Swing check valves are used widely in piping systems where sustained flow reversal is not permitted. One common problem associated with such valves is that they can slam-shut. This action can generate severe water hammer and unacceptable overpressure. The dynamic interaction between the valve and the fluid strongly influences the check valve behavior in such a situation. Numerical simulation of water hammer due to check valve slams is hampered by insufficient data characterizing the hydraulic torque on the valve disk. This is an industry-wide problem unresolved at present.; This research proposes a method of characterizing the hydraulic torque on the disk of a top-hung swing check valve. The hydraulic torque is regarded as composed of two parts: the torque created by the through flow on the fixed disk, and the torque resulting from the rotation of the disk. These torques are expressed in the terms of stationary and rotational coefficients, in a manner analogous to the conventional drag coefficient of bluff bodies. These coefficients are established by laboratory tests. The results show that the stationary coefficient is a function of the angular position of the disk and the direction of the through flow. The rotational coefficient is a function of the angle and velocity of the disk, and the magnitude and direction of the through flow.; Separate physical tests were conducted on check valve slam, followed by simulations using the hydraulic torque coefficients established in this research. The dynamic interaction between the valve and the fluid is captured via the moment of momentum equation of the valve disk and the wave propagations in the pipeline. The validity of the approach to characterizing the hydraulic torque is demonstrated by the close agreement between the simulated and measured time traces of the valve disk angle and the pressure at the discharge side of the check valve.
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