ARCA rounds off the proven series of ECOTROL® control valves at the high end with the new development of the nominal size DN 700 (28”). This valve has been specially optimised for use as an anti-surge valve on turbocompressors, but can also be used for all control applications involving liquid and gaseous media.
The requirement profile for the new development was:
• High flow coefficient KVS, which usually well exceeds the delivery capacity of the turbocompressor. The quantities of gas trapped inside the pipelines and heat ex-changers can therefore also be relaxed in a very short space of time upon safety shutdown of the compressor.
• Face to face dimension according to the specifications of EN 558.
• Mechanical resistance to the energy converted at the anti-surge valve and to mechanical forces due to pressure fluctuations or unfavourable pipeline layouts.
• Favourable acoustic characteristic values.
• Short actuating times – usually considerably less than 2 seconds for the complete 0 – 100% valve opening.
The overall length in accordance with EN 558 represents a particular constructive challenge in the case of globe style control valves, especially with large nominal sizes, since the ratio of seat diameter (ideally the same as the nominal size of the valve) to the overall length becomes increasingly unfavourable the larger the nominal size becomes. For this reason the parametric modelling technique using an upfront CAE tool was applied for the first time for the fluidic optimisation of the housing shape.
In this development process the component to be developed is defined (apart from fixed boundary conditions such as the process connections, the wall thicknesses and the trim) by a variable, parameter-controlled geometry. Beyond that, with reference to the target market as an anti-surge valve, the relaxation of an ideal gas with a pressure ratio x = (p1-p2)/p1 = 0.7 and the flow direction ‘flow to open’ were specified. In constant alternation between variation of the geometry and evaluation of the results (in the case of the valve housing the flow coefficient determined by means of CFD), the system converged after more than 60 variants to an optimum solution with a 25% higher coefficient of flow (in comparison with a conventional design).
In combination with the associated spring-return pneumatic piston actuator, which can be operated in both single-action mode and (for significant improvement of the control dynamics while maintaining a defined safety position in case of a failure of signals or power) double-action mode, this valve offers a technically and economically ideal solution for many applications. To learn more.