U.S. patent number 3,782,128 [Application Number 05/042,052] was granted by the patent office on 1974-01-01 for cryogenic storage vessel.
This patent grant is currently assigned to Lox Equipment Company. Invention is credited to Cesar Cavanna, Paul J. Eifel, Robert S. Hampton, Stasys J. Kungys.
United States Patent |
3,782,128 |
Hampton , et al. |
January 1, 1974 |
CRYOGENIC STORAGE VESSEL
Abstract
A vessel for storing and transporting cryogenic fluids such as
liquid helium. The vessel comprises a plurality of elongated
containers supported one within another in coaxial circumjacent
relation in a manner minimizing heat transmission therebetween, and
it further comprises a cooling system forming a temperature barrier
that restricts inward migration of heat from the outer to the inner
container. Respecting the support system, the inner fluid-receiving
container is supported by an encapsulating intermediate heat shield
container which in turn is supported by an outer jacket surrounding
and enclosing the intermediate heat shield. The support means
effecting such interrelationship includes both transverse support
structure constraining the containers relative to each other
against transverse or radial displacements and longitudinal support
structure interconnecting the containers one with another and
constraining the same against relative longitudinal displacements
at least at one end of the vessel. The transverse support structure
constitutes a plurality of structurally independent supports as
respects the interconnection of the inner container with the
intermediate heat shield and interconnection of the heat shield
with the outer jacket; and all of the support structures define
restricted thermal flow paths through which heat migration from the
outer container to the inner container is sharply limited.
Respecting the cooling system, two flow-separated cooling coils
surround the heat shield container, one of which carries a coolant
such as liquid nitrogen and the other of which connects both with
the inner fluid-receiving container and with a delivery system
through which fluid is withdrawn from the inner container.
Inventors: |
Hampton; Robert S. (Livermore,
CA), Cavanna; Cesar (Livermore, CA), Kungys; Stasys
J. (Livermore, CA), Eifel; Paul J. (Walnut Creek,
CA) |
Assignee: |
Lox Equipment Company
(Livermore, CA)
|
Family
ID: |
21919809 |
Appl.
No.: |
05/042,052 |
Filed: |
June 1, 1970 |
Current U.S.
Class: |
62/45.1;
220/560.12; 220/901 |
Current CPC
Class: |
F17C
3/08 (20130101); F17C 13/086 (20130101); F17C
2203/0643 (20130101); F17C 2203/032 (20130101); F17C
2260/031 (20130101); F17C 2205/0314 (20130101); F17C
2203/0631 (20130101); F17C 2227/0353 (20130101); F17C
2201/052 (20130101); F17C 2203/01 (20130101); F17C
2203/012 (20130101); F17C 2201/0109 (20130101); F17C
2250/0408 (20130101); F17C 2205/0326 (20130101); F17C
2203/016 (20130101); F17C 2227/0386 (20130101); F17C
2221/014 (20130101); F17C 2223/033 (20130101); Y10S
220/901 (20130101); F17C 2201/035 (20130101); F17C
2223/0161 (20130101); F17C 2203/015 (20130101); F17C
2221/017 (20130101); F17C 2205/0332 (20130101); F17C
2250/043 (20130101); F17C 2203/0639 (20130101); F17C
2203/0308 (20130101); F17C 2203/0395 (20130101) |
Current International
Class: |
F17C
3/00 (20060101); F17C 3/08 (20060101); F17C
13/08 (20060101); F17c 007/02 () |
Field of
Search: |
;220/10,9LG,15
;62/45,51,50 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Perlin; Meyer
Assistant Examiner: Capossela; Ronald C.
Attorney, Agent or Firm: Gardner; Joseph B.
Claims
What is claimed is:
1. A vessel for cryogenic fluids and the like, comprising: a
plurality of longitudinally extending containers supported one
within another in spaced apart relation, one of said containers
being an inner storage container adapted to receive such fluid
therein, a second thereof being an intermediate heat shield
enclosing the inner container, and a third being an outer jacket
enclosing all of said containers; and support means interconnecting
said containers to maintain the same in spaced apart relation and
at the same time minimize conductive heat migration through the
support means between said outer and inner containers, said support
means including transverse support structure providing adjacent
each end of said vessel a plurality of relatively thin and narrow
spaced apart inner transverse supports substantially confined
within the space between said inner storage and intermediate heat
shield containers and extending outwardly from the center portion
of said inner container at each end thereof generally adjacent its
longitudinal axis to the outer portions of said heat shield
generally adjacent its cylindrical surface to interconnect the same
adjacent the ends thereof, said transverse support structure
further providing adjacent each end of said vessel a plurality of
relatively thin and narrow spaced apart outer transverse supports
substantially confined within the space between said intermediate
heat shield and outer jacket containers and extending outwardly
from the center portion of said heat shield at each end thereof
generally adjacent its longitudinal axis to the outer portion of
said outer jacket generally adjacent its cylindrical surface to
interconnect the same adjacent the ends thereof, said inner and
outer transverse supports disposed in structural parallelism and
functional serialism and being relatively long with the length of
the thermal path defined thereby between said inner container and
outer jacket being materially greater than the transverse distance
therebetween to define relatively long thermal paths restricted in
cross sectional area and effective to reduce conductive heat
migration therethrough.
2. The vessel according to claim 1 in which said inner transverse
supports include a plurality of angularly spaced inner spokes
adjacent each end of said inner container and being connected
therewith and extending generally radially outwardly therefrom to
areas of connection with said intermediate heat shield container to
constrain said inner container against transverse displacements
relative thereto, and in which said outer transverse supports
include a plurality of angularly spaced outer spokes adjacent each
end of said intermediate heat shield container and being connected
therewith and extending generally radially outwardly therefrom to
areas of connection with said outer jacket to constrain said
intermediate heat shield container against transverse displacements
relative thereto.
