Solutions to Mechanical Vibration Issues
GMC Presentation: Oct 7, 2013
Phase 2: Scrubber & Suction Bottle Vibration Control
Wally Bratek, Principal Engineer
Kelly Eberle, Principal Engineer
Joshua Shaver, Atmos Energy
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Acknowledgement to the Project Team
The following companies donated funds and staff
participation during this project.
Phase 2: Project Sponsors
• Dresser-Rand – Martin Hinchliff
• Atmos Energy – Joshua Shaver
• El Paso
• Cameron
• Ariel Corporation
• Exterran
• Compressor Systems Inc
• Valerus
• Propak
• Boardwalk
10/7/2013
© Beta Machinery Analysis
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Phase 2: Scrubber & Suction Bottle Vibration
Scrubbers and Suction Bottles are a common area for vibration problems and fatigue failures.
Suction bottles may
have high vibration and
develop cracks in
cylinder nozzles.
Vertical scrubbers
may have high
vibration leading to
small-bore
instrumentation
failures.
5/15/2013
© Beta Machinery Analysis
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Project Overview, Agenda
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Developed “best practice” recommendations to avoid vibration
problems.
Conceptual design, detail design, and tested 2 products:
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Vibration Absorber – completed.
Damper Link – ongoing/extension (2013; proposed 2014 project)
Report – available late 2013
Vibration
Absorber
5/15/2013
Damper
Link Brace
© Beta Machinery Analysis
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Best Practices
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Many problems can be avoid through better design practices
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Layout considerations
Fabrication techniques
Installation methods
Optimization, project management
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Developed by Project Team
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Provided input/content for GMRC/ACI High Speed Guideline
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Valuable for packagers, OEMs, owners, and vibration design
consultants
5/15/2013
© Beta Machinery Analysis
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Product #1: Vibration Absorbers
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A vibration absorber is a
small mass that is
attached to a larger
vibrating system
Adds “sacrificial” degree
of freedom to the system.
Based on old
technology/patents
Crude designs sometimes
applied by field vibration
analysts (but often found
failed)
Cancels vibration at
resonance frequency,
creates 2 lower-amplitude
resonant frequencies
5/15/2013
© Beta Machinery Analysis
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Problems with Existing Vibration Absorbers
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No products are readily available on the
market for piping/compressor applications.
Some successfully implemented designs are
very expensive, and not practical for
compressor packages.
Past designs have a reputation for failing
(absorber fails due to excessive stress)
…due to lack of proper design.
Designs were not able to be field adjusted.
The GMRC Vibration Absorber addresses these
market/technical issues
5/15/2013
© Beta Machinery Analysis
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Design: How It Works
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Based on leaf spring concept
No stress concentrations, designed to have
infinite life
Adjustable mass and mass position (to
achieve desired frequency and separation)
Clamp-on design, easy to implement.
Magnetic and weld-pad attachment methods
could also be used.
5/15/2013
© Beta Machinery Analysis
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Advantages of GMRC’s Vibration Absorber
Easy mounting to small
and large diameter vessels
• 5600 PSI pk dynamic stress
in plate at measured
vibration amplitudes.
• Since no stress
concentrations, stress is
acceptable.
Interchangeable
mass/spring
Slotted holes in spring –
field adjustable
5/15/2013
© Beta Machinery Analysis
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Changing the Mass Ratio Has Benefits
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Mass ratio can be adjusted
Provide options for difficult applications
Sizing support required
Different Mass Ratios Will
Change the “Frequency Shift”
5/15/2013
© Beta Machinery Analysis
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Vibration Absorber Test at Beta
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Vibration absorber has
been manufactured and
installed on vertical
scrubber, anchored to
concrete
VFD/Rotating Weight
Shaker Excitation
Measured vibration of
scrubber and absorber
5/15/2013
© Beta Machinery Analysis
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Vibration Absorber
5/15/2013
© Beta Machinery Analysis
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Vibration Measurements on Scrubber and Absorber
Vibration on the Absorber.
