BEHAVIOR OF LONGITUDINALLY ALIGNED CORROSION PITS

Corrosion normally results in pits or groups of pits being formed loca lly or over an area of the pipe wall. To assess the severity of such c orrosion, the analytical techniques of the American Gas Association, R eport NG-18, have been used as the basis of existing American and Cana dian pipeline design codes. (1,2) (Ref. 1-ANSI/ASME, Guide for Gas Tra nsmission and Distribution Piping Systems, AGA, Virginia, 1986; Ref. 2 -CAN/CSA-Z184-M86, Gas Pipeline Systems, CSA, Ontario, 1986). These co des address isolated corrosion pits and do not provide guidance for de aling with adjacent pits. As the distance between two corrosion pits d ecreases, they will begin to interact reducing the burst strength of t he pipe. The effect of this interaction is a function of the pit dimen sions, their separation and the loading conditions. This paper summari zes the results of a series of burst tests on pipe-containing corrosio n pits lying on a longitudinal axis. The finite element method is used to analyze the test data and to investigate geometric parameters not considered experimentally.