Anatomy of the Bedplate Design
Design Guidelines
Perform design tasks to highest industry standards
Gale Force Designs conducts all tasks to the latest industry best-practices. This includes measuring and developing design loads using the IEC 61400 suite of wind turbine standards, as well as the GL Guidelines for wind turbine design, and IIW Fatigue Assessment Recommendations.
Experience
Over a 100 years of engineering,
manufacturing & servicing experience
Gale Force Designs (GFD) engineers have a combined 50+ years of wind turbine design experience. Our chief design engineer published his PhD dissertation on sources of wind turbine fatigue. Our chief test engineer has conducted loads measurement campaigns on turbines from 1 kW to over 200 kW in size, and performed accelerated fatigue tests on a wide array of turbine components. Our supply chain team has over 40 years experience manufacturing and assembling heavy industrial machinery including wind turbine components. GFD personnel also have over 18 years of experience servicing as well as designing tools and procedures for servicing Endurance wind turbines.
Load Determination
Determine accurate loading
Loads were measured on a highly-instrumented E3120 wind turbine operating at the Windward Engineering test facility, using strain gauges located on the blades, main shaft, tower and other locations on the turbine. Loads were collected for normal operation from 2 to 23 m/s, during high-wind braking, and during intentionally induced overspeeds. There are no substitutes to load measurements on an operating turbine for verifying assumptions and for uncovering the unexpected turbine behavior or high loading.
Load Selection
Develop a worst-case design scenario
Measured loads were mined to extract the worst-case combinations in order to develop a design condition that reflects the most challenging wind site. This accounts for extreme turbulence, vertical winds, extreme wind shear, yaw errors, as well as frequent grid outages. This approach is taken to ensure that there is no location where the component cannot withstand a lifetime of operating conditions.
Baseline Analysis
Understanding the failings of the existing design
Although we don’t have access to the details of the original bedplate design we do know that it is failing, where it is failing and how it is failing. Understanding the known problems is critical when designing a retrofit. Analysis of the existing bedplate also gives an indication of how much stronger the GFD bedplate is. Theoretical calculations show the GFD bedplate has a fatigue life orders of magnitude longer than the original Endurance bedplate. Fatigue life estimates are validated through accelerated fatigue testing of both the OEM and GFD bedplates.
Finite Element Analysis (FEA) Modeling
Input loads and design criteria shape the design
A solid model is created using the design and manufacturing criteria. Input loads are then applied to the FEA model to determine stress and ultimately fatigue resilience and fatigue life. An iterative design process is used to optimize the design. Once the design is finalized a pre-production unit is built and the FEA stress analysis validated to ensure that any discrepancies between the built component and the computer modeling don’t compromise the desired design life.
Material Selection
Utilize the proper materials in construction
Material selection is critical in design to ensure quality that consistently meets requirements. Gale Force Designs works closely with our suppliers to develop our designs using quality materials that can be readily sourced. Our selection of plate material as opposed to structural tubing is one such decision based on quality assurance.
Manufacturability
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Simplify fabrication requirements
Equally important as designing to expected loads and material properties is designing for manufacturability. Utilizing simple, common fabrication techniques as well as avoiding exotic materials helps ensure consistent quality and workmanship. Avoiding complex welds, for example, provides confidence that the fabricated design will perform to design expectations.
Weld Design
Design with Minimal and Simple Welds
It is well understood that welds present a challenge in designing for fatigue. Welds themselves, and the heat-affected-zone around them can compromise the material properties of a component. This is why fatigue cracks are often discovered in or near welds. Gale Force Designs seeks to minimize welds in the critical load path, avoid compound welds (multiple welds meeting at a single point) in the structure, and to keep any necessary welds simple and easy to fabricate. Welds are often inevitable in a complex structure, and any welds that are required are managed and accounted for in the structural loading analysis.
Smoothly Transfer the Loads
Avoid sharp corners and complex geometries
Sharp corners present stress amplifiers in a structure. It is critical to avoid such corners or steps in the critical load path of a structure, or to account for the resulting stress amplification (which can be as high as three times or more!) in the design. This is why you will not find any such sharp corners or steps in the Gale Force Designs bedplate.
Building it Right
Supply chain management
Having confidence in your design is only half the equation. Having confidence that your suppliers can deliver on your design requirements is the other half. Gale Force Designs ensures confidence in our supply chain by choosing suppliers with wind turbine manufacturing experience, utilizing ISO certified suppliers, using traceable materials, and auditing our suppliers consistently. This ensures our parts are built to specifications and perform as designed.
Test Fitment
Confirm fit of replacement parts
In the virtual world components are designed to fit perfectly, unfortunately the real world isn’t always as forgiving. Any wind turbine component must fit into the real world assembly. This requires that all parts meet required tolerances for fit and finish. Gale Force Designs tests all new parts to ensure they will properly fit into the assembly as expected.
Proof Testing
Testing for a 20 year fatigue life
Gale Force Designs believes that no design is complete until it has been thoroughly tested. The Gale Force Designs bedplate is designed to be a lifetime replacement for the E3120, so we tested it using an accelerated fatigue life test rig that applied 20 years worth of extreme cyclic loads over a period of a few months. The bedplate completed testing with no signs of fatigue cracks anywhere in the structure. Gale Force Designs is confident that our bedplate provides customers with a permanent solution for the E3120 wind turbine.