Recently, all 12 anchor legs of Asia’s first cylindrical floating production storage and offloading unit (FPSO) Haikui No 1 (海葵一号; “Anemone No 1”) in the deep water area of the eastern waters of the South China Sea have been laid.
It is reported that the anchor leg is generally composed of anchor chains and steel cables, which can provide a huge anchoring force to tightly pull the upper floating body, firmly anchored in the seabed, so that the floating structure is stable and settled.
The sea area where “Haikui No 1” is located is more than 300 meters deep, with variable wind direction and complicated sea conditions. Also, the FPSO faces mooring problems such as large diameter and shallow draft.
Therefore, the anchor leg structure adopts a new form of “anchor chain + mid-water float + polyester cable”, which can achieve lower cost while providing sufficient mooring tension compared to the traditional solution of “anchor chain + steel cable”.
This is also the first time that China’s self-developed polyester cables and anchor chains have been applied on a large scale, promoting China’s deep-sea mooring system design, manufacturing and installation technology to achieve an all-round upgrade.
The anchor chains of the 12 anchor legs of Haikui No 1 are independently designed and manufactured by domestic manufacturers.
The anchor leg adopts multi-point mooring technique, which is divided into 3 groups, 4 in each group and 12 in total to tie up the FPSO in a more stable way.
In terms of mooring system design, the single anchor leg has a mooring radius of 2,500 meters and a breaking load of 2,300 tons, which is the largest in the industry.
The FPSO has a prominent a cylindrical design that has been developed to withstand super typhoon conditions and to ensure a service life of 30 years. The FPSO is the first in Asia to adopt such a design, which guarantees continuous operation for up to 15 years before requiring drydocking.