8% n ratio = 1.00

n ratio = 1.00 d n E k n a r C

End 4C Step 1 = 31.2% nc = 1.25

ne = 1.24



179

Characterizing the compressor Leaking HE suction valve: LogP-LogV K200 - C cylinder 4 8/29/1996 10:52:08 AM HE ratios calculated using geometry. CE ratios calculated using geometry.

d n E d a e H

ne = 1.35

nc = 1.10

End 4H Step 1 = 28.8% n ratio = 1.23

Normal n ratio = 1 n ratio = 1.00 d n E k n a r C

End 4C Step 1 = 31.2% nc = 1.25

ne = 1.24



180

90

Characterizing the compressor Leaking HE discharge valve: LogP-LogV K200 - C cylinder 4 8/29/1996 10:52:08 AM HE ratios calculated using geometry. CE ratios calculated using geometry.

d n E d a e H

ne = 1.35

nc = 1.23

End 4H Step 1 = 28.8% n ratio = 0.85

Normal n ratio = 1 n ratio = 1.00 d n E k n a r C

End 4C Step 1 = 31.2% nc = 1.25

ne = 1.24



181

Characterizing the compressor Leaking rings: LogP-LogV K200 - C cylinder 4 8/29/1996 10:52:08 AM HE ratios calculated using geometry. CE ratios calculated using geometry.

d n E d a e H

ne = 1.26

nc = 1.26

End 4H Step 1 = 28.8% n ratio = 1.00


End 4C Step 1 = 31.2% nc = 1.25

ne = 1.24



182

91

Characterizing the compressor Flow balance 

Flow balance is the ratio of suction capacity to discharge capacity. Flow Balance =

Suction Capacity Disch arg e Capacity

Suction Capacity ∝ VEs Disch arg e Capacity ∝ VEd

Ideally, this ratio should be 1.00.  Valve and ring leaks can change VEs and VEd and cause flow balance to deviate from 1.00.  Flow balance is a “Normalized Parameter” because it is relatively independent of operating conditions. 



183

Characterizing the compressor Discharge temperature delta (DTD) 









DTD is the difference between the actual and theoretical discharge temperatures. The actual discharge temperature is measured in the discharge nozzle. The theoretical discharge temperature is calculated from the gas properties, Ts, Pd and Pd. A high DTD indicates that the discharge gas is hotter than expected. This is often caused by friction as the gas passes through a restriction such as a leaking valve or ring.

DTD = Td,actual − Td,theoretical © 2003 DYNALCO CONT ROLS


184

92

Characterizing the compressor Normal valve cap temperatures K200 - C Cylinder 4 8/29/1996 10:52:08 AM Discharge

175

Usually less than Td

150

Usually warmer than Ts

) F 125 ( e r u t a r100 e p m e T

Suction

75 50 25 0

S2

S1

D2 D1 Head End (St age# 1)


S2

S1 D2 Crank End ( Stage# 1)


D1

185

Compressor Faults



Pressure Leaks



186

93

Pressure Leaks Sources of leaks and analysis tools 

Examples



Suction valves  Discharge valves  Packing  Rings

PV card  Vibration patterns  Temperatures  Flow Balance  LogP-LogV




Analysis tools 


187

Pressure Leaks CE suction valve leak: PT/VT 1250

-------------- -------------- -------------- ---------------------------

1200

3CD4 ULT - Scale 30.0 126 DGF

1150 1100 1050

3CD3 ULT - Scale 30.0 148 DGF

) g 1000 i s p ( 950 e r u 900 s s e r 850 P

3CS2 ULT - Scale 30.0 86 DGF

800 750

3CS1 ULT - Scale 30.0 78 DGF

700

650 600 0

45

90

135

180

225

270

315

360



188

94

Pressure Leaks HE Suction valve leak: PT/VT Unit1-C cylinder 4 1/22/2002 8:35:12 AM HE Period 4, CE Period 7 -------------- 4HD3 VT1 - Scale 8.0 - 95 DGF --------------- 4HD4 VT1 - Scale 8.0 - 94 DGF --------------- 4HS1 VT1 - Scale 8.0 - 61 DGF --------------- 4HS2 VT1 - Scale 8.0 - 73 DGF --------------

1000 950 900

) g i s p ( e850 r u s s e r P800

750 700 650 0

45


90

135


270

315


360

189

Pressure Leaks HE Suction valve leak: PV Unit1-C cylinder 4 1/22/2002 8:35:12 AM HE Period 4, CE Period 7 1000 950 900

) g i s p ( e r 850 u s s e r P800

HE PT HE theoretical PT

750 700 650 0


25


75


100

190

95

Pressure Leaks HE Suction valve leak: LogP-LogV Unit1-C cylinder 4 1/22/2002 8:35:12 AM

d n E d a e H

nc = 0.73

ne = 1.14 End 4H Step 9 = 61.1% n ratio = 1.55


End 4C Step 9 = 66.3% nc = 1.34 ne = 1.36



191

Pressure Leaks HE Suction valve leak: Valve Cap Temps High temperature

Unit1-C Cylinder 4 1/22/2002 8:35:12 AM

100 90

Discharge

80 )70 F ( e r60 u t a r e p50 m e T

Suction

40 30 20 10 0

S1

S2


D3 D4 Head End (St age# 1)

S1

S2 D3 Crank End (Stage# 1)


D4

192

96

Pressure Leaks HE suction valve leak: Health Report Compressor Health Report Unit Name: Location:

Unit1-C Pipeline 1

Model: UnitMfr:

Mechanical Efficiency, % Overall Efficiency, %

95 85

Atmospheric Pressure, psia Load Step D TS , Di sc har ge T em pe rat ur e, F TORQ, Torque, %

14.0 9 86 89

Clr Cyl Stg Set End (%)

Pressure Ps Pd (psig)

Rod ConRod Diam Length (ins) (ins)

Bore (ins)

HBA CLARK

Date: Serial No.:

