The cost and complexity of deploying deepwater moorings is driving the development of new mooring line technologies and deployment methodologies. First Subsea, in collaboration with Lankhorst Ropes and Offspring International, has developed the LankoFirst fibre rope connector specifically for mobile drillng unit (MODU) deepwater fibre mooring line connections.
Current H-link, Pearlink and Platelink connections are labour-intensive, and often time consuming to assemble offshore. Moreover, they are prone to being weakened by the bending moments experienced when deployed over the anchor handling vessel's stern roller.
Drawing on the findings of First Subsea's metals forging research project, and developments in polyester rope splicing technology, the LankoFirst fibre rope mooring line connector has been developed that meets the following requirements:
- Higher engineering integrity than current plate links and thimbles connectors
- Smaller and lighter than current connectors for the same MBL
- Safer and easier to assemble offshore, whether vertically or horizontal
- Easier to run and retrieve across stern rollers and on anchor handling vessels
- Suitable for all fibre rope mooring connections including rope-rope, rope-wire and rope-chain connectors
Trials in offshore Norway has shown that the LankoFirst connector can be assembled in 15 minutes, compared with at least 1 hour 15 minutes for a traditional shackle. In addition only two people are needed to assemble the connector unlike a shackle which usually requires at least three people. This means fewer people are required on deck during hazardous line make-up operations.
In place of a large spliced soft eye, normally used with H-link and shackle connections, the LankoFirst uses a sub-connector Donut which is integrated into the rope termination during manufacture. This innovative and smaller donut splice is much easier to handle offshore.
Fibre Rope Connections
The connector design relies on the rope being spliced into a forged steel, sub-connector during rope manufacture. These are subsequently secured within the connector during connector make-up offshore. This has clear practical benefits in terms of the ease and speed of mooring line deployment offshore.
LankoFirst can connect to fibre rope to fibre rope (R2R) and fibre rope to chain (R2C): The connection is made by inserting the sub-connector Donut into the open clam, and then bolting the clam shut. This contrasts with the assembly of the shackle connection which involved inserting the shackle into the splice eye and then hammering in the large diameter retaining bolt.
Quick Release System
With a quarter of the world's undiscovered oil and gas reserves in the Arctic, at water depths up to 3,000m, the search is on for safe and reliable mooring systems for drilling and production vessels and platforms. Innovative quick disconnect and reconnect mooring connector technology by First Subsea will enable platforms to respond safely to ice field movements.
Based on proven ball and taper mooring technology, the Quick Disconnect and Reconnect (QDR) connector is designed for FPSO submerged turret production (STP) buoy mooring. It is:
- Capable of handling loads over 2,600T per line
- Approved to API 8C, and material toughness tested at -45C
- QDR's ball and taper configuration is based on proven Casing Running Tool (CRT) technology successfully used in drilling and casing handling operations in Alaska
The QDR provides a failsafe and quick disconnection, which is operable in low temperature water, and capable of releasing the mooring line under load without damage to the mooring line, FPSO and buoy. The reliability of the QDR connectors is critical, even in the event of power loss. To ensure reliability, the QDR is spring loaded and held in place by a hydraulic system to ensure a reliable release.
Safe Disconnection and Reconnection
The QDR is designed to allow buoy disconnection to be completed within 15 minutes.
It begins by closing emergency shut-down valves and ceasing production activities. The jumper lines are extended and the buoy lowered below the FPSO hull. The QDR connectors are then simultaneously released and the buoy sinks to its submerged equilibrium depth. The FPSO is fully disconnected and sails away. During a planned disconnection, a buoy is lowered by the pull-in winch and the mooring lines disconnected.
When the FPSO returns on-station, the buoy can be remotely located and retrieved using a Ballgrab® pull-in tool with in-built GPS, sonar and camera. It allows quick buoy recovery and retrieval even in adverse weather conditions - a safer option than exposing crew to the severe weather.
Due to the mechanical design of the QDR, once the buoy is locked in position, the FPSO mooring lines can be reconnected. The design of the QDR is so that disconnection can be triggered at any time should the weather condition deteriorate such that the FPSO is unable to stay on-station.
Arctic and severe weather moorings present many environmental and technical challenges. First Subsea's QDR offers the prospect of enabling rapid emergency disconnection moorings while providing simple and quick reconnect.