Note: Descriptions are shown in the official language in which they were submitted.
884~
CORNER STRUCTURE FOR CRYOGENIC INSUI~TION SYSTEM
The present invention relates to containers, tanks, or
ships, for the storage or transportation of cryogenic
liquids such as liquid natural gas (L~G), and is partic-
ularly concerned with containers, tanks or ships of the
above type containing non-metallic, e.g. plastic, foam
insulation and one or more liners, ancl preferably a low
temperature resisting, e.g. low thermal expansion, liner
such as high nickel steel, and a simple yet strong
support structure for the liner or membrane at the
10 corners, such corner structure being readily fitted into
the foam insulation at the corner and permitting trans-
mis~ion of loads at various angles f~om the liner to the
tank wall or ship hull, with minimum heat transmission
to the cold contents.
15 A containex or tanker for the storage and/or transporta-
tion of a cryogenic liquid must be designed to withstand
extremely cold temperatures. Generally vessels oE this
type axe composed of an outer wall of a rigid structure,
a heat insulating layer provided at the inside surface
20 of such wall and an inner membrane on the inside surface
of such heat insulating layer. Often several heat insu-
~ .
lating layers of non-metallic, e.g. plastic, foam insul-
ation, are employed and one or more membranes, particul-
arly an inner liner or membrane such as a nickel steel
25 liner in contact with the cryogenic liquid and one or
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more additional secondary liners positioned between foam
insulation layers. The primary liner, generally made of
a thin low temperature resistant (low thermal expansion)
material s~ch as nickel steel, is maintained in close
contact with the surface of the adjacent heat insulating
layer and transmits the internal pressure applied by the
low temperature liquefied gases through the heat insula-
- ting layers to the outer container or the hull of a
tanker.
10 of particular importance, the container or its insulation
system must be capable of withstanding the thermal strains
; induced by the cold liquid and the transients during the
cooling and warming cycles caused by the loading and unl-
oading of the liguid, and the mechanically induced strains
15 from the ship hull or container displacement during
operation.
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Critical portions of such cryogenic insulation systems
for supporting the primary liner are at the corners where
loads to which the liner i9 subjected, are transmitted
20 to the container wall or ship hull. In membrane systems
of the above type, designed to contain cryogenic liguids,
the coLners must be secured against movement caused by
membrane contraction and deflection of the supporting --~
,
I structure. Such corner structures must resist loads at
25 various angles and in a number of different directions
with minimum heat transmission to the cold cargo.
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However, one of the main difficulties of the relatively
complex corner structures of the prior art is the
difficulty involved in fitting the cryogenic insulation
around the various components forming these corner
structures, involving the use of intricate specially cut
pieces of foam for this purpose, which substantially
increases the cost of such cryogenic insulation systems.
The present invention provides a container for cryogenic
li~uefied gases which comprises a container wall, at
10 least one fiber reinforced plastic insulation layer
disposed within said container wall, a low temperature
resistant metal liner in contact with the inner side of .
sai~ at least one foam insulation layer, said corrtainer
having corners and including at least one corner struc-
15 ture, said corner structure comprising a corner support,
said corner support being disposed in said at least one
foam insulation layer adjacent said metal liner at said
corner of said container wall, a low temperature resis-
tant metal angle member, means connecting said metal
20 liner to said angle member, means connecting said angle
member to said corner support, a plurality of metal
strips, means connecting said metal strips adjacent one
end thereof to said angle member, and means connecting
said metal strips adjacent the other end thereof to the
25 wall of said container, said strips being substantially
in the plane of said liner, said strips transmitting
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loads from said metal liner to the wall of said
container.
The corner structure can be incorporated at corners of
the tank of varying angles. ThUs, the corner structure
can be incorporated into a 90 corner~ in which case
the angle member is a goo angle, and the first series
of strips are disposed at a 90 angle to the second
series of strips. If the corner structure of the
invention is incorporated in a corner having an acute
10 angle, the angle member is accordingly in the form of
an acute angle, and the first series of strips are
disposed similarly at an acute angle to the second
serie~ oE strips. If the corner structure of the inven-
kion is incorporated at an obtuse angle of the container,
15 the angle member is in the form of a corresponding
obtuse angle, and the first series of strips are disposed
at an obtuse angle to the second series of strips. In
certain instances, as described more fully hereinafter,
only one series of strips may be required at a corner.