M ar ke r C or re ct io n A ng le, d eg 156.0 Stroke, (ins) 17.000 Speed, RPM SPDW, Suction Pressure, psi S TS , S uct io n T em per at ur e, F Temp. Ts Td

1/22/2002 8:35:12 AM 302

P er io ds C ol lec te d ( PT) 296 722 41

Specific Gravity DPDW, Discharge Pressure, psi T AM B, Am bi ent T em pe rat ur e, F

Calc. Indicated Suction Disch. Dis T Com p. Capacity Power Loss Loss Flow Delta Ratio (mmscfd) (ihp) (ihp) Balance (F) (ihp)

11 0.554 946 46

Rod Load (%)

SVE DVE (%) (%)

1H

1

61 10.500

N/A 45.000

710

939

54F

8 1F

1.32

14.79

181.9

-0.4

12.6

0.96

-10

41C

74

1C

1

67 10.500 3.000 45.000

712

953

54F

8 1F

1.33

15.56

185.9

-1.7

2.5

0.99

-12

33T

84

67

2H

1

61 10.500

719

941

53F

81F

1.30

15.18

182.7

5.3

11.8

0.98

-7

40C

75

62

N/A 45.000

61

2C

1

67 10.500 3.000 45.000

715

957

53F

8 1F

1.33

15.62

187.3

2.5

-1.7

0.97

-11

33T 84

69

3H

1

61 10.500

N/A 45.000

723

940

53F

81F

1.29

15.57

193.6

11.6

15.7

0.97

-6

40C

76

64

3C 4H

1 1

67 10.500 3.000 45.000 61 10.500 N/A 45.000

726 724

948 929

53F 52F

81F 88F

1.30 1.28

15.16 13.16

182.2 185.6

13.5 13.4

6.5 15.6

0.99 1.34

-6 9

32T 39C

80 85

65 54

52F 88F RPM R PM RPM RPM

1.30

16.13 194.6 12.6 Rated Power, (bhp) Derated Power, (bhp) Percent Torque Load, % Compressor Efficiency, %

6.3 1760 1739 90 92

1.01 @ 300 @ 296 % %

5 RPM RPM

33T

86

70

4C 1 67 10.500 3.000 45.000 727 Total Indicated Power, (ihp) 1494 Gas Power, (ghp) 1573 Auxiliary Power, (bhp) 0 Compressor Total Power, (bhp) 1573


952 @ 296 @ 296 @ 300 @ 296


193

Pressure Leaks Leaking rings C-140 cylinder 4 07/26/2002 11:55:03 AM

C-140 cylinder 4 07/26/2002 11:55:03 AM

End 4H Step 4 = 27.5% 1800

d n E d a e H

1700

) 1600 g i s p1500 ( e r 1400 u s s 1300 e r P

nc = 1.45 ne = 1.48 n ratio = 1.02

End 4C Step 4 = 30.0%

d n E k n a r C

1200 1100 1000 0

25

50

75

Percent swept volume

Minor ring leak in a hydrogen compressor. Iron oxide was coming through the pipeline wearing the rings down. Filters were installed in the suction inlet to solve the problem. 


nc = 1.51

n ratio = 0.86

ne = 1.30

100

The bulging beyond the expansion and compression lines indicates a minor ring leak.




194

97

Pressure Leaks Severely leaking rings PV curve for a severe ring leak

Log P - Log V plot for a severe ring leak

1000 End 2H Step 1 = 115.9% n ratio = 2.57 d n E d a e H

950

) 900 g i s p ( e r u s s e r 850 P

ne = 4.17

nc = 1.62

End 2C Step 1 = 116.5% n ratio = 1.95 d n E k n a r C

800

nc = 1.73

ne = 3.37

750

0

25

50 75 Percent swept volume

100



195

Pressure Leaks Analysis summary Observation

Typical characteristics

Suction valve leak



Discharge valve leak




Gas passing vibration pattern when the differential pressure across the valve is high. Vibration leak pattern is highest in the leaking valve.  Flow balance > 1.05  n ratio for LogP-LogV > 1.03  E levated discharge temperature delta. Elevated valve cap temperature.  Rounded discharge toe on the PV. Discharge toe pressure drops.  Cylinder end capacity drops  Expansion and compression lines on PT and PV below theoretical Gas passing vibration pattern when the differential pressure across the valve is high. Vibration leak pattern is highest in the leaking valve.  Flow balance < 0.97 n ratio for LogP-LogV < 0.98   Rounded suction toe on the PV  Suction toe pressure rises  Abnormal discharge temperature delta and valve cap temperature. Expansion through the discharge valve may actually lower the valve cap and discharge temperature.  Cylinder end capacity drops  Expansion and compression lines on PT and PV above theoretical GMRC 2003 GAS MACHINERY CONFERENCE SHORT COURSE: BASIC ENGINE & COMPRESSOR ANALYSIS TECHNIQUES

196

98

Pressure Leaks Analysis summary (cont.) Observation


Packing leak



Ring leak



A ll packing leaks a small amount. Excessive leakage looks similar to a leaking suction valve.  Leakage pattern in crank end valves. Move the vibration sensor closer to the packing to confirm.  P acking temperature increases. Check packing vent flow rate if so equipped.  Expansion and compression lines on PT and PV below theoretical  Gas passing vibration pattern near crank end when the pressure in the crank end is higher than atmospheric.  Flow balance > 1.05  n ratio for LogP-LogV > 1.03 Gas passing vibration pattern in all valves when the differential pressure across the rings is high.  Flow balance generally increases.  Rounded suction and discharge toes on the PV  Suction toe pressure rises and discharge toe pressure falls.  Increase in discharge temperature delta.  Expansion and compression lines on PT and PV do not follow the ideal gas law: PVn=constant.



