(b) Steel fabrication typically contains less steel than
the reinforcement steel of a concrete platform.
However, the disadvantages include:
(a) The long installation programme once in position, in-
cludes a major piling operation to anchor the platform
to the sea-bed. This and the fitting of accammodation
modules are vulnerable to delays from bad weather and
interruptions in the extended supply lines for materials.
(b) Even with protective coatings and cathodic protection
systems, steel platforms have suffered severely from
sea-water corrosion.
2.1. Steel Oil-Production Platforms have three main components:
(a) The jacket, so called because it wraps around the
oil conductors.
(b) The deck, fitted to the top of the jacket.
(c) Modules which accommodate living units, drilling
equipment and processing equipment.
The jacket comprises 4 or 6 large tubular legs which stand
on the sea-bed. Each leg is surrounded by about 8 piles
which run to the full height of the jacket and are driven
into the sea-bed to anchor the structure. These piles are
held in position by a series of collars or pile guides
fitted to the legs. In the centre of the jacket, are a
series of conductor guide panels; these protect and guide
the conductors carrying the oil up from the wells driven
into the sea bed.
A series of bracing tubulars interconnect the various com-
ponents joining at specially reinforced nodes.
The overall size of the jackets may be l60m tall with a
base of 90m by 75m. The main legs are typically 5m dia-
meter; but up to 20m diameter in some designs.