3. The vessel according to claim 2 in which said inner and outer
spokes adjacent one end of said vessel are relatively flexible in
longitudinal directions so as to accommodate limited relative
longitudinal displacements of said containers, the relatively great
lengths of said flexible spokes being contributive to the
longitudinal flexibility thereof.
4. The vessel according to claim 1 in which said inner and outer
transverse supports are angularly disposed relative to a transverse
plane normal to the longitudinal axis of said vessel so as to
accommodate thermally induced relative changes in said containers
without excessively stressing said supports.
5. The vessel according to claim 4 in which the angular orientation
of said inner supports is selected to define the relationship in
which any thermally induced change in the radial length of an inner
support tends to be compensated by the radial change in the
distance between the ends thereof as such support swings between
its selected angle and a more nearly transverse disposition as a
consequence of thermally induced relative longitudinal changes in
the lengths of said containers.
6. A vessel for cryogenic fluids and the like, comprising: a
plurality of longitudinally extending containers supported one
within another in spaced apart relation, one of said containers
being an inner storage container adapted to receive such fluid
therein, a second thereof being an intermediate heat shield
enclosing the inner container, and a third being an outer jacket
enclosing all of said containers; and support means interconnecting
said containers to maintain the same in spaced apart relation and
at the same time minimize conductive heat migration through the
support means between said outer and inner containers, said support
means including transverse support structure providing adjacent
each end of said vessel of plurality of spaced apart inner
transverse supports substantially confined within the space between
said inner storage and intermediate heat shield containers and
extending outwardly from the center portion of said inner container
at each end thereof to the outer portions of said heat shield to
interconnect the same adjacent the ends thereof, said transverse
support structure further providing adjacent each end of said
vessel a plurality of spaced apart outer transverse supports
substantially confined within the space between said intermediate
heat shield and outer jacket containers and extending outwardly
from the center portion of said heat shield at each end thereof to
the outer portion of said outer jacket to interconnect the same
adjacent the ends thereof, said transverse supports thereby being
relatively long with the length of the thermal path defined thereby
between said inner container and outer jacket being materially
greater than the transverse distance therebetween to define
relatively long thermal paths effective to reduce conductive heat
migration therethrough, said support means further including
longitudinal support structure providing inner longitudinal
supports interconnecting said inner storage and intermediate heat
shield containers, and also providing outer longitudinal supports
interconnecting said intermediate heat shield and outer jacket
containers, said longitudinal support structure being effective to
resist relative bodily displacements between said containers in
longitudinal directions.
7. The vessel according to claim 6 in which said inner and outer
longitudinal supports are entirely located adjacent one end portion
of said vessel.
8. The vessel according to claim 7 in which each of said inner and
outer longitudinal supports comprises an elongated longitudinally
extending rod interconnected one with another in a serial
relationship so as to minimize conductive heat migration
therethrough between said outer and inner containers as
aforesaid.
9. The vessel according to claim 8 in which said longitudinal
support structure further includes a pair of universal joints
respectively located adjacent the ends of said inner rod and being
connected therewith and with said inner and intermediate heat
shield containers so as to accommodate limited transverse
displacements therebetween.
10. The vessel according to claim 8 in which each of said rods is
hollow so as to reduce the cross sectional area of the conductive
heat path defined thereby.
11. The vessel according to claim 8 in which said inner and outer
transverse supports are angularly disposed relative to a transverse
plane normal to the longitudinal axis of said vessel so as to
accommodate thermally induced relative changes in said containers
without excessively stressing said supports.
12. The vessel according to claim 11 in which the angular
orientation of said inner supports is selected to define the
relationship in which any thermally induced change in the radial
length of an inner support tends to be compensated by the radial
change in the distance between the ends thereof as such support
swings between its selected angle and a more nearly transverse
disposition as a consequence of thermally induced relative
longitudinal changes in the lengths of said containers.
13. The vessel according to claim 8 in which said inner transverse
supports include a plurality of angularly spaced inner spokes
adjacent each end of said inner container and being connected
therewith and extending generally radially outwardly therefrom to
areas of connection with said intermediate heat shield container to
constrain said inner container against transverse displacement
relative thereto, and in which said outer transverse supports
include a plurality of angularly spaced outer spokes adjacent each
end of said intermediate heat shield container and being connected
therewith and extending generally radially outwardly therefrom to
areas of connection with said outer jacket to constrain said
intermediate heat shield against transverse displacements relative
thereto; and in which said inner and outer spokes adjacent one end
of said vessel are relatively flexible in longitudinal directions
so as to accommodate limited relative longitudinal displacements of
said containers, the relatively great lengths of said flexible
spokes being contributive to the flexibility thereof.
14. The vessel according to claim 13 in which said inner and outer
transverse supports are angularly disposed relative to a transverse
plane normal to the longitudinal axis of said vessel so as to
accommodate thermally induced relative changes in said containers
without excessively stressing said supports.
