Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITE STRUCTURE VESSEL AND TRANSPORTATION SYSTEM FOR
LIQUEFIED GASES
FIELD OF THE INVENTION
[0001] The invention relates to a composite structure vessel and
transportation system for
liquefied gases.
BACKGROUND OF THE INVENTION
[0002] The use of liquid carbon dioxide (C02) and liquid nitrogen (N2) in the
natural gas and oil
industries has been widespread over the last ten years.
[0003] In the natural gas industry, as natural gas drilling activity has
increased as a result of
increased market demand for natural gas and the extraction of natural gas
becoming more
marginal in terms of initial productivity and decline rates from gas wells, so
has the requirement
to stimulate (i.e., fracture) wells to maximize production. Liquid CO2 is a
prominent fluid used in
well fracturing procedures within natural gas wells.
[0004] In addition, within the oil industry, CO2 injection is the most
commonly used enhanced
oil recovery (EOR) technique. In this technique, CO2 is injected into an oil
reservoir to expand
and thereby push additional oil to a production wellbore and/or it is used to
dissolve in the oil to
lower its viscosity and enhance the movement of the oil to a wellbore.
[0005] Liquid nitrogen is primarily used in Coal Bed Methane (CBM)
applications. In this
technique, N2 is injected at high rates into a CBM well. The pressure build-up
eventually causes
fracturing mechanics to occur (i.e. causes seams in the rock formation to
expand) opening
channels for methane to flow to the wellbore for capture.
[0006] In each of the above, the liquefied carbon dioxide and nitrogen gases
are manufactured at
specialized cryogenic plants. These cryogenic plants are ideally,
strategically located across an
area such that they are located as close as possible to the customers and are
built at locations
based on the actual or anticipated demand for the liquefied gases such that
the transportation costs
for the gases between the well site and gas plant can be optimized. Clearly
however, as a result of
the operating efficiencies and capital costs of building cryogenic facilities
together with long-term
shifts in demand for product, the end-result is that significant volumes of
liquefied gases will be
transported significant distances between a cryogenic plant and a specific
well site. Moreover, at
present, liquefied gases are transported to a specific well site using
specialized trailers with
tankers designed to withstand the temperatures and pressures of a specific
cryogenic cargo.
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[0007] Specifically, and in the case of a tanker for liquid carbon dioxide, it
is typical to use a
tanker that can safely contain the liquefied product at approximately 300 psi
and a temperature of
-50 C whereas in the case of a tanker for transporting liquid nitrogen, it is
typical to use a tanker
that can safely contain the liquid nitrogen at atmospheric to 50 psi pressure
and -170 C.
[0008] A typical liquid carbon dioxide tanker usually has an insulated carbon
steel structure
whereas a liquid nitrogen tanker usually has a vacuum-sealed dual-wall
stainless steel structure.
Both tankers may incorporate insulation on the inner surfaces to limit heat
gain from the exterior
of the vessel. In the case of liquid nitrogen, insulation is of particular
importance.
[0009] The total trailer weight (trailer plus payload) and the dimensions of
heavy vehicles used
in infra- and inter- provincial/state transportation are subject to strict
federal and provincial/state
standards. For example, in the province of Alberta, Canada, maximum legal
weights for a Tridem
Drive Truck - Tridem Semi Trailer are shown in Table 1. The normal maximum
total weight of
cargo and tanker permitted in the United States is typically about 35,000 kg.
[0010] Table I- Trident Drive Truck - Trident Semi Trailer Legal Weights
Axle Weight ft)
Steering Axle 7,300
Tridem Drive Axle 23,000
Tridem Trailer Axle 24,000
Gross Vehicle Weight 54,300
saead
Vdheelbase inMSaee5yacdng S ead
[0011] More specifically, the general structure and payload capacities of
currently used tankers
for liquid carbon dioxide and liquid nitrogen transportation are as shown in
Tables 2 and 3,
respectively.
[0012] Table 2- Liquid Carbon Dioxide Tanker
Vessel Construction Insulated carbon steel
Vessel Capacity 31,272 kg
CO2 Payload 28,000 kg maximum (while
trans ortin )
Pressure 300 psi
Temperature -50 F
Empty Trailer Weight 12,088 k
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[0013] Table 3-Liquid Nitrogen Tanker
Vessel Construction Vacuum sealed stainless steel (dual wall)
Vessel Capacity 31,544 k
N2 Payload 28,000 kg maximum (while transporting)
Pressure 50 psi
Temperature -325 F
Empty Trailer Weight 10,646 kg
[0014] In the past, the different conditions required to maintain CO2 and N2
in liquid phase (CO2
= high pressure and warmer temperature versus N2 = low pressure and cold
temperature) has
resulted in the construction of unique trailers/tankers for each product.
