Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
4
Case History
Project Scope
This project involved emergency onsite strain and vibration measurements concerning a 50 inch outside diameter disk/arbor assembly at a customer’s repair facility in the US. The CT disk was made of Inconel and the temporary arbor was steel. The purpose of these measurements was to verify and document centrifugal expansion and yielding of the disk, particularly in the tangential (hoop) direction at the disk bore.
Throughout this project, DyRoMa conventions were used, particularly regarding vibration
sensor naming and orientation. In other words, the disk/arbor assembly and balance stand unit is “viewed” as being from driver (first electric drive motor) toward driven (disk/arbor). Therefore, the coupling side bearing supporting the disk/arbor would be bearing #1 and the non-drive end (outboard) disk/arbor assembly bearing would be bearing #2. This balance stand has permanently installed dual XY orthogonal shaft relative proximity probe sensors in the “vertical” or “Y” direction (45 degrees left, “45L”, of top dead center, TDC) and “horizontal” or “X” direction (45 degrees right, “45R”, of top dead center, TDC) at each of the two bearings. This disk/arbor assembly also had two proximity probes “observing” the outside diameter of the disk in the radial direction. These probes were mounted on a fixture beneath the disk. A tangential and axial strain gage were also bonded to the inside diameter of the disk bore (discussed below).
This disk/arbor assembly was also equipped with a proximity probe sensor that functioned
as the phase trigger (keyphasor®). The orientation of this phase trigger reference or keyphasor® and the direction of rotation (CCW, counterclockwise) follow this same DyRoMa convention. The phase trigger was oriented at 90 degrees right (90R) of TDC and located adjacent to the balance stand drive shaft. This phase trigger is a proximity probe which senses the passage of a protruding key on the balance stand drive shaft once per revolution, thus yielding a speed and phase reference signal. This phase reference is critical in the process of balancing rotor in balance stand.
For these measurements, a Data Physics 32 channel Abacus® Turbo vibration data
acquisition system was field wired using BNC patch cables and tee connectors into the Bently Nevada ADRE® 208 inputs to acquire the XY shaft relative proximity probe signals at bearings #1 and #2. Signals from the disk OD proximity probes were also acquired using BNC patch cables and tee connectors at the BNC terminal strip adjacent to the ADRE® system in the back of the control panel. The strain gage signals were obtained via BNC cables at the output BNC connection on the two wireless telemetry systems. The Abacus was used in this instance for strain and vibration measurements; however it can also be used for dynamic balancing of rotating machinery.
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
5
Onsite strain and vibration measurements took place on November 22nd. The strain and vibration data was acquired during transient and steady state operation of the disk/arbor assembly, while the disk/arbor was in the balance stand bunker under vacuum. A Data Physics Abacus® Turbo 32 channel data acquisition system was used to capture strain, disk radial expansion, speed, and arbor shaft relative vibration signals. Objectives for this project were outlined as follows:
• Record and document the strain and vibration response characteristics of the
disk/arbor assembly during transient and steady state operating conditions.
• Review and evaluate the strain and vibration response characteristics and prepare a summary with recommendations.
• Provide a final documentation covering significant aspects of the project.
Instrumentation
To measure the disk inside diameter tangential and axial strains, two uniaxial encapsulated strain gages (Micro-Measurements J2A-06-S047K-350, 0.060 inch gage length) were bonded to the bore surface using a quick curing epoxy adhesive, see drawing 1. A third strain gage was also bonded to the bore in the tangential direction as a backup gage; however it was not used during the measurements. The tangential strain gage was bonded to the bore surface at 3.35 inches from the arbor shoulder, and the backup strain gage was at 2.875 inches. The axial strain gage was bonded at 1.58 inches, see photo 1. These lead wires were bonded to the inside diameter of the disk bore using a 5 minute epoxy. The leads were feed through an arbor radial hole to an arbor center drilled axial hole, then to a telemetry system housing mounted on the non-drive end of the arbor, see photos 2 and 3.
Within this housing, these strain gages were connected to two Wheatstone bridge
circuits using strain gage lead wires; one bridge circuit for each bonded strain gage, see drawing 2. Excitation voltage for the bridge circuits was provided by the ATi wireless telemetry transmitters; see drawing 3 and photo 4. Bridge excitation voltage was 5 volts DC. Each transmitter also “senses” the bridge output voltage of the attached bridge circuit, which it then broadcasts this voltage to the ATi wireless telemetry receiver. With no strain in the disk bore, each Wheatstone bridge circuit is “balanced” because the resistance of the strain gage is 350 ohms, which matches the other three resistors in the bridge circuit so the bridge output voltage (VG) is zero. If a tensile strain occurs at the strain gage, the gage resistance increase, which cause the bridge circuit to be “unbalanced” and a positive voltage proportional to the magnitude of the strain occurs at the bridge output. Conversely if a compressive strain occurs at the strain gage, the gage resistance decrease, which cause the bridge circuit to be “unbalanced” and a negative voltage proportional to the magnitude of the strain occurs at the bridge output.
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
6
Drawing 1: Disk and arbor assembly
Drawing 2: Wheatstone bridge circuit
Disk
Arbor
Disk Bore
Shoulder
350 Ohm Strain Gage
Excitation Voltage
5VDC
350 Ohm
Resistor R3
350 Ohm
Resistor R1
350 Ohm
Resistor R2
VG is Bridge Output
Voltage
Tapered
Sleeve
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
7
Drawing 3: Wireless telemetry system arrangement, TX#1 is transmitter 1, TX#2 is transmitters 2
Wheatstone bridge circuits
9V Batteries
Plastic Cover Plate
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
8
Photo 1: Tangential and axial strain gages
Photo 2: Disk/arbor with wireless telemetry system installed
Tangential Strain Gage
Axial Strain Gage
Lead Wires
Lead Wires
Receiver Antenna Receiver Antenna
Wireless Telemetry
Transmitter Housing
Temporary Tape
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
9
Photo 3: Disk/arbor with wireless telemetry system installed
Photo 4: Telemetry transmitters and 9V batteries installed in “plug”
At the start of the measurements with the disk/arbor at zero rpm, each Wheatstone bridge is balanced to zero volts output at the telemetry receiver and then a 10,000 ohm shunt calibration resistor is momentarily connected in parallel to one of the 350 ohm resistors of the bridge circuit to adjust the telemetry systems span. This shunt resistor simulates a strain of 16,577 microstrain (1 microstrain = 10-6 in/in, or 10,000 microstrain = 1% strain) resulting in an output of 4.300 volts DC at the receiver. Therefore, 10,000 microstrain at the strain gages
Receiver Antenna
#1
Receiver Antenna
#2
Wireless
Telemetry
Transmitter
Housing
Transmitter #1 for
tangential strain gage
Transmitter #2 for
axial strain gage
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
10
causes a receiver output voltage of 2.594 volts DC. Therefore, the strain gage signal channels have sensitivity of 0.2594 millivolts per microstrain.
