To meet growing concerns about the integrity of mooring systems among oil and gas operators, First Subsea is undertaking the industry's first investigation into mooring systems forging in collaboration with the University of Sheffield's world class Institute for Microstructural and Mechanical Process Engineering (IMMPETUS).

The characterisation of the metals used in subsea mooring is now a 'live' issue for offshore companies around the world. This follows concerns about the engineering integrity of forged metals and their implications for the integrity of shackles, triplates, cable sockets and H-links raised in January this year by the US Department of the Interior Minerals and Management Services (MMS), Gulf of Mexico OCS Region. The objective of the First Subsea two-year research project is to fully understand what happens during the forging process and, in so doing, better characterise the micro structure of forged metals, its relation to Charpy toughness values and the design and integrity of ball and taper connectors.

Ultimately it is expected that the project will lead to the production of a First Subsea standard for characterising the forged materials used in a ball and taper subsea connector that can be used by offshore engineers when specifying their mooring connection systems.

Brian Green, general manager, First Subsea Ltd, commented, ”First Subsea has always taken quality management and adherence to international standards very seriously. This project will ensure our mooring systems continue to set the benchmark for engineering integrity. It will also allow us to work more closely with offshore engineers when they are specifying their mooring systems.”

The MMS announcement followed two separate incidents concerning the failure of a mooring shackle and a mooring system for a MODU. In both cases the manufacturing procedures were thought to have been defective. Heat treatment after forging apparently resulted in a metal unable to meeting the “Charpy” standards for materials “toughness”. The First Subsea / University of Sheffield project will involve establishing the optimum conditions for defining chemical composition and both internal and external quality control of the ingot, pre-heating, forging parameters, heat treatment and testing procedures.

IMMPETUS provides world-leading experimental facilities for hot deformation of metals, through process modelling, materials characterisation and novel materials processing. Dr Bradley Wynne, project research leader, IMMPETUS, commented, ”Although forging is widely used there is little academic research in this area. For this reason this is significant opportunity to review the entire forging process and identify those critical variables that influence large scale forging operations. At the end of the project First Subsea will lead the industry in knowledge of forged materials characterisation.”

Tags: First Subsea Ltd