Managed by UT-Battelle for the Department of Energy 10/2013 SNS
VISION T0 Chopper Vibration Diagnostics and Testing PRESENTED TO
DENIM 2013 Blake Van Hoy Electro-Mechanical Systems and Simulation
Staff Member SNS Staff Members William McHargue David Anderson
Danny Williams
Slide 3
2 Problem Statement Blake, when are you getting here?
Slide 4
3 Problem Statement The T0 chopper exhibited excessive
vibration The vibration appeared to be speed dependent The chopper
had been balanced to a high precision grade per the ISO standard
This excessive vibration kept the magnetic bearing safeguards on
the Bandwidth Chopper from allowing it to operate The Bandwidth
Chopper was required for the beam line to reach full operational
status
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4 4 Z Y
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5 5
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6 6 Vision Beam Line Vibration Efforts Data Acquisition and
Analysis Ultimately 27 channels of data were acquired totaling 30
Gbytes with Smart Office software and VibPilot hardware Drive up,
drive down, coast down, steady state, resonance testing, and motor
current signature analysis were performed The data is very rich in
features, i.e. harmonics abound out past the tenth run speed, sub
harmonics, modulations, and frequencies that have no relation to
the drive are all present The accelerometer signals yield an
audible source that significantly changes during run up or run
down. The data were analyzed for traditional mechanical / machinery
issues such as misalignment, imbalance, magnetic center, etc.
Structural resonances were investigated with impact testing
Maintenance history and processes were discussed and reviewed and
found satisfactory with Jerry Stocktons and Bill McHargues help
Engineering history and design details were reviewed and two issues
came to light thanks to the engineering staff efforts. All possible
analytical causes were pursued in an effort to qualify and quantify
this phenomena.
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7 7
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8 8
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9 9
Slide 11
10 Vision Beam Line Vibration Sensor Installation 10
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11 Vision Beam Line Vibration Sensor Installation 11
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12
Slide 14
13 Accelerometers Provide a Great Way to Hear what is Going On
During Steady State and Transients Test Point 10 (T0), Test 2,
April 24, 2012Test Point 15 (BW), Test 2, April 24, 2012
8s5s8s5s
Slide 15
14 Vibration Magnitudes Increased with Run Speed but were
Generally Repeatable During Drive Up and Coast Down Drive Up Coast
Down Test point 10 (T0) vibration magnitudes are shown, and have
been referenced to full run speed (e.g., vib = 1.0 at 3600 RPM) * ~
410 mG ~ 610 mG
Slide 16
15 TP-10 Vibration and Phase A Motor Current During Drive Up
Show Slight Correlation in Overall Magnitudes Test Point 10
Vibration Waveform During Test 47 Drive Up Phase A Motor Current
Waveform During Test 47 Drive Up
Slide 17
16 High Frequency Content 16
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17 Waterfall of Same Signal 17
Slide 19
18 Beam Line Axis Impact Resonance Results 18
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19 Vertical Axis Resonance Results 19
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20 Time Domain Captures Across System 20 Runup PT 4 on the
baseplate Runup PT 5 on the baseplate Runup PT 14 on the baseplate
Runup PT 17 on the baseplate
Slide 22
21 Operation Deflection Shape Animations 21
Slide 23
22 Conclusions Prior to August Shutdown 22 The issues exhibited
on the beam line are not exhibited in the assembly/balance area in
the chopper shop The vibration magnitude changes during run up or
run down by a large amplitude. The data were analyzed for
traditional mechanical / machinery issues such as misalignment,
imbalance, magnetic center, etc and none were found. The signatures
in this system point to a lot of things going on and yield a
complex signature for what looked like a fairly simple system The
animations from the Operation Deflection Shapes analysis would
indicate that we have a system driven by the T0 Chopper and the
response of the base plate and the Bandwidth Chopper become
problematic to this excitation The Bandwidth chopper response and
higher amplitude than the T0 chopper appears to be an issue of a
cantilevered response to the base plate motion
Slide 24
23 Conclusions 23 The unbalance of the T0 chopper is specified
to be a precision balance at a small value at the balance shop and
is a much greater measured value on the beam line. This is not from
a bad balance job but the actual rotor is balanced as a separate
component on a balance machine and it does not take into account
the actual mounting and boundary conditions when installed on the
beam line. The plates that compose the T0 mounting system and the
actual installed base plate are suspect. The mis-alignment, the
bolt recessed dimensions, and the animations all point to a lack of
stiffness and a forced response that moves the structure in such a
manner that the magnetic bearing Bandwidth chopper cannot run. This
is the short term issue that has to be addressed.