With the tangential and axial strain gages measuring the deformation of the disk bore, two proximity probes were mounted beneath the disk to measure radial expansion of the disk as it rotated. These probes were also calibrated prior to performing any measurements. The disk itself was used as the target material (Inconel). Proximity probe sensitivities for the first radial probe (Probe1) were 0.246 volts per mil, and the second radial probe (Probe2) was 0.262 volts per mil. These probes were gapped to -19.0 volts (Probe1) and -19.8 volts (Probe2), so that the radial expansion would cover the linear range of the two probes.
Vibration of the arbor at bearings #1 and #2 was measured using XY orthogonal shaft
relative proximity probes. These shaft relative proximity probes were orientated in the “vertical” or “Y” direction (45 degrees left, “45L”, of top dead center, TDC) and “horizontal” or “X” direction (45 degrees right, “45R”, of top dead center, TDC) at each of the two arbor bearings. The disk/arbor rotational speed or rpm was also being measured with an additional proximity probe orientated at 90R at the input drive shaft, and was detecting the once per revolution passage of a protruding key. This phase trigger probe (keyphasor®) provided speed and phase information throughout these measurements.
Strain gage and proximity probe signals were acquired with a 32 channel Data Physics
Abacus® Turbo data acquisition system, see photo 5. This system was setup to acquire synchronously and asynchronously sampled data with vector samples obtained every 3 seconds and/or 30 rpm change. Spectral bandwidth was limited to 30,000 cpm with 800 spectral lines of resolution.
Photo 5: Data Physics Abacus Data Acquisition System
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
11
Summary
Three preliminary runs of the disk/arbor were conducted prior to the final run discussed below. During these first three runs, rotational speed of the disk/arbor was kept at or below 6000 rpm. During these initial three runs, the tangential and axial strain gages were cycled to reduce residual strain from bonding and curing of adhesives during installation. This is a normal strain gage practice and is called a “zero return” or “stability” test (see Vishay Micro measurements VMM-8 application document).
The speed profile for the fourth and final run is shown in figure 1. The maximum
rotational speed was 8236 rpm at 12:44:49 EST. Overall (unfiltered) and synchronous (1X) vibration amplitudes and phase information for vibration at arbor bearings #1 and #2 are shown in figures 2 and 3. Vibration amplitudes at 8000 rpm were acceptable. These shaft relative vibration measurements also revealed a first critical speed (first balance resonance) of the disk/arbor assembly at about 3700 rpm, see figure 4.
The change in disk radius was also measured during this final run, see figure 5. These
trends do not include a correction for the arbor centerline position change due to arbor journal lifting due to the bearing oil wedge. These shaft centerline position changes or movements are shown in figures 6. When arbor centerline motion is included, disk radial expansion is increased, see figure 7. The maximum expansion occurred at 8236 rpm, and it was 62.4 mils and 62.2 mils for radial probes #1 and #2 respectively. Figure 8 shows a bode plot of the disk radial expansion during startup and shutdown. Clearly, the disk radius appears greater during shutdown. The final bore radius changes were 3.2 mils and 3.5 mils for probes #1 and #2. This effect could be due to yielding of the disk or the tapered sleeve being stuck and not fully retracting during the shutdown. Disk bore diametric measurements would be required to confirm whether the disk had yielded and to what degree.
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
12
12:24:2911/22/2013
12:27:4811/22/2013
12:31:1111/22/2013
12:34:3111/22/2013
12:37:4811/22/2013
12:41:0711/22/2013
12:44:3111/22/2013
12:47:4811/22/2013
12:51:0711/22/2013
12:54:2911/22/2013
12:57:4911/22/2013
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Mag
, R
PM
XY RPM 1 vs Time¤ PT1
Company: Sulzer
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Figure 1: Rotational speed profile, Disk/arbor, Fourth Run
1588.5 RPM12:24:29
11/22/2013
4708.9 RPM12:27:48
11/22/2013
6555.3 RPM12:31:11
11/22/2013
6997.7 RPM12:34:31
11/22/2013
7963.7 RPM12:37:48
11/22/2013
8100.2 RPM12:41:07
11/22/2013
8031.4 RPM12:44:31
11/22/2013
6958.1 RPM12:47:48
11/22/2013
5970.8 RPM12:51:07
11/22/2013
3298.8 RPM12:54:29
11/22/2013
524.3 RPM12:57:49
11/22/2013
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
mil
s (
pk-p
k)
DE X¤DE YNDE XNDE Y
X: DE X 45°R Direct
Y: DE Y 45°L Direct
X: NDE X 45°R Direct
Y: NDE Y 45°L Direct
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Figure 2: Trend Plot, Shaft Relative Vibration, Overall (unfiltered) Amplitude, Bearing #1 X Probe (blue trace) and Y
Probe (red trace), Bearing #2 X Probe (green trace) Y Probe (magenta trace)
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
13
1588.5 RPM12:24:29
11/22/2013
4708.9 RPM12:27:48
11/22/2013
6555.3 RPM12:31:11
11/22/2013
6997.7 RPM12:34:31
11/22/2013
7963.7 RPM12:37:48
11/22/2013
8100.2 RPM12:41:07
11/22/2013
8031.4 RPM12:44:31
11/22/2013
6958.1 RPM12:47:48
11/22/2013
5970.8 RPM12:51:07
11/22/2013
3298.8 RPM12:54:29
11/22/2013
0
0.50
1.00
1.50
2.00
2.50
200.00300.00
