BTC - Connectors

In 2013 Equinor was planning the installation of the Mariner field which uses a submerged turret buoy to connect to the FSO. Equinor had collected their field experience and concluded as a previous study compiled for the UK HSE by Nobel Denton that a mooring line failure of some form would occur every 8 project years.

Over the life of the field therefore multiple interventions were likely to be required and a simple method of disconnection of the mooring lines was required. It is also a requirement that the connection must have two articulations – one for inclination and the other for azimuth rotation. Where there is chain in the top line a means to overcome out of plane bending is also required.

The major challenge however particularly on submerged turret buoys is how to pull in and disconnect the line with the buoy connected to the hull with the FPSO in production. Space is extremely tight and the only intervention possible is by ROV.

The BTC system uses a ROV insertable sheave locked in position above the BTC female mounted on trunnions. This sheave allows a manmade fibre rope to be led through the bore of the BTC female and connected to the BTC male mid water. Pulling on the rope brings the male into engagement with the female and a cam mechanism rotates the two halves such that the pin can be inserted into the assembly. The sheave is removed by the ROV and rope disconnected.

Disconnection is achieved by simply reversing this sequence.