Undersea energy pipelines constitute a vital physical link between deep water wells and onshore refineries, but it's not like we can just lay these lines like oversized bendy straws. That task of constructing and sinking these tubes instead falls to vessels like Allseas' newest addition to its pipelaying fleet, the Audacia.
Over short distances, sure, use an ROV. But when running a pipe across, say, the English Channel, submersible robots won't cut it. Instead, these enormous undertakings fall to ships like the 225m long, 32m wide Audacia, which has been in service since 2007. The vessel can carry up to 270 crew members and over 12,000 tonnes of pipe ranging from 5cm to 150cm in outside diameter.
As the pipe sections are hoisted from the bowels of the ship, they travel down a firing line comprised of seven welding stations, followed by a non-destructive testing station, and then by three coating stations before being shoved overboard through the vessel's prominent bow spur, where it sinks to the seafloor. At maximum capacity, the Audacia can set down nearly 30m of steel tube every minute.
To ensure that the pipes reach their underwater destination undamaged, the Audacia combines an advanced full dynamic positioning system (which guides the ship along a precise route using GPS signals) with a powerful pipe tensioner, which regulates how quickly the pipe is let out.
"We also took care of all the automation, navigation and communication equipment, and the frequency-regulated systems for the thrusters and the pipelaying system," Cor van Miltenburg, BU Director of IM Tech (the company that installed the ship's DP system), said in a press statement. "These ensure that the pipeline remains stable during the entire process, from the welding path to the sea bottom. What is unique to the Audacia is that the pipeline is set into the sea over the bow using the stinger. In this way, it was able to keep its original stern with its fast propulsion. The Audacia can thus head off to a new pipeline laying location anywhere in the world."
And it looks like the Audacia is getting herself a big sister soon pretty soon. Allseas is in the midst of constructing an even bigger pipelaying vessel, the $US1.7 billion Pieter Schelte. At 380m long and 124m wide, this vessel will likely become the largest pipelayer ever constructed when it's delivered in 2020. [All Seas - Wiki - IM Tech]