[0015] However, the use of unique trailers for each type of product will often
result in poor or
inefficient utilization of a company's resources when both products are being
sold by the
company. In certain circumstances, the physical locations of cryogenic plants
may cause one
tanker type to be driven significant distances without a cargo and/or during a
period of reduced
industry activity, a fleet of specialized tankers may be inactive. For
example, when CBM
activity is reduced as a result of lower gas prices, a liquid nitrogen tanker
may see lower
utilization.
[0016] Other problems with existing systems are discussed below:
[0017] The useful life of a typical steel vessel tanker/trailer is
approximately fifteen years. Over
that time, steel vessels will require preventive maintenance and/or repair and
patch work as a
result of rust and corrosion. As part of a preventive maintenance program,
most operators at a
minimum will require at least three re-painting overhauls over the life of one
N2 trailer which is
both expensive and time consuming. Further still, an operator having multiple
trailer designs will
also require specialized mechanics with the knowledge and capability to handle
separate repair
techniques and tools for each type of trailer.
[0018] Accordingly, as a result of the foregoing problems, there has been a
need for a
tanker/trailer system and method of operation that is capable of transporting
different
gas/liquefied gas cargoes within the same vessel to provide enhanced
operational efficiencies in
the geographical delivery of gas/liquefied cargoes between gas plants and
consumers. More
specifically, there has been a need for a cryogenic gas/liquid transportation
system capable of
transporting both liquid carbon dioxide and liquid nitrogen within the same
vessel at different
times.
[0019] A review of the prior art indicates that such a system and method has
not been previously
described. For example, US Patent 5,419,139, US Patent 6,047,747, US Patent
6,708,502, US
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Patent 7,147,124, US Patent 6,460,721 US Patent 3,163,313 each describes
various vessel
structures for transporting single gases/liquid gases. US Patent 1,835,699, US
Patent 3,147,877,
US Patent 3,325,037, US Patent 3,406,857 and US Patent 7,024,868 describe
various pressure
vessels. US Patent 5,385,263 describes a transportation system for compressed
gas using
composite cylinders.
SUMMARY OF THE INVENTION
[0020] In accordance with the invention, there is provided a composite vessel
for operative
connection to a truck trailer system for transporting at least two gas
products within the
composite vessel at different times, the composite vessel comprising: an inner
liner for contacting
a gas product within the composite vessel; a composite layer operatively
connected to the inner
liner, the composite layer including a plurality of resin-impregnated fiber
layers wound to provide
pressure and structural integrity to the composite vessel while transporting
each gas product; a
thermal insulation layer operatively bonded to the exterior of the composite
layer for providing a
thermal barrier between the interior and exterior of the composite vessel;
and, an outer protective
layer operatively bonded to the thermal insulation layer for providing
abrasion and impact
resistance to the thermal insulation layer during truck movement.
[0021] In further embodiments, collectively each of the inner liner, composite
layer and thermal
insulation layer have a heat transfer coefficient that minimizes atmospheric
gas loss to less than
2% of the total volume of gas product from the composite vessel over a 24 hour
time period at
ambient temperatures.
[0022] In a preferred embodiment, the composite vessel is cylindrical having
isotensoid geodesic
ends. Each isotensoid geodesic end will preferably include a penetration
extending from the
exterior to the interior of the vessel with each penetration supporting a boss
and a seal ring
operatively connected to the composite vessel between the inner liner and
composite layer
adjacent the penetration.
[0023] In further embodiments, the composite layer includes a plurality of
alternating helical and
hoop wound layers. In various embodiments, the helical layers are wound at an
angle of 15-25
to the longitudinal axis of the vessel and the hoop layers are wound at 80-90
to the longitudinal
axis of the vessel.
[0024] In another aspect of the invention, the invention provides a method of
manufacturing a
composite vessel having an inner liner, composite layer, insulating layer and
protective layer, the
composite vessel for operative connection to a truck trailer system for
transporting at least two
gas products within the composite vessel at different times, comprising the
steps of. assembling
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the inner liner and two pairs of a boss and a seal ring on a supporting axle;
rotating the assembled
liner about a longitudinal axis of the supporting axle and applying layers of
resin-impregnated
fiber over the liner at series of desired angles to form a composite vessel;
allowing the composite
vessel to cure; applying the insulating layer to the exterior of the vessel;
and, assembling the
protective layer onto the exterior of the insulating layer.
