An essential requirement of most pipeline systems is that they remain in-service even when repairs must be carried out or when branch lines must be added, This need has led to the development of widely accepted practices of making in-service repairs and hot-taps. While both of these practices necessarily entail some risks (i.e., because of the pressures or contents of the systems) experience has shown that they can be carried out safely and effectively. In the case of repairs to defective areas, however, the approach has historically been one of well-justified overconservatism, that is, repairs...
An essential requirement of most pipeline systems is that they remain in-service even when repairs must be carried out or when branch lines must be added, This need has led to the development of widely accepted practices of making in-service repairs and hot-taps. While both of these practices necessarily entail some risks (i.e., because of the pressures or contents of the systems) experience has shown that they can be carried out safely and effectively. In the case of repairs to defective areas, however, the approach has historically been one of well-justified overconservatism, that is, repairs have usually been made only to relatively innocuous defects that might not have caused a problem even if left alone. In many cases costly shut-downs and pipe replacements were effected when an in-service repair would have sufficed simply because the effectiveness of the known repair methods had never been evaluated. This report describes a program undertaken to evaluate the degree of effectiveness of full-encirclement split sleeves and deposited weld metal with respect to repairing a variety of potentially serious defects. The evaluations were made on full-scale line pipe samples containing different kinds of actual and artificial (machine-cut) defects. The ultimate goal was to arrive at criteria for making safe permanent repairs through an understanding of how and why these repairs strengthened defective areas. The study revealed that when properly used, either type of repair can greatly improve the strength of defective areas of pipe.