The unit is designed and tested to
withstand these high vibrations
for “infinite life”
Vibration on the
Scrubber:
Reduced from 4 ips to nil
5/15/2013
© Beta Machinery Analysis
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Vibration Absorber Endurance Test
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Ran at design absorber amplitude, 10 IPS PK
17.9 Hz, 7 Days = 1.08 e7 cycles
• Since the number of cycles
completed is beyond the fatigue
limit asymptote, the low-stress
design will last forever (theoretically
speaking).
• No cracks in flex plate, or loosening
of hardware after 10 million cycles.
© Beta Machinery Analysis
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Atmos Energy - Vibration Absorber Field Test
MNF (Bump Test) Data, Unit Inlet Piping
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2-Throw, Arrow compressor, Groesbeck, TX.
Installed on the unit inlet piping
Wide Speed Range (1300 – 1800 RPM)
Extreme vibration at this frequency (9 ips)
MNF with no absorber is 43.25 Hz
MNFs with absorber are now 36.75 and 47.75 Hz.
© Beta Machinery Analysis
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Atmos Energy - Vibration Absorber Field Test
Peak Hold/Speed Sweep Data, Unit Inlet Piping
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Vibration Absorber reduces vibration by greater than 50%.
Works across entire speed range (1300-1800 RPM)
Baseline Measurements, No vibration
absorber, 9.2 IPS.
Vibration Absorber Installed, 4.0 IPS.
© Beta Machinery Analysis
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Summary of GMRC Vibration Absorber Advantages
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No braces required, no “ground”
structure needed
Relatively easy to select the right design
(some knowledge is necessary)
Readily available to solve vibration
problems
Cost effective, simple design
Can be used on piping systems and
vessels
Field adjustable
Won’t fail from excessive vibration
Designed for wide variety of sizes
Fixed and Variable Speed Applications:
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• Vibration effectively
canceled at original
resonant frequency.
• Reduction of vibration
at all speeds.
Ideal for fixed or narrow speed range
Also applicable for wide speed range.
Vibration cut in half (acceptable for many
applications)
© Beta Machinery Analysis
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Vibration Absorber Limitations and Next Steps
Limitations:
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Designed for 1 frequency/direction. If there are multiple vibration modes,
vibration absorber may not be practical.
Reduced amplitude of vibration may still be too high in some cases for
variable speed applications.
Next Steps:
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Design details will be available to industry in the final report
Beta can supply absorber on field applications
Further refinements are being evaluated (damping), but not required
Valuable solution during design stage (for resonant scrubbers)
5/15/2013
© Beta Machinery Analysis
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Product #2: Design Goal
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Many problems occur because mechanical resonance cannot be avoided.
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Traditional braces are not effective because they simply shift the vibration to
a higher frequency.
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Industry needs a device to dampen the vibration.
5/15/2013
© Beta Machinery Analysis
Advantages of Damping over Traditional Support
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Traditional Support:
Adds stiffness, increasing the MNF
Resonance will still occur (at higher frequency)
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Damping + Support:
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Damping will suppress vibration response (broad band,
including resonance)
Adds some stiffness (not primary role)
Higher damping = very large reduction in vibration amplitudes
Much smaller support than traditional “beefy” support
Traditional Support
5/15/2013
© Beta Machinery Analysis
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Product #2: Damper-Link
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A small brace (support) that contains damping material
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Damping applied in shear
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Damping absorbs vibration
Damping Material – absorbs
vibration in shear
© Beta Machinery Analysis
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Damper-Link Development
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A search of applicable damper products was completed during
phases 1 and 2 of this project.
A supplier of “damper links” was identified. This technology is
based on an viscoelastic material applied in shear.
The supplier participated in the
project by providing application
advice.
Beta Machinery Analysis was not
able to gain full access to the
technology used in the damper
link.
