fixed offshore platform

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Fixed Offshore Platform

Components, Definitions and Terminologies

HelideckA raised level on a platform to facilitate helicopter landings. Normally, solar panelsare mounted just below the helideck framing to facilitate auxiliary-power for the platform'sequipment.

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Vent / flare boomA long truss that supports a vent or a flare line. Topsides (or Deck structure)The upper part of the platform (generally above the reach of

the highest wave height) that houses most of the equipment related to Process, Mechanical,Electrical, Piping and Instrumentation. Also houses generally some form of housing (Doghouse, LQ or Workshop, Battery room, etc).

Jacket structureThe part of the platform that supports the topsides and is generallysubmerged below the water line. A jacket may simply be called a supporting frame of theplatform. Its design is mainly governed by the wave loads.

Crane pedestalA large structural tube that supports an offshore crane for lifting purposes.Sometimes, crane pedestals also function as diesel storage tanks since their diameter is largeenough to house fuel.

Piles, Skirt pilesMajor structural members that are driven through hollow leg tubes to reachand embed below sea-bed for depth that is adequate to support the platform in its worst 'in-service' conditions. The pile embodiment is generally governed by the capacity of soil towithstand platform loads and forces of environment (wave & wind) that act upon theplatform. Pile also connects the jacket structure to the topsides. Skirt piles are required whenthe soil is very weak and the existing number of piles formed by the geometry of the platform

is not adequate. Skirt piles are run close to the main pile/leg as a cluster of 2, 3, 4, etc. Transition pieceA structural element generally in the form of a cone that links the topsides

and jacket structure. It is generally a cone since the topsides leg sizes are smaller in diametercompared to that of jacket legs.

ConductorsLong hollow straight or curved tubes that embed into the sea-bed and throughwhich drilling for oil, gas or both is performed. To support such long length of tube,conductor framings are provided to act as lateral support guides to conductors. Hence such

plan framings are called conductor framings. RisersLong slender tubes that carry the crude or partially processed oil/gas to another

location for further processing either to a land based facility or to another platform by way ofunder water pipelines. Risers are generally clamped to the jacket structure.

Boat landing, Barge bumper and Riser guardsAs the name suggests, this component ofthe platform is for berthing of supply vessels. To facilitate a smooth berthing, barge bumpers(that are equipped with shock cells) are mounted on each side of boat landing to facilitate a

reduced vessel impact on the structure. A riser guard is another protective structure thatprotects the oil/gas carrying risers. They are designed for accidental vessel impacts.

Launch trussSometimes, the jacket structures are very large and cannot be lifted even withlarge cranes, hence permanent structures like launch trusses are provided on one side of thejacket to facilitate the loading out on to the barge. If the jacket is designed for buoyancy, the

jacket is launched in the sea after reaching its destined position for a natural append andleveling. When the jacket is launched, it floats due to buoyancy. The jacket legs are thensequentially flooded to make it upright and stand over the sea-bed before the piles are driventhrough the legs to fix it to the sea-bed. The launch truss helps in skidding the jacket from thebarge (large flat surface vessel) to the sea.

MudmatAs the name suggests, mudmat is the bottom-most framing of the platform thathelps resist the natural forces of nature towards stability of the platform before the piles are

driven through the legs. The mudmat is like a large raft made up generally of timber thathelps resist platform's sinking deeper if the soil is too soft near the top layer of sea-bed andalso provides adequate resistance to overturning.