=Paper=
{{Paper
|id=Vol-2248/paper11
|storemode=property
|title=Verification & Validation Plan - A Case Study of a Turbine Bucket Design Modification
|pdfUrl=https://ceur-ws.org/Vol-2248/paper11.pdf
|volume=Vol-2248
|authors=Marco Mariottini
|dblpUrl=https://dblp.org/rec/conf/ciise/Mariottini18
}}
==Verification & Validation Plan - A Case Study of a Turbine Bucket Design Modification==
https://ceur-ws.org/Vol-2248/paper11.pdf
Verification & Validation Plan
A Case Study of a Turbine Bucket Design Modification
Marco Mariottini
Gas Turbine Systems Engineering @ Baker Hughes, a GE Company - Florence, italy
marco.mariottini@bhge.com
ABSTRACT ➢ Assure the same parts life (buckets and wheel) and
operation
BHGE, when developing new products, verifies and
➢ Reduce the risk of failure (cover plates)
validates critical system requirements of gas turbine and its
➢ Simplify the assembly procedure
own components before deploying them in the market.
➢ Improve parts management
In this paper a case study of Verification and Validation
➢ Reduce parts cost
(V&V) approach for a gas turbine 1 st Stage Bucket is
➢ Be fully interchangeable with baseline bucket
presented.
One of the main requirement for this component is
SYSTEM REQUIREMENTS: These needs have been translated
operative life, in particular with respect to vibrational
into the following system requirements:
behavior (High Cycle Fatigue): Systems Engineering
1. Typical failure modes shall fall within internal Design
approach for V&V has been applied to compare actual
Practices limits
aeromechanical characteristics versus the ones predicted by
2. Bucket weight and center of mass shall not change (or
Finite Elements Models.
improved at most) not to negatively affect stresses on
As verification technique, an aeromechanical test, named
wheel
“Wheel Box Test”, has been performed on buckets installed
3. Cover plates shall be integrated into bucket casting
on a dummy rotor: preparation, performance and results
4. Interfaces with surrounding components shall not
management of such test are described.
change
Stakeholders’ requirements were finally validated on a real
engine by acceptance endurance test at customer site.
DESIGN DEFINITION: Having considered the bucket as the
INTRODUCTION System of Interest, its features have been drilled down; since
the sequential approach has been utilized, detailed features
In the Oil & Gas Industry, new technology injection is key have been reported in the Vee diagram.
to improve plant production, equipment installation and
maintenance and to increase the lifetime of parts. Machines
usually operate in harsh and tough service conditions and
their components are exposed to extreme thermal and
mechanical loads.
Gas Turbines can be categorized among the most critical
machines operating in an Oil & Gas plant, surely
withstanding the toughest working conditions; they are
employed to provide driving force for compressors and
electrical generators, converting the chemical energy of a
(usually) hydrocarbon fuel into mechanical energy.
The most critical component of a gas turbine is the 1 st
stage bucket: a rotating object, subject to the highest
temperature and mechanical forces. Its purpose is to convert
the thermodynamic energy contained in the pressurized and
hot gases coming from the combustion chamber into a Figure 1 – Vee Diagram [1]
tangential force applied to a wheel, transformed consequently
into shaft torque and then in output power. As per system requirements, new bucket design provides
The bucket herein described has an approximate weight for the elimination of cover plates as separate components,
of 4.5kg, spins @5100RPM on a diameter greater than 1m becoming integrated in the body of the bucket itself, without
and is subject to a pulling centrifugal force of about 65 tons any impact on performances and life cycle of the part.
each (there are 80 buckets on the wheel) and a temperature of It covers the needs for increased quality, reliability and
~900°C. parts management as well as cost reduction: integrated cover
plates allow an easier, faster and error-proof installation
TECHNICAL PROCESSES: STAKEHOLDERS’ NEEDS, (with a reduced number of parts, from 5 to 1) while
SYSTEM REQUIREMENTS AND DESIGN DEFINITION safeguarding full interchangeability with current design;
reduction of part numbers brings a significant improvement
STAKEHOLDERS’ NEEDS: The needs fulfilled by this project in warehouse management and makes the buckets kit cheaper
come, following a market analysis, from the Product than baseline.