15. A vessel for cryogenic fluids and the like, comprising: a
plurality of containers supported one within another and including
an inner storage container adapted to receive such fluid therein,
an intermediate heat shield enclosing the inner storage container,
and an outer jacket enclosing the latter; and a bipartite cooling
system defining a temperature barrier restricting the inward
migration of heat from said outer jacket to said inner container
and including first and second flow conduits located intermediate
said inner container and outer jacket and each being formed to
define a cooling coil therebetween disposed in heat exchange
relation with said heat shield; a reservoir for a coolant such as
liquid nitrogen or the like, the first of said flow conduits being
connected adjacent one end thereof to said reservoir and adjacent
its other end being vented to atmosphere to enable liquid coolant
converted to the gaseous phase by absorbing heat to escape to
atmosphere, and the second of said flow conduits being connected
adjacent one end thereof to said inner storage container and
adjacent its other end enabling cryogenic fluid to be released
therefrom, heat migrating inwardly from said outer jacket toward
said inner container being absorbed at least in part by any flow of
coolant through the coil defined by said first flow conduit and any
flow of cryogenic fluid through the coil defined by said second
flow conduit and temperature- responsive valve means disposed in
said first flow conduit and being operative to control the flow of
such coolant therethrough in accordance with predetermined
temperature values.
16. The vessel according to claim 15 and further comprising support
means interconnecting said containers to maintain the same in
spaced apart relation and at the same time minimize conductive heat
migration through the support means between said outer and inner
containers and including transverse support structure, the length
of the thermal path defined between said inner container and outer
jacket by said transverse support structure being materially
greater than the transverse distance therebetween.
17. The vessel of claim 16 in which said transverse support
structure includes inner transverse supports substantially confined
within the space between said inner storage and intermediate heat
shield containers and interconnecting the same adjacent the ends
thereof, and further includes outer transverse supports
substantially confined within the space between said intermediate
heat shield and outer jacket containers and interconnecting the
same adjacent the ends thereof; and in which said inner transverse
supports extend outwardly from the center portion of said inner
container at each end thereof to said heat shield, and said outer
transverse supports extend outwardly from the center portion of
said heat shield to said outer jacket, whereby said transverse
supports are relatively long and define relatively long thermal
paths so as to reduce conductive heat migration therethrough.
18. The vessel according to claim 17 in which said transverse
support structure includes inner transverse supports extending from
said inner storage container adjacent the center portion of an end
thereof to said heat shield, and further includes outer transverse
supports extending from said heat shield adjacent the center
portion of an end thereof to said outer jacket, said inner and
outer transverse supports being angularly disposed relative to a
transverse plane normal to the longitudinal axis of said vessel so
as to accommodate thermally induced relative changes in said
containers without excessively stressing said supports, and in
which the angular orientation of said inner supports is selected to
define the relationship in which any thermally induced change in
the radial length of an inner support tends to be compensated by
the radial change in the distance between the ends thereof as such
support swings between its selected angle and a more nearly
transverse disposition as a consequence of thermally induced
relative longitudinal changes in the lengths of said
containers.
19. The vessel according to claim 17 in which said support means
includes transverse support structure comprising inner transverse
supports interconnecting said inner storage and intermediate heat
shield containers, and further comprising outer transverse supports
interconnecting said intermediate heat shield and outer jacket
containers; and in which said longitudinal support structure
includes inner longitudinal supports interconnecting said inner
storage and intermediate heat shield containers, and further
includes outer longitudinal supports interconnecting said
intermediate heat shield and outer jacket containers.
20. The vessel according to claim 19 in which said inner transverse
supports include a plurality of angularly spaced inner spokes
adjacent each end of said inner container and being connected
therewith and extending outwardly therefrom to areas of connection
with said intermediate heat shield container to constrain said
inner container against transverse displacements relative thereto,
and in which said outer transverse supports include a plurality of
angularly spaced outer spokes adjacent each end of said
intermediate heat shield container and being connected therewith
and extending outwardly therefrom to areas of connection with said
outer jacket to constrain said intermediate heat shield against
transverse displacements relative thereto; and in which said inner
and outer spokes adjacent one end of said vessel are relatively
flexible in longitudinal directions so as to accommodate limited
relative longitudinal displacements of said containers.
21. A vessel for cryogenic fluids and the like, comprising: a
plurality of longitudinally extending containers supported one
within another in spaced apart relation, one of said containers
being an inner storage container adapted to receive such fluid
therein, a second thereof being an intermediate heat shield
enclosing the inner container, and a third being an outer jacket
enclosing all of said containers; and support means interconnecting
said containers, said support means including longitudinal support
structure interconnecting said containers so as to resist relative
bodily displacements therebetween in longitudinal directions and
providing inner longitudinal supports interconnecting said inner
storage and intermediate heat shield containers and further
providing outer longitudinal supports interconnecting said
intermediate heat shield and outer jacket containers, each of said
inner and outer longitudinal supports having an elongated
longitudinally extending rod interconnected one with another in a
serial relationship so that the length of the thermal path defined
between said inner container and outer jacket by said longitudinal
support structure is materially greater than the transverse
distance therebetween so as to minimize conductive heat migration
through the support means between said outer and inner containers,
said support means further including transverse support structure
interconnecting said containers so as to resist relative bodily
displacements therebetween in transverse directions.
22. The vessel according to claim 21 in which said inner and outer
longitudinal supports are entirely located adjacent one end portion
of said vessel.
23. The vessel according to claim 22 in which said longitudinal
support structure further includes a pair of universal joints
respectively located adjacent the ends of said inner rod and being
connected therewith and with said inner and intermediate heat
shield containers so as to accommodate limited transverse
displacements therebetween.
24. The vessel according to claim 22 in which each of said rods is
hollow so as to reduce the cross sectional area of the conductive
heat path defined thereby.
Description
This invention relates to a vessel for storing and transporting
cryogenic fluids, such as helium and nitrogen, either in their
liquid phase or as a cold gas so that large quantities of any such
fluid can be handled economically and have maximum refrigerative
properties when used.