197

Compressor Faults



Valve Dynamics



198

99

Valve Dynamics Some causes of valve failures

Mechanical wear and fatigue  Foreign material in the gas stream  Abnormal action of the valve elements  Excessive valve lift for the application  Multiple opening and closing, valve flutter  Slamming  Resonance and pressure pulsations  Corrosive gases  Liquids in the gas  Deposits on the sealing elements and springs 



199

Valve Dynamics Approach to analysis 

Compare vibration patterns and look for differences check history  check similar valves 







Valve opening event is usually larger than closing event Valve closure is usually quiet. The sealing element is lowered onto seat by the springs as the gas velocity drops near TDC and BDC Monitor valve loss since it represents wasted energy



200

100

Compressor Analysis: valve slamming (poppet) Unit2-C cylinder 1 6/5/2001 10:02:42 AM HE Period 1, CE Period 7 Channel Resonance is corrected -------------1CD3 VT1 - Scale 5.0 106 DGF

950 900

--------------

Unit2-C cylinder 1 1/3/2001 7:55:21 AM HE Period 5, CE Period 2 Channel Resonance is corrected 850 ) g i s p (

--------------

e 800 r u s s e r P 750

950 900

1CD4 VT1 - Scale 5.0 105 DGF --------------

1CD3 VT1 - Scale 5.0 8 4 D GF

1CS1 VT1 - Scale 5.0 73 DGF

--------------

850 ) g i s p ( e 800 r u s s e r P 750

--------------

1CD4 VT1 - Scale 5.0 8 6 D GF

700 650

1CS2 VT1 - Scale 5.0 73 DGF

--------------

0

45

90

135

--------------

1CS1 VT1 - Scale 5.0 180 2255 2 D GF270 Crank Angle (deg)

315

360

--------------

700

1CS2 VT1 - Scale 5.0 5 2 D GF

650

0 DYNALCO 45 CONT90 © 2003 ROLS

-------------GMRC 2003 GAS MACHINERY CONFERENCE 135 180 225 270 315 360 SHORT COURSE: BASIC ENGINE & COMPRESSOR ANALYSIS TECHNIQUES Crank Angle (deg)

201

Valve Dynamics Multiple opening events RTC10002 - C cylinder 2 8/6/1992 11:27:32 AM HE Period 1, CE Period 1 Channel Resonance is corrected 200


175

150

) g i s p ( 125 e r u s s e r P100

75

50

0

45

90

135

180

225

270

315

360



202

101

Valve Dynamics Flutter JC1A cylinder 5 1/29/2001 10:18:56 AM HE Period 9, CE Period 6 2250 -------------- 5CD2 ULT - Scale 10.0 - 183 DGF --------------- 5CS1 ULT - Scale 10.0 - 85 DGF

2000

)1750 g i s p ( e r u s 1500 s e r P

1250

1000

-------------0

45


90

135


270

315


360

203

Valve Dynamics Analysis summary Observation


Hard opening Hard closure Late closure Broken springs









Early closure

 


May be caused by stiction on the seal or backguard. Stiction occurs when the force required to start motion is greater than the force required to sustain it. If slamming occurs at both opening and closing, it is likely that the springs are too light or that they have been weakened or broken due to excessive cycling. High lift valves such as poppet valves may take some time to close. If closure is too late the drag of the gas in the wrong direction may slam the valve closed. Pulsation may cause the pressure differential to increase suddenly causing hard closure. Excessive spring tension. Pulsation may cause the pressure differential to decrease suddenly causing early closure.


204

102

Valve Dynamics Analysis summary (cont.) Observation


Flutter







Multiple opening








Occurs when the valve plate oscillates between the seat and the guard. It occurs because the flow of gas through the valve is insufficient to lift the plate fully off the guard. On the vibration pattern, you will see multiple opening and closing impacts. Very heavy oscillation usually indicates that the springs are too stiff. Light oscillation usually indicates that the lift is too high. Valve flutter may also be present if there is excessive pulsation in the suction or discharge lines. To correct the problem, reduce the valve lift and/or spring tension; minimize pressure pulsation. If valve lift is too great, the gas velocity will not be sufficient to keep the valve open. The valve will then open and close multiple times. To correct the problem, reduce valve lift to increase the pressure drop across the valve. Pulsations may cause the pressure differential across the ring to decrease and increase to the point that the valves close and reopen. Heavy springs may cause the valve to close early. The cylinder pressure may cause the valve to reopen late in the stroke.


205

Valve Dynamics Analysis summary (cont.) Observation


Excessive loss

 

 



Mechanical vibration




Valve and passage loss calculated from the PV > 10% (rule of thumb) Gas passing vibration patterns when the valve is open caused by high velocity. Valve lift or flow area insufficient. Some of the sealing elements in the valve may be stuck reducing the effective flow area. PT and PV curve appears rounded during the suction or discharge phase. Mechanical vibration during the suction or discharge phase can be caused when plates or poppets hang up due to stiction or worn guides.


206

103

Compressor Faults



Losses



207

Compressor Losses Calculating HP

It takes work to transport gas through a pipe  That work is the area inside the PV curve  The rate of doing work is horsepower  If we plot the PV card as pressure (psi) versus volume (% stroke), we can use: 

IHP =


PLAN 33,000

where: P : Area inside the PV card L : Stroke length A : Area of the piston N : cycles per minute (RPM)


208

104

Compressor Losses Pressure drop 





The actual indicated power consumed compressing gas is always somewhat larger than the theoretical IHP The main power difference is due to pressure drops as the gas flows through the suction piping, suction valves, discharge valves, and discharge piping. To overcome these losses, the cylinder pressure must drop below the suction pressure pressure during the effective suction stroke and rise above the discharge pressure during the effective discharge stroke.



209

Compressor Losses No-loss IHP K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800

Actual PV

750 700

Theoretical PV

650

) g i s p600 ( e r u s s550 e r P

No-loss indicated power (IHP). Minimum IHP required to move the gas

500 450 400 350 0


25


75


100

210

105

Compressor Losses Total IHP K200 - C cylinder 4 8/29/1996 10:52:08 AM HE Period 9, CE Period 8 800

Total discharge loss, IHP

750 700 650

) g i s p600 ( e r u s550 s e r P

Total indicated power (IHP), including losses.

