Pipe in Pipe
04.49
A PiP (pipe-in-pipe) is a pipe inserted inside
another pipe. The created intermediate annulus can be used to place an
insulation material usually known as dry insulation. Indeed this insulation
material is protected by the outer pipe from the hydrostatic pressure and from
water penetration. PiP generally allow reaching optimized thermal performance
compared with wet insulated lines.
Over the past two decades, the pipe-in-pipe
(PiP) product has become an essential part of the subsea field development
engineer's "tool box." Due to its high insulation performance it
minimizes heat losses from the transported fluid to the environment that more
traditional subsea coatings cannot provide. This is achieved using thermal
insulation of very low thermal conductivity, such as aerogel, encased in dry
atmospheric conditions between the inner pipe or "flowline," which
transports the fluid, and the outer pipe or "carrier," which provides
the mechanical protection from the subsea environment.
Other benefits of the PiP solution include
compatibility with high temperatures (in terms of material and enhanced
compliance with large axial loading), stability on the seabed, and protection
by the outer pipe against external loads. In some cases this may obviate the
need for burial.
During manufacture, flowline and carrier
pipeline stalks are first welded and inspected. Then the flowline stalk is
progressively sleeved into the carrier pipe stalk, while thermal insulation
panels and nylon rings are hand-applied at regular intervals. The function of
the nylon rings, known as centralizers, is to maintain the two pipelines
concentric and to mechanically protect the thermal insulation during each phase
of the PiP assembly, installation, and operational life. Once full PiP stalks
are completed, they are spooled onto the reel-lay vessel following intermediate
tie-in connections.
The next major milestone was the first
implementation of a reeled PiP on a deepwater project, BP's Nile field in the
Gulf of Mexico (GoM) in 2001. Novel features introduced for this installation included
microporous insulation, designed to meet the field's challenging thermal
demands, and the implementation of qualified buckle arrestors and waterstop
features. The aim was to limit the potential consequences of a (very unlikely)
wet buckle event. Experience gained on this deepwater project proved important
for future projects in the GoM, West Africa, and Brazil.
Sumber:
http://www.offshore-mag.com/articles/print/volume-75/issue-2/pipelines-flowlines/
http://www.itp-interpipe.com/products/pipe-in-pipes/pipe-in-pipes.php
0 komentar