Influence of eccentric valves on the vibration of fluid conveying pipes

Abstract

The dynamic stability of motion of fluid conveying pipes has been the subject of numerous studies. Theoretical interest was stimulated by the non-conservativeness of these systems. Design requirements for pipelines and nuclear related systems provided the additional impetus. Recently, the assessment of the probable influence that large, rigid valves frequently encountered on piping systems might have on the behavior of the overall system was required. In spite of the above mentioned wealth of literature, a great paucity of information was found on the influence of lumped masses. Consideration of rotatory inertia is apparently non-available. The motivation and contents of the present study stem from these facts. A variational formulation is followed by a Galerkin approximation that is applied to simply supported and cantilever pipes. Lumped translational and rotatory inertia are introduced. The results are reported for values of dimensionless parameters selected in a representative manner. Substantial modifications on the magnitudes of the frequencies are shown. The influence of the eccentricity is found of greater importance than that of the mass for constant eccentricity factor. The character of the equilibrium configurations associated with vanishing frequencies is a function highly dependent on the mass and eccentricity of the valve. The need for ensuing research on coupled out-of-plane bending and twisting of the pipe system is also established.