Bend limiters improve cable performance

Working cables are often subject to tensile loads with high side loads resulting in large bending moments. These transverse loads and flexing motions reduce the life of cable systems. To accomodate these loading conditions a bend limiting or Bending Strain Relief (B.S.R.) device can be added to the cable termination system. These devices incorporate support features to resist transverse load and minimize bending distortion, thus increasing the life and usefulness of the cable. This paper reports on an experimental-analytical effort on the behavior of Bending Strain Relief devices for underwater cables. Analysis of cables with B.S.R. devices rerequires a knowledge of the bending stiffness of individual components. The construction of the cable from various helical elements and the numerous modes of reinforcing mechanisms used in the supplemental support device offer a real challenge to meaningful design-analysis efforts. Computations and test results for models and several prototype designs are included. Bending fatigue data is presented which demonstrates the beneficial effort of bending control devices for specific cables and hardware. The use of supplemental B.S.R. hardware in conjunction with available termination fittings offers numerous advantages in obtaining efficient cable support hardware for a wide spectrum of load combinations. Results and design examples are given for typical offshore petroleum production and tow cable devices.