LNG
Pipe-in-Pipe Techology
Richard Rankin M.B.Mick AMEC Paragon Inc. Houston OGJ Nov 14, 2005 The
large number of proposed LNG projects currently vying
for public and governmental approval on a global basis has led to an
increased
focus on associated safety, economic, environmental, and aesthetic
issues. LNG
project teams will consider designing LNG terminals
using subsea or buried onshore LNG pipelines in an effort to offer
safe,
robust, cost-effective, and environmentally and visually appealing
alternatives
to more traditional technology. AMEC Paragon used this approach for the
Camisea
LPG export terminal offshore Peru. Using
InTerPipe's (ITP) subsea cryogenic pipeline system,
AMEC Paragon
proposed a marine export terminal design that allowed the client
(Pluspetrol
SA, Buenos Aires) to obtain critical local approval for the project. This article discusses the technical,
economic, safety, and local acceptance advantages of a terminal based
on subsea
or buried onshore LNG pipelines. Public
scrutiny
LNG
projects face significant public scrutiny
worldwide. Local populations object to
real and perceived safety, environmental, and inconvenience aspects of
siting
an LNG facility in their communities. In
siting LNG terminals and dealing with the public,
potential
developers need to be reminded of the basic equation developed by Peter
Sandman, a pre-eminent risk communication consultant: Risk
= Hazard + Outrage.
"Hazard"
is the technical risk engineers are
trained to assess. "Outrage"
is the public's perception of risk. "Outrage"
is made up of factors such as trust,
responsiveness,
control, etc.
Clearly,
with the difficulties experienced by developers of
some projects in obtaining local approval, a successful approach must
balance
technical and economic feasibility with political realities specific to
each
location. For each project, the
"Outrage" factor of the risk equation must be managed as effectively
as the "Hazard" factor. Alterative technologyFig. 1
It
is
technically and economically feasible to transport
cryogenic fluids (including LNG and LPG) at typical loading-offload
rates
(10,000 cu m/hr) over relatively long distances (~10 miles) via
straightforward, robust pipe-in-pipe loading lines.
This
feasibility provides wider options for siting an LNG
terminal than had previously been available. For projects where there
is strong
public concern about LNG carriers approaching residential areas, the
berth can
be moved further offshore. The LNG might also move via pipeline from a
berth to
an inland location where siting LNG tanks is more acceptable, or to a
facility
which has waste heat for regasification (refinery, alumina plant, etc.).
While
double-wall and triple-wall pipe-in-pipe options are
both thermally and mechanically feasible using ITP's LNG pipe
technology, we
have chosen to describe the triple-wall option.
Additionally
since the mechanical properties of ITP's
Izoflex insulation make it safe to weld directly over it the field
joints are
insulated in exactly the same manner as the running pipe, eliminating
any cold
spots. Elimination of expansion loops or bellows, which are typically
required
to accommodate the expansion and contraction caused by low operating
temperatures (-256o F), also increases both the robustness
of the
design and the feasibility of this approach.
Using
the 36% nickel steel inner pipe in the pipe-in-pipe
design allows expansion loops to be eliminated. The high thermal
performance of
the ITP insulation system also allows for a compact pipe-in-pipe
configuration. Pipe-in-Pipe
technology Lay barges using J-Lay, S-lay, reeled, or towed equipment weld and install these pipes in water depths exceeding 5,000 ft. ITP's technology uses the same DNV design code (DNV OS-F101 Submarine Pipeline System) employed for oil and gas pipe-in-pipe installations. High-performance
insulation
Another
important, field-proven component of the ITP LNG
pipeline is ITP's Izoflex insulation. It
is microporous insulation.
Unlike
other solid insulation materials, microporous
insulation has a thermal conductivity lower than the thermal
conductivity of still
air. Izoflex have been installed in
subsea oil and gas pipelines since 1998. Currently
105 miles of installed ITP subsea pipe-in-pipe
line has this
insulation. An additional 40 miles will
be installed in 2006 offshore Angola. |