Performance Analysis And Research Of Seals Used For Single Point Mooring System Slip Ring

Offshore oil and gas industry is currently the focus of China,and it has put forward higher request on relevant technical equipment.Single point mooring system is one of the most important parts in the offshore vessel.The sealing effect directly affects the function of oil and gas transmission.Once the sealing failure and leakage accidents occur,it will seriously affect the progess of the project and even cause large area of offshore oil pollution.This paper mainly focuses on the type selection,seal performance simulation analysis,thermal-structure coupling analysis and fatigue life prediction for the seal used in the slip ring structure of single point mooring system.The main researching contents are as follows:(1)By consulting relevant literatures and practices,expounded the research status and existing problems of sealing rings.According to the working conditions of slip ring,the O-seal,Y-seal,helical spring seal and U-spring seal were selected as the proper seal rings for the structure.The judging criteria of seal failure and sealing performance were introduced.(2)In order to study the seal characteristics of different sealing rings,2-D axisymmetric model of the four selected seals was established and carried out the simulation analysis of sealing performance by using the finite element analysis software ANASYS.The effects of medium pressure,compression ratio and friction coefficient on the sealing performance of different seals were analyzed in detail.According to the analysis results,compared the sealing performance of the four kind seals.The results show that the four seals meet the sealing requirements.The sealing performance of the spring accumulator seals is better than O-seal and Y-seal,and the U-spring seal is the best.(3)The thermal loading method for thermal structure coupling analysis was improved.The temperature field distribution of the sealing ring under different temperature conditions and the influence of medium temperature on the sealing performance of the sealing ring were analyzed by using the improved method.Designed and installed the experimental device used for measure the resistance moment of the seal.The temperature field distribution and coupling analysis results before and after the improved method were compared.The results show that the improved thermal loading method is more consistent with the actual situation.The reduction of contant stress under high temperature can result in decreased sealing performance.The O-seal and Y-seal have the danger of sealing failure because their maximum contact stress is very close to the mediun pressure.But the spring accumulator seals can maintain good sealing performance because their maximum contact stress is still far greater than the medium pressure.(4)A mathematical model for fatigue life prediction was established based on fracture mechanics.Combined with the three principal stress analysis results of the finite element analysis of the sealing ring,the location of fatigue dangerous section of each seal ring was determined.Calculated and analyzed the fatigue life of the seal ring based on this method.The results show that the fatigue life of O-seal and Y-seal are 3.76×106 and 1.0×107.The helical spring seal and U-spring seal are 2.02×109 and 3.35×108.The fatigue life of the seals is within the estimated range,and the life of spring accumulator seals is better than that of O-seal and Y-seal.