Design optimization and reliability enhancement for hydraulic-release couplings of pillars and substructures for fixed marine platforms

Abstract

Object and purpose of research. This paper discusses hydraulic-release couplings of pillars and substructures for fixed marine platforms. This topic is relevant because at some platforms hydraulic-release couplings contribute to crack initiation. The purpose of this study was to work out design solutions that would mitigate residual strains so as to preclude pillar cracking due to hydraulic release, thus making the pillars more durable. Achieving this purpose will make hydraulic release more suitable for routine operation, and will also make Russian manufacturers of fixed marine platforms more independent from Western patent holders of hydraulic release system designs. Subject matter and methods. Design solutions suggested in this study were tried out through finite-element simulation of hydraulic release process. Plastic straining of pillars was taken into account by means of a linear kinematic model of hardening. Main results. The study covered seven possible designs of hydraulic release units and yielded load diagrams for both plastic straining of pillar over the entire working cycle of hydraulic release (with indication of maximum accumulated plastic strain) and subsequent pillar pull-out from substructure. Conclusion. The study yielded an optimal design solution for hydraulic release joint that both reduces plastic straining of pillar and increases axial stiffness of the joint itself.