40.00
140.00
240.00
340.00
80.00
180.00
280.0020.00
Mag
, m
ils (
pk-p
k)
; P
hase l
ag
, d
eg
DE X¤DE YNDE XNDE Y
X: DE X 45°R SR Comp 0.7 mils @ 150° 1X
Y: DE Y 45°L SR Comp 0.6 mils @ 211° 1X
X: NDE X 45°R SR Comp 0.4 mils @ 230° 1X
Y: NDE Y 45°L SR Comp 0.3 mils @ 314° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
Figure 3: Trend Plot, Shaft Relative Vibration, Synchronous (1X) Filtered Amplitude and Phase, Bearing #1 X
Probe (blue trace) and Y Probe (red trace), Bearing #2 X Probe (green trace) Y Probe (magenta trace)
1000 2000 3000 4000 5000 6000 7000 80000
1.0
2.0
3.0
4.0
5.0
200300
40
140
240
340
80
180
28020
RPM
Mag
, m
ils (
pk-p
k)
; P
hase l
ag
, d
eg
DE X¤DE YNDE XNDE Y
X: DE X 45°R SR Comp 0.7 mils @ 150° 1X
Y: DE Y 45°L SR Comp 0.6 mils @ 211° 1X
X: NDE X 45°R SR Comp 0.4 mils @ 230° 1X
Y: NDE Y 45°L SR Comp 0.3 mils @ 314° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
Figure 4: Bode Plot, Shaft Relative Vibration, Synchronous (1X) Filtered Amplitude and Phase, Bearing #1 X Probe
(blue trace) and Y Probe (red trace), Bearing #2 X Probe (green trace) Y Probe (magenta trace)
First balance resonance, first critical speed
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
14
Figure 5: Trend Plot, Disk Radial Probes #1 and #2, Disk Radial Expansion
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
15
-4 -2 0 2 4
T
XY
0
2.0
4.0
6.0
8.0
T
XY
159
399
688
1018
1498
2038
2609
3209
3509
3659
5369
6007
6268
6765
7481
8159
mils
mil
s
SCL 5, 6¤
X: DE X 45°R
Y: DE Y 45°L Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
-4 -2 0 2 4
T
XY
0
2.0
4.0
6.0
8.0
T
XY
159
459
8981048
1708
2428
3089
3539
4769
5549
5987
6449
6795
7314
7959
mils
mil
s
SCL 7, 8¤
X: NDE X 45°R
Y: NDE Y 45°L Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Figure 6: Shaft Centerline Plots, Bearing #1 (top), Bearing #2 (bottom)
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
16
Figure 7: Trend Plot, Disk Radial Probes #1 and #2, Disk Radial Expansion, Arbor shaft centerline movement
included
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
17
Figure 8: Bode Plot, Disk Radial Probes #1 and #2, Disk Radial Expansion, Arbor shaft centerline movement
included The tangential and axial strain trend/histories for the final run are shown in figure 9. As
expected, the tangential strain gage showed tensile (positive) strain, which reached a maximum of +9785 microstrain at 8236 rpm. The axial strain gage showed compressive strain as expected, and it too reach a maximum at 8236 rpm. Maximum compressive (negative) axial strain was -4445 microstrain. A bode plot of the strain histories clearly show residual tensile strain in the bore tangential direction and compressive strain in the bore axial direction, see figure 10. The final residual strains were +2356 microstrain and -1955 microstrain for the tangential and axial directions respectively. Again, this effect could be due to yielding of the disk or the tapered sleeve being stuck and not fully retracting during the shutdown. As mentioned previously, disk bore diametric measurements would be required to confirm whether the disk had yielded and to what degree.
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
18
Figure 9: Trend Plot, Tangential and Axial Strain Gage, Strain Histories, Initial Residual Bridge Zeroing Voltage
Removed/Corrected (zero initial strain @ zero rpm)
Figure 10: Trend Plot, Tangential and Axial Strain Gage, Strain Histories, Initial Residual Bridge Zeroing Voltage
Removed/Corrected (zero initial strain @ zero rpm)
Residual tangential strain
Residual axial strain
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
19
Conclusions
• Disk bore diametric measurements were subsequently performed and confirmed that the disk had yielded to its target strain level during the final run.
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
20
•
Appendix A Data Plots
12:24:2911/22/2013
12:27:4811/22/2013
12:31:1111/22/2013
12:34:3111/22/2013
12:37:4811/22/2013
12:41:0711/22/2013
12:44:3111/22/2013
12:47:4811/22/2013
12:51:0711/22/2013
12:54:2911/22/2013
12:57:4911/22/2013
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Mag
, R
PM
XY RPM 1 vs Time¤ PT1
Company: SulzerFrom 11/22/2013 12:21:12 To 11/22/2013 12:58:15
1588.5 RPM12:24:29
11/22/2013
4708.9 RPM12:27:48
11/22/2013
6555.3 RPM12:31:11
11/22/2013
6997.7 RPM12:34:31
11/22/2013
7963.7 RPM12:37:48
11/22/2013
8100.2 RPM12:41:07
11/22/2013
8031.4 RPM12:44:31
11/22/2013
6958.1 RPM12:47:48
11/22/2013
5970.8 RPM12:51:07
11/22/2013
3298.8 RPM12:54:29
11/22/2013
524.3 RPM12:57:49
11/22/2013
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
Mag
, m
ils (
pk-p
k)
DE X¤DE YNDE XNDE Y
X: DE X 45°R Direct
Y: DE Y 45°L Direct
X: NDE X 45°R Direct
Y: NDE Y 45°L Direct
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
21
1588.5 RPM12:24:29
11/22/2013
4708.9 RPM12:27:48
11/22/2013
6555.3 RPM12:31:11
11/22/2013
6997.7 RPM12:34:31
11/22/2013
7963.7 RPM12:37:48
11/22/2013
8100.2 RPM12:41:07
11/22/2013
8031.4 RPM12:44:31
11/22/2013
6958.1 RPM12:47:48
11/22/2013
5970.8 RPM12:51:07
11/22/2013
3298.8 RPM12:54:29
11/22/2013
0
0.5
1.0
1.5
2.0
2.5
200.0300.0
40.0
140.0
240.0
340.0
80.0
180.0
280.020.0
Mag
, m
ils (
pk-p
k)
; P
hase l
ag
, d
eg
DE X¤DE YNDE XNDE Y
X: DE X 45°R SR Comp 0.7 mils @ 150° 1X
Y: DE Y 45°L SR Comp 0.6 mils @ 211° 1X
X: NDE X 45°R SR Comp 0.4 mils @ 230° 1X
