Metallurgical failure analysis was requested after an acetylene gas manufacturing plant exploded. An examination of the various parts of the acetylene producing equipment was requested. The accident investigation focused on the gasket joint in a fill hopper as the probable source of leaking acetylene gas. Testing revealed a defective flange design. Design analysis and exemplar flange testing showed that the acetylene gas fill hopper gasket would squeeze out of the joint under normal operating conditions resulting in a physical gap through which the acetylene gas could leak.