Total suction loss, IHP

Actually required to move the gas.

500 450 400 350 0

25



75


100

211

Compressor Losses Magnitude of losses 

Factors affecting the magnitude of losses are: valve design  suction and discharge pressure  suction and discharge temperature  compressor speed  gas composition  suction and discharge piping design  compressor passage design 



212

106

Pulsation Pressure waves caused by the suction and discharge events in the compressor ends Can cause vibration in piping Vibration may be extreme if the pulsation coincides with:



 

the acoustic resonance frequency of the piping  the mechanical natural frequency of the piping 



Affects compressor performance when valves open and close  volumetric efficiency (capacity)  HP consumed moving gas 



213

Pulsation Nozzle Pressure Trace RTC21000 - C cylinder 1 4/28/1994 8:18:32 AM Channel Resonance is corrected --------------VT1 --- 1HD1 Scale 2.0 -- 9 1 DGF ------------------ 1HD2 VT1 -- Scale 2.0 -- 9 2 DGF ----------------VT1 --- 1HD3 Scale 2.0 -- 9 1 DGF ------------------ 1HS1 VT1 -- Scale 2.0 -- 7 6 DGF ----------------- 1HS2 VT1 -- Scale 2.0 -- 5 0 DGF ----------------- 1HS3 VT1 -- Scale 2.0 -- 7 4 DGF ---------------

Pressure in discharge nozzle

850 800 )750 g i s p ( e r700 u s s e r P650

Pressure in suction nozzle

600 550 500 0

45


90

135


270

315


360

214

107

Pulsation Total HE Power RTC21000 - C cylinder 1 4/28/1994 8:18:32 AM HE Period 1 Channel Resonance is corrected 850

800

750 ) g i s p ( 700 e r u s s e r650 P

Total HE Indicated Power = 514 IHP

600

550

0

25



75


100

215

Pulsation No-loss HE Power RTC21000 - C cylinder 1 4/28/1994 8:18:32 AM HE Period 1 Channel Resonance is corrected 850

800

750 ) g i s p ( 700 e r u s s e r650 P

No-loss IHP

600

550

0


25


75


100

216

108

Pulsation Total losses RTC21000 - C cylinder 1 4/28/1994 8:18:32 AM HE Period 1 Channel Resonance is corrected 850

800

750 ) g i s p ( 700 e r u s s e r650 P

Total Discharge loss = 104 IHP, or 20%

Total Suction loss = -11 IHP, or -3%

600

550

0

25



75


100

217

Pulsation Valve and Passage loss RTC21000 - C cylinder 1 4/28/1994 8:18:32 AM HE Period 1 Channel Resonance is corrected 850

800

750 ) g i s p ( 700 e r u s s e r650 P

Discharge valve and passage loss = 24 IHP

Suction valve and passage loss = 31 IHP

600

550

0


25


75


100

218

109

Pulsation Effect on HP Compressor Horsepower And Capacity Report Unit Name: Location:

RTC21000 - C FLL

Load Step:

3

Cyl End

Model: Unit Mfr:

TCV10 DRESSER RAND

Date: Serial No.:

C le ar an ce Indicated B ra ke T ot al ; L os s Valve & Pass; Loss Total Loss Calculated Capacity % of Swept Power Power (ihp) (ihp) (%) (mmscfd) Flow Volume (ihp) (bhp) Suction Disch. Suction Disch. Suction Disch. SVE* DVE** Balance

Stage:

1

4/28/1994 8:18:32 AM

bhp/mmscfd Calc. Theor.

New Stage

1H

158

514

541

-10.67 103.52

30.56

23.79

-2.08

20.13

32.00

35.05

0.913

16.9

14.0

1C

92

565

595

14.04

58.39

42.59

30.47

2.48

10.33

39.82

38.49

1.035

15.5

14.6

3H

132

546

575

29.33

28.31

36.02

32.57

5.37

5.18

37.00

35.27

1.049

16.3

15.5

3C

87

587

618

28.89

58.15

31.82

17.08

4.92

9.91

40.93

38.80

1.055

15.9

14.1

5H

127

609

641

27.22 101.62

32.76

38.29

4.47

16.70

36.86

38.90

0.948

17.4

14.1

5C

94

592

623

33.22

33.20

28.36

5.61

8.61

40.72

38.98

1.044

16.0

14.6

3 41 3

3 59 3

206.95 170.57

3.58

11.75

227.34

225.49

16.3

14.5

S ta ge T o tal s:

51.00

1 22 .0 4 4 00 .9 9

Auxiliary Power CompressorTotal Power This is equivalent to Rated driver load to Current torque level is

61 3654 3632 4200 86.4

bhp at 330 RPM bhp and 225.49 mmscfd at332 bhp and 224.14 mmscfd at330 bhp at 330 RPM % of rated load at rated speed.