Leadership internal to the company; the new bucket shall:
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In Figure 2 a comparison between baseline bucket with Critical, during this phase, was the evaluation of the
separated cover plates (the latter in red) on the left and the architecture of data storage and data sharing procedures:
new design bucket on the right. starting from the raw data, a first elaboration was done
directly by the acquisition personnel, then data was
transferred for the final post processing and data matching.
A final review with Chief Engineers, including data from
previous tests done on baseline bucket, confirmed the
alignment between analytical models and test results, closing
the verification phase.
Figure 2 – Buckets Comparison
VERIFICATION & VALIDATION PLAN
Numerical simulations have been developed and used to
analyze operating thermal and mechanical loads, verify
Figure 3 – Wheel Box Test – Test Cell
interfaces with surrounding components (clearances) and
check the aeromechanical behavior and damping effect VALIDATION – SITE ENDURANCE TEST: the new bucket has
(provided by pins, installed between buckets, that dissipate been then installed on a real engine at customer site for the
vibration energy by friction, reducing vibration amplitude) to validation.
accurately evaluate the robustness of the design and The unit was chosen since it is constantly monitored by
ultimately to verify it against the typical failure modes of a remote diagnostic: a bunch of parameters were selected to be
turbine bucket. kept under control by engineering department, confirming all
A correct aeromechanical evaluation of the bucket is operational parameters inside the limits.
important to avoid the High Cycle Fatigue (HCF) Boroscope inspection was done to verify the interfaces
phenomenon to be catastrophic for the bucket itself (bucket with surrounding components.
failure means GT failure). Completion of several thousands of running hours
Typically, the design of a new GT bucket is verified and validated the aeromechanical behavior (in case of resonance,
validated, from the aeromechanical standpoint, by a Full HCF takes few hours to reach a catastrophic failure).
Engine Test, meaning that an entire gas turbine must be
instrumented, installed on a test bench capable of full CHANGE MANAGEMENT
speed/full load operation and run for the amount of time New bucket has been introduced issuing new part codes and
needed to gather all necessary data: roughly this requires 1 passing through Product Configuration Board (PCB), a
year for preparation and execution and costs around 5M€. process that involves an interdisciplinary team to evaluate all
The application of Systems Engineering principles the impacts of the change: supply chain (supplier
allowed the avoidance of the Full Engine Test in favor of an qualification), warehouse management (old parts depletion),
easier and cheaper aeromechanical test, named Wheel Box fleet impact (service bulletin).
Test (WBT), for requirements verification, followed by and
endurance test at customer site for stakeholders’ needs CONCLUSIONS
validation.
For this project the right definition of a suitable
VERIFICATION - WHEEL BOX TEST: together with system Verification and Validation plan was key from the very
requirements definition, the characteristics of beginning, since the “usual” testing method (engine test) was
aeromechanical test have been developed; among the others, not affordable and, without an alternative, this situation
the main features of the verification method included: would have stopped the project.
- Possibility to test baseline and new design buckets at the Moving from stakeholders’ needs and together with
same time system requirements definition, the V&V plan was
- Possibility to test different damper pins determined, starting the test facility scouting and test
- Possibility to easily change forcing frequencies preparation in the earliest phases of the project.
- Possibility to verify real damping effect (use air instead Test preparation and execution absorbed a quite huge
of oil as forcing mean) portion of resources dedicated to this project, in terms of
budget and engineering efforts, but test outcomes were really
Test facility was scouted, and test campaign was designed satisfying and allowed, for the first time in BHGE, to release
and realized in close collaboration with facility owners; main the design of such a critical gas turbine component without
activities during preparation phase included but were not an in-house full engine test.
limited to: test cell architecture evaluation, interfaces
management, special components design and manufacturing, REFERENCES
data collection system evaluation, safety procedures [1] INCOSE Systems Engineering Handbook: A Guide for
establishment (e.g. LOTO). System Life Cycle Processes and Activities, 4th edition