Abstract: An apparatus and process for monitoring the diameter and length of a helical corrugated metal pipe while the pipe is being formed from a strip of corrugated sheet metal. The apparatus includes a sheet metal strip length sensor located on a corrugated helical metal pipe forming machine. A series of length sensors are located along a formed pipe axis and are responsive to presence or absence of the formed pipe at their locations. A digital computer receives information from the sensors and is connected to various peripheral devices. The process of monitoring the diameter and length of the pipe involves measuring sheet metal strip length, determining presence of formed pipe at the various length sensor locations, and determining pipe length and diameter as a function of sheet metal width and length of sheet metal strip used.