Floating Production, Storage and Offloading vessels (FPSO) are moored to the sea bed with an array of anchors and chains to the turret of the FPSO; the ship rotates around the turret to face into the weather and to position itself for offloading the cargoes of oil onto tankers.
The 8 or 10 chains are tensioned and stored in the turret of the FPSO; the chains run down a guide tube the height of the turret and are guided out of the tube in the direction of the anchor position by fairleaders which rotate in the horizontal plane, the fairleader supports the anchor chain wheel which turns and engages in every chain link.
The fairleaders including the chain wheels can weigh between 16 to 23 tonnes each.
Particular attention has to be paid to the coefficient of friction in the fairleader slew bearings because in a static mooring application such as an FPSO or Floating Production Platform when the fairleaders are static for many years they will stiffen up or seize.
With bearings in a stiff or seized condition the fairleaders will see side loads they have not been designed to withstand.
We believe on an FPSO the fairleaders should be able to withstand chain MBL while seized until the turret breaks-out.
We design and manufacture fairleaders to the highest standards and which comply full in detail and intent with DNV-OS-E301 Class Rules.