With fluids of this type, it is most desirable to store and
transport the same in their liquid phase, but maintenance of the
liquid condition is not always possible because of the very low
critical temperature values of such fluids (critical temperature
usually being defined as the temperature above which liquefaction
of a particular gas cannot occur). Considering helium as an
example, the critical temperature thereof is slightly below
-450.degree.F at which temperature liquefaction can be effected at
approximately 2.26 atmospheres. Evidently then, in order to store
and transport liquid helium (and other similar fluids) as a
single-phase fluid, special equipment and conditions must be
provided, and equipment for this purpose has been developed and is
presently in use. Stated generally, the vessels used for storing
and transporting cryogenic fluids are large Dewar vessels which
constitute an inner container for the fluid and an outer insulating
shell or jacket enclosing the same.
In storing and transporting large quantities of a cryogenic fluid,
vessels of considerable size and capacity are necessary, and in
contrast to small vessels, the difficulty of supporting one vessel
within another while at the same time minimizing the paths of heat
migration through the support structure has been a considerable
problem. In this reference, consider the case of a vessel intended
to transport from 10,000 to 20,000 gallons of a fluid such as
liquid helium, such a vessel would have a length that might be
considerably greater than 40 feet, and it will be apparent that
considerable support structure is required to adequately maintain
or suspend the inner fluid-receiving vessel within the outer shell
or jacket. If massive support elements are employed, they
necessarily define substantial paths for heat transmission from the
outer jacket (which is at ambient temperature substantially
exceeding the low-temperature requirements of the cryogenic fluid)
to the inner container, thereby tending to boil off the product or
to elevate the temperature of the fluid confined therewithin.
An object of the present invention is to provide an improved vessel
for storing and transporting cryogenic fluids such as liquid helium
and the like.
Another object is in the provision of an improved cryogenic storage
vessel that includes a plurality of containers supported one within
another in substantially concentric relation, and in which improved
support means are employed to support the containers in such
relative circumjacent relation so as to readily accommodate the
static and dynamic loads imparted thereto and at the same time
minimize heat transmission via the support structure from the outer
container or jacket to the inner container in which the cryogenic
fluid is stored.
Still another object is that of providing an improved cryogenic
vessel of the type described in which the support means employed
accommodate, particularly at one end of the vessel, flexing of one
container relative to another such as might be enforced thereon
because of temperature changes and because of variation in the
static and dynamic loads to which the vessel may be subjected.
Yet another object is to provide a vessel of the character set
forth in which the support means comprises transverse support
structure effective to connect one container with another so as to
prevent relative transverse displacements therebetween, and which
also comprises longitudinal support structure connecting one vessel
with another so as to constrain the same against relative
longitudinal displacements.
A further object is in the provision of transverse support
structure that includes a plurality of angularly spaced spokes
adjacent each end of the vessel for supporting one container with
respect to the container circumjacent thereto, and in which the
aforementioned longitudinal support structure includes rod
components located at one end of the vessel and arranged so as to
change their direction in a manner such that certain of the
longitudinal dimensions thereof are disposed in parallel to reduce
the overall length thereof but in which the functional advantages
are the equivalent of a rod arrangement in which such dimensions
would be oriented in serial relation.
Still a further object is that of providing a vessel for cryogenic
fluids and the like having a bipartite cooling system defining a
temperature barrier restricting the inward migration of heat from
an outer jacket container to an inner fluid-receiving container,
the two cooling arrangements of such system being substantially
independent in their operation.
Yet a further object is to provide a vessel of the type described
in which one of the bipartite cooling systems in one mode of
operation thereof utilizes the fluid withdrawn from the inner
container to effect the temperature barrier, and in another mode of
operation utilizes a separate and independent cooling media.
Additional objects and advantages of the invention, especially as
concerns particular details and features thereof, will become
apparent as the specification continues.
An embodiment of the invention is illustrated in the accompanying
drawings in which:
FIG. 1 is a longitudinal sectional view of a cryogenic storage
vessel embodying the invention;
FIG. 2 is an enlarged broken longitudinal sectional view of the
upper left hand corner portion of the vessel as it is shown in FIG.
1;
FIG. 3 is a broken transverse sectional view taken generally along
the line 3--3 of FIG. 1;
FIG. 4 is a broken transverse sectional view taken generally along
the line 4--4 of FIG. 1;
FIG. 5 is a broken transverse sectional view taken along the line
5--5 of FIG. 1;
FIG. 6 is an enlarged, broken longitudinal sectional view of the
upper right hand corner portion of the intermediate container of
the vessel as it is shown in FIG. 1;
FIG. 7 is an enlarged, broken end view in elevation taken
substantially along the line 7--7 of FIG. 1;
FIG. 8 is a broken longitudinal sectional view taken along the line
8--8 of FIG. 7;
FIG. 9 is a broken top plan view taken along the line 9--9 of FIG.
8;
FIG. 10 is a broken longitudinal sectional view taken along the
line 10--10 of FIG. 7;
FIG. 11 is generally a side view in elevation of the intermediate
heat shield container (the outer container being broken away)
showing the cooling coils in position thereabout;
FIG. 12 is a transverse sectional view taken along the line 12--12
of FIG. 11;
FIG. 13 is a transverse sectional view taken along the line 13--13
of FIG. 11;
FIG. 14 is a schematic diagram of the cooling system for the
vessel; and
FIG. 15 is a broken longitudinal sectional view, somewhat
diagramatic, of the upper left hand corner portion of the inner
storage container and intermediate head shield, the former being
shown by broken lines in a contracted position.
