Pressure-Containing Sleeve Alternatives

The work described in this paper was completed to assess the expected performance of various repair sleeve configurations on an NPS 30, Grade X70 pipeline. A total of ten sleeve variations were studied, and these included sleeve-on-pipe, sleeve-over-collar, and sleeve-over-double collar configurations. The comparisons were based on the stress results of axisymmetric finite element modeling of the sleeve geometries, and included examining sleeves with different thickness, models with and without a gap between the sleeve and the pipe, and cases in which the annulus between the sleeves and pipe were either pressurized or not pressurized. Complementary tasks involved with this work included the specification of recommended epoxy materials and steel grades for reinforcing sleeves. The results of the analyses are presented in terms of contour plots of stress at the maximum operating pressure of the pipe, showing the general stress distribution and indicating areas of stress concentration. This study demonstrates how the loads vary amongst the different sleeve types, and shows how variations in geometry and loading conditions between models affect the operating stresses.