Feasible Engineering, Detail Design Engineering, Fabrication, Inspection and Grouting

The Client

Nautec was appointed by PTSC Mechanical and Construction Co., Ltd (PTSC) to design, supervise fabrication and grout structural clamps for the repair of two damaged diagonal members of a newly installed platform in Vietnam.

The Scope

The job involved Feasible Engineering, Detail Design Engineering, Fabrication, Inspection and Grouting with Ultra High Performance Cementitious Material NaX® Q140; a specialist high strength grout especially formulated and developed for offshore applications.

The Challenges

The Detail Finite Element Analysis was carried out to understand stress reduction before and after clamping. The strengthening methodology was designed according to API RP2A WSD in order to improve the fatigue life of the platform.

The Services

The clamps and the new diagonal member were fabricated by the main contractor in Vietnam, while supervised by Nautec’s engineers who assisted the installation of the clamps offshore. A total of 24 clamps with steel usage of circa 80tonnes have been installed and as a result of thorough onshore preparation the installation ran smoothly with high client acceptance and satisfaction.

Client Benefit

The clamps were used to reinstate a new 813mm diameter diagonal member connected to an X-node at EL-32m and a K-node at leg joint EL-45m. The jacket leg was 1558mm in diameter. Another vertical diagonal member was repaired using grout infill and encased with a straight clamp to relieve stress concentration at the damaged perforation. The analysis and design of the clamps and new diagonal member has been verified and approved by Bureau Veritas.

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