New fatigue rules and lower cost designs may evolve from results obtained on this test rig in TWI's laboratory.
Results of a TWI project may lead to cost reductions in offshore structures. New work is investigating fatigue of girth welded tubulars used for offshore applications such as production and export risers and tendons of tension leg platforms.
Project leader, Reza Razmjoo explains: "Fatigue is a major design consideration in offshore structures, but there is a limited amount of fatigue data available for girth-welded tubulars. Results from the project may lead to relaxation of the current conservative design rules for one-sided girth welds. This is good news for an industry looking to reduce costs".
This international project has nine global sponsors and a budget of over $900,000. Seven major oil companies from as far apart as Norway and Brazil are already signed up as well as the UK's Health & Safety Executive and Scotland-based BARMAC.
Fabrication and fatigue testing of 56 full size girth welds is underway with up to 40 small scale specimens taken from the tubulars also scheduled for comparative testing. The project aims to provide evidence for establishing acceptable new fatigue rules for one-sided girth welds to broaden their use for lower cost welds in structural tubular members and to establish the fatigue performance of flush ground girth welds.
The resonance test rig, designed, fabricated and commissioned at TWI specifically for this project, is capable of fatigue testing tubulars of 325mm diameter and 20mm wall thickness at a loading frequency as high as 33Hz.
For information about TWI's capabilities please contact us.