The "last mile" for delivering LNG from the terminal to a tanker ends in a remarkable set of articulating arms that connect to the LNG tanker's cargo manifold connections. On February 22nd, crews began their work to erect and perform final assembly of the set of four cargo arms at the new, second LNG tanker dock.
The steps leading to the delivery of the new cargo arms included: increasing the size of the dock basin by dredging and removing 1.2 million cubic yards of soil, driving thirty-two 54-inch wide by 120-foot long concrete piles, on which to build the dock platform, and ten 96-inch wide by 160-foot long steel piles to support the mooring dolphins.
Once the dock piles were driven, crews laid concrete panels on top them, then large rebar mats were added, onto which a thick concrete deck was poured to hold the embedded bolts for securing the piping, the dock gantry structural steel and the anchor bolts to which the cargo arm bases would be secured. Each articulating cargo arm would then be mounted on top of one of the four pedestal type bases.
The second dock is a critical component of the terminal’s export capabilities. When the liquefaction facility is at full production, it will be capable of making well over 38,000 metric tons of LNG per day—more than the existing, single dock can service. Adding a second dock will facilitate the loading of two ships at the same time and realize the envisioned volume of LNG export capability.
The cargo arms were designed and built in Germany by SVT. They were transported by ship to the Port of Freeport. From there, they were transported by truck to a pre-assembly location within the construction site where they were partially assembled. When the cargo arm bases were ready to receive the rest of the arm structure, they were loaded onto self-propelled transport platforms and driven to the construction dock. There, the transport platforms were driven onto a barge and the barge was towed to the new dock. A large barge-mounted crane then lifted the cargo arms onto their respective bases.
On the morning of February 22nd, the arms sat poised on the crane barge. Each arm, weighing 66,000 pounds, was slowly and carefully lifted, set and attached to its base. Afterwards, a set of counterbalance weights were added, weighing 20,000 pounds apiece. These are absolutely necessary to be positioned on the back side of the cargo arm in order to balance the weight of the arm when it is extended out to be connected to a ship’s cargo manifold.
Finally, a triple swivel was connected. These swivels provide the ability to rotate the outermost section of the arm so that it fits perfectly on to the ship’s cargo manifold.
In the set of four cargo arms, three are used to deliver LNG to the ship. The fourth is a return gas line that transports natural gas from the ship’s cargo tanks that are being filled with LNG back to the liquefaction facility for recompression and reliquefaction. When operating, one cargo arm will be able to deliver approximately 4,000 cubic meters of LNG per hour. At this rate, a tanker could be loaded in seventeen to eighteen hours. Maintenance on the arms consists of monthly, quarterly and yearly inspections to determine the physical condition of the bearings and the swivels, and to determine if additional lubrication or repair/replacement of components is necessary.
"When I first came down to this area, and before I was working here," says Alan Higginbotham, Interface Superintendent for Freeport LNG, "I went across the bridge going over into Surfside. You look back in this direction and you can see the air tower and you can see the loading arms standing up. It’s a pretty impressive sight."