As indicated hereinbefore, the storage vessel is intended for use
with cryogenic fluids that are necessarily stored and transported
at very low temperatures in an effort to maintain the fluid in its
liquid phase. By way of example, one of the cryogenic fluids
commonly stored and transported is helium and the critical
temperature-pressure values (i.e., the temperature-pressure
conditions above which helium as a liquid cannot exist) thereof are
5.2.degree. Kelvin (i.e., -267.96.degree.C or -450.328.degree.F)
and 2.26 atmospheres. Therefore, as heretofore stated, if helium is
being stored within the vessel, it is desirable to maintain the
temperature-pressure conditions at or below the critical values for
this fluid so that the fluid phase thereof can be preserved.
However, it is very difficult to maintain these values, and often
the helium will become a two phase system and finally change into
the gaseous phase. Even when change to the gaseous phase occurs,
with a vessel embodying the present invention a very substantial
quantity (as much as 70 percent or more) of liquid helium can be
reclaimed by depressurizing the vessel by venting the same through
its gas phase line which cools the remaining helium, thereby
causing the same to revert to its liquid phase. Nevertheless, it is
necessary to minimize to negligible amounts any heat migration
between the cryogenic fluid and the ambient environment in which it
must be stored and transported.
The vessel illustrated most completely in FIG. 1 provides this
desirable result, and it is designated in its entirety with the
numeral 15. The vessel 15 may be used either for stationary storage
or for mobile storage and transport, and in the latter case it will
be equipped with wheels (not shown) that enable it to be rollingly
transported by any suitable truck tractor as disclosed in the
copending patent application of Cesar E. Cavanna, Ser. No. 817,986,
filed Apr. 21, 1969. Although the size and capacity of any
particular vessel 15 may vary considerably, by way of indicating a
general order of magnitude of typical vessels, the overall length
of one wheel-equipped vessel intended to transport approximately
10,500 gallons of liquid helium is about 40 feet and the outer
diameter thereof is about 8.0 feet.
The vessel 15 includes a plurality of axially elongated containers
disposed one within another in substantially concentric relation,
but it should be noted that exact coaxiality is not a requisite
although in the usual case the containers will be coaxially related
one to the others in radially spaced relation. As shown in FIG. 1,
such a plurality of containers includes a first or inner storage
container 16, a second or intermediate heat shield container 17,
and a third container or outer jacket 18 enclosing the intermediate
heat shield 17 and, therefore, the first or inner storage container
16 which is adapted to receive and store the cryogenic fluid
therewithin. For convenience of illustration and because it forms
no part of the present invention, the filler and discharge systems
for the container 16 have been omitted, but should details
concerning such system be desired, reference may be made to the
copending patent application of Robert S. Hampton, Ser. No.
808,765, filed Mar. 20, 1969 now U.S. Pat. No. 3,602,003.
The vessel 15 is generally similar from end to end thereof, but
there is some departure therebetween as concerns the support means
interconnecting the various containers 16, 17 and 18. In this
respect, a functional difference between the two ends exists, and
the left end of the vessel as it is shown in FIG. 1 may be referred
to as the "flexible end" and the right end as the "fixed end".
Adjacent the ends of the vessel 15, the hollow cylindrical sidewall
19 of the inner container 16 is respectively equipped with
bulkheads 20 and 21 which are outwardly convex or dish shaped and
are welded or otherwise rigidly and sealingly related to the
sidewall 19. A suitable material for fabrication of the inner
container 16 is stainless steel, although many other materials can
be used.
The intermediate container or heat shield 17 includes an elongated
hollow cylindrical sleeve 22 of somewhat greater diameter than the
sidewall 19 and of substantially greater length. Adjacent the
flexible end of the vessel 15, the sleeve 22 is close by a bulkhead
23 that is also outwardly convex closed dish shaped but has much
less curvature than the bulkhead 20, as shown in FIG. 1, and
telescopes into the end portion of the sleeve 22 to which it is
welded or otherwise fixedly and sealingly related. Adjacent the
fixed end of the vessel 15, the sleeve 22 of the intermediate
container 17 is equipped with a pair of bulk heads identifiable as
an inner bulk head 24 and an outer bulkhead 25.
The bulkheads 24 and 25 are spaced apart axially except at their
circumferential edges so as to define a closed chamber 26
therebetween, and they are welded or otherwise rigidly and
sealingly secured to each other and to the sleeve 22. Inspection of
FIG. 1 makes it evident that the heat shield container 17 is spaced
from the inner container 16 both along the sidewalls and at each
end, and the chamber defined therebetween is generally denoted with
the numeral 27. As with the inner container 16, a suitable material
for fabrication of the intermediate heat shield container 17 is
stainless steel, although other materials can certainly be
used.
The outer container or jacket 18 is also formed of an elongated
hollow cylindrical sleeve 28 having a greater diameter than that of
the sleeve 22 so as to be spaced radially outwardly therefrom, and
it is also of greater length. Adjacent its opposite ends, the
sleeve 28 is equipped with end closures or bulkheads 29 and 30 that
are each outwardly convex or dish shaped and approximate the
curvature of the respectively adjacent bulkheads 23 and 25 of the
intermediate container 17. The bulkheads 29 and 30 are welded or
otherwise rigidly and sealingly connected to the sleeve 28, and
together therewith define a compartment 31 about the intermediate
heat shield 17. Various materials may be used to fabricate the
outer jacket 18, and a suitable material is ordinary carbon
steel.
Evidently, the containers 16, 17 and 18 require support means
interconnecting the same to enforce the spaced apart relationship
shown and described, and such support means includes radial or
transverse support structure so as to prevent transverse
displacements of one container relative to the others, and further
includes longitudinal support structure to prevent bodily
displacements of one container relative to the others in axial
directions. Such support means will now be described with the
transverse support structure being first considered, and the order
of description thereof will proceed from the flexible or left end
of the vessel to its fixed or right end because such order
advantageously progresses from the more simple construction to that
of greater complexity.
