• Submerged Turret Loading

    The Submerged Turret Loading (STL™) system represents state-of-the-art technology within offshore loading. The STL technology offers a flexible, safe and cost-effective solution for Oil Loading Tankers (OLT) and Floating Storage and Offloading (FSO). STL technology has a high availability in harsh environments and is well proven since 1993.


    STL Basics

    A buoy moored to the seabed is pulled in and secured in a mating cone in the vessel. the buoy incorporates a turret connected to the mooring and the riser(s). All STLs are based on standardized mating cone geometry in the vessel.



    The STL system allows for schedule decoupling between the offshore and the shipyard work. STL, mooring and riser ca be completed independently from the OLT or FSO. The system is intalled on site prior to the FSO or OLT arrival at the field. Upon arrival, the vessel hooks up on to the STL on its own. The disconnect feature of the buoy simplifies unplanned repair, upgrading, inspections and replacement of the FSO, as well as abandonment of the field. The system accounts for connecting in sea states between 5 and 7 m Hs (significant wave height). 

    Permanent or Disconnect Mooring  

    The STL system can be designed for disconnect service (OLT or shuttles) or for permanent mooring throughout the field life (FSO). Disconnection takes only a couple of minutes and can be performed in any weather condition. The buoy drops clear of the vessel, and floats in an equilibrium position approximately 30-50 meters below sea level.  

    STL Integration

    With bearing structures integrated in the STL buoy, as opposed to bearings integrated directly in the hull, the turret integration in vessel is simplified. Vessel modifications are limited to standard steelwork. The STL compartment is a cylinder extending from bottom to upper deck with the receiving cone as the lower part. With a diameter of 10 to 12 meters, the impact on the hull is minimal. 

    STL System References  

    STL systems in service cover a wide range of application from the harsh North Sea environment to cyclone prone areas such as China or Australia. The mooring caters to sea as high as 19 m Hs (significant wave height), water depth up to 2500 m, vessel sizes up to ULCCs, throughput up to 600,000 BOPD.etc. 

    STL for High Pressure LNG Re-Gas

    The STL is widely used to moor LNG carriers either FSRUs or Regas Vessels (RV). 

    STL in Ice  

    Icebergs and ice ridges in arctic environments are better addressed with the quick disconnect features provided by the STL system. STL systems are verified in ice environments and model tests have documented survival of a vessel moored in 1.6 m level ice with drift speed of 0.75 m/s.


    • A buoy moored to the seabed is pulled into and secured in a mating cone into the vessel.

    • The buoy incorporates a turret connected to the mooring and the riser(s). 

    • All STLs are based on standardized mating cone geometry in the vessel. 

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