A Comprehensive New Look at Type B Sleeves

Abstract

Type B full encirclement steel sleeves have been used for the past fifty-plus years as a viable repair method for most, if not all, features encountered on a pipeline. A Type B sleeve includes an in-service weld at both ends of the sleeve. The science behind performing these welds in a safe manner has greatly evolved over the past 20+ years. However, many of the original concepts regarding the design and application of a steel sleeve have not been further examined since the original research on the subject. This paper investigates a series of sleeve circumstances to better understand the long-term integrity of the common repair method. The circumstances examined within this paper include: the effect of a fabricated sleeve vs split pipe, the influence of the Bauschinger effect on fabricated sleeve properties, the effect of filler material applied within a dent, the effect of steel sleeve fit-up, and the influence of a mill groove relief for a longitudinal backing strip. All test configurations examined confirm the long-term integrity of a Type B sleeve, however, the information presented in this paper from the above tests can be used when utilizing a Type B sleeve as a permanent repair. A combination of sub-scale and full-scale tests were performed to fully investigate the circumstances mentioned above. Sub-scale tests were performed to evaluate the Bauschinger effect, which indicated minimal effect from the fabrication processes of the sleeve. Full-scale tests were performed for the remaining circumstances. Through a series of one-for-one comparison tests, a fabricated steel sleeve performed in an equivalent manner to split pipe. The application of filler material, and the application of a suitable filler material, had a large effect on the load sharing of the repair. During this test protocol, tight fitting sleeves resulted in a life approximately 3.5 times longer than one installed in a loose manner. While a mill groove did not affect the life of the sleeve, it does result in a tighter fitting sleeve, shown to have a significant benefit if the sleeve becomes pressurized.