Referring in particular to FIGS. 1, 2 and 3 it will be noted that
the bulkhead 20 at the flexible end of the inner container 16 is
provided centrally with a hub or mounting plate 32 welded or
otherwise rigidly anchored to the bulkhead along the outer surface
thereof. The plate 32 has an offset step or annular recess 33
formed along the outer edge thereof and into which seat the inner
ends of a plurality of spokes or arms 34. The spokes 34 are welded
to the plate 32 and extend outwardly therefrom in angularly spaced
relation that, in the particular configuration shown, are radially
oriented with respect to the center of the plate 32 and to the
longitudinal axis of the vessel 15. At their outer ends, each of
the spokes 34 is fixedly secured to the bulkhead 23 of the
intermediate head shield 17, and for this purpose, the heat shield
is provided with a plurality of openings 35 (FIG. 2) formed therein
and into which the spokes project.
Each spoke 34 is welded to the bulkhead 23 at the location of its
projection therethrough, as shown in FIG. 2. The openings 35 may or
may not be closed by the welds, for in any case the chambers 27 and
31 are otherwise in open communication for vacuumizing purposes.
Adjacent the spokes 34 at the location of their connection with the
bulkhead 23 is a reinforcing and stiffening ring 36 formed of a
plurality of angular segments 37, as is most evident in FIG. 3. The
segments 37 are disposed and welded together in end to end relation
and define a substantially endless ring that is continuously welded
to the bulkhead 23 so as to be fixed with respect thereto.
It will be observed in FIG. 3 that the arcuate segments 37 vary in
angular length generally progressing in length from top to bottom
of the vessel 15. In this connection, a segment 37 is associated
with each of the spokes 34 which traverses its adjacent segment at
about the midpoint thereof. Accordingly, a greater number of spokes
34 are disposed along the upper semicircular portion of the vessel
15 than along the lower portion thereof, and in the specific
embodiment being considered, there are five spokes located above
the horizontal center plane of the vessel and four spokes located
therebelow. Although the spokes 34 constrain the inner and
intermediate containers 16 and 17 against transverse or radial
displacements with respect to each other, they accommodate some
relative longitudinal displacements or flexing, as will be
described hereinafter.
The transverse or radial support structure further includes at the
flexible end of the vessel 15 a plurality of angularly spaced outer
spokes or arms 38, as shown best in FIG. 4, that are radially
oriented and extend outwardly from an inner plate or abutment 39
welded or otherwise rigidly secured to the bulkhead 23 of the heat
shield 17, and which hub or plate 39 has a circumferential groove
or recess 40 formed thereabout and into which the spokes 38 seat at
their inner ends so as to be welded or otherwise rigidly secured to
the plate 39. At their outer ends, each of the spokes is welded to
the bulkheads 29, as shown best in FIG. 2, and all of the spokes 38
are reinforced and stiffened at their outer ends by a ring 41
comprised of a plurality or arcuate segments 42 connected by
welding in end to end succession to define a continuous ring as
shown in FIG. 4. The segments 42 are welded to the bulkhead 39 and
are in substantially contiguous relation with the spokes 38 at
their outer ends.
The segments 42 increase in angular length from top to bottom of
the vessel 15, and each spoke 18 is disposed so as to traverse the
associated segment at about the midpoint thereof. Accordingly,
there are more spokes 38 throughout the upper section of the vessel
15 then along the bottom section thereof, and in the specific
vessel being considered, there are five spokes angularly spaced
from each other about the upper half of the vessel and four
angularly spaced spokes of the bottom half thereof. The spokes 38
are effective to radially relate the intermediate container 17 and
outer container 18 so as to prevent relative transverse
displacements therebetween but they permit some longitudinal
movement therebetween as will be considered hereinafter.
The radial support structure adjacent the fixed end of the vessel
15 will now be considered, and particular reference will be made
first to FIGS. 1, 5 and 6 as concerns the interconnection of the
inner and intermediate containers 16 and 17, and second to FIGS. 1,
7, 8 and 9 as concerns the transverse interconnection of the
inermediate and outer containers 17 and 18.
The bulkhead 21 of the inner container 16 is equipped centrally
with a plate or hub 43 that may be welded thereto and is provided
along its outer edge with an annular groove or recess 44. Seated
within the recess 44 are the inner ends of a plurality of angular
spaced inner spokes or arms 45 that, in the form shown, are
radially disposed and may be welded or otherwise rigidly secured to
the plate 43. At their outer ends, each of the spokes 45 is welded
to the inner bulkhead 24 of the intermediate container or heat
shield 17, as shown best in FIG. 6. Each of the spokes 45 is
reinforced or stiffened by a plurality of respectively associated
plate elements or segments 46 that are welded to the inner bulkhead
24 in substantially contiguous relation with the respectively
associated spokes 45 along the outer sides thereof, as shown in
both FIGS. 5 and 6. Since the spokes 45 are radially disposed, they
interrelate the inner container 16 and intermediate container 17 in
a manner preventing relative transverse displacements
therebetween.
As illustrated best in FIG. 6, the bulkheads 24 and 25 are welded
to the cylindrical wall 22 of the heat shield container 17, and the
bulkhead 24 projects inwardly to a greater extent than the bulkhead
25 so as to underlie the cylindrical wall 22 of this container. A
generally square-shaped bar bent so as to conform to the outer
circumference of the bulkhead 24 and of sufficient width to
substantially engage the inner surface of the circumjacent wall 22
is interposed between the bulkhead and wall to form an endless ring
47 that is welded to the bulkhead as shown.
