Stress Analysis Of Pipe System For FPSO In Ultra-Deepwater

Floating production storage and offloading is one of the basic facilities to exploit and product the oil and gas in deep sea. FPSO has been the main measure of ocean engineering equipment facing with deep sea oil and gas field development, for its good moving, accommodating oil extraction in deep water, great resistance to the winds and waves, processing capacity of oil-gas-water outstandingly, the advantages of large crude oil storage capacity and so on. Normal operation of piping systems plays a vital role for the safety of ships, personnel and equipment. High risk of harsh offshore operating environment oil and gas production puts forward higher requirements for FPSO piping systems as well. Therefore, stress analysis for the deep-sea FPSO piping system is significantly necessary.The paper takes the piping systems of FPSO which weighs 0.3 million tons and works in the South China Sea as an example to study the influence of stress when piping systems suffering from wind loads, wave loads, additional displacement generated by hull deformation and other loads. Static analysis has been done for ballast system, exhaust system and deck cargo system of FPSO to check for primary stress and secondary stress. Based on the static analysis, research on water hammer and vibration of equipment to piping stress has also been worked on. The following is the main contents of the paper.1、Taking the generator exhaust pipe system as an example to do research on the influence to pipe stress, restraint loads and displacement between the combination method of load cases and individual load method, and then find the advantage of them as well as their range for using.2、Checking for primary stress and secondary stress of exhaust pipe system and deck cargo pipe system on FPSO. When doing static analysis for deck cargo pipe system, wind loads and hull deformation have been considered, and fatigue damage by the alternating effect of hull deformation.3、Using the dynamic module of CAESAR II to do research on the ballast system of FPSO on the influence of stress when the pipe system suffering from water hammer, and some restraints will be modeled for the stress overpassed by the code to make it work when meet fatal water hammer load.4、Research on the influence of vibration for single pump and combination vibration for more pumps has been done, taking the vibration intensity of two levels for good and danger. The largest stress changing with rotate speed has been studied and the result of two levels has been compared.