The buoy locking mechanisms provide securing of the STP Buoy to its fixed position in the Mating Cone. The locking mechanisms consist of a number of hydraulically operated locking jacks distributed around the upper mating ring.

The locking mechanisms are remotely operated by hydraulics. A mechanism is arranged so that the lifting tip of the mechanism first move in under the buoy locking recess ring before it is lifted upwards. After the locking mechanism engages hydraulically to the correct pretension value, a mechanical nut is manually engaged to lock the locking mechanism in a permanent fixed position. The hydraulic pressure is not removed until all the locking mechanisms are mechanically locked in pre-tensioned condition.

The FPSO is permanently connected to the buoy, but the locking mechanisms may be operated individually for maintenance purposes.