Y: NDE Y 45°L SR Comp 0.3 mils @ 314° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1588.5 RPM12:24:29
11/22/2013
4708.9 RPM12:27:48
11/22/2013
6555.3 RPM12:31:11
11/22/2013
6997.7 RPM12:34:31
11/22/2013
7963.7 RPM12:37:48
11/22/2013
8100.2 RPM12:41:07
11/22/2013
8031.4 RPM12:44:31
11/22/2013
6958.1 RPM12:47:48
11/22/2013
5970.8 RPM12:51:07
11/22/2013
3298.8 RPM12:54:29
11/22/2013
-1.500
-1.000
-0.500
0
0.500
1.000
1.500
2.000
2.500
3.000
V
Strain Tang¤Strain Axial
Strain Tang 0° Direct
Strain Axial 0° Direct
Company: Sulzer
Machine: Disc
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
22
1588.5 RPM12:24:29
11/22/2013
4708.9 RPM12:27:48
11/22/2013
6555.3 RPM12:31:11
11/22/2013
6997.7 RPM12:34:31
11/22/2013
7963.7 RPM12:37:48
11/22/2013
8100.2 RPM12:41:07
11/22/2013
8031.4 RPM12:44:31
11/22/2013
6958.1 RPM12:47:48
11/22/2013
5970.8 RPM12:51:07
11/22/2013
3298.8 RPM12:54:29
11/22/2013
-24.000
-22.000
-20.000
-18.000
-16.000
-14.000
-12.000
-10.000
-8.000
-6.000
V
OD Deflect1¤OD Deflect2
OD Deflect1 0° Direct
OD Deflect2 0° Direct
Company: Sulzer
Machine: Disc
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
T
0°
180°
90°270°T
6 mils (pk-pk)
1591378
2459
2819
3059
3209
3329
34193509
3568
3629
3659
3688
3719
3749
3779
3839
3898
39894079 4169
4289
4439
4769
78974739 4528 4348
4168
4049
3959
3868
3779
365935393359
3179
2939
Polar 3 Slow Roll Comp¤
OD Deflect1 0° SR Comp 0.6 mils @ 340° 1X
Company: Sulzer
Machine: Disc
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
23
T
0°
180°
90°270°T
6 mils (pk-pk)
1591348
2488
2849
3089
3239
335934493509
3568
3629
3659
3688
3719
3749
3779
3839
3898
3989 40794169
4289
4439
4739
72248214
45884408
4228
4108
4018
3928
3839
374936283479
3269
3029
2624
Polar 4 Slow Roll Comp¤
OD Deflect2 0° SR Comp 0.6 mils @ 345° 1X
Company: Sulzer
Machine: Disc
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
T
0°
180° 90°
270°
T
2.5 mils (pk-pk)
1591258
2248
2909
31493299 3389
3479
3539
3568
3629
3659
3688
3719
3749
380838693929
3989
4049
4109
4199
4319
4499
7987
8058
5052
4678
4528
4378
419940493928
3839
3779
3719
3659
3599
35093389
Polar 5 Slow Roll Comp¤
X: DE X 45°R SR Comp 0.7 mils @ 150° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
24
T
0°
180°
90°
270°
T
1.2 mils (pk-pk)
1591018
20992339
2519
2669
2819
2968
3089
3209
3329
3479
3568
3599
3659
3719
380838693929
4019
4079
4139
4289
4499
6298
7165
7405
7748
7897
8018
80268122
7675
7495
482846194439
4168
3988
38983779
3688
3479
3299 1634
Polar 6 Slow Roll Comp¤
Y: DE Y 45°L SR Comp 0.6 mils @ 211° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
T
0°
180° 90°
270°
T
2.5 mils (pk-pk)
159
8681018
1348
1649
1919 2248
25793089 3239
3359
3449
3509
3539
3568
3599
3629
3659
3688
3719
377938393898
3959
4019
4079
4139
4228
4349
4739
7995
4468
428840783898
3808
3749
3688
3628
3568
3509
33893209
Polar 7 Slow Roll Comp¤
X: NDE X 45°R SR Comp 0.4 mils @ 230° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
25
T
0°
180°
90°
270°
T
1.6 mils (pk-pk)
159
838 1288 1708
1978
2129
22792459
2579
2968 3119
3269
3359
3419
3479
3509
3539
3568
3599
3629
36593719
3779
3839
3898
3959
4019
4079
4169
4319
4859
7314
7511
7719
7807
7928
8026
7971
7907
7872
8165
7854
45593599
3479
3359
3269
31192864
Polar 8 Slow Roll Comp¤
Y: NDE Y 45°L SR Comp 0.3 mils @ 314° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1000 2000 3000 4000 5000 6000 7000 80000
2.0
4.0
6.0
8.0
10.0
0
200
40
240
80
RPM
Mag
, m
ils (
pk-p
k)
; P
hase l
ag
, d
eg
Bode 1X 3 Slow Roll Comp¤
OD Deflect1 0° SR Comp 0.6 mils @ 340° 1X
Company: Sulzer
Machine: Disc
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
26
1000 2000 3000 4000 5000 6000 7000 80000
2.0
4.0
6.0
8.0
10.0
200
300
40
140
240
340
80
180
RPM
Mag
, m
ils (
pk-p
k)
; P
hase l
ag
, d
eg
Bode 1X 4 Slow Roll Comp¤
OD Deflect2 0° SR Comp 0.6 mils @ 345° 1X
Company: Sulzer
Machine: Disc
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
27
1000 2000 3000 4000 5000 6000 7000 80000
2.0
4.0
6.0
8.0
10.0
300
40
140
240
340
80
180
280
20
RPM
Mag
, m
ils (
pk-p
k)
; P
hase l
ag
, d
eg
Bode 1X 5 Slow Roll Comp¤
X: DE X 45°R SR Comp 0.7 mils @ 150° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1000 2000 3000 4000 5000 6000 7000 80000
2.0
4.0
6.0
8.0
10.0
200
40
240
80
RPM
Mag
, m
ils (
pk-p
k)
; P
hase l
ag
, d
eg
Bode 1X 6 Slow Roll Comp¤
Y: DE Y 45°L SR Comp 0.6 mils @ 211° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
28
1000 2000 3000 4000 5000 6000 7000 80000
2.0
4.0
6.0
8.0
10.0
200
40
240
80
RPM
Mag
, m
ils (
pk-p
k)
; P
hase l
ag
, d
eg
Bode 1X 7 Slow Roll Comp¤
X: NDE X 45°R SR Comp 0.4 mils @ 230° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1000 2000 3000 4000 5000 6000 7000 80000
2.0
4.0
6.0
8.0
10.0
300
40
140
240
340
80
RPM
Mag
, m
ils (
pk-p
k)
; P
hase l
ag
, d
eg
Bode 1X 8 Slow Roll Comp¤
Y: NDE Y 45°L SR Comp 0.3 mils @ 314° 1X
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
Ref: Compensation
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
29
-4 -2 0 2 4
T
XY
0
2.0
4.0
6.0
8.0
T
XY
159
399
6881018
1498
2038
2609
3209
3509
3659
5369
6007
6268
6765
7481
8159
mils
mil
s
SCL 5, 6¤
X: DE X 45°R
Y: DE Y 45°L
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
-4 -2 0 2 4
T
XY
0
2.0
4.0
6.0
8.0
T
XY
159
459
8981048
1708
2428
3089
3539
4769
5549
5987
6449
6795
7314
7959
mils
mil
s
SCL 7, 8¤
X: NDE X 45°R
Y: NDE Y 45°L
Company: Sulzer
Machine: Arbor
From 11/22/2013 12:21:12 To 11/22/2013 12:58:15
