EXHIBITIONS
Pioneering a new virtual dimension of valve design
T
imes are changing for valve development and process optimisation. Prototypes are
increasingly being phased out, as making them is time-consuming and expensive. Simulations, in contrast, are already available now and have a promising future. The revolution has been taking place for quite some time now, and will have numerous trends in store. Valves with large nominal diameters pose a great challenge to engineers when designing a prototype. Making one and testing it is a laborious affair. Add time pressure to the picture, making delays unwelcome. Meanwhile, however, things are speeding up. Today, a flow simulation allows manufacturers to construct and produce a large diameter valve faster and easier than before.
Analysis of flow behaviour Ebro, for example, is rather chuffed about this. The manufacturer of industrial valves, drives and automation technology uses FEM calculations to optimise the strength and functionality of its valve components. “Valve
components used to be calculated using strength calculations from recognised technical guidelines, or based on the state of technology,” states chief designer Andreas Kohlscheen. Programmes such as Mathcad and Excel were used here. Meanwhile, CFD programmes for the analysis of flow behaviour are being used. They allow flow behaviour to be optimised, leading to increased flow rates and flow coefficients.
Prototype construction not required Valve manufacturer Mankenberg also knows the use of simulations. “3D simulations make it possible to conduct cost efficient preliminary tests, without constructing prototypes and performing test measurements,” explains Michael Schröter, technical manager Mankenberg. This makes the development process considerably faster. “A new construction can be assessed at a far earlier stage”. There are numerous reasons why valve manufacturers are increasingly making use of simulations. Simulations create “better insight for explaining and coordinating things with customers and project partners,” reports Werner Hartmann, head of sales at Hartmann Valves. Complex components can be represented far more clearly in 3D than in 2D. Errors are prevented thanks to the higher degree of clearness. Design data (CAD) is transferred to a computer- aided manufacturing programme (CAM). This considerably reduces effort for programming the manufacturer’s machines.
Determining edge conditions Valve manufacturer Mankenberg also recognises the value of simulations. How do simulations achieve their results? First, a 3D
model, for example of a valve disk, is created in a CAD programme. The model’s environment is then implemented around it, setting the edge conditions such as body, shaft and seat. “All conditions are then determined for the component, such as pressure, temperature, bed and additional, external loads, like gravity, torque, as well as axial forces,” explains Andreas Kohlscheen, Ebro. “Taking the correct edge conditions and loads into account, the model is analysed in view of sufficient strength in a FEM programme,” Kohlscheen continues. Should there be need optimisation following the first run, the model is redesigned and the process repeated. Modern simulation software offers additional support and routines for such tests. “If the model fulfils all strength conditions, the flow coefficient for various opening angles is determined, in order to simulate the flow behaviour of the disc for later operation”.
Attractive for continuous geometry changes For practically implementing a flow simulation, the geometry is simplified for the simulation, and the flow body is then designed accordingly. Subsequently, the edge conditions are set. “This data is used to start and evaluate the simulation in an own solver,” says Michael Schröter, Mankenberg. The trend is currently going towards cloud-based solutions. “The required licenses are only leased and made available on the servers of the software provider”. Werner Hartmann of Hartmann
Valves sees simulations as especially useful for constantly varying geometries, in order to fulfil any special customer requirements. “3D design is especially worthwhile for custom
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designs”. Nearly none of the analyses conducted by Hartmann Valves can be transferred, as geometry or material vary between components. “Material independent kinematic, as well as stress and strain analyses where the material parameters have a decisive influence, are performed,” adds Hartmann.
Saving research and development costs The results simulations provide are impressing, be it structural mechanics/ dynamics, calculation of temperature fields, or flows. “At the end of all successful simulations stands the actual production of the component with a very high degree of certainty in view its functionality,” declares Andreas Kohlscheen, Ebro. Simulations are especially useful for expensive and complex parts, with high production costs and a long life- cycle. Companies can thus steer clear from costs resulting from changes to and optimisations of the finalised component. Simulations shorten
development time and lower costs. “A flow laboratory with time- consuming scheduling, sample
IMT December 2017 29
Photo: Messe Düsseldorf/ctillmann
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