Characteristics And Experimental Research On Performance Of The Seal Structure Of Deepwater Collet Connector

Subsea tie-in connector is one of the core equipment used for deepwater pipeline connection in subsea production system,collet connector is the main developing direction of subsea tie-in connector.As the pipeline connection tool operated in complex deepwater environment,good sealing performance is an important feature of collet connector,reasonable sealing structure is an important foundation of realizing the feature,research on the collet connector sealing structure and its sealing performance is of great significance and practical value.The 6” vertical stab non-integral collet connector was studied based on the domestic and foreign sealing technology of collet connector and traditional high-pressure pipeline sealing technology.Research on the collet connector sealing structure was done in three aspects,namely,planning the scheme of connector seal,analyzing the mechanics characteristic of sealing structure,doing experimental research on sealing performance.According to the high pressure of oil and gas and large temperature difference between inside and outside of the connector,a scheme of lens-typed combined with O type ring gasket was proposed.A detailed design was carried out from two aspects of connector function requirements and trajectory of fingers and actuator ring,the motion simulation analysis of the connector and the selection of part material was made.Based on the sealing mechanism of lens-type gasket and the theory of Hertz contact,the mechanical model of core seal part in preloading and operating condition was established.The structure parameters that affect the sealing performance was analyzed from two aspects of minimum axial pretightening force and maximum contact stess.The structure optimization problem of the best sealing performance and minimum pretightening force was solved with the finite element method,the optimal structure dimension was obtained,and the analysis of contact characteristics of the finial structure was made.According to the sealing principle of the connector,mechanics characteristic of the seal part in preloading and operating condition was analysed,force transmission relation of each part was deduced,and the contact characteristic simulation results show that the sealing structure has the characteristic of enlarging axial pretightening force.Aiming at the problem of connector structure damage under jumper’s load,a method of calculating connector bearing capacity based on the hoop stress was proposed,and the limit of external load was calculated.Taken the sealing structure test device and the connector prototype as test-bed,gasket small sample test,gasket sealing performance test,and connector sealing structure performance test were done to investigate the effect of the hardness of the material,metal coating and other factors on the performance of sealing structure,and the design and analysis methods of the connector sealing structure in this dissertation are verified through comparisons between the experimental results and the computational results.Sea trials was carried out in 300 m underwater,the result shows that the connector can coordinate with other systems to complete the underwater connection operation,verifying the effectiveness and practicability of connector seal structure.