Influence of Ocean Transport on the Design of Onshore and Offshore Constructions, Modules, Topsides, Jackets and Towage on FPSO Design

Oil and gas installations both onshore as well as offshore are often built in modules and components on a different location than where those facilities are commissioned. Although stress and fatigue damage have proven to be significant on these structures during ocean transport, ocean transportation is often not adequately accounted for during design. Prior to arrival on its final destination, constructions are exposed to severe motions when carried on a modules carrier, a general purpose vessel or towed by 1 or more ocean tugs. The authors argue that calculations on the significance and effect of these motions should be based on proper motion response calculations instead of currently used ‘rules of thumb’. Especially regarding the continuing growth of the size of these carriers and the weight of the structures which both increase the negative effect of sea behavior and affects the loads on the constructions. This article aims to explain the importance of design for transport during the design-phase of these onshore and offshore structures. A distinction is made between structures transported aboard a barge, semi-submersible or general purpose vessel and floating structures transported through a ‘wet-tow’ operation.