[0025] In yet another embodiment, the invention provides a tanker trailer
comprising: a tridem
trailer; a composite vessel for operative connection to the tridem trailer,
the composite vessel for
transporting at least two gas products within the composite vessel at
different times, the
composite vessel having: an inner liner for contacting a gas product within
the composite vessel;
a composite layer operatively bonded to the inner liner, the composite layer
including a plurality
of resin-impregnated fiber layers wound to provide pressure and structural
integrity to the
composite vessel while transporting each gas product; a thermal insulation
layer operatively
bonded to the exterior of the composite layer for providing a thermal barrier
between the interior
and exterior of the composite vessel; and, an outer protective layer
operatively bonded to the
thermal insulation layer for providing abrasion and impact resistance to the
thermal insulation
layer during truck movement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention is described by the following detailed description and
drawings wherein:
Figure 1 is a cross-sectional drawing of a composite tank in accordance with
one
embodiment of the invention showing detail of a boss and sealing system.
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DETAILED DESCRIPTION
[0027] In accordance with the invention and with reference to the figure,
embodiments of a
tanker having a composite structure for transporting cryogenic liquids are
described.
[0028] In its broadest sense, a composite structure is described for
transporting different
cryogenic liquids within the same vessel at different times. In more specific
embodiments, a
composite structure system is described for storing and transporting both
liquefied carbon dioxide
and nitrogen. The composite structure results in a significant weight
reduction in the empty
weight of tanker system thus enabling approximately 20% more cargo to be
transported by a
single tanker.
[0029] Structure
[0030] The structure of the composite vessel in accordance with the invention
is comprised of
various layers of material as outlined in Table 4.
[0031] Table 4-Composite Vessel Structure
~, h t
++11..,, `1'C C ess:~ Descript;oirFunction
vvR_ 4 'noIIlinal~
Outer Protective 2mm Thermal spray coating Wear and corrosion
Layer Clear CoatTM, composite, or protection, concealment, very
metal low weight
Insulation 120mm Polyurethane foam (2 - 2.5 lb. Thermal barrier, impact
density) protection
Composite Shell 6mm Carbon-fiber or Fiber-glass Pressure strength, thermal
reinforcement barrier
Inner Liner 6mm Polymeric material (e.g., Payload contaminant barrier,
polyethylene, epoxy, thermal barrier
dic clo entadiene, urethane)
[0032] More specifically and as shown in Figure 1, the system 10 includes an
outer protective
layer 12, an insulation layer 14, a structural composite layer 16 and inner
liner 18. The composite
vessel will also include at least two bosses 20, one of which will be
permanently sealed according
to safety regulations, the other for accessing the interior from either end of
the vessel. Each of
these layers are described in greater detail below:
[0033] Outer Protective Layer 12
[0034] The outer protective layer provides wear and corrosion protection to
the underlying
structures. The outer protective layer has a nominal thickness of 2-3mm and
may be a thin metal
layer such as stainless steel or a composite material such as fiberglass. In
addition to protection
this layer may also assist in concealing the cargo. It is preferred that the
outer protective layer is
light weight in order to not substantially contribute to the overall weight of
the vessel and cargo.
[0035] Insulation Layer 14
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[0036] The insulation layer is the primary thermal barrier between the
exterior and interior of the
vessel. The insulation layer has a nominal thickness of 120 mm. A preferred
insulating material is
polyurethane foam (2-2.5 lb density) spray coated to the underlying composite
layer. In addition,
the insulation layer will also provide impact protection to the main
structural composite layer 16.
[0037] Composite Structural Layer 16
[0038] The composite structural layer 16 is the main structural layer of the
vessel and is
comprised of composite layers of carbon-fiber and/or fiber-glass within a
resin matrix. Other
fibers may also be used, such as basalt, polyethelyne, Kevlar, etc. as known
to those skilled in the
art. For most systems, the composite layer will have a nominal thickness of 6-
8 mm. The
composite layer is preferably comprised of sub-layers of resin-impregnated
fibers wound at
varying orientations to provide multi-axis structural strength to the vessel
including burst, torque
and bending strength. For example, circumferentially (or hoop) wrapped fibers
are used to
provide structural strength in a radial direction with respect to the vessel's
horizontal/longitudinal
axis (i.e. burst strength) whereas longitudinally or helically wrapped fibers
(or fibers wrapped at
smaller angles relative to the vessel's horizontal/longitudinal axis)
generally provide strength
along a transverse axis of the vessel. The combination of the two layers
provides bending/torque
strength. The composite layer also provides an additional thermal barrier to
the interior of the
vessel.