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20 In a preferred embodiment, a corner support panel is
provided around the corner structure for supporting the
foam insulation at such corner. Alternatively, the foam
insulation can be bonded directly to the inner wall of
the container or shLp hull.
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The corner structure for supporting the membrane or
liner can be employed in conjunction with a metal memb-
rane having a low coefficient of thermal expansion to
contain cryogenic liquids in any type of container or
storage tank for marine or land use.
'
The use of metal strips or fingers, formed of a material
of low thermal conductivity and high strength such as
stainless steel, in conjunction with a membrane formed
of a material of low coefficient of expansion such as
10 nickel steel results in efficient transmission of memb-
rane loads in varying directions and angles from the
inner metal membrane to the outer wall of the container
or ship hull, and afEords a minimum heat loss and
minimum disruption of the foam insulation, thereby
15 peJmitting facile incorporation of the foam insulation
into and around such corner structure. The strip or
finger width and/or thickness can be sized so as to
accommodate or match the expected load intensity.
Further, the strip~ extending in one direction can be
20 wider and/or thicker than the strips in the other
direetion of the eorner strueture. In addition, where
a secondary or inner liner such as a fibergla~s liner,
is employed in conjunction with the primary metal liner,
the use of strips of fingers in the corner structure of
25 the invention for connecting the primary liner to the
eontainer wall or ship hull, permits the passage ~f the
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fiberglass liner through the foam at the corner struct-
ure, thus assuring structural continuity of such ~iber-
glass liner.
The present invention will be more ~ully understood by
the description below of certain preferred embodiments,
taken in connection with the accompanying wherein:
Fig. l is a perspective view showing a methane (LNG)
container or tanker containing an insulation system and
corner structure according to the invention;
lO Fig. l~ illustrates a preferred type of Eiber rein~orced
insulation material termed herein "3D" Eoam insulation
employed in the system of Fig. l;
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Fig. 2 is a 90 transverse corner section of the tank
or tanker~ taken on line 2-2 of Fig. l, showing the
15 corner structure of the invention;
Fig. 3 shows the corner structure of the invention which
is employed in the foam insulation system illustrated in
Fig. 2;
Fig. 4 is a plan view of the corner structure shown in
20 Fig. 3;
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Fig~ 5 is an isometric view showing the alternate or
staggered relation of one series of strips or fingers,
with respect to the other series of strips in the corner
structure;
Fig. 6 is a section simi~lar to Fig. 2v showing use of
the corner structure of the invention at a corner of a
tank forming an obtuse angle;
Fig. 7 is a section similar to Fig. 2, showing the use
; of the corner structure of the invention at a corner of
10 a tank forming an acute angle; and
Fig. 8 is a section taken Oll line 8-8 oE Fig. 1, show:lng
a corner according to the invention employing only one
series of strips. I
Referring to Fig. 1 of the drawing, numeral 10 indicates
15 a cryogenic liquid or LNG tanker having an inner hull 12
and an insulation system 13 positioned around the inner
hull. Such insulation system is comprised of an outer
Eiber reinforced foam insulation layer 1~ disposed
against the inner hull 12, and an inner fiber reinforced
20 foam insulation layer 16. Such fiber reinforced foam
insulation layers are preferably three-dimensional glass
fiber reinforced polyurethane foam layers. Such fiber
reinforced insulation material comprises blocks or
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planks of closed cell polyurethane foam having layers
of glass fibers, each layer of fibers extending in both
a horizontal and transverse direction, the X and Y
reinforcement fibers, and layers o~ f:ibers extending in
a vertical direction, the Z reinforcement fibers.
Fig. lA illustrates this type of material comprising
blocks 17 of closed cell polyurethane foam having layers
of.glass fibers 19 embedded in the foam and having
e~posed fiber ends 21 to facilitate bonding of the rein-
10 forced polyurethane blocks 17 to a structural membersuch as a tank wall. The polyurethane block 17 has
other glass fibers 23 extending vertically, with exposed :.
fiber ends 25 to facilitate bonding of the individual :
blocks to each other, and layers of other fibers 27
15 extending horizontally and normal to the fibers 19. :
This type of reinforcement is known as X-Y-Z reinforce- ...
ment, the X fibers being longitudinal fibers, the Y
fibers transverse fibers and the Z fibers vertical
; fibers~ and t~e resulting reinEorced foam is also known
20 as "3D foam." Preferably, planks of such 3D polyure-
thane foam are bonded together, as at 13 in Fig. 2 by a .~.
suitable adhesive, preferably a polyurethane adhesive,
to form the outer and inner .insulation layers 14 and 16,
respectively.