RPM RPM



219

Horsepower Cost of horsepower loss Engine And Compressor Economic Condition Report Unit Name: Location:

RTC21000 - C FLL

Load Step: Percent Load:

Model: Unit Mfr:

TCV10 DRESSER RAND

Date: Serial No.:

4/28/1994 8:18:32 AM

3 86.4 %

UNIT COSTS Fuel Cost: Brake Power from the load: Cost of Each BHP:

1673.37 3654.50 0.46

$/day bhp $/bhp-day

8675.17 7434.80

BTU/BHP - hr BTU/BHP - hr

1240.36 239.26 7282.35 87388.25

BTU/BHP - hr $/day $/month $/year

ENGINE COSTS Percent of Fuel Cost Actual Fuel Consumption: Predicted Fuel Consumption: Deviation From Predicted: Cost of Deviation:

1 4. 3

%

COMPRESSOR COST OF LOSSES Total L oss es Valve and Passage Losses: Pulsation Losses: Gas Recirculation Losses:

397.38 153.18 0.78

Total Compressor Cost:

bhp bhp mmscfd

Adju ste d Los ses ( Not e 7) Estimated Cost of Losses 377.51 145.52

bhp bhp

172.86 66.63 5.97

Per cent of F ue l C ost

$/day $/day $/day

1 0. 3 4.0 0.4

% % %

245.46 7 47 1 .3 2 8 9 65 5 .8 6

$/day $ / mo nt h $ /y e ar

1 4. 7

%

484.72 14753.67 177044.11

$/day $/month $/year

TOTAL DEVIATION FROM PREDICTED

Percent of Fuel Cost 2 9. 0 %

Unit running 365.25 days per year



220

110

Compressor Rod Load

Why do we care about rod load?  What are the forces acting on the rod? 



221

Compressor Rods Compressor piston rods bear all the force that is applied to the gas  The manufacturer of the rods will specify the maximum allowable rod load  Depending on the rod material and design, the rod can bear in excess of 200,000 lbf  The crosshead pin must also bear these forces  Improper rod load can cause: 

excessive wear in the crosshead bushing and pin  failure of the crosshead bushing  stress on the piston, piston nut, and other load bearing components 



222

111

Compressor Rods Forces

Gas force - exerted by pressure on both sides of the piston  Inertial force - exerted by the mass and acceleration of the reciprocating components  Total force = Gas force + Inertial force  Compressor rods should alternate from tension to compression in each cycle. This is important for lubrication of the crosshead pin and bushing 

API 618 (June 1995) says: “…the duration of this reversal shall not be less than 15 degrees of crank angle, and the magnitude of the peak combined reversed load shall be at least 3 percent of the actual combined load in the opposite direction.” 



223

Compressor Rods Gas force Gas ForceCE = PCE ∗ AreaCE PCE

=

CE cylinder pressure π

AreaCE

= 4

[(piston diameter )

2

−

(piston rod diameter )

2

]

Gas ForceHE = PHE ∗ AreaHE PHE

=

HE cylinder pressure π

AreaHE

= 4

[(piston diameter )

2

−

( tailrod diameter )

Compression (PHE ∗ AreaHE ) > (PCE ∗ AreaCE )


2

] Tension (PHE ∗ AreaHE ) < (PCE ∗ AreaCE )


224

112

Compressor Rods Gas force K200 - C cylinder 1 9/23/1998 9:52:15 AM HE Period 9, CE Period 9 60000 50000 40000

Maximum Rodload Tension: 60000

600

550

30000 20000

) s b l ( 10000 d a o 0 L d o -10000 R

500

) g i s p ( 450 e r u s s e r P 400

Zero Rodload

-20000 -30000

350

-40000

Gas force

300 -50000 -60000

Maximum Rodload Compression: 60000 250 0


45

90

135


270

315

360


225

Compressor Rods Inertial force 







Inertial Force = (mass of recip components) x (instantaneous acceleration) Differentiate piston displacement (top graph) with respect to time to derive the velocity (middle), then the differential of velocity with respect to time gives acceleration (bottom) Rod load due to inertia takes the form of the acceleration curve Inertial forces are more significant in:

t n e m e c a l p s i D


90

180

270

360

0

90

180

270

360

90

180

270

360

y t i c o l e V

n o i t a r e l e c c A

high mass piston and rod assemblies  high speed compressors  low compression ratio services GMRC 2003 GAS MACHINERY CONFERENCE 

0

0

Crankshaft Angle (degrees)

SHORT COURSE: BASIC ENGINE & COMPRESSOR ANALYSIS TECHNIQUES

226

113

Compressor Rods Inertial force K200 - C cylinder 1 9/23/1998 9:52:15 AM HE Period 9, CE Period 9 60000 50000 40000


600

550

30000 20000

) s b l ( 10000 d a o 0 L d o -10000 R

500

) g i s p ( 450 e r u s s e r P 400

Zero Rodload

-20000 -30000

350 Inertia

-40000 300 -50000 -60000

Maximum Rodload Compression: 60000 250 0

45


90

135


270

315


360

227

Compressor Rods Total rod load force K200 - C cylinder 1 9/23/1998 9:52:15 AM HE Period 9, CE Period 9 60000 50000 40000


600

550

30000 20000

) s b l ( 10000 d a o 0 L d o -10000 R

500

) g i s p (

e450 r u s s e r 400 P

Zero Rodload

-20000 -30000

350 Inertia

-40000

Gas force

300 -50000 -60000

Maximum Rodload Compression: 60000

Total

250 0


45

90

135


270

315


360

228

114

Compressor Rods Tension only 301C - C cylinder 4 7/17/1997 8:23:05 AM HE Period 5, CE Period 6 75000

50000


1000

Rod is in tension throughout the cycle

900 800

25000

) s b l ( d a o L d o R

0

-25000

)700 g i s p ( 600 e r u s s500 e r P

Zero Rodload

400 300

-50000

Inertia Gas force

200

Total -75000

100

Maximum Rodload Compression: 75000 0


45

90

135


270

315


360

229

Compressor Rods Compression only RTC13003 - C cylinder 2 11/9/1992 8:08:46 AM HE Period 1, CE Period 1 50000

Maximum Rodload Tension: 50000 1100

40000 30000 20000

1000

) s b 10000 l ( d a o 0 L d o R -10000

) g950 i s p ( e r 900 u s s e r P850

-20000

800

-30000

750

-40000

700

-50000

Rod is in compression throughout the cycle

1050

Zero Rodload

Unloaded CE Inertia Gas force Maximum Rodload Compression: 50000

Total

650 0


45

90

135


270


315

360

230

115

Compressor Rods Crosshead pin knock RTC13002 - C cylinder 3 12/4/1991 7:43:52 AM HE Period 1, CE Period 1 60000