[0039] More specifically, in one embodiment, the composite structural layer
will be carbon fiber
consisting of distinct layers of wound fiber that are wound at different
angles (both positive and
negative angles) to the horizontal axis of the vessel. In order to promote
maximum strength
between adjacent layers, successive layers of both helically and
circumferentially wrapped layers
are alternated. For example, a first layer may comprise two winds of helically
wound carbon
fiber, wound at an angle of approximately 15-25 degrees to the horizontal
axis. The wind angle
will generally be determined during design of a specific tank using known
mathematical
modelling techniques that seek to minimize void space and resin volume within
a composite
matrix while maximizing the fiber volume ratio for a given boss diameter and
end radius (i.e. a
geodesic isotensoid dome described in greater detail below) without gaps or
overlap in the
composite structure. For example, for a given ratio of boss diameter to dome
end radius, 18.7
degrees may be a preferred wind angle at both positive and negative wind
angles. A larger ratio
would generally require a larger wind angle. A second layer may comprise
circumferentially
wound carbon fiber, wound at an angle between 80 and 90 degrees to the
horizontal axis (wound
at both positive and negative wind angles). Each of the first and second
layers may then be
alternated as desired or in accordance with another sequence to form a vessel
having a desired
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hoop:helical stress ratio. In a preferred embodiment, the vessel will comprise
approximately 18
hoop layers interspersed with 6 helical layers resulting in a total nominal
thickness of
approximately 5-8mm.
[0040] Liner 18
[0041] The inner liner layer provides both payload contaminant protection and
an additional
thermal barrier to the interior of the vessel. The inner liner layer has a
nominal thickness of 6mm
and may be comprised of a suitable polymeric material such as a polyethylene,
epoxy,
dicyclopentadiene and/or urethane having a low porosity. Stainless steel can
also be used as a
liner.
[0042] In the case of a thermoplastic liner, the liner may be manufactured by
roto-molding as a
single component or as multiple components and welded together.
[0043] The composite vessel will also preferably include internal baffles to
minimize product
shifting (sloshing) during transport. In a preferred embodiment, the baffles
(not shown) are
polyethylene baffles welded to the vessel liner after assembly of the vessel.
[0044] Boss 20
[0045] In a preferred embodiment, a boss 20 is located at each end of the
vessel. One or more
additional bosses 20a may also be located at other locations where
penetrations through the
cylindrical wall of the vessel are desired or necessary.
[0046] In a preferred embodiment, the vessel 10 has both a cylindrical mid-
section 10a and
geodesic isotensoid dome ends 10a. As such, there are three main functions of
the end bosses.
[0047] The first is to provide a finite radius polar fitting at the terminus
of the geodesic
isotensoid dome. The radius of each polar end boss will depend on the diameter
of the tank and
the helical wind angle used in the filament winding process.
[0048] The second function of the end boss is to transmit forces acting on the
boss and cap 26
from the pressurized fluid inside the tank to the vessel structures. That is,
these loads are
transmitted via a radial flange 22a that is contoured to match the geodesic
dome contour.
[0049] The third function of the end boss is to provide a port for
instrumentation, maintenance of
internal components, or any other purpose.
[0050] The function of any additional bosses penetrating the cylindrical wall
will vary depending
on the purpose of the opening. Typical purposes include fluid inlets or
outlets, instrumentation
ports, or inspection ports, for example. The size and shape of these bosses
will depend on their
function and location on the tank, as well as tank geometry and other factors.
Each boss may be
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fabricated from metal, polymer, ceramic, glass, composite or other materials
as known to those
skilled in the art.
[0051] As shown, both the boss 22 and composite layer 16 will include
appropriate tapers in
order to maximize the strength at boss/composite interface. Maximum thickness
of both the
composite layer and boss will be incorporated closest the opening in order to
maximize strength
of the vessel adjacent to and around the opening. That is, the composite layer
will taper to the
nominal composite layer thickness away from the opening and, similarly, the
boss will also taper
from a greater thickness adjacent the opening to a narrow end away from the
opening.
