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In addition to loading and unloading their cargo in ports, oil and gas tankers transfer cargo at FPSO and FSO facilities located offshore.


A Floating Production, Storage and Offloading (FPSO) unit is a floating vessel used by the offshore industry for the processing of hydrocarbons and for storage of oil and gas. A FPSO vessel is designed to receive hydrocarbons produced from nearby platforms or subsea template, process them, and store them until they can be offloaded onto a tanker or transported through a pipeline. A FPSO can be a converted oil tanker or a purpose built vessel. When used only to store oil (without processing it) the vessel is referred to as a Floating, Storage and Offloading vessel (FSO). Shuttle tankers transport oil and gas from the FPSO/FSO to a refinery or storage facility somewhere ashore. Vessel-to-vessel operations at sea are typically very difficult and dangerous to execute. Operational safety is hugely enhanced if the relative positions of both vessels can be accurately visualized throughout approach, connection, offloading and disengagement maneuvers.

tandem mooring

As the software component of a precision navigation system, Qastor provides the pilot and master with a real-time, accurate and independent picture of the relative positions and movements between two vessels. Hardware components include a fixed system on the FPSO that delivers positioning, heading and velocity data, and a portable system also supplying real-time positioning, heading and velocity data. Both sets of data are sent wirelessly to the pilot/master’s laptop running Qastor, which has a dedicated “FPSO mode” for monitoring the entire operation, whether the vessels use tandem or side-by-side mooring. Switching Qastor to FPSO mode changes the side panel contents, and attaches two speed vectors to


each vessel, one at the bow, the other at the stern. For tandem mooring, Qastor shows relative bearing, distance and speed of the shuttle tanker in reference to the FPSO/FSO. In the approach phase, shuttle tanker speed and distance are closely monitored. During connection and offloading operations the relative bearing of the two vessels becomes as important as distance. Relative distance and bearing are carefully scrutinized to avoid undue stress on the tether, and for early warning of developing jackknife situations.

side-by-side mooring

For side-by-side mooring the shuttle tanker docks alongside the FPSO/FSO. In this case, the side of the FPSO/FSO hull is used to generate a “virtual mooring line” in Qastor, which is utilized on the shuttle tanker to check bow and stern distance from, and speed towards, the FPSO/FSO. Qastor uses special distance indicators displayed between the two vessels, while the side panel window shows the relative bearing and speed between the two vessels.

single point mooring

A Single Point Mooring (SPM) is a loading buoy anchored offshore that serves as a mooring point and interconnect for tankers loading or offloading gas or liquid products. SPMs are the link between geostatic subsea manifold connections and weathervaning tankers. They are capable of handling any size ship, even very large crude carriers (VLCC) where no alternative facility is available.
Qastor is again an ideal tool for visualizing this type of operation. At a distance the unmanned SPM is visible, but at some point the SPM disappears behind the bow of the vessel. Receiving positioning, heading and velocity data from both the fixed navigation sensors on the buoy, and the portable pilot unit, Qastor shows the exact position of the SPM in reference to the shuttle tanker at all times and continuously displays relative speed and distance.


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Quality Positioning Services B.V. | privacy statement | disclaimer | Terms and Conditions of Sale and Service | Powered by Atlassian Confluence / Adaptavist Builder