Page 485 - Pipelines and Risers

452 Chapter 24

is terminated by bulkheads which are stress distribution diaphragms. To facilitate the
installation, ballast chains are attached to the bundle for the purpose of submerged weight
adjustment and to suit installation by towing. Spools, which are short rigid flowlines, are
needed to facilitate tie-in of the bundles/flowlines to structures.

The advantages of this concept include onshore fabrication and pressure test, simplified
installation, thermal insulation and mechanical protection for the internal flowlines, etc.

24.3.2 Bundle Configurations

Bundle configurations can be grouped into two kinds namely conventional configuration and
innovative configuration.

Conventional configuration is mainly carrier-based system as sketched in the figure below.
All the rests of the bundle system are within the carrier pipe which provides buoyancy and
acts as mechanical protection.

Innovative configuration is the one without carrier pipe or no inner sleeve pipes. One option is
to use external single or multiple buoyancy pipe(s) for all flowlines as sketched in Figure
24.1.
The bundle configuration shall fulfill the weight and buoyancy requirements. In addition, the
following principles shall be considered when selecting the bundle configuration:

0 The center of gravity of the bundle has to be situated as near as possible to the vertical
center line of the carrier and as far as possible below the horizontal center line of the
carrier.
0 The bundle should be configured at the bulkhead such that sufficient distance exists
between the flowlines to allow for access during fabrication.
The minimum clearance between the flowlines and the sleeve pipe shall be selected to
allow for heat transfer.
0 The configuration must allow for the design of suitable spacers.