The Research Of Offshore Platform Mooring Monitoring And Measuring Devices

Because of complex and uncertain marine environments, the structure of offshore platforms will be affected badly and the security of the platforms will meet some risks. In order to ensure the security of the platform, optimize the design of the platform structure, the prototype measurements are necessary for offshore platforms.In the background of the South China Sea "TiaoZhan" FPS, this paper studies the prototype monitoring technology of the semi-submersible offshore platform and especially focused on the mooring system monitoring technology. Since the strong coupling of floating body and mooring system, the position and movements of the floating body affected the stress of mooring system. As the "TiaoZhan" FPS doesn’t have a fix point, WADGPS is adopted to monitor the positions of platform. However, the accuracy of WADGPS can only reach several centimeters and expensive fees are needed for the WADGPS service. Precise Point Positioning (PPP) was proposed to measure the positions of platform in this paper. The difficult and essential points were summed up and the PPP software was developed in this paper. There are two ways in monitoring mooring system. One is directly measuring the horizontal pressure of the mooring chain by using the load cell, the other one is indirectly measuring the pressure which was calculated by monitoring the attitude of the chain. For the first way, the current mooring monitoring system had several defects in "TiaoZhan" FPS, so a new integrated system which could store long-term monitoring data, simple analyze the data and generate the daily report file was developed. For the second way, an Underwater Self-contained Attitude Measuring Device was developed. This device can measure acceleration and inclination angle of mooring chain in different depth, thus mooring force could be calculated by using the measure data. Maximize the battery life by low-power design of both hardware and software.According to several experiments, the accuracy of the developed PPP software could achieve centimeter level in static positioning mode and 10 centimeter level in kinematic positioning mode. Besides, the integrated mooring monitoring system could display, store and alarm the mooring tension time series. The Underwater Self-contained Attitude Measuring Device has been applied in "TiaoZhan" FPS mooring monitoring and the measure data could meet the need of mooring monitoring.