The topsides on a boat, ship, watercraft, or
floating production storage and offloading
A floating production storage and offloading (FPSO) unit is a floating vessel used by the offshore oil and gas industry for the production and processing of hydrocarbons, and for the storage of oil. An FPSO vessel is designed to receive h ...
(FPSO) vessel, is that part of the
hull between the
waterline
The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line (positioned amidships), that indi ...
and the
deck.
[Rognaas, G., Xu, J., Lindseth, S., & Rosendahl, F. (2001). Mobile offshore base concepts. Concrete hull and steel topsides. ''Marine Structures'', ''14''(1-2), 5-23.] It includes the visible parts of the
bow,
stern
The stern is the back or aft-most part of a ship or boat, technically defined as the area built up over the sternpost, extending upwards from the counter rail to the taffrail. The stern lies opposite the bow, the foremost part of a ship. Ori ...
, sheer, and, if present,
tumblehome
Tumblehome is a term describing a hull which grows narrower above the waterline than its beam. The opposite of tumblehome is flare.
A small amount of tumblehome is normal in many naval architecture designs in order to allow any small projection ...
.
On an offshore
oil platform
An oil platform (or oil rig, offshore platform, oil production platform, and similar terms) is a large structure with facilities to extract and process petroleum and natural gas that lie in rock formations beneath the seabed. Many oil platfor ...
, topsides refers to the upper half of the structure, above the sea level, outside the splash zone, on which equipment is installed. This includes the
oil production plant
An oil production plant is a facility which processes production fluids from oil wells in order to separate out key components and prepare them for export. Typical oil well production fluids are a mixture of oil, gas and produced water. An oil prod ...
, the accommodation block and the
drilling rig
A drilling rig is an integrated system that drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to drill wat ...
. They are often modular in design and so can be changed out if necessary allowing expensive platforms to be more readily updated with newer technology. It contrasts with the jacket structure, which constitutes the lower half of the platform structure (the supporting legs and lattice framework), partly submerged in sea.
References
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Nautical terminology
Oil platforms