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
30
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
31
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
32
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
33
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
34
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
35
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
36
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
37
0 1 2 30
2000.0
4000.0
6000.0
8000.0
10000.0
12000.0
14000.0
16000.0
18000.0
order
Mag
, m
ils (
pk-p
k)
Spectrum 1¤
Strain Tang 0°
Company: Sulzer
Machine: Disc RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
38
0 1 2 30
2000.0
4000.0
6000.0
8000.0
10000.0
12000.0
14000.0
order
Mag
, m
ils (
pk-p
k)
Spectrum 2¤
Strain Axial 0°
Company: Sulzer
Machine: Disc RPM = 8122
11/22/2013 12:44:38
0 1 2 30
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
order
Mag
, m
ils (
pk-p
k)
Spectrum 3¤
OD Deflect1 0°
Company: Sulzer
Machine: Disc RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
39
0 1 2 30
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
order
Mag
, m
ils (
pk-p
k)
Spectrum 4¤
OD Deflect2 0°
Company: Sulzer
Machine: Disc RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
40
0 1 2 30
0.05
0.10
0.15
0.20
0.25
0.30
0.35
order
Mag
, m
ils (
pk-p
k)
Spectrum 5¤
X: DE X 45°R
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
0 1 2 30
0.1
0.2
0.3
0.4
0.5
order
Mag
, m
ils (
pk-p
k)
Spectrum 6¤
Y: DE Y 45°L
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
41
0 1 2 30
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
order
Mag
, m
ils (
pk-p
k)
Spectrum 7¤
X: NDE X 45°R
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
42
0 1 2 30
0.1
0.2
0.3
0.4
0.5
0.6
0.7
order
Mag
, m
ils (
pk-p
k)
Spectrum 8¤
Y: NDE Y 45°L
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
0 10000 20000 300000
2000.0
4000.0
6000.0
8000.0
10000.0
12000.0
14000.0
16000.0
18000.0
CPM
Mag
, m
ils (
pk-p
k)
Spectrum 1¤
Strain Tang 0°
Company: Sulzer
Machine: Disc RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
43
0 10000 20000 300000
2000.0
4000.0
6000.0
8000.0
10000.0
12000.0
14000.0
CPM
Mag
, m
ils (
pk-p
k)
Spectrum 2¤
Strain Axial 0°
Company: Sulzer
Machine: Disc RPM = 8122
11/22/2013 12:44:38
0 10000 20000 300000
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
CPM
Mag
, m
ils (
pk-p
k)
Spectrum 3¤
OD Deflect1 0°
Company: Sulzer
Machine: Disc RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
44
0 10000 20000 300000
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
CPM
Mag
, m
ils (
pk-p
k)
Spectrum 4¤
OD Deflect2 0°
Company: Sulzer
Machine: Disc RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
45
0 10000 20000 300000
0.05
0.10
0.15
0.20
0.25
0.30
0.35
CPM
Mag
, m
ils (
pk-p
k)
Spectrum 5¤
X: DE X 45°R
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
0 10000 20000 300000
0.1
0.2
0.3
0.4
0.5
CPM
Mag
, m
ils (
pk-p
k)
Spectrum 6¤
Y: DE Y 45°L
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
46
0 10000 20000 300000
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
CPM
Mag
, m
ils (
pk-p
k)
Spectrum 7¤
X: NDE X 45°R
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
0 10000 20000 300000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
CPM
Mag
, m
ils (
pk-p
k)
Spectrum 8¤
Y: NDE Y 45°L
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
47
0 0.02 0.04 0.06
T
XY
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8 X-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1.0 Y
T
XY
sec
X: 0.2 mils/div
mil
s
Y:
0.2
mil
s/d
iv
Orbit 5, 6¤
X: DE X 45°R Direct 1.1 mils
Y: DE Y 45°L Direct 1.1 mils
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
0 0.02 0.04 0.06
T
XY
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8 X-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1.0 Y
T
XY
sec
X: 0.2 mils/div
mil
s
Y:
0.2
mil
s/d
iv
Orbit 7, 8¤
X: NDE X 45°R Direct 1.1 mils
Y: NDE Y 45°L Direct 1.2 mils
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
48
0 0.02 0.04 0.06
T
XY
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5 X
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6 Y
T
XY
sec
X: 0.1 mils/div
mil
s
Y:
0.1
mil
s/d
iv
Orbit 5, 6 Waveform Comp¤
X: DE X 45°R Waveform Comp Direct 0.8 mils
Y: DE Y 45°L Waveform Comp Direct 0.6 mils
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
Ref: Compensation
0 0.02 0.04 0.06
T
XY
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5 X
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6 Y
T
XY
sec
X: 0.1 mils/div
mil
s
Y:
0.1
mil
s/d
iv
Orbit 7, 8 Waveform Comp¤
X: NDE X 45°R Waveform Comp Direct 0.7 mils
Y: NDE Y 45°L Waveform Comp Direct 0.9 mils
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
Ref: Compensation
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
49
-0.30 -0.20 -0.10 0 0.10 0.20 0.30
-0.2
-0.1
0
0.1
0.2
0.3
T
XY
X, mils
Y,
mil
s
Orbit1X 5, 6¤
X: DE X 45°R 1X 0.3 mils; 178°
Y: DE Y 45°L 1X 0.5 mils; 242°
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
-0.20 0 0.20 0.40
-0.2
0
0.2
0.4
T
XY
X, mils
Y,
mil
s
Orbit1X 7, 8¤
X: NDE X 45°R 1X 0.5 mils; 247°
Y: NDE Y 45°L 1X 0.7 mils; 12°
Company: Sulzer
Machine: Arbor RPM = 8122
11/22/2013 12:44:38
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
50
Appendix B
ROTATION vs. PRECESSION
Rotation is the angular motion of the rotor about its geometric center, or shaft centerline.
