Turning restrictions into effective, integrated designs
Sapura Navegação Marítima (Sapura) was contracted by Petrobras to lay flexible pipe in the pre-salt regions offshore Brazil. Therefore, the joint venture between Seadrill and Sapura Energy needed to build a fleet of pipe laying vessels. Limitations in terms of dimensions in combination with large pipe laying capacity requirements, called for an innovative approach.
Sapura specified that the vessels should be able to lay flexible pipe with a diameter of 100 to 630 mm in water of up to 3,000 meter in depth. For this reason, a large 550t vertical flex-lay system is required. This kind of system usually exceeds a height of 50 meters. However, a bridge en-route to the Brazilian port of Vitoria, where the vessels will load pipe, dictates a maximum draft of 48 meters. Additionally, the port itself prescribes a maximum vessel length of 146m, so space on deck is also limited.
To ensure maximum efficiency and workability of the vessel within the limited space available, Royal IHC came up with a solution that integrates all the critical mission equipment into the concept design of the vessel. By doing so, we could offer an innovative solution that ticked all the boxes, and more…
The design of the 550t flex-lay tower includes a tiltable top, that folds away in a matter of minutes to meet the height limitations. In addition, the vertical lay system is positioned directly aft of the accommodation in a forward orientated manner. Compared to the usual design for flexible pipe laying vessels, in which the tower faces towards the stern and tilts towards the deck, this results in more free deckspace, which is important considering the length limitations.
Another smart solution to save valuable space on deck, is the integration of the chutes into the steel structure of the vessel for pipe loading over the stern. Pipe is fed through a loading tensioner on deck and passes over intermediate guide chutes, before being loaded into one of two underdeck carousels (2,500t and 1,500t).
These solutions could only be achieved by opting for a single supplier for both vessel and equipment. By included the pipe lay equipment in the concept design of the vessel, we could ensure the best technical solutions were applied and vessel, pipe lay equipment and interfaces are integrated seamlessly. Moreover, Sapura had one point of contact for the entire duration of the project.
Sapura Annual Report 2015: “We have seen excellent progress of the Brazil operations with SAPURA DIAMANTE, SAPURA TOPAZIO and SAPURA ÔNIX operating at a commendable average utilisation rate of between 98%- 99%.”
To achieve the maximum air draft of 48 meters, the A&R post, top aligner and tower top crane of the 550t flex lay tower can be tilted in a matter of minutes.
Depending on the diameter of the pipeline, different pads on the tensioners are required. With 350 pads per tensioner, this can be quite time consuming. IHC devised an innovative system with a single retainer – and pin to remove it – making it as quick and easy as possible.
The vertical lay tower is positioned directly aft of the accommodation and over the moon pool. This arrangement allows for a large worktable to carry out activities on pipes and pipe ends, leaving an additional large free deck area.
To accommodate pipe loading over the stern without exceeding the maximum length of 146m, the chutes are integrated into the steel structure. Pipe is fed through a loading tensioner on deck and passes over intermediate guide chutes, before being loaded into one of the underdeck carousels (2,500t & 1,500t).
Integration of platform and mission equipment has been achieved through the use of the Integrated Vessel Management System. This integrates the vessel’s Power Management System (PMS), DP system and Alarm & Monitoring System (AMS) with the control and monitoring logics of the main switchboards and Variable Frequency Drives (VFD’s), and communicates with the lay tower control system.
To limit the need for spare parts, and to maximise uptime, IHC has designed the 550t pipe laying vessels for Sapura with a uniformity of components in mind. And as the 550t vessels are identical, operational and technical crew members are able to work on all vessels without the need for additional training.