L51847 Fatigue Strength of Seamless Line Pipe and Modern ERW Line Pipe

Abstract

To resolve the question as to whether or not ERW pipe might prove inferior to seamless pipe in terms of resistance to cyclic stresses, the PRCI member companies decided to fund the project described herein to assess the performance of ERW pipe versus seamless pipe. Presented herein are the results of a research project on the serviceability of seamless line pipe and modern high-frequency-welded ERW (electric-resistance-welded) line pipe. Full-scale samples of both kinds of pipe were subjected in a laboratory environment to pressure cycles simulating hundreds of years of service. Four samples of ERW pipe and one sample of seamless pipe were tested. Each sample consisted of a 20-foot length of the material fabricated with end caps. Coupons were cut from the remaining pieces to accommodate tensile and impact tests and base-metal metallography. The 20-foot specimens were subjected to pressure cycles ranging from a minimum of 100 psig to the pressure level corresponding to 46 percent of the measured ultimate tensile strength of the material.