Study On Monitoring Method For Deepwater S-lay Installation

S-lay operation exhibits the good advantage for offshore pipeline laying process due to its good stability, high efficiency and the wide applicability. However, there still exists uncertainties for the applicability of the ocean environmental loading model. The numerical solutions to the complex mechanical problem are difficult. The model test is influenced by the scaling-effect and difficulties in achievement of the real environment load factor. Due to the above limitations, failure risk for stinger and pipe are still existed during S-Lay laying process.In order to determine the load characteristics in the laying of sea areas, verify the rationalization of load model what is used for design, measure the real response of pipeline and stinger to verify the design index and evaluate the safety of the structure during S-lay installation process. The present paper develops a proto-type monitoring strategy for S-lay operation. Based on the load model and the failure model of structure, the paper summarizes and puts forward the contents of in-situ monitoring. Especially, regarding to the state parameter and mechanical parameter of pipeline isn’t able to contact measurement underwater, the monitoring information are decided by state parameters of stinger, tensioner, water depth etc. For the difficulty of measuring each node of stinger, combined with the overall and local numerical analysis of the stinger,the hotspot position of the strain measurement is determined. According to the determinate measurement information and program, combine with the actual environment and operation conditions, prototype measurement scheme is established. In order to verify the validities and feasibilities of the monitoring plan, the in-situ test was conducted in the existing monitoring station. Two numerical examples are made in this paper, the good agreements show the correctness of present internal force measurement scheme for segbend section of pipeline. At the same time, safety evaluation scheme is established according to main failure mode of structure and the integrated system is designed. Through the monitoring system, the security behavior of structures can be evaluated during S-Lay laying process.