25 Referring to Figs. 1 and 2, a thin primary liner or
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barrier membrane 18 is positioned in contact with the
inner 3D foam insulation layer 16 and can be connected
thereto in any suitable manner, such as by the mechan-
ical fastener means comprising tongues 16 (see Fig. 8)
which are received and held in position in tongue
retainer means in the form of plywood strips 17 which ,~
are bonded to the foam insulation layer. The liner 18
is formed of a series of parallel sections or strakes
19, the strakes having upstanding flanges along their '
10 longitudinal edges, the flanges of adjacent strakes
being connected together. The tongues 15 are positioned
between the strake flanges 21 of adjacent strakes 19.
Such structure which is described in the above applic-
ations forms no part oE the present invention.
15 The primary membrane preferably is a low temperature
' resistant (low thermal expansion) material such as nickel
steel, preferably a high nickel steel such as the ,
material marketed as Invar (Registered Trade Mark). The
,~ membrane 18 is a fluid impermeable material and forms
20 an interior membranous vessel for containment of the ,
cryogenic liquid. A secondary liner 20 is sandwiched
' between the outer 3D foam insulation layer 14 and the
inner 3D foam insulation layer 16. Such liner can be a
fibe,rglass cloth liner or a combination of fiber glass
25 cloth with a thin metal, e.g. aluminum, foil, or such
secondary liner can be a resin impregnated fiber glass
cloth,e.g. impregnated with polyurethane resin, or such
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resin impregnated fiber glass cloth in combination with
a polyvinyl fluoride film marketed as Tedlar (Registered
Trade Mark). Such secondary liner can be an imperforate
liner, which prevents penetration of cryogenic liquid
from the inner foam insulation layer 16 to the outer
foam insulation layer 14.
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Referring to Figs. 2 to 5 of the drawing, the corner
structure of the invention is here illustrated as
incorporated at a 90 corner. At such corner there is
10 provided an angle member 22 which, like the primary
membrane 18, is comprised oE a low temperature resistant
material having a low coefficient of thermal expansion,
such as nickel steel, preEerably a high nickel steel
such as Invar, which is attached as by welding at 2~, to
15 the primary membrane or liner 18. A support member or .
back~up 26 for the angle member 22, is incorporated in
the inner ~oam insulation layer 16 adjacent the angle
member, the support member being bonded at 28 to the
~oam. Such support or back-up member 26 is preferably
20 in the form of plywood and i9 comprised of a pair or
support or plywood members 30 and 32 positioned at a 90
; angle to each other and in contact with the outer
surfaces of each face of the 90 angle member 22. The
support or back-up member 26 not only serves as a
25 support for angle member 22, but also serves to stabilize
the primary membrane 18 and provide a base for welding.
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The angle member 22 is attached to the plywood support
or back-up member 26 by means of screws 34.
A first series of metal strips 36 are connected at their
inner ends as by welding at 38, to one face 40 of an~le
member 22, and a second series of metal strips 42,
similar to strips 36, are similarly connected at their
inner ends as by welding at 43 to the other face 44 of
angle member 22. The strips or fingers 36 and 42 are
comprised of a low thermal conductivity (low coefficient ~-
10 of thermal conductivity) and high strength material,
such as stainless steel, for transmission of loads from
the primary liner 18 to the ship hull 12. It will be
seen in Fig. 3 that the first series of strips 36 and
t~e second series of strips 42 are positioned at a 90
15 angle to each other, and that the first series of strips
36 are in substantially the same plane as the primary
membrane 18 and angle member 22 in one direction thereof
at the corner, and the second series of strips 42 are
i substantially in the same plane as the primary liner 18
1 20 and angle member 22 in the other direction thereof at
; the corner.
Referring to Figs. 4 and 5, it will be seen that the
first series of strips 36 is comprised of a plurality
of spaced parallel strips, and the second series of
25 strips 42 are likewise in the form of a plurality of
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spaced parallel strips, the second series o:~ strips
being staggered or alternated with respect to the first
series of strips at the corner. It will be noted that
the inner ends of the respective strips 36 and 42 are
5 positioned in grooves 46 formed in the respective
postions 30 and 32 of the support member 26 and hence
as previously noted, the support member 26 functions as
a base for the welding of membrane 18 to the angle :.
member 22, as indicated at 38 and 43. The fingers 36
10 and 42 are proportioned, particularly with respect to
the width thereof, to accommodate and match the predeter-
mined load intensities to be transmitted from the primary
liner 18 to the ship hull 12.