Slide 25
24 Results 24 So after that diagnosis SNS Instrument
Engineering began work on address the suspected Plate from multiple
angles. Groups involved included SNS Instrument Support, Scientific
Staff, Survey & Alignment, Neutron Choppers, Structural Design,
Radiation Safety, ES&H/Industrial Hygiene, and others The plate
design was revised into 4 sections mechanical separation,
additional anchors, modal analysis The lead engineer assigned to
the task coordinated all the events, built a schedule, and had
daily meetings (usually only 10 minutes). The Physicists watched
and attended all the meetings to make sure everything went well. I
Didnt Sleep Very Well for a couple of weeks
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25 Details 25
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26 Details 26
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27 Details 27
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28 Details 28
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29 Details 29
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30 Details 30
Slide 32
31 Installation of the New Base Plate
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32 Results shown for Point 11 and Point 19 vertical
Slide 34
33 Data for Point 11 on T-0 Chopper taken in April 2012
Spectrum Versus the Calculated ISO Condition Standard 33 Vision
Beam Line Chopper Vibration Per ISO Standard level is in the Danger
Zone
Slide 35
34 Data for Point 11 on T-0 Chopper taken in August 2012
Spectrum Versus the Calculated ISO Condition Standard 34 Vision
Beam Line Chopper Vibration Vibration Level Reduction on the T-0
Chopper by a Factor of 4.7 X and running at the level for a new
machine. Plot scale change on vertical scale by a factor of
10.
Slide 36
35 Data for Point 19 on Bandwidth Chopper April 2012 Spectrum
Versus the Calculated ISO Condition Standard 35 Vision Beam Line
Chopper Vibration Per ISO Standard levels are in the Danger Zone
and the higher the level the shorter the Mechanical Life
Slide 37
36 Data for Point 19 on Bandwidth Chopper August 2012 Spectrum
Versus the Calculated ISO Condition Standard 36 Vision Beam Line
Chopper Vibration NOTE -10X vertical scale change compared to
previous slide. Vibration Level Reduction on the Bandwidth Chopper
by a Factor of 30 X and also in the Regime of a New Machine.
Slide 38
37 Chart for Balance and Run Quality Per ISO 1940 for T0 Values
37 At 60 Hertz Run Speed A Vibration of 6 mm/sec (.00178 in.) is
equivalent to a G16 and G 40 classification. G40 is for crankshafts
of trucks and locomotives. G16 is for Agricultural machinery and
crushing machines. At the Re-designed and re- worked values of 1.27
mm/sec (0.00037 in.) you are running at a G1 G2.5 classification.
G1 is for phonographs (for those of you who remember what those
are), and precision grinding machines. G2.5 is machine tool
spindles and computer drives.
Slide 39
38 Chart for Balance and Run Quality Per ISO 1940 for Bandwidth
Chopper Values 38 At 60 Hertz Run Speed A Vibration of 9.5 mm/sec
(0.0028 in.) is close to a G40 classification. G40 is for
crankshafts of trucks and locomotives. At the Re-designed and re-
worked values of 0.31 mm/sec (0.00009 in.) you are running at
slightly better than a G1 classification. G1 is for phonographs
(for those of you who remember what those are), and precision
grinding machines.
Slide 40
39 Magnetic Bearing Bandwidth Chopper De-Levitated Orbit Plot
Before August Shutdown Plot courtesy of Bill McHargue 39 The
Bearing Hard Stops are At ~ +/- 150 Micrometers
Slide 41
40 Magnetic Bearing Bandwidth Chopper De- Levitated Orbit Plot
After August Shutdown Plot courtesy of Bill McHargue 40
Slide 42
41 Magnetic Bearing Bandwidth Chopper Levitated Orbit Plot
After August Shutdown Plot courtesy of Bill McHargue 41 This
measurement could not be made previously with the T 0 Chopper
running as it was here. The Mag Bearing limits would shut down the
levitation to prevent damage.
Slide 43
42 Final Results 42 Current vibration run levels are
satisfactory for long term operation. Bandwidth Chopper runs
satisfactorily while T0 is also running. Base stiffness plays a
very important role in vibration levels. Further work is proceeding
to tweak mechanical components and processes to achieve lower
vibration values and forces generated by the choppers under the
guidance of Bill McHargue.
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43 Summary 43 Similar design on Corelli was also modified based
on the findings for VISION. Corelli still under construction, but
plate had already been installed. Timely response, excellent
support from SNS ( project management, engineering and
maintenance), and a full team atmosphere all contributed to the
successful diagnosis and repair.