In the absence of any external forces, a perfectly balanced rotor will spin in place around
the geometric center, of the shaft without any change in position (vibration) of that center.
Precession is the vibration of the rotor’s geometric center in the xy plane that is
perpendicular to the axis of rotation. The vibration of the rotor’s geometric center in the xy
plane results in the shaft orbit. The direction of precession (vibration) can be expressed as
counterclockwise (CCW) or as clockwise (CW).
When the direction of precession (vibration) is the same as the direction of rotation, then
the vibration is defined as being forward precession.
When the direction of precession (vibration) is opposite to the direction of rotation, then
the vibration is defined as being reverse precession.
These concepts of forward and reverse precession have powerful application in full
spectrum and in the diagnosis of certain types of malfunctions.
If the only force acting on the rotor is unbalance; i.e. by definition a circular, forward,
sinusoidal force, and if the restraining stiffnesses are equal in all directions, then the
resulting orbit will also be perfectly circular, and forward in precession.
Uni-directional forces that push on the rotor; i.e. misalignment, stiffness asymmetry, rubs,
aerodynamic loading, etc. will restrain the vibration in one plane, resulting in the orbit
becoming, to some degree, elliptical in nature. By definition, an elliptical orbit is comprised
of both forward and reverse vibration components.
As the orbit shape changes the forces and restraints acting on the system are becoming
more complex.
The orbit of the rotor can range from purely circular to a very complicated shape containing
many frequencies of vibration.
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
51
DATA PLOT FORMATS
Orbit/ Timebase plots are used to
primarily examine the shape or form of
the vibration; i.e. the two dimensional
centerline motion of the shaft as it
vibrates in the xy plane perpendicular
to the axis of rotation.
Amplitude information is
simultaneously plotted from a pair of
orthogonal (90°) transducers. The
amplitude information, coupled with a
phase angle reference, is essential for
analyzing the dynamic motion of the
rotor. Interpretation of Orbit/
Timebase plots provides insight into
the nature of the vibration, i.e. the
presence of steady state preloads as
well as system asymmetry.
The leading edge of the phase trigger
appears on both the orbit and
timebase plots as a blank, with the
trailing edge displayed as a dot.
Vibration precession around the orbit
is from blank to dot and is forward if it
is in the direction of rotation and
reverse if it is opposite the direction of
rotation.
0 0.02 0.04 0.06 0.08 0.10 0.12 0.14
T
Y
X
-3.50-3.00-2.50
-2.00-1.50
-1.00
-0.500
0.501.001.50
2.00
Y
-2.50
-2.00-1.50
-1.00-0.50
0
0.501.00
1.502.002.50
3.00X
T
Y
X
sec
X: 0.5 mils/div
mil
s
Y:
0.5
mil
s/d
iv
Orbit 1, 2¤
Orbit 1, 2X=0 secY=-1.74 mils,-0.86 mils
Y: 1Y 60°L Direct 5.26 mils
X: 1X 30°R Direct 3.39 mils
Company: Nova Scotia Power, Inc.
Machine: HP Steam Turbine RPM = 3600
10/25/2010 17:03:52
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
52
Shaft average centerline plots
are used to observe changes in the
average position of a rotor within its
radial bearing clearance. Changes in
shaft centerline position can provide a
warning for changes in the alignment
state of a machine and may indicate
bearing wear. Average shaft radial
position indicates the presence of
preloads as well as overall bearing
stability.
-20.0 -10.0 0 10.0 20.0
TXY
0
10.0
20.0
30.0
40.0 T
XY
875.31000.0
1392.3
1753.7
2036.4
2302.7
2601.9
2911.8
3161.9
3381.9
3540.2
milsm
ils
SCL 15, 16¤
SCL 15, 16X=1.68 milsY=14.7 milsSpeed=3.60k RPM
X: 8X 45°R
Y: 8Y 45°L
Company: Nova Scotia Power, Inc.
Machine: Generator
10/26/2010 09:30:20
Spectrum plots are used to
examine the frequency
components useful for
identifying certain machine
problems as some machine
malfunctions produce
vibrations at characteristic
frequencies. Since many
machines exhibit similar
vibration frequency
characteristics, spectral
analysis must be utilized with the
time domain to fully appreciate the
dynamic characteristics of the rotor
/ bearing system.
0 10000.00 20000.00 30000.00
0
0.10
0.20
0.30
0.40
CPM
Mag
, m
ils (
pk-p
k)
Spectrum 9¤
Y: 5Y 60°L
Company: Nova Scotia Power, Inc.
