Date of Award

5-2013

Degree Type

Report

Degree Name

Master of Science (MS)

Department

Civil and Environmental Engineering

Committee Chair(s)

Michael C. Johnson

Committee

Michael C. Johnson

Committee

Blake P. Tullius

Committee

Kevin P. Heaslip

Abstract

Butterfly valves are versatile components widely used in hydraulic systems as shutoff and throttling valves. Butterfly valve components must be able to withstand the forces and torques that are generated with use. Dynamic torque data are usually obtained in a test lab for a variety of steady state flow conditions; however the dynamic torque under transient (unsteady flow) conditions may be significantly different than that found in the laboratory. If a valve is closed too fast, especially in long systems, large transient pressures are generated and travel as waves through the pipeline. These transient waves increase the pressure difference across the valve, which in turn increases the dynamic torque that is applied to the valve. The effects of the increased dynamic torque are more significant in larger butterfly valves since dynamic torque is a function of the diameter raised to the third power. If the increased dynamic torque is larger than the torque that the valve was built to withstand, valve or actuator failure could result. The objective of this research was to examine the effect of transients on dynamic torque in a 48-inch diameter butterfly valve operation as a function of pipe length and valve closure time (starting at full open) and compare the results to traditional steady state dynamic torque data. It was found that longer pipeline lengths along with smaller valve closure times created the largest percent difference in transient dynamic torque from the steady state dynamic torque. This difference was as high as 711% in a 20,000-foot long pipeline when the valve was closed in 36 seconds. Transient effects should be considered in the design and manufacturing of butterfly valves as well as during the operation of the valve once it is installed.

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