1100 1050

40000 30000

1000

20000

) 950 g i s p ( 900 e r u s s850 e r P

) s b l ( 10000 d a o 0 L d o -10000 R

-------------Knocks near rod reversal points

50000

- 3T VT1 -

Zero Rodload

- Scale 0.5 -

800

-20000

-

-30000

750

-40000

700

-

Inertia

-50000

Gas force

650

Maximum Rodload Compression: 60000

-60000 0

45


90

135

-

Total --------------


270

315

360


231

Compressor Rods Excess load C-47 cylinder 1 07/26/2001 7:24:05 AM HE Period 9, CE Period 1 Channel Resonance is corrected Maximum Rodload Tension: 11000 -------------1XH VTL - Scale 5.0 Zero Rodload -------------1XA VT1 - Scale 1.0 Inertia Gas force Total Maximum Rodload Compression: 11000 --------------

350 10000 300 5000 ) s b l ( d a o L d o R

0

) g i s250 p ( e r u s s e r P200

-5000 150 -10000 100 0


45

90


270

315


360

232

116

Compressor Rods Crosshead knock C-47 cylinder 1 07/26/2001 7:24:05 AM HE Period 9, CE Period 1 Channel Resonance is corrected 350 10000 300 5000 ) s b l ( d a o L d o R

0

) g i s250 p ( e r u s s e r P200

-5000

Crosshead Knock

150 -10000

Maximum Rodload Tension: 11000 -------------1XH VTL - Scale 5.0 Zero Rodload -------------1XA VT1 - Scale 1.0 Inertia Gas force Total Maximum Rodload Compression: 11000 --------------

100 0

45

90


270

315



360

233

Compressor Rods Analysis summary Observation


Rod load is above limit



Insufficient rod load reversal



Knock at reversal




The crosshead pin, crosshead, piston, linkages and rod are stressed above the manufacturer’s specified limit.  Adjust the loading on the compressor.  Change the line pressures. API 618 (June 1995) says: “…the duration of this reversal shall not be less than 15 degrees of crank angle, and the magnitude of the peak combined reversed load shall be at least 3 percent of the actual combined load in the opposite direction.”  Unloading crank end suction valves can lead to insufficient reversal.  Adjust the loading on the compressor. Check the low frequency vibration reading types. Look for knocks when the rod load changes from tension to compression and vice versa.


234

117

Compressor Rod Motion

What is rod motion?  How is rod motion measured?  Analysis tools 



235

Rod Motion Why is it important?

Ideally, rods should have translational recip motion only  Motion is more complex due to: 

imperfect alignment  flexibility of the rod 



Analysis of rod motion is often used to identify: cylinder alignment problems  rider band wear  cylinder liner wear  wear in the crosshead shoes 



236

118

Rod Motion Cylinder rod runout and history (at 240 degrees) 2 ROD RODOUT cylinder 2-RR Top Probe Rod Motion 6/4/2002 9:48:02 AM 3.5

Current

3.0 2.5

) l i 2.0 m ( n1.5 o i t o1.0 M d0.5 o R -0.0

-0.5 -1.0

Previous

-1.5 -2.0 0

45

6 5 4 3 2 1 0 -1 -2

90

6/26/2001

135 180 225 270 315 Rod Motion History at 240 degrees for the Top Probe.

9/18/2001

11/27/2001

2/21/2002

6/4/2002



360

237

Rod Motion Rod runout 2 ROD RODOUT cylinder 2-RR 6/4/2002 9:48:02 AM m o t 5 t o B d 4 n a e 3 b o r P 2 p o T ) 1 l i m ( t 0 u o n u -1 R y a -2 l r e v O-3 e b o r -4 P

Bottom probe sees rod rising

Top and bottom probes see similar motion (rod movement)

Top and bottom probes indicate opposite motion (rod wear)

Top probe sees rod dropping

-5 -6 0

45

90

135

180

225

270

315

360

Crank Angle (deg)



238

119

Rod Motion Analysis summary Observation


Trend of rod motion over time drops

  

The top and bottom probes follow a W path from 0 to 360 degrees.



The top and bottom probes form a V shape from 0 to 360 degrees



The top and bottom probes form an inverted V shape from 0 to 360 degrees



Patterns for top and bottom probes separate on the rod runout plot. Top drops and bottom rises.




Check for signs of rider band and liner wear. Examine the PV and LogP-LogV for signs of ring leakage. It is possible that the crosshead shoes are wearing out. Check shoes and crosshead lubrication. The probes see the rod dropping most at 90 and 270 degrees appearing to rise at TDC and BDC. The most common type of liner wear has a barrel shape, more in the center than at the ends.

The liner is tapered, with most wear occurring in the crank end.  Check for excessive packing wear.  Check cylinder alignment. The liner is tapered, with most wear occurring in the head end. Check for excessive packing wear.  Check cylinder alignment. 

The rod is worn where the separation occurs. If this is around BDC, check the rod for wear near the packing.


239

Frame Faults



Main bearings and crank pins



240

120

Main and crank bearings Behavior

Journals should ride on an oil film in the bearing  There should be no metal-to-metal contact  We can often hear impact-type vibration if 

the journal hits the bearing  the bearing shell is loose 

Sometimes you can even feel it on the frame  This vibration can be detected with an analyzer 



241

Main and crank bearings Some causes of abnormal bearing wear Insufficient oil  on startup  while running  Fatigue  detonation  overload  non-uniform dynamic loading  Contaminated oil  particles  water 


Poor alignment  main bearings  bent conrod  Improper installation  excessive or insufficient clearance  damaged bearing or journal  Cavitation in the oil  Improper oil viscosity  Fretting while stationary 


242

121

Main and crank bearings Measurements 

It is difficult to get good data from main and crank bearings: The transmission path is long  There is a great deal of noise from other sources  Difficult to distinguish main and crank bearing vibration 



