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Alliance Engineering’s lightweight topsides designs result in efficient, lower cost facilities for Perdido

Alliance Engineering uses 3D design software to bring projects to life before they are built.

 

Alliance Engineering, a Wood Group Company, has expertise in successfully developing topsides for major offshore fields for a variety of project types, including deepwater platform topsides, floating production, storage and offloading (FPSO) unit topsides, and fixed structures. In particular, Alliance has a well-established and well-earned reputation for designing and implementing lightweight, single-lift deepwater topsides. Alliance is associated with numerous world records, including the deepest tension-leg platform (TLP), deepest spar, deepest semi-submersible platform, deepest dry tree unit, first dry tree mini-TLP, and first mini TLP.

This reputation is one reason Shell chose Alliance to provide front-end engineering and design and detailed design of the Perdido spar topsides. Alliance also provided conceptual design services, fabrication and installation support, and commissioning support for the unique topsides.

 

Reducing weight at every opportunity

 

The topsides design techniques were a key enabler to permit Shell to advance the Perdido project. Designing a deck for single-lift installation avoids redundant steel weight and results in improved deck space utilization, lower installation cost, more complete pre-commissioning, and faster offshore hook-up and commissioning. A lightweight topsides reduces hull displacement and mooring loads, provides a faster overall project schedule, and improves overall project economics.

In partnership with Shell, Alliance demonstrated ingenuity and flexibility by engineering a fit-for-purpose topsides design by investigating and implementing many solutions to reduce weight. Alliance challenged equipment suppliers to reduce the size and weight of their equipment. Combined with Shell’s innovative solutions to reduce the riser load on the spar, this approach resulted in significant weight reduction and a significant savings in time and cost. The facility accommodates production from five subsea direct vertical access separation caissons.

 

Sophisticated instrumentation and control

 

Alliance worked very closely with the main automation contractor to design and implement a world class facility control system for Perdido. Every facet of the facility’s processes, including topsides, hull, and subsea, can be managed from Perdido’s central control room. The process control portion of Perdido’s facility control system is based on Yokogawa’s Centum CS 3000 distributed control system (DCS). For safety shutdown and emergency support, Yokogawa’s ProSafe RS for safety integrated systems was used. The ProSafe RS is a TUV SIL-3 rated safety system.

The Centum CS 3000 DCS and ProSafe RS safety system communicate seamlessly, allowing safe integration of the controls and shutdown systems for the facility.

 

Project success

 

The topsides were installed onto the Perdido spar in March 2009. At 9,350 short tons of the deck, excluding rigging and materials, this lift is the heaviest ever made in the U.S. Gulf of Mexico. At a water depth of 7,817 feet, Perdido is the world’s deepest spar.

Alliance Wood Group Engineering, L.P.
330 Barker Cypress Rd.
Houston, TX 77094
Tel: 281-828-6000
Website: www.alliance-engineering.com


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