Machine: DF Low Pressure Steam Turbine RPM = 3600
10/25/2010 17:03:52
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
53
Bode’ and Polar plots show the
synchronously filtered change of
amplitude and phase angle as a
function of shaft rotative speed. The
bode plots enhances the amplitude
response and provides the
information to calculate other rotor
/ bearing system parameters such as
the Synchronous Amplification
Factor (SAF). In the Bode format,
the amplitude and phase
information is plotted as a function
of rotative speed, whereas in the
Polar format it is the vibration
vector, plotted in polar coordinates,
as a function of rotative speed.
1000.00 2000.00 3000.000
0.20
0.40
0.60
0.80
1.00
1.20
200
300
40
140
240
340
RPM
Mag
, m
ils (
pk-p
k)
; P
hase,
deg
Bode 1X 14 Slow Roll Comp¤
Bode 1X 14 Slow Roll CompX=31.60 RPMY=0.01 mils,289.66°
X: 7X 45°R SR Comp 0.16 mils @ 59° 1X
Company: Nova Scotia Power
Machine: Generator
From 10/24/2010 16:08:07 To 10/24/2010 20:26:16
T
0°
180°
90°
270°
T 4 mils (pk-pk)
160.4
935.4
385.4 2015.7
2151.6
2251.6
2351.7
2426.7
2476.7
2576.8 2726.6
2776.6 3001.6
3026.6
3051.6
3201.7
3226.7
3276.6
3351.7
3401.8
3426.7
3485.53565.6
3592.5
3568.7
3518.6
3470.2
Polar 1 Slow Roll Comp¤
Polar 1 Slow Roll CompAngle=326.64°Y=0.43 milsSpeed=160.40 RPM
Y: 1Y 45°L SR Comp 0.77 mils @ 77° 1X Company: Sulzer Turbo ServicesMachine: Steam Turbine Outboard From 10/27/2011 08:22:56 To 10/27/2011 14:49:50Ref: Compensation
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
54
Trend plots are used to detect
changes of any measured variable
from any channel over a period of
time. A change in a parameter,
increasing or decreasing, is often an
early indication of possible
problems.
3599.3 RPM17:51:12
10/25/2010
3601.1 RPM20:37:52
10/25/2010
3601.9 RPM23:24:32
10/25/2010
3601.1 RPM02:11:12
10/26/2010
3600.1 RPM04:57:52
10/26/2010
3601.1 RPM07:44:32
10/26/2010
0
1.00
2.00
3.00
mil
s
Trend 9¤Trend 10Trend 11Trend 12
Trend 9X=874.0 RPM 15:05:27 10/25/2010Y=0.86 mils
Y: 5Y 60°L Direct
X: 5X 30°R Direct
Y: 6Y 60°L Direct
X: 6X 30°R Direct
Company: Nova Scotia Power, Inc.
Machine: DF Low Pressure Steam Turbine
From 10/25/2010 15:05:17 To 10/26/2010 08:21:02
Full Spectrum plots (The Spectrum
of an Orbit) are enhanced spectrum plots
produced by using the dynamic data
from orthogonal (90°) XY transducers to
calculate the amplitudes of the forward
and reverse (backward) vibration
frequency components. The full
spectrum presents shaft vibration orbital
data in a complex filtered data
presentation. Any shaft orbit that is not
purely circular by definition is
comprised of both forward and reverse
vibration components. In the orbit
timebase plot, this is appreciated by
directly viewing the ellipticity of the
orbit. In the full spectrum data plot, this
same evaluation is made by evaluating
the relative amplitudes of both the
forward and reverse components at a
given frequency.
-30000.00 -20000.00 -10000.00 0 10000.00 20000.00 30000.000
2.00
4.00
6.00
8.00
10.00
12.00
CPM
Mag
, m
ils ,
mil
s (
pk-p
k)
Full Spectrum 1, 2¤
Y: 1Y 30°R
X: 1X 60°L
Company: Nova Scotia Power, Inc.
Machine: HP Steam Turbine RPM = 3600
10/25/2010 17:03:52
Notes on Full Spectrum Data Plots:
In much the same way that a traditional spectrum plot breaks down a complex vibration waveform into its
individual filtered frequency components that can be summed back to reproduce the original complex
waveform, the full spectrum data plot breaks down a complex orbit shape into its individual filtered
frequency orbits that can be summed back to reproduce the original complex orbit shape. Mathematically it
can easily be shown that any filtered orbit can be represented by two vectors, one which rotates in the
direction of rotation (forward) and one which rotates opposite of rotation (reverse). The ratio of the
forward to the reverse vector indicates the ellipticity of the filtered orbit at that frequency. For example,
consider the full spectrum shown above. The forward vibration component at 3600 cpm is approximately
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
55
4.5 times as large as the reverse component at -3600 cpm. The resulting filtered orbit at 3600 cpm is
elliptical with a minor axis that is approximately 77% the length of the major axis.
“Complicated orbits will have forward and reverse [vibration] components at many frequencies. Each pair of
components represents a set of vectors that rotate in forward and reverse directions at a specific frequency.
The most complex orbit can always be described by a set of such vectors and full spectrum lines. The lines in
the full spectrum represent the precessional structure of the orbit…..The entire orbit can be expressed as the
sum of its forward and reverse components in the same way that a timebase waveform can be expressed as
the sum of its sine wave components.
At first glance, the full spectrum might seem abstract. What is significant about forward and reverse
precession? It lets us easily identify key orbit characteristics that might otherwise be obscured. Precession
direction and ellipticity provide insight into the state of health of a machine. More importantly, some rotor
system malfunctions can have characteristic signatures on a full spectrum plot that are not available on
traditional spectrum plots. These characteristics can be used to discriminate between different malfunctions
that produce vibration with similar frequencies.”1
The 1st Law of Machinery Diagnostics
=∑
∑
uuuuuuuuuuruuuuuuuuuuuuuuur
uuuuuuuuuuuuuuuuuuuuuuuurForces
DisplacementDynamic Stiffness
[1]
Equation 1 is often referred to as the “1st Law of Machinery Diagnostics”. The 1st Law reminds us that
vibration is not a scalar quantity; it is a vector quantity in that it has both a magnitude and a direction.
Additionally, the 1st Law acknowledges that if the vibration displacement changes in amplitude, either
increasing or decreasing, it is due to either a change in the applied forces to the rotor bearing system,
a change in the dynamic stiffness of the rotor bearing system, or both.