Measurement location 



Shortest transmission path is near frame cross members

Measurement types Low frequency phased acceleration  Unphased (free running) velocity 



243

Main and crank bearings Phased, low frequency vibration UNIT #4-E 7/17/2002 10:51:55 AM Engine Vibration: Phased Vibration VT4:

1.0

UNIT #4-E 7/17/2002 10:51:55 AM Engine Vibration: Phased Vibration VT4:

1.0

) 3 d e 0.5 M ( 1 G R B0.0 E 4 #

0.5

0.0

T I -0.5 N

-0.5

-1.0 1.0

-1.0 1.0

U

U N I T # 4 -E B R G 4 ( M e d 4 )

U N I T # 4 -E B R 0.0 G 5 ( M e -0.5 d 7 )

) 1 d e 0.5 M ( 2 G R B0.0 E 4 #

0.5

T I -0.5 N U

Look for vibration like these that are not caused by crosstalk

-1.0 1.0 ) 1 d e 0.5 M (

-1.0 1.0

0.5

3 G R B0.0 E 4 # T I -0.5 N U

0.0

-0.5

-1.0

U N I T # 4 -E B R G 6 ( M e d 1 0 )

-1.0

0

90

180

270


360

450

540

630

720

0

90

180

270

360

450


540

630

720

244

122

Main and crank bearings Analysis summary Observation


Low frequency vibration shows mechanical knocktype vibration






Vibration is strongest near the source – move the transducer around to find it. This will also help eliminate crosstalk from some other component. Always check oil analysis data. Look for babbitt material and dirt that might contribute to wear.


245

Conventional vibration

Some concepts  Applications 



246

123

Conventional Vibration Some concepts

Vibration is the response of a machine, structure, piping, fluid or gas to an excitation  Excitation is the disturbance (dynamic force) that causes motion in the machine 





Response is the motion of the system caused by the application of all combined excitations 



Imbalance of a rotor

Vibration that you feel

To really understand vibration, you must understand: What the dynamic forcing functions are  What is responding to the force  How to measure the response 



247

Conventional Vibration Free-running, non-phased data

Vibration is recorded independent of crankshaft position  Returns 

Overall vibration level  Spectrum showing frequency components 



Common applications: Structural vibration  Supports, foundations  Turbochargers  Oil and water pumps  Pressure pulsation 



248

124

Conventional Vibration Overall level

We can use a single number to indicate how much vibration is present  We call this the “overall” vibration level  Our industry typically uses the following units: 

Displacement: mil (peak-peak)  Velocity: ips (peak)  Acceleration: g (peak) 



We use guidelines to evaluate overall vibration severity

SINUSOIDAL MOTION UPPER

RMS NEUTRAL

PEAK PEAK TO PEAK

LOWER



249

Conventional Vibration Spectrum

We can get a sense of the level of vibration by looking at the overall level  But - to understand vibration, we need to know what frequencies are in it  “All periodic time domain signals can be represented as the sum of a set of sine waves”  The frequency domain plot, or spectrum, tells us about these components 



250

125

Conventional Vibration Acceleration, velocity and displacement Type

Useful frequency range

Applications

Displacement

up to 30Hz (1800 CPM)



30Hz (1800 CPM) to 2 kHz (120 kCPM)



1 kHz (60 kCPM) and higher



Velocity

Acceleration


Mechanical looseness Imbalance  Misalignment  Oil film bearing faults 

Imbalance Misalignment  Vane/blade passing  Oil film bearing faults  Rolling element bearing faults  Pulsation, acoustics 

Vane/blade passing Early rolling element bearing wear detection  Gear faults 


251

Frame Faults



Frame vibration



252

126

Frame vibration Behavior

In relative terms, reciprocating machinery has high mass and runs at slow speed  Forcing functions: 

Mass imbalance  Misaligned bearings  Dynamic loading from the engine and compressor  Mechanical looseness (bolts, clearance) 



Response is increased when stiffness is low 



Foundation or supports are weak

These responses occur at low frequencies therefore we are normally interested in displacement



253

Frame and piping vibration Trend of frame vibration: broken anchor bolts 9 8

Horizontal displacement, oil pump end, mil-p-p High

7 6

Broken anchor bolts discovered

5 4

Vertical displacement, oil pump end, mil-p-p

High

3 2

High

1 0

After repair

Axial displacement, oil pump end, mil-p-p

Low Low

-1 1994


1995

1996

1997

1998


254

127

Frame vibration Overall levels

Low Speed Nomograph 0 0 0 , 1

0 0 1

ShaftSpeed (RPM)

0 0 0 , 0 0 1

0 0 0 , 0 1

100

The overall level can be easily compared with norms to determine vibration severity  For frame vibration this is usually enough 

10

V E R Y R O U G R S L H I G O U G H T H L Y R O F A U G I H G O R O D V E R Y S M G O O O O D V E T E X R Y S H T R M O E M O T E L Y S H M O O T H

) k p 1 k p s l i m ( t n e m e c a l p 0.1 s i D

.6 2 8 I N / .3 1 S E C 4 I N / S E .1 5 C 7 I N / S E .0 7 C 8 5 I N S E .0 3 / C 9 2 I N S E .0 1 / C 9 6 I N S E .0 0 / C 9 8 I N S E .0 0 / C 4 9 I N / S E C

0.01

0.001



) k a e p c e s / s e h c n i ( y t i c o l e V n o i t a r b i V

255

Frame and piping vibration Spectrum: Typical frame vibration (IR 412 KVGB) K102P-V Testpoint OPEV 7/27/2001 6:54:52 AM 2.00 1C

1.75

2C

1.50

3C

4C

5C

6C


Watch for increases in the overall level and in low orders of run speed

) k p k p -1.25 o d u e s p1.00 ( l i m

0.75 0.50 324.091

Testpoint : OPEV VIB No. Of Lines : 400 No. Of Averages : 4 Calc Overall 8C : 2.200 9C 7C Trap Overall : 2.200

Engine speed is 324 RPM. This is the first order of run speed.

