Allseas’ Solitaire, the world’s largest pipelay vessel, left Rotterdam after being retrofitted in preparation to lay a section of the Nord Stream natural gas pipeline in the Gulf of Finland.The dynamically-positioned pipelay vessel will be able to carry out precise manoeuvring without anchors, thus ensuring additional safety as it lays the 342.5 kilometre section of the pipeline in this congested part of the Baltic Sea from kilometre point (KP) 7.5 in Russian waters to KP 350 in the Finnish Exclusive Economic Zone (EEZ).
Before starting its journey to the Baltic Sea, the Solitaire was adapted to Nord Stream requirements in Rotterdam. Each piece of equipment was thoroughly tested in port and will be tested in operational offshore conditions in the Baltic Sea before the vessel starts laying pipe.
For accurate positioning the Solitaire is equipped with ten thrusters with an integrated propulsion power of 50,000 kW. These thrusters keep the pipelay vessel automatically in position. The thrusters are steered by a computer system that constantly monitors the actual position of the vessel in comparison to its target position (in this case the agreed pipeline route). Should there be any deviation, the thrusters instantly propel her back into the target position, so that the vessel is always operating along the precise agreed route. This positioning system enables the Solitaire to safely work even in adverse weather conditions, and it is ideal for pipe-laying operations in the Gulf of Finland, which is one of the most congested areas of the Baltic Sea.
The sections in Russian and Finnish waters adjoining the 342.5 kilometres of pipeline to be laid by the Solitaire are being constructed by Saipem’s Castoro Sei pipelay vessel, including the section at the Russian landfall. A third pipelay vessel, Saipem’s flat-bottomed Castoro Dieci, is responsible for constructing the pipeline in the shallow waters at and near the German landfall.
Sea trials will ensure that Nord Stream’s high level of HSE (health, safety, and environmental) standards are met from day one. The trials will be used to fine-tune the equipment and familiarise the crew with the project-specific on-board procedures. These trials will be attended by independent inspectors from the certification institute DNV (Det Norske Veritas, Norway) to ensure that the project’s high quality standards are met.
At 300 metres long (excluding stinger) by 40.6 metres wide the Swiss-based Allseas Group’s Solitaire is the length of three football pitches and is manned and equipped to lay pipe 24 hours a day 7 days a week. She accommodates 420 people and has work stations on several levels to enable her to receive and store the 12 metre long 25-tonne pipes, weld them together, test the welds, join the pipes to the pipeline and lay it on the seabed along the agreed route at a rate of about 2.5 kilometres a day.
When completed in 2012, the Nord Stream Pipeline will be 1,224 kilometres long, and comprise 202,000 concrete weight coated steel pipes. The pipeline will transport 55 billion cubic metres (bcm) of natural gas a year to Europe.