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Rotating Machinery
Mechanical Solutions, Inc. performs worldwide machinery and fluid system analysis, test, design, and
Research and Development for all types of rotating machinery, reciprocating machinery, pumps, fans, and electric
motors. Particular strengths include impact modal testing while the equipment remains operating, operating deflection shape (ODS) vibration testing,
3D Finite Element Analysis (FEA) for stress & vibration, rotordynamics, Computational Fluid Dynamics
(CFD), and troubleshooting of difficult plant problems.
MSI has led the successful failure investigations of centrifugal, reciprocating, and screw pumps, compressors of all sizes,
steam turbines from 10 MW to 660 MW, as well as aeroderivative gas turbines of various manufacture. A specialty is design auditing of new or re-rated
machinery trains. These audits have successfully avoided start-up problems on behalf of firms in the U.S. and throughout the world.
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What's new?
Mark your calendar
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What's new?
MSI welcomes Dr. Edward Bennett as our Director of Fluids Engineering. He comes to us from Aerojet and
brings with him an outstanding Turbomachinery background. For a more detailed look at Ed, please refer to his resume.
Featured Case Study:
Root Cause Analysis (RCA) – Axial Compressor
Example
In general, MSI’s role in helping to ensure equipment reliability takes place at three levels: a) preconstruction audits and analysis during the design phase
to help prevent problems, (b) using specialized testing and analysis techniques to solve performance, acoustic, vibration, stress, or thermal
problems before failure takes place, and (c) performing root cause analysis (RCA) after a failure. MSI recently performed RCA to determine the root cause of cracks
found in multiple blades on several rows in the low pressure (LP) section of a large axial compressor. The key deliverable was recommendations, supported by analysis
results and experience, for extending blade life.
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To accomplish the RCA, following inspection of the failed components and detailed interviews with End User personnel, MSI performed a detailed 3D Finite Element Analysis
focused on determining the mean and worst-case alternating stresses during normal operation and surge events. Natural frequencies of each single blade and the assembly disk were also determined by
analysis calibrated by non-operating modal testing in order to verify possible resonances in the system.
The cracks were found at the base of
the blades (above the fillets) where they meet the
platform. Based on MSI's RCA, the root cause of the
cracks in the LP section blades was determined to be a
consequence of several surge events that occurred during
uncontrolled shut-downs of the units after power outages
of the self generated power of the plant. These events
generated non-linear loading that was 10 to 20x the gas
bending load at low frequency, which increased the
alternating load producing low cycle fatigue cycles in
the material.
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The plant could not guarantee that the root cause occasional surge events would not be repeated. Therefore, the solution needed to be a design
change to the axial compressor blading, the plant could not guarantee that the root cause occasional surge events would not be repeated. Therefore, the solution needed to be a design
change to the axial compressor blading, along with suggested system improvements.
The Interference Diagram of the disk assemblies did not show potential interferences with any typical direct excitation source such as Blade
Pass Frequency or difference excitation source between rotating blades and stationary vanes. Forced response analysis performed indicated that there was sufficient
separation margin from potential excitation sources, resulting in stress levels that would not lead to a failure of the blade under expected design conditions.
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Contact Analysis. Von Mises stress from combined centrifugal and pressure bending loads.
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The detailed stress and modal analyses performed for each failed blade revealed that the blade designs would be adequate for the normal operating condition of the unit.
However, excessive cyclic stresses near the blade fillet were likely during surge events. There was limited space to place a larger fillet between the airfoil and
the platform to reduce surge stresses and improve the life of the blades. Therefore, different materials were considered for the blades with higher endurance limits
that would allow for considerably more cycles before crack initiation. In addition, an option was suggested that entailed increasing airfoil thickness at the base.
MSI also recommended system and operational modifications to try to minimize the number of surge events. These recommendations included adjusting
the anti-surge system by slightly opening the vent valves before shut down of the unit, relocation of the recirculation valves to improve response during upset conditions,
and suggestions for better maintenance of the recirculation valves. Finally, a sensor system was specified that would monitor potential crack development by sensing a
permanent blade displacement change, as calibrated by MSI FEA results.
Mark your calendar
6/09 - 06/13/08
ASME Turbo Expo 2008
Berlin, Germany
MSI Booth #401
ASME TURBO EXPO
brings together the very best and the brightest in the world-wide
gas turbine industry to present the newest developments and the
toughest problems for solution. There is no other place where you
will find such a concentrated gathering of top level professionals
dedicated to the goals of gas turbine markets!
What attendees have said about TURBO EXPO:
- "The networking opportunities are the best...no other
conference provides the ability to connect and reconnect with as
many key engineers in the industry."
- "[Turbo Expo] provides us with high-quality leads and good
exposure to the right clientele."
- "It is a necessary part of a career in Turbine
aerodynamics..."
Don’t Miss this Opportunity to Attend these
Excellent Training Courses Being Held at the Estrel Berlin prior to
Turbo Expo 2008!!!
June 7 & 8, 2008 -
Gas Turbine Aerothermodynamics and Performance Modeling Course
June 8, 2008 -
Basic Gas Turbine Engine Technology Course Review and Exam
June 8, 2008 -
Gas Turbine Repair & Metallurgy Course
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