tailieunhanh - Failure Analysis Case Studies II Episode 3

Tham khảo tài liệu 'failure analysis case studies ii episode 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 58 stiffness. Obviously comparable reductions in chain diameter to reduce the rope tension would have equivalent effects. The operation analysed here is only one example of a process which can induce rotation though this is perhaps the category of operation most likely to induce the higher amounts of twist. Inevitably when working in even greater water depth much higher twists will be involved. It must also be pointed out that the torque tension model used for these calculations is fairly simple and has not been validated for ropes of the size used offshore. The analysis reported here has also been performed using the even simpler two-term model of rope response 9 predicting a 35 lower rotation in the pendant rope but otherwise a very similar pattern of behaviour. The reported facts relating to the P34 mooring line losses are that the deployment procedure was as described above and that the spiral strand was found to be torsionally damaged beyond recovery when connected to the FPSO. The mechanism described here has been deduced from an analysis of the operation. There are no observations that can confirm or otherwise the relative states of twisting in different components at each stage but no other explanation has been advanced. 9. Steps to avoid induced torsion Apart from expensive solutions such as using two lines to different AHVs or other devices attached to the connection between components to prevent the transfer of turns what else might be done to avoid this kind of problem There are essentially three categories of solution one involving rotating connectors swivels the second involving the use of torque balanced ropes and the third involving the selection of twist tolerant components. The merits of each are considered below . Rotating connectors Conventional swivels are of little use here because they have high friction and therefore really only operate at very low tension. This is ideal to release torque to facilitate handling of a rope adjacent to a .