The outer bulkhead 25 has rigidly affixed thereto at a central
location along the longitudinal axis of the vessel a plate or hub
48 provided with an outer annular groove or recess 49 cut
therealong, as shown in FIGS. 1, 8 and 10. Extending radially
outwardly from the hub or plate 48 are a pair of hanger or
suspension spokes 50 and 51 which, as shown best in FIG. 9, are of
T-shaped configuration. As is most evident in FIGS. 1 and 7, the
flange of each of the hangers 50 and 51 seats within the recess 49
formed in the plate 48, but the webs of each hanger extend across
the plate 48 in a lap joint.
The hangers 50 and 51 are angularly spaced from each other by about
70.degree. (i.e., 35.degree. from each side of a vertical plane
through the center of the vessel) and along their outer end
portions they respectively project through openings 52, FIG. 8,
formed in the bulkhead 30 of the outer container 18. At their outer
extremities, the hangers 50 and 51 are respectively welded to cover
plates 53 and 54 that are welded to the bulkhead 30 and are also
welded to arcuate enclosures 55 and 56, respectively, configurated
to conform to the arcuate shape of the bulkhead 30 and are welded
thereto. Accordingly, each of the openings 52 formed in the
bulkhead 30 are sealingly closed by the respectively associated
plates and covers 53, 55 and 54, 56 which also rigidly connect the
hangers 50 and 51 to the outer container 18.
In contrast to all of the aforementioned spokes 45, 38, and 34
which are all relatively thin, generally planar components, the
hangers 50 and 51 are T-shaped and therefore provide considerable
resistance to flexure along the longitudinal axis of the vessel 15
because of the presence of the web of each hanger which is disposed
at right angles to the flange thereof. Each of the hangers 50 and
51 also provides resistance to transverse flexure because in such
direction, the flanges thereof lie in the planes of such tendency
toward flexure and serve as beam webs to resist generally
transverse flexure. Accordingly, it may be said that the hangers 50
and 51 and components associated therewith establish a relatively
rigid interconnection of the outer container or jacket 18 with the
intermediate container or shield 17 through the outer bulkhead 25
thereof.
The aforementioned support means, as indicated hereinbefore, also
include longitudinal support structure interconnecting the various
containers one with another adjacent the fixed end of the vessel 15
so as to constrain the containers against significant longitudinal
or axial displacements relative to each other. Such longitudinal
support structure will now be described with particular reference
to FIGS. 1, 7 and 10.
Considering first the longitudinal interconnection of the inner
container 16 with the intermediate container or heat shield 17, the
bulkhead 21 of the inner container is provided at angularly spaced
locations (respectively offset in opposte directions from the
vertical center plane of the vessel by about 45.degree., as is most
evident in FIG. 7) with an opening through which projects a
cylindrical pipe or rod 57 defining an axially extending cylinder
58 therewithin. Adjacent one end, the pipe 57 is welded to the
bulkhead 21 so as to be rigidly and sealingly related thereto, and
it is supported adjacent its inner end by one or more straps 59
secured to the wall 19. The inner end of the pipe 57 is closed by
an end wall 60 that is welded thereto and carries a universal joint
61 one component of which is fixedly attached to the closure wall
and the other components of which is rigidly affixed by means of a
closure plug 62 to a hollow cylindrical rod 63 of substantially
greater length than the pipe 57 so as to project outwardly through
the open end thereof toward the inner bulkhead 34 of the
intermediate head shield 17, as shown in FIG. 10.
At its opposite end, the tubular rod 63 is closed by a plug 64
having attached thereto one component of a universal joint 65 the
other component of which is rigidly attached to an end closure 66
located within and sealingly and rigidly related to a hollow
cylindrical shell 67 in axial alignment with the pipe 57 and
extending through openings provided therefore in the bulkheads 24
and 25. The shell 67 is welded to each of the bulkheads so as to be
sealingly and fixedly secured thereto. It will be appreciated that
the structure described rigidly interconnects the inner container
16 with the intermediate container 17 because at one end the rod 63
is fixed to the bulkhead 21 of the inner container through the
hollow pipe 57 and intermediate components constituting the closure
60, universal joint 61 and plug 62 and at its other end it is fixed
to the intermediate container 17 through the shell 67 and
intermediate structure constituting the closure 66, universal joint
65 and plug 64.
The universal joints 61 and 65 are advantageous in that they permit
easy assembly of the components in the event of dimensional
discrepencies resulting from manufacturing tolerances, and they
also accommodate any slight tendency toward transverse
displacements of the inner container 16 relative to the
intermediate container 17 such as may result from the weight or
static load carried by the inner container and any road shocks or
dynamic loads that might be transmitted to the vessel 15 during
transport thereof. The effective length for thermal transmission
purposes of the longitudinal support interconnecting the inner and
intermediate containers is substantially equal to the longitudinal
length of the rod 63 because of its being insulated from
circumjacent pipe 57 and connected thereto only at one end via the
universal joint 61. In a structural sense, the longitudinal support
actually changes direction and while mechanically relating the
individual lengths of the pipe 57 and rod 63 in parallel,
functionally the relationship thereof is one of serial
interconnection.
In the event of the inner container 16 tending to shift
longitudinally to the right as viewed in FIG. 10 relative to the
intermediate container 17, the rod 63 will be compressively
stressed and the pipe 57 will be placed in tension. Conversely, any
tendency for the inner container 16 to shift in the opposite
direction will place the rod 63 in tension and enforce a
compressive stress upon the pipe 57. The long effective length of
the pipe 57 and rod 63 is advantageous in that these components
function as very stiff springs accommodating limited axial
displacements of the inner container relative to the intermediate
container and, as is well known, the longer the length of any such
spring, the lower is the fatigue thereof resulting from cyclically
repetitive compression and elongation.