[0052] Cap 26
[0053] Each boss where fluid inlet or outlet plumbing will not be attached
will require a cap 26
that may be configured for other purposes. For example, an instrumentation
port will be sealed
with a cap that has features necessary for attachment of a particular
transducer and for
transmission of the transducer's signal from the inside of the tank to the
outside.
[0054] The cap, like the boss, can be made from virtually any solid material.
In a preferred
embodiment, the caps will be made from compression molded carbon fiber
composite with a
hydro-formed liner of stainless steel or aluminium. As composite material can
be porous, a metal
lining will prevent fluid from seeping into the composite, potentially causing
the composite
material to swell or the microstructure to weaken.
[0055] The cap will interface and seal with the boss using an appropriate lock
and seal system.
[0056] Seal Ring 24
[0057] The vessel includes a seal ring 24 to prevent fluid from flowing
between the tank liner
and a particular boss. The seal ring may be manufactured from any suitable
material including
stainless steel and includes a cylindrical bore 24b and a conical outer
surface concentric with the
bore that interfaces with a matching conical surface on the tank liner. The
seal ring is secured
within the boss 22 by an array of fasteners 22a that pass through the boss 22
to engage with the
cylindrical bore 24b. The fastener 22a causes a series of redundant lip seals,
glands, or ridges 24a
to tighten against both the liner 18 and boss 22 to prevent fluid from flowing
between the seal
ring and the liner 18 and boss 22 at the conical interface. As a result,
pressurized fluid is
prevented from entering the region where the boss meets the tank liner.
[0058] The conical wedge seal ring design is intended to allow the pressurized
fluid inside the
tank to activate the sealing mechanism. Pressure acting on the exposed face of
the seal ring
forces the seal ring deeper into the conical pocket where it seals against the
liner and boss. In
addition, the conical wedge seal ring design provides a mechanism for
compensating for any
creep, a phenomenon characteristic of polymers that may be used for the liner.
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[0059] As a result, this design allows for a simplification of maintenance
procedures wherein,
for example, service personnel will adjust the tension in the fastener 22a to
pull the seal ring into
the pocket. In another embodiment, the fastener 22a may be provided with a
tensioning system
that provides a constant force on the seal ring throughout its expected range
of movement during
the design service life of the tank. For example, helical coil springs 22b
might be installed
beneath a fastener screw head that are tightened in order to pull the seal
ring into the pocket. The
coil springs 22b would then provide a constant tension in the fasteners to
compensate for any
polymer tank liner material creep at the seal interface such that as any creep
occurs, the seal ring
will move deeper into the pocket.
[0060] Manufacture
[0061] In one embodiment, the vessel is manufactured in accordance with the
following process:
a. The inner liner is manufactured and assembled to form a rigid/semi-rigid
structure. As noted, the inner liner may be manufactured as a single component
by roto-molding or assembled from smaller extruded/molded components.
b. The inner liner is assembled onto a supporting axle together with the
bosses and
seal ring. That is, preferably the end bosses, seal ring and liner are
assembled
onto a central supporting axle wherein the bosses, seal rings and liner are
secured
together. If necessary, the inner liner once assembled on the supporting axle
may
be moderately pressurized in order to increase the rigidity of the structure
for
winding.
c. The supporting axle is rotated and appropriate layers of resin-impregnated
fiber
are laid down over the liner at the desired angles.
d. The vessel is allowed to cure for an appropriate time period based on the
resin-
system utilized. It should be noted that the selection of the resin-system
must
consider a cure time and associated thermal characteristics to ensure that a
thermoplastic liner is not damaged during curing.
e. After curing, the insulation layer and outer protective layer are assembled
on the
cured vessel.
f. The supporting axle is removed and any finishing is completed including the
assembly of anti-slosh baffles within the vessel.
[0062] Composite Vessel Parameters
[0063] The required operating range for the parameters of pressure and
temperature for the
composite vessel to safely contain both a liquid carbon dioxide and liquid
nitrogen cargo are
outlined in Table 5.
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[0064] Table 5-Composite Vessel Parameters
Prafneter Range
Pressure 0-350 psi
Temperature 60 C to -200 C
[0065] Other features/specification of the composite vessel and tanker/trailer
system are detailed
in Table 6.
[0066] Table 6-Composite Vessel/Tanker/Trailer Specifications
E1 mentlParamcter Punction/Vai
Liquid level indicator/ measurement accurately indicate the 1%
system amount of liquid in the
composite vessel
Pressure indicator/regulator/ accurately indicate and 1%
measurement system regulate the pressure of
the fluid in the composite
vessel
Valve and piping system facilitate loading and unloading of the composite
vessel
using a single pump to reduce weight.
