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Development of a ball valve with PVD-coated metal-to-metal sealing mechanism

conventional ball valves are based on elastomeric sealing technologies which exhibit restricted wear resistance in the presence of network impurities while re-quiring high operating torques. in the described investigations, the elastomeric sealing of a 2-inch floating ball valve was replaced by a metal-to-metal seating for attaining specific application requirements, without major dimensional changes. in order to avoid the use of elastomerics and achieve a high performance rating of the valve (Class VI shut-off), computational fluid dynamics (CFD) simulations were employed to predict the optimum contact geometry of ball/seating. A high accuracy contact was obtained through precision turning of the hard-ened metal shell (ball seating) and by grinding of its counter ball body. Both com-ponents, ball and seating, were appropriately heat treated and subsequently coated with a nanostructured diamond like carbon (DLC) coating, applied by physical vapour deposition (PVD) techniques, providing superior surface strength charac-teristics and nearly frictionless operation.