The longitudinal support structure further includes an arrangement
for interconnecting the intermediate container 17 and outer
container 18 and, as shown in FIG. 7 and 10, such means are
respectively arranged with the two angularly spaced inner
longitudinal support structures just described. In this respect,
the outer support structure includes a flat plate-like web 68
rigidly related to the closure 66 and to the shell 67 so as to be
anchored by the latter to the heat shield or intermediate container
17. The plate 68 extends outwardly beyond the end of the shell 67
and is enlarged thereat, as shown in FIG. 7, and welded along such
enlargement to brackets 69 and 70 that are welded to a ring plate
71 circumjacent the outer end of the shell 67 and which is welded
both to the shell and to the bulkhead 25. Each of the members 69
and 70 is shaped to conform to the curved configuration of the
bulkhead 25, as shown in FIG. 10, and the ring plate 71 extends
upwardly for substantially the entire height of each of the members
69 and 70.
The members 69, 70 and 71 extend upwardly through an opening 72
provided therefor in the cylindrical shell or wall 28 of the outer
container 18. Also extending upwardly through the opening 72 is a
reinforcing member 73 that is disposed intermediate the brackets 69
and 70 and is welded thereto, as well as being welded to the
cylindrical wall 22 and bulkhead 25 of the intermediate container
17. Located along the outer surface of the container wall 28 is a
flat fin-like connector 74 that at one end is disposed intermediate
the brackets 69 and 70 and is welded thereto and to the upper end
of the ring plate 71.
The connector 74 extends longitudinally toward the flexible end of
the vessel 15 and projects into a slot provided therefor at one end
of a hollow tubular rod 75 and is welded to the rod so as to be
firmly attached thereto. At its opposite end, the rod 75 is slotted
and a similar fin-like connector 76 is seated therein and welded
thereto. The connector 76 is welded to an end wall 77 of an
enclosure 78 having an inverted generally U-shaped configuration,
as shown in FIG. 7. At the opposite end of the enclosure 78 an end
wall 79 is provided and such end wall 79 together with the end wall
77 and entire enclosure 78 are welded to the outer container 18 so
as to be rigidly and sealingly related thereto and thereby form an
hermetic enclosure about the opening 72.
As stated hereinbefore, it is necessary that the various containers
be thermally insulated one from another so as to sharply restrict
the rate of heat migration therebetween, and as will be explained
hereinafter, the support means comprising the transverse support
structure located at each end of the vessel 15 and the longitudinal
support structure located at the fixed end thereof provide an
arrangement for so minimizing transmission of heat between the
inner and outer containers. In addition, the chambers 27 and 31
respectively surrounding the inner container 16 and intermediate
container 17 are thermally insulated spaces, and cooling means
within the chamber 31 cool the intermediate heat shield 16, as will
be explained hereinafter. However, the insulation and insulating
means form no part of the present invention and have been omitted
for simplification and clarity, but for general information it may
be mentioned that such spaces may be evacuated or vacuumized and/or
filled with one of the very effective modern insulations used
extensively in the cryogenic field and sometimes referred to as
"supper insulation".
In the vessel 15 shown, an evacuation valve and flow conduit system
are arranged with the outer chamber 31 so as to vacuumize the same,
and a plurality of getter structures 80 (FIG. 5), such as two at
each end of the vessel, are carried by the bulkheads 20 and 21 of
the inner container 16 so as to absorb fluid within the compartment
27, thereby reducing the fluid pressure therewithin. Each getter
structure 80 may constitute a generally cylindrical hollow
projection from the associated bulkhead of the inner container, and
such projection is closed by a wire mesh screen 81 held in place by
spring clips 82 and adapted to contain a predetermined quantity of
activated charcoal and a getter molecular sieve material. Also, the
cylindircal space within the shell 57 circumjacent the hollow rod
63, the space within the rod 63, the space within the housing 78
about the hollow rod 75, and the space within the hollow rod 75 may
also be provided with an insulating material as, for example,
aluminized Mylar sheeting wrapped about the rods or coiled within
the space, as the case may be. As previously suggested, the
vacuumizing system reduces the pressure in each of the
interconnected chambers 27 and 31.
Since the steel materials used to construct the vessel 15 are
relatively good thermal conductors, minimizing the rate of heat
conductivity along the support means interconnecting the various
containers 16, 17 and 18 is of major significance, and both the
transverse support structure and longitudinal support structure
accomplish such minimization by sharply restricting or limiting the
magnitudes of the paths of heat migration. Thus, at both the fixed
and flexible ends of the vessel 15, the inner container 16 is
connected to the intermediate container or heat shield 17 only by
the spokes 34 and 45 each of which is relatively narrow and
mechanically contacts the inner container only at the arrow areas
of engagement with the plates 32 and 43, which plates respectively
define rather restricted areas of engagement with the bulkheads of
the inner container.
At their outer ends, each of the spokes 34 and 45 also has a
restricted area of engagement with the intermediate heat shield 17,
and in this respect it should be observed (see FIGS. 2 and 6) that
each of the reinforcing segments 37 at the flexible end of the
vessel are spaced from the respectively associated spokes 34 and 45
because of their relative angular orientations, thereby further
minimizing the areas of contact and paths for heat migration.
Further, it should be observed that the markedly superior tensile
strength of the steel materials forming the spokes 34 and 45 is