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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. 10/2013. Problem Statement. Blake, when are you getting here?.
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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 10/2013
Problem Statement Blake, when are you getting here?
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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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 Stockton’s and Bill McHargue’s 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.
Accelerometers Provide a Great Way to Hear what is Going On During Steady State and Transients Test Point 10 (T0), Test 2, April 24, 2012 Test Point 15 (BW), Test 2, April 24, 2012 8s 5s 8s 5s
Vibration Magnitudes Increased with Run Speed but were Generally Repeatable During Drive Up and Coast Down ~ 610 mG 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 Drive Up Coast Down
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
Time Domain Captures Across System Runup PT 4 on the baseplate • Runup PT 5 on the baseplate • Runup PT 14 on the baseplate • Runup PT 17 on the baseplate
Conclusions Prior to August Shutdown ● 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
Conclusions • ●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.
Results • 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 Didn’t Sleep Very Well for a couple of weeks
Data for Point 11 on T-0 Chopper taken in April 2012Spectrum Versus the Calculated ISO Condition Standard Vision Beam Line Chopper Vibration Per ISO Standard level is in the Danger Zone
Data for Point 11 on T-0 Chopper taken in August 2012Spectrum Versus the Calculated ISO Condition Standard 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.
Data for Point 19 on Bandwidth Chopper April 2012Spectrum Versus the Calculated ISO Condition Standard Vision Beam Line Chopper Vibration Per ISO Standard levels are in the Danger Zone and the higher the level the shorter the Mechanical Life
Vision Beam Line Chopper Vibration Data for Point 19 on Bandwidth Chopper August 2012Spectrum Versus the Calculated ISO Condition Standard 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.
Chart for Balance and Run QualityPer ISO 1940 for T0 Values • 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.
Chart for Balance and Run QualityPer ISO 1940 for Bandwidth Chopper Values • 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.
Magnetic Bearing Bandwidth Chopper De-Levitated Orbit Plot Before August ShutdownPlot courtesy of Bill McHargue The Bearing Hard Stops are At ~ +/- 150 Micrometers
Magnetic Bearing Bandwidth Chopper De-Levitated Orbit Plot After August ShutdownPlot courtesy of Bill McHargue
Magnetic Bearing Bandwidth Chopper Levitated Orbit Plot After August ShutdownPlot courtesy of Bill McHargue 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.
Final Results • 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.
Summary • 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.
