Due to the tight project deadlines, it was not possible for our client to build prototype valves to test their design modifications for use in a safety critical defence application. Each valve design and size had to be seismically tested using a shaker table. Our approach enabled our client to validate their designs much more rapidly, considering many more variable scenarios and allowed for the minimum amount of physical testing.
The client, a leading supplier of butterfly valves, had been awarded a large order for a range of valve sizes and actuation types. As the valves were to be used in a safety critical defence application, it was vital that they could withstand a range of extreme loadings, including seismic and shock events. A requirement was that each valve design and size had to be seismically tested using a shaker table.
Due to the tight project deadlines, it was not possible to build prototype valves to be tested before long lead items for the full order needed to be ordered. We were asked to validate each valve design for the seismic design spectra that would be used for the shaker table tests. Taking this approach allowed the client to validate the designs significantly earlier than using the “traditional” approach and capture any required design changes prior to manufacture of the test valves. It was also necessary to consider a range of disc positions (open/closed) and valve orientations, as the valves were not all installed in the same direction. As part of the analysis task, the worst-case position and orientation for each valve were to be identified; this would justify the selected testing setup and would allow for the minimum amount of physical testing.
We took the end user’s specification and translated this into a detailed analysis specification. It was critically important that not only the assessment method but also the setup of the model was identical to that used for the actual tests. This required an amount of collaboration with the test house.
Once the parameters of the test had been confirmed, we used ANSYS DesignModeler in order to simplify the valve geometry to create a computationally efficient model. A critical part of the geometry simplification was to ensure that the model response remained accurate whilst removing features and components which were not relevant to the assessment. During the model setup within ANSYS Mechanical, using the ANSYS Parametric Design Language (APDL) graphical user interface, it was also important to define representative connections and interfaces between all the valve components, thus ensuring the load path between components was accurately modelled.
In order to capture the seismic response of the valves, a response spectrum analysis was used. The first part of the analysis involved running a modal analysis which calculated the natural frequencies of the valve and also the relevant modal mass. The results of the modal analysis were reviewed to ensure that the response of the components was representative and also that the range of frequencies captured the total mass of the assemblies. Following this stage, the response spectrum analysis was solved using the relevant seismic spectra for each of the orthogonal directions. The results of the analyses were combined using the square root sum of the squares (SRSS) method. Finally, the results were assessed against the relevant allowable stresses. When the manufactured valves were physically tested, they all passed the test successfully.
- We decreased risk by allowing valves to be “tested” in the virtual world prior to manufacture
- We significantly reduced our client’s timescales by removing the need to manufacture and test multiple prototype valves
- We significantly reduced our client’s costs by allowing the minimum amount of testing to be completed to reach a compliant valve solution