5/15/2013
© Beta Machinery Analysis
1.6mm Viscoelastic Material
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Potential Applications for Damping Support
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Particularly helpful for variable speed machine (compressors and
pumps)
Broadband damping will ensure vibration is suppressed for all
excitation forces, frequencies:
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Steady state
Transients (machine start, stop, changes in conditions)
Applications:
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5/15/2013
scrubber
bottles
piping
cylinder supports
small bore piping
© Beta Machinery Analysis
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Damper Link Details
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Viscoelastic material does not fatigue, can withstand large
deformation, and is self repairing when broken.
Broad-Band Vibration Reduction
Hysteretic damping model (not viscous) Modeled as complex
stiffness.
Environmental factors like UV light, excessive temperature (100+
C), dirt and oil can damage viscoelastic material.
Typically indoor temperatures of 10C to 40C inside are acceptable.
© Beta Machinery Analysis
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Product Testing: 2012 and 2013
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Purchased prototype design for testing on suction bottle
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5 month delay in getting samples (from Sweden)
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DR Testing (December 2012)
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Beta Shop Testing (Feb 2013)
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Installed on compressor with high vibration
Some disappointing results
 Stiffness helped
 Damping doubled, wanted 5x or 10x
Built test stand
Tested using shaker and at different temperatures
Promising results
Testing at Atmos (Josh Shaver)…(Sept 2013)
5/15/2013
© Beta Machinery Analysis
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Damper Link Test at D-R (Painted Post)
5/15/2013
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Conclusions From D-R Test of Damper Link
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Field data showed 50% reduction in vibration; additional 1%
damping with damper link braces
FE Simulations determined that increase in damping of 1.7% would
be required to match field amplitudes
Disappointing Result. Damping increased and vibration reduced
but not as much damping as we had expected
Original Vibration
5/15/2013
© Beta Machinery Analysis
Vibration with
Damper Link Braces
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Additional Test of Damper Link at Beta
Initial results with braced
scrubber indicated very stiff
link, low damping.
5/15/2013
© Beta Machinery Analysis
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Heated Damper Link Brace
Heat applied by (2) 50 watt electric
warming blankets. Temperature
measured with thermocouple.
5/15/2013
© Beta Machinery Analysis
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Scrubber Bump Test Results - Exciting Results
No Brace Installed
Braced, 72 F
Braced, 104 F
Braced, 116 F
Braced, 118 F
Braced, 121 F
Braced, 124 F
Braced, 129 F
MNF
20 Hz
36.9 Hz
35.8 Hz
34.4 Hz
33.6 Hz
31.9 Hz
30.3 Hz
28 Hz
Damping
(% critical Damping)
2.0%
1.8%
6.3%
11.6%
13.7%
16.8%
18.6%
18.0%
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MNF (Hz)
12
33
10
31
8
Damping Ratio (%)
14
35
6
29
4
27
2
25
0
70
80
90
100
110
120
130
Damper Link Temperature (F)
5/15/2013
© Beta Machinery Analysis
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Scrubber Bump Test Results
Damper Link at 72F
5/15/2013
© Beta Machinery Analysis
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Scrubber Bump Test Results
Damper-Link at 121F
5/15/2013
© Beta Machinery Analysis
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Atmos Energy – Damper Link Instron Load/Deflection Tests
Completed by Josh Shaver, Danny Athar
Steel Brace
Typical Damped
Response
(3M 4004)
Damper-Link Materials Tested:
• Black Neoprene
• 3M 4004
• 3M 4504
• 3M VHB
• 3M 2552
• 3M 3939
Hysteretic (material) damping,
characteristic of visco-elastic materials.
Based on Instron Tests, (2) Materials selected for field brace Installation
© Beta Machinery Analysis
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Atmos Energy - Damper-Link Field Test
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Site Identified for DamperLink Installation
2-Throw, Arrow compressor,
Groesbeck, TX.
3.7 IPS vibration (48 Hz)
measured on suction piping.
