scope:

Two vessels with torespherical heads were pressurized to destruction. The objective was to determine pressures at which observable or measurable indications of failure could be detected. For Vessel 1, the only observable action was a slow formation of some waviness of the knuckle profile. It lost pressure at 700 psi when a crack developed at a nozzle weld at the bottom of the shell. For Vessel 2, no indication of any sign of failure was observed until it burst at a pressure of 1080 psi by ductile fracture along the longitudinal weld of the shell. After-test examination revealed no measurable waviness of the knuckle. The main conclusion is that there is a problem in the applicatioan of the double elastic slope collapse criterion to torispherical heads. It was determined that when using this criterion a collapse pressure signaling excessive deformation cannot be determined with any certainty. For a material with sufficient ductility, the use of an estunated vyrst oressyre aooears oreferavke, A design criterion based on the membrane stress at the crown of a torispherical head reaching the ultimate tensile strength is proposed. Publication of this document - WRC Bulletin No. 414 was sponsored by The Pressure Vessel Research Council of the Welding Research Council, Inc.