0.25 0.00 0 © 2003 DYNALCO CONT ROLS

500

1000

1500 cpm

2000

2500


256

128

Frame Vibration Analysis summary Observation

Troubleshooting

Vibration (displacement) readings indicate vertical motion on the outer end of the cylinder



Check the cylinder supports for loose bolts or cracked base. Depending on the mass of the cylinder and speed of crankshaft, the displacement should be below 5 mils.

Vibration (displacement) indicate axial motion on the outer end of the cylinder



Some cylinder motion is normal (< 5mils). If axial cylinder motion is excessive or increases, check that distance piece and cylinder bolts are tight.

Excessive vibration (displacement) on the base of the frame





 





Excessive piping vibration detected visually or using displacement readings

 




Check anchor bolt torque. Look for cracks in the concrete base. Check condition of grout that supports the frame. Eliminate standing oil since it acts as a hydraulic wedge in cracks and reduces friction on the chocks Check cylinder alignment and piston runout to ensure that components are all running true. Fundamental spectrum component is at one-times run speed. Check piping supports. Review vibration spectra to identify frequency components. Perform a bump test to measure the mechanical natural frequency of the piping. Determine if the vibration is a result of exciting the MNF. Measure pressure spectra in the piping to determine if the forcing function is pulsation or mechanical imbalance.


257

Auxiliary Equipment



Turbocharger/Blower



258

129

Turbocharger/blower vibration Behavior 

There may be many forcing functions present  Structural faults Mechanical looseness (1x-5x engine speed)  Shaft faults Mass imbalance (1x-5x RPM) Misaligned rotor (1x-5x RPM)  Bearing faults Oil film bearing (1x-5x RPM) Rolling element bearing (10x RPM)  Gear faults Gear mesh frequency (1x-3x GMF) We are likely to use a GMF = #teeth x RPM combination of displacement, velocity and acceleration  Vane faults readings to measure the Vane passing frequency (1x-3x VP) response to each of these forcing functions VP = # vanes x RPM 



















259

Turbocharger Normal velocity spectrum (Elliot on KVR 512) 206-T Testpoint PWRH 3/10/2003 11:10:17 AM Turbo speed

15277.696

0.35

1X

0.30

0.25

) k p o d u0.20 e s p ( s p i 0.15

2X

Testpoint : PWRH IPP No. Of Lines : 800 No. Of Averages : 4 Calc3X Overall : N/A Trap Overall : 0.140 Peak At Frequency 0.050 at 1050.0 0.040 at 900.0 0.033 at 2475.0 0.029 at 1950.0 0.026 at 3525.0 0.025 at 1425.0 0.020 at 375.0 0.015 at 1575.0 0.013 at 2100.0 0.012 at 3150.0

Small component at 1X. Slight at 2X and 3X run speed

0.10

0.05

0.00 0

5 000

1 0000


1 500 0

2 0000

25 00 0

30 00 0 cpm

35 00 0

40 00 0

45 00 0

50 00 0


5 500 0

260

130

Turbocharger Normal acceleration spectrum (Elliot on KVR 512) 206-T Testpoint PWRH 3/10/2003 11:10:17 AM

2.5

Turbo speed

15.278

1X

2.0

2X 3X

4X 5X

6X 7X

8X 9X

T est po in t : P WR H G P No. Of Lines : 800 No. Of Averages : 4 Calc Overall : N/A Trap Overall : 1.500

10X


) k1.5 p o d u e s p ( g

1.0

Components at 1X, 2X and 3X are very small

0.5

This is probably exhaust turbulence exciting resonance frequencies in the structure and transducer

0.0 0

50

100

150 kcpm

200

250



261

Turbocharger Rotor Rub (Elliot turbo on KVR 512) 206-T Testpoint PWRH 7/2/2003 3:09:23 PM 6.0

Turbo speed

16.083

5.5

1X

5.0

2X

3X

4X

5X

6X

7X

8X

9X

10X

T est po in t : P WR H G P No. Of Lines : 800 No. Of Averages : 4 Calc Overall : N/A Trap Overall : 11.900 Peak At Frequency 4.612 at 31875.0 4.418 at 8250.0 4.362 at 40125.0 1.917 at 56250.0 1.806 at 16125.0 1.167 at 49125.0 0.889 at 24000.0 0.861 at 38625.0 0.834 at 48000.0 0.667 at 30750.0

4.5 4.0 ) k p - 3.5 o d u e 3.0 s p ( g 2.5

Increased audible noise, high overall vibration level

2.0 1.5

Harmonic and subharmonic components appear with elevated spectrum floor

1.0 0.5 0.0 0


50

100

150

kcpm

200

250


262

131

Turbocharger Rotor Rub (Elliot turbo on KVR 512)



263

Turbochargers and blowers Analysis summary Observation

Troubleshooting

Displacement readings from the turbocharger frame increase



Velocity or acceleration spectra show increased components at around ½ shaft speed



Velocity or acceleration spectra show increased components at low orders of run speed



Increases vibration at several low orders of shaft speed often indicates rotor instability, looseness or rub.

Velocity or acceleration spectra show elevated vibration at gear mesh frequencies



On blowers, vibration data is recorded near bearings where the vibration energy from gears is transmitted. When gear teeth nolonger mesh properly, they generate vibration at gear mesh frequency.

Vibration from rolling element bearings follows the characteristic wear phases



Rolling element bearings usually pass through a sequence of phases before failure. These can be described as:

Check the turbocharger supports for weakness or loose bolts. If the unit is mounted high off the floor, lower stiffness may worsen the response. Oil whirl can occur in oil film (hydrodynamic) bearings. This phenomenon appears near ½ order of shaft speed.

Early high frequency vibration Excitation of bearing natural frequencies Excitation of rolling element faults Elevated vibration at shaft orders  



264

132

Basic Engine and Compressor Analysis

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