The other ends of the ~ingers 36 are attached as by
15 welding at 48 to a metal strip 50 which in turn is
supported on a :~itting, such as the "T" fitting 52, which
in turn is connected to the ship hull 12. Thus, the strip
50 is mounted in vertical position in a groove 54 withln
the upper portion of the "T" 529 and is held therein by
20 angle 56 which abuts the outer surface of :eingers 36 and
is connected to the lower portion o:E the "T" :fitting by
a nut and bolt ~astener 58. The "T" 52 is connected as
by welding at 60 and by means of stud 62 to the inner
ship hull 12, a metal shim 64 being interposed between .
25 the flat outer sur:Eace of the "T" and the adjacent cont- :
ainer wall or ship hull 12.
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A similar system of components is utilized for
attaching the outer ends of the second series of strips
42 to the ship hull 12, including elements 50, 52, and
56 to 64.
5 A corner support panel 66 is provided and mounted on the
two "T" fittings 52 at the corner, by means of the studs -
62, for supporting the foam insulation layers 14' and
16' at the corners. It is noted that the corner support
panel 66 is preferably formed of a metal such as steel.
10 Longitudinal support panels 68, preferably of plywood,
are also provided and connected to the nut and bolt
connections 58 of the "T" fittings 52 at opposite corners,
;Eor supporting the ma:in body of outer and inner foam
insulation layers 14 and 16, along the length and width
15 of the tank, and spaced from the wall of the ship hull
12. The insulation support panels 66 and 68, which main-
tain the foam insulation system spaced from the inner
wall of the container or ship hull, afford a water sump
to trap water adjacent the inner ship hull.
20 There is also provided adjacent the corners, as seen in
Fig. 2, a member 70 incorporated in the foam adjacent . .
the ends o~ the primary liner 18, such fitting 70 conta-
ining a plurality of gas purge channels 72 for removal
of gases from behind the primary liner 18. Such fitting
25 70 is supported on a member 74 inserted in a suitably
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provided groove 76 in the inner foam insulation liner
16, the support member 74 preferably being formed, for
example, of plywood, and adhesively bonded to the
adjacent foam insulation layer 16.
Viewing particularly Fig. 2, it will be seen that the
simple construction of the corner support of the
invention, consisting essentially of the two series of
strips or fingers 36 and 42, connected to the anyle
member 22 and to the "T" fittings 52, permit the fitting
10 of the insulation layers 14' and 16' into the corner
and around and between the strips or fingers 36 and 42
with a minimum or disruption or discontinuity Oe the
~oam insulation and without re~Uiring the fitting oE
specially shaped and small pieces o~ foam around the
15 elements, as required in the prior art. Also, it will
be seen that the strips or fingers 36 and 42 permit the
passage of the secondary, e.g. ~iberglass cloth, membrane
20 therebetween, at the corners, thus assuring structura
continuity of this membrane.
20 The corner strUcture of the invention comprised essent-
ially of the strips 36 and 42 connected at one end to
the angle member 22 and at the other end to the "T"
fittings 92, is particularly designed to take high corner ,~
loads in tension and also to take compression loads,
25 applied by the primary membrane. ~uch strips or fingers
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preferably comprised of a low thermal conductivity and
high strength material such as steel, particularly
transmit the membrane loads in the various directions
and angles to the wall of the tank or ship hull, with
minimum disruption or potential damage to the adjacent
foam insulation.
It is noted that both the primary membrane or liner 18,
and the angle member 22 are formed of a material,
preferably high nickel steel such as Invar, having a
lO very low coefficient of thermal expansion. In contrast,
the strips or fingers 36 and 42 have a higher coefficient.
of thermal expansion, but a lower coeEficient of thermal
conductivity~ and are stronger than khe material of
membrane 18 and anyle member 22. This prov.ides the
15 advantages that less heat is transmitted from the outer ::
tank structure to the primary membrane, and there is
greater strength in the support structure for withstand-
ing and transmitting loads from the primary membrane to .
the outer tank wall or hull. Another advantage is that
20 by use of strips or fingers to support the primary
membrane at the corners instead oE larger single pieces
of metal, loads are not developed in a longitudinal .
direction along the strips, and shrinkage loads at the ;
ends of the strips are thus sobstantia1ly reduced. ' .
