8 Water Hammer Effects on Breathing Stresses for Pipes and Other Components

Hoop stresses are seldom the maximum pipe stresses in a pipe system, but their study is fundamental to the concept of dynamic stresses, since most of the available experimental data to support dynamic stress theory was found for cases of simple, cylindrical, pipe sections. Dynamic hoop stresses are frequently referred to as breathing stresses, due to the pulsating, albeit rapid, motion of pipes subjected to sudden internal pressures. Breathing stresses consist of a primary stress that occurs in the wake of a shock wave traveling the bore of a pipe. In front of the shock wave, precursor waves similar to Rayleigh surface waves also occur, and examples are provided here to describe dynamic hoop stresses along with appropriate derivations.