Controllable, variable output flow allows fluid to be pumped out of the
composite vessel at a
rate system controllable rate.
Appropriate shields/enclosures protect the pump, valves and piping from
potential impacts
from rocks or debris or in the event of a collision
Maximum product loss rate resulting 1% per 24 hour period
from heat transfer/ pressure relief
Tank ambient temperature range. +50 C to -50 C
Maximum allowable working 200 psi (pressure test to 1000 psi)
pressure (MAWP):
Primary relief pressure 32 si
Secondary relief pressure 355 psi
Minimum pump flow rate 1.51 m /min
Minimum tank payload 34,000kg
Maximum tank length 14.17m
Maximum tank width 2.44m
Man-way diameter 51 cm
Minimum design service life 25 years
Temperature range for liquid nitrogen -210 C <_ T:5 -196 C
Temperature range for liquid carbon -50.0 C <_ T:5 -40.0 C
dioxide
Maximum wheelbase (kingpin to 10.95m
center rear triple-axle centerline)
Maximum frontal overhang (kingpin 1.46m
to front of tank):
Maximum rear overhang (center rear 35% of wheelbase = 3.83m
triple-axle centerline to rear of
trailer):
Axle spacing 1.52m
Kingpin load 45% of sprung trailer weight (including payload)
Trailer axle set load 55% of sprung trailer weight (18.33% per axle, for
triple
axle configuration)
Maximum combined weight of trailer 43,500kg
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and payload
Minimum ground clearance at mid- 50cm
wheelbase
Maximum impact load at tank 2.5g impact load
centerline (directed vertically
upward; load applied directly to
pump / piping protective housing or
trailer frame; blunt object assumed to
provide impact force.
Maximum height of trailer (measured 3.35m
from ground level to highest part of
tank or trailer)
Inlet pipe diameter 6"
Outlet pipe diameter 6"
Vapor relief pipe diameter 2"
[0067] In addition the tanker/trailer system will also incorporate
compartments for housing
appropriate hoses/tools typically required for connecting the fluid delivery
(pump and piping)
systems to external equipment as appropriate valve, piping and openings
connected to or as part
of the vessel.
[0068] Further still, the system will generally meet the appropriate US and
Canadian codes to
operate on Canadian and US highways as understood by those skilled in the art.
While there are
no specific regulations governing the design criteria for such a
tanker/trailer system, it is
understood that the system will be designed to comply with the primary
integrity, safety and
testing criteria as required by US and Canadian regulations. Specifically, it
is intended that the
tank design and test procedures for the integrity of the tank will comply with
Canadian Standards
Association B620-03 (Highway Tanks and Portable Tanks for the Transportation
of Dangerous
Goods), applicable sections of Code of Federal Regulations (CFR) Title 49 and
ASME code
Section 10 which are incorporated herein by reference.
[0069] Advantages
[0070] The composite vessel as described herein provides the following
advantages over past
systems.
= an increased volumetric capacity (payload) of the trailer system;
= reduced weight of the tank, trailer and plumbing components.
[0071] In addition, the system provides economic advantages over conventional
tanker systems.
Primarily, by enabling an approximate 20% increase in cargo capacity for a
given total maximum
weight of a loaded tanker and trailer, a liquefied product supplier can
effectively deliver 20%
more cargo for an equivalent shipping cost.
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[0072] Further still, when a shipper is obtaining product from a number of
geographically
distributed gas plants, the ability of the current design to accommodate
different cargoes may be
used to optimize the deployment of a fleet of tankers to different gas plants
and customers. That
is, based on customer demand, customer location, and gas plant location, a
common fleet of
tankers may be deployed to ensure that each tanker is traveling a minimum
distance between a
customer and gas plant based on current demand. Importantly, if tankers do not
necessarily have
to return to a specific type of gas plant, the distance a tanker may travel to
obtain a new cargo
may be minimized.
[0073] The systems and methods described herein may also be adapted for use in
hauling of
other industrial gases including oxygen for chemical and pharmaceutical
manufacturers,
hydrogen for fuel cells or rare gases such as krypton, neon or xenon for
lighting, lasers, or
medical imaging.
[0074] Although the present invention has been described and illustrated with
respect to
preferred embodiments and preferred uses thereof, it is not to be so limited
since modifications
and changes can be made therein which are within the full, intended scope of
the invention.
