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Companion Guide to the ASME Boiler & Pressure Vessel Code, Volume 2, Second Edition: Criteria and Commentary on Select Aspects of the Boiler & Pressure Vessel and Piping Codes

K. R. Rao
K. R. Rao
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ASME Press
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Chapter 36, authored by Frederick J. Moody, covers fluids. Frederick is a recognized authority in the field of fluids; he explains briefly the force predictions from fluid phenomena and behavior, which are significant in the formulations and criteria employed in the ASME B&PV Code. He focuses on the nature of fluid forces imposed on vessels and piping systems from the standpoint of designers, who require guidelines for both the design and operational recommendations of fluid-transport systems. Fluid forces are the result of pressure and shear phenomena and are caused by the energy transfer at pumps or turbines or by disturbances arising from sources such as valve operation, pipe rupture, vapor-void collapse, and the motion of the frame to which the system in question is anchored. A fluid disturbance generally occurs over a predictable time period, and the fluid may respond simultaneously (bulk-flow response) or in a propagation sense (waterhammer response), depending on the system geometry. The nature of bulk-flow and waterhammer responses is significantly different, making it essential to identify the specific fluid response before calculating the resulting forces.

With appropriate equations and references, Frederick covers the basic formulations resulting in fluid forces. He describes the nature of such fluid forces as hydrostatic forces and pressure, as well as shear forces from fluid motion. Predictions made of fluid forces of concern in boiler and piping design are from pressure and shear within internal-flow systems. However, fluid forces are of significant concern in external-flow systems as well, where structures are sub-merged in fluids. Frederick discusses disturbance sources, including motor- or manual-operated valves, safety-relief valves, check-valve closures, pipe ruptures, liquid-column impact at area contractions, liquid-column separation, condensation-induced waterhammer, centrifugal pumps, pipe movements, positive-displacement pumps, gas cushions, and vortex shedding. Frederick also addresses bulk-flow and propagative-flow modeling in pipes, the estimation of fluid-flow forces in pipes, and fluid forces, such as acceleration and standard drag forces, on submerged structures.

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