25 Fig. 6 illustrates application of the simple yet rugged
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corner structure of the invention at an obtuse angle of
the tank or tanker. Thus, it will be seen that the
angle member 78, which is connected to the primary liner
18 in the manner noted above, forms an obtuse angle,
and the two series of metal strips 36' and 42' are
disposed at a similar obtuse angle with respect to angle
member 78, the first series of metal strips 36' being
substantially in the same plane as one face 18a of the
primary membrane at the corner, and the other face 18a'
10 of the primary liner at the corner. The corner structure `
of the embodiment oP Fig. 6 is otherwise the same as the
;corner structure Por the 90 angle shown in Fig. 2.
Fig 7 shows the application of the corner structure oE
the invention at a corner o~ a tank or tanker in the
15 form of an acute angle. In this embodiment, angle
member 80, similar to angle member 22, forms an acute
angle at the corner, and the first series of strips 36"
and the second series oP strips 42" form a similar angle,
with the strips 36" again being substantially in the
20 same plane as one direction or face 18a of the primary ``
liner 18, and the other series of strips ~2" being sub-
stantially in the same plane as the other face or
direction 18a' oP the primary liner 18.
It will be noted that in the corner structure of Figs.
25 2, 6 and 7, employing two series of strips or Pingers,
the upstanding parallel strake flanges 21 on the primary
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liner strakes 19, in both directions of the liner 18 at
the corner, are perpendicular to the corner, as also
seen in Fig. 1, adjacent the section taken on line 2-2
thereof.
However, where the strake flanges in one direction or
face of the primary liner at the corner are perpendicular
to the corner, and the strake flanges in the other dire-
ction or face of the primary liner at the corner are
parallel to the corner, then only one series o~ fingers
10 need be employed, for connecting and supporting that
liner portion with the strake Elanges perpendicular to
the corner, to the container wall or ship hull. This
is illustrated in Fig. 8, showing the corner structure
at a 135 corner of the tank in Fig. 1. In this modif- i
15 ication, it will be seen that the upstanding strake
flanges 21 connected to the face 18a' of the liner 18
in one direction thereof at the corner, are perpendicu-
lar to the corner, whereas the upstanding strake flanges
21' connected to the face 18a of the primary liner 18
20 in the other direction thereof at the corner are disposed
parallel to the corner, as seen more clearly in Fig. 1
at the section taken on line 8-8 thereof.
Under the latter conditions, viewing Fig. 8, only one .
i series of metal strips 42", similar to strips 42, are
25 connected to the angle member 82 and to the "T" fitting
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52', the series of metal strips 42" in Fig. 8 being
substantially in the same plane as the face 18a' of the
primary membrane containing the strake flanges 21 which
are perpendicular to the corner. This corner structure
S employing the fingers 42" thus supports the primary
liner portion 18a', for example, when it is subjected
to contraction loads, for example. However, the other
face or portion 18a of the primary liner at the corner,
and in which the strake flanges 21' are disposed parallel
10 to the corner, can absorb contraction loads without
requiring the support of ths metal fingers such as 42"at
the corner, and hence no metal ~ingers are used to connec;t
}iner portion 18a at the corner to the container wall or
ship hull in this modiEication.
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15 The corner structure of Fig. 8 is otherwiss similar to
that of Fig. 2 employing substantially the same elements,
except that a plywood panel 86 is utilized at the corner
for supporting the foam insulation layers 14" and 16" at
the corner, instead o~ the metal support pane} 66 in Fig.
20 2. Such corner support panel 86 is mounted on stucls 88
connected to the inner ship hull 12.
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From the foregoing, it is seen that the invention
provides an improved corner structure for supporting the
primary liner of a cryogenic insulation system for tanks
2~5 and ships, designed especially to transmit loads in
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various directions from the primary membrane to the
inner ship hull, employing a simple structure comprised
essentially of a plurality of parallel strips, which
substantially reduces the complexity of the oam insul-
ation at the corner structure, and reducing heat leaks
to the cold contents of the container.
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Although the cryogenic insulation system of the inventionis particularly effective for use on ships or tankers,
such system can be used on any container for cryogenic
lO li~uids~ including barges, storage tanks, aircraft or
space vehicles. The thickness o~ the 3~ Eiber reinforced
~oam insulation in the system can be varied to limit the
boiloff to suit the need of the specific design.
While we have described particular embodiments of the
15 invention for purposes of illustration, it is understood
that other modifications and variations will occur to
those skilled in the art, and the invention accordingly
_ is not to be taken as limited except by the scope of the
appended claims.
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