Analysis confirms elevated
vibration levels due to cylinder
stretch excitation.
© Beta Machinery Analysis
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Atmos Energy - Damper-Link Field Test
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Brace fabricated by Atmos
Energy
Simulations showed
promising results
© Beta Machinery Analysis
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Atmos Energy - Damper-Link Field Test
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(2) Braces Installed. (Neoprene and 3M
VHB 4991)
Thanks also to Atmos personnel
David Link and Robert Millward for
assistance during testing.
© Beta Machinery Analysis
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Atmos Energy - Damper-Link Field Test – 3M VHB 4991
-Peak Hold/Speed Sweep Data (1300 – 1800 RPM), Suction Piping
Baseline Measurements, No brace.
4.3 IPS, 1% Damping
VHB 4991 Brace Installed
2.1 IPS, 2.5% Damping
© Beta Machinery Analysis
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Atmos Energy - Damper-Link Field Test – Neoprene
-Peak Hold/Speed Sweep Data, Suction Piping
Baseline Measurements, No brace.
4.3 IPS, 1% Damping
Neoprene Brace Installed
2.5 IPS, 2% Damping
© Beta Machinery Analysis
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Atmos Energy - Damper-Link Field Test – 3M VHB 4991
-Bump Test of Brace Itself, Vertical Direction
3M VHB 4991…Potential for 10%
damping.
Conclusions from Damper-Link Testing at Atmos Energy Facility:
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Installed braces reduced vibration significantly from baseline, increase in
damping from 1 to 2.5%.
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Atmos Damper-Link braces have potential to add up to 10% damping.
© Beta Machinery Analysis
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Conclusions From Damper Link Testing
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The 3rd party designed Damper Link provided excellent results when at
a higher temperature. The Atmos design showed positive results, but
design and application needs refinement.
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Broad band vibration reduction
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Stiff attachment methods are required with Damper Link
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If application problems could be solved, this could be a very promising
solution (temperature and endurance testing)
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More work is required before this could be commercialized
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Potential project extension in 2014
5/15/2013
© Beta Machinery Analysis
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Damper Link Options for New Project
1. Conclude the project and finalize the report.
2. Extend the project to continue research on the damping product.
The proposed plan would involve:
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5/15/2013
More investigation into the sizing and modeling of the damping
material. Identify if the damping brace can be properly
designed for required temperature range.
Investigate alternative suppliers for this material.
Design 2-3 different versions of the damper link for shop
testing. This would provide a better understanding of the
temperature limitations, stiffness, and mounting implications.
Atmos has volunteered to test the damper link properties using
their Instron machine. This would provide valuable dynamic
stiffness information.
Design test to accurately measure/control temperature;
characterize damping and stiffness as function of temperature.
More detailed investigation on life expectancy.
© Beta Machinery Analysis
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Comparison of Vibration Control Devices
Advantages
Vibration ABSORBER
Damper Link SUPPORT
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Easy to install (no support required)
Easy to select the right size and tune in
the field
Moderate vibration across speed range
Parts readily available “off-the-shelf”
Sufficient reduction in vibration for many
applications
Cost effective ($1500 -$3500)
Very long life
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Must be sized/tuned correctly
Not applicable for severe vibration
problems
Designed for 1 frequency/direction
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Challenges;
Limitations
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10/7/2013
© Beta Machinery Analysis
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Effective across wide
speed (frequency) range
Potentially very large
reduction in vibration – up
to 10X!
Ideal for complicated,
resonant applications
Avoids the need for tuning
Requires brace to ground
(stringent mounting
requirements)
Life expectancy is not well
understood
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Project Summary
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Best Practices – valuable to avoid many problems in the design
stage.
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Two new product ideas to solve vibration problems (field verified)
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Valuable information on damping technologies that have appeal for
many applications.
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Extra time/money spent on project than originally budgeted but
overall a worthwhile and interesting project.
5/15/2013
© Beta Machinery Analysis
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