Although beyond the scope of this report, it can be readily shown that:
Dynamic StiffnessK
= ( ) ( )2− Ω + − ΩK M j D Dω λω λω λω λ
[2]
In Equation 2, K is the spring stiffness, M is the rotor modal mass, D is the rotor/bearing viscous modal
damping, and ω is a term that represents the frequency of the vibration precession (or orbiting), which
may be different from the rotation speed, Ω. λ is the Fluid Circumferential Average Velocity Ratio of
the fluid in the bearing or seal. The first two terms to the left of the equal sign, contained in the first
set of parentheses of Equation 2, are the spring stiffness K (shaft, bearing, support pedestal, etc.) and
the mass-inertial stiffness, –MΩ2. The spring and mass-inertia stiffnesses form the Direct Dynamic
Stiffness. It is called Direct because the Direct Dynamic Stiffness acts directly along the line of action of
the summation of forces Fuur
that are applied to the rotor system. Also, the Mass-Inertia Stiffness, –
MΩ2, is a speed squared dependent term. When the magnitude of the Mass-Inertia Stiffness, –MΩ2, is
equal to the Spring Stiffness K, the Direct Stiffness becomes zero; i.e. the undamped natural frequency
or critical speed of the rotor / bearing system.
1 Fundamentals of Rotating Machinery Diagnostics; Bently, Donald. E.; Chapter 8, pages 120-122
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
56
The next two terms, contained in the second set of parentheses, of Equation 2, are the Quadrature
Dynamic Stiffness Terms, i.e. the Damping Stiffness, +jDω, and Tangential Stiffnesses, –jDλΩ2. It is
called Quadrature because, as indicated by the +j (i.e., 1− ), acts at 90° to the line of action of the
summation of the applied forces, Fuur
.
When a fluid, either liquid or gas, is constrained within the space between two concentric cylinders,
one rotating and one stationary, the fluid in the clearance between the two cylinders will be set into
circumferential motion. This can happen in rotating machinery within the fluid-lubricated bearings,
seals, around pump impellers, or in any fluid filled gap between the rotor and the stator.
In a hydrodynamic, fluid film bearing, the fluid velocity at the surface of the bearing is zero, while the
fluid velocity at the surface of the rotor is equal to the rotor surface speed. The fluid near the rotor
surface moves at a slightly slower velocity that continues to decrease with the distance from the rotor
and reaches zero at the bearing surface. It is easy to see that the fluid must have some overall average
velocity which is less than the rotor speed, and that the faster the rotor turns, the faster the average
fluid velocity must be. In fact, previous work has shown that the fluid circumferential average angular
velocity in the bearing can be expressed as λΩ, where λ is the Fluid Circumferential Average Velocity
Ratio, and Ω is the rotor rotative speed, with the value of λ normally less than ½X; i.e., 0.43X to 0.48X.
If a radial load is applied to a rotor operating in the center of a fluid-lubricated bearing, the rotor will
be displaced from the center of the bearing. The reduced clearance on one side will restrict the flow of
fluid around the journal bearing clearance. Because of this restriction, the fluid has to slow down as
the available flow area gets smaller. As the fluid slows down, the pressure in this region increases. The
pressure exerts a force on the rotor. This force can be separated into a radial part, which points back
toward the center of the bearing, and a tangential part, which acts at 90° to the radial force, in the
direction of fluid flow; i.e. shaft rotation. Both the radial and tangential forces are proportional to the
displacement of the rotor from the center of the bearing. Thus, the lubricating fluid acts like a spring
with a complex stiffness. The radial part of the fluid wedge stiffness is referred to as the Direct
Dynamic Stiffness and the tangential part of the fluid wedge stiffness is referred to as the Quadrature
Dynamic Stiffness as defined by Equation 2 above.
It is this complicated spring effect that provides the primary support for the rotor. The rotor and the
fluid pressure "wedge" move until the fluid spring forces in the bearing exactly balance the summation
of radial loads applied to the rotor and the rotor settles into an equilibrium position.
If the rotor is disturbed from the equilibrium position, the direct spring stiffness acts to return the
rotor to the equilibrium position. However, the net force produced by the damping stiffness acting in
the direction opposite of rotation and the tangential stiffness acting in the direction of rotation
2 Cross coupled stiffness
1643 Collinsdale Ave., Cincinnati, Ohio 45230 Tel (513) 231-1748 / (513) 633-5429 | Fax (513) 231-2104
57
prevents that from happening and the rotor orbits (vibrates) around the equilibrium position at some
displacement amplitude.3
If the forces that perturb the rotor could be removed, the orbit would spiral back to the equilibrium
position. It is the complicated effect of these forces that maintains rotor stability.
Figure A1 is a graphical representation showing that in reality the overall system Dynamic Stiffness is
comprised of a series of springs from the rotor to ground with the weakest (smallest) spring being
the fluid film stiffness of the bearing itself. This fact is logical in that it is the weakest spring that will
control vibration. Furthermore the resulting Dynamic Stiffness resulting from these springs in series
will always be less than the stiffest spring in the series.
In the case of the bearing fluid film, vibration energy is absorbed and dissipated via the direct damping
term, Dωωωω , which is the rotor pushing on the fluid – the shock absorber effect. However, for adequate
damping to occur within the bearing, the bearing must be rigidly mounted to the foundation spring
and the foundation spring rigidly connected to ground. Any looseness between the bearing and the
housing, the housing to the foundation, the foundation to ground will result in unwanted seismic
relative motion which will adversely affect damping within the bearing. Any looseness between the
bearing and its housing, the housing and the foundation, or the foundation and ground will reduce
overall damping which can lead to elevated vibration amplitudes at one or more frequencies.
3 A Short Course in the Practical Application of Rotordynamics as a Tool for Machinery Diagnostics; Thomas, G. Richard,
Paper presented at the Canadian Machinery Vibration Association Annual Meeting / Seminar; 29 October 2009
M
SHAFT
BEARING
FOUNDATION
Terra Firma
Keffective
MM
SHAFT
BEARING
FOUNDATION
Terra Firma
Keffective
Figure A1