Damage assessment for GRP submerged buoyancy

Abstract

Submerged buoyancy is used for many different subsea applications, especially with reliving connections between the seabed and surface installations. As CSUB specialises in composites structures for subsea installations, there focus is now on how they can implement their knowledge to these products. Based on previous results there should be great benefits if the GRP shell related to submerged buoys could be beneficial in relation to depth rating. One has therefore presented and carried out a pressure experiment which focuses on how GRP relates to being a water barrier. The results show that laminates of 2.4 mm with single sided pressure can uphold of 40 bar without water penetrating. Laminates of 4.8 mm thickness have given the same result at 80 bar. However, testing done with impact damaged specimens have given various results, and seen as requiring further research to sufficiently determine the damage threshold of the laminate before water penetration occurs. As there is also done a complementary absorption experiment, these results is further used to validate the results. Stable conditions is assessed to be reached between 0.1 \% and 0.2 \% of weight increase at only 500 hours. This is therefore assessed that it can be neglected for the pressure experiment. On the discussion on how the results correlates to the feasibility CSUB can improve their buoyancy solutions, there is positive conclusion. Although one does not believe, at this stage, that the confidence tied to GRP would be sufficient to be a stand alone solution, one believes that the demands of safety factors tied to existing solutions can be decreased.