Integrity Assessment of Soft Yoke Moored FPSO for the Hinge Point Problems

Single point mooring system is widely used in the world. Soft yoke mooring system (SYM), one kind of the best single point mooring systems, is applied to moor FPSO in shallow water in Bohai Bay of China. SYM has 13 hinge points, which could be relieved by 3 freedoms in wave frequency motion (roll, pitch and heave), but only be restricted in low frequency motion (surge, sway and yaw) so that the tank could fix a position in a certain area. Due to the reasons of longterm use, improper maintenance and harsh ocean environmental conditions, the hinge points will occur some problems, such as rust, which may cause the damage of the yoke and other dangerous even drag down the tower platform. Thus the problems of the hinge points need to be taken care of. In this paper, an integrity assessment method of SYM for hinge point problems is proposed based on field monitoring technology. The internal structure of the hinge point is analyzed and the main failure modes of the hinge point were disused. Based on the analyses, the field monitoring method for hinge point problems was given. Through the monitoring information, the integrity assessment of the SYM was given.