Weak-Link Analysis of Motor-Operated Butterfly Valve

The purpose of this paper is to address the structural integrity of the motor operated butterfly valve assembly by providing the methodology and equations to quantitatively determine the permissible component load in the load path from the operator to the valve. The weak link analysis is to determine the maximum allowable torque on the butterfly valve by equating the stresses caused by the torque and seismic load with the appropriate allowable stress value, and then the unknown torque is solved. Analysis methods are based on classical static force balancing equations and on classical axial, shear, and bending stress equations using the worst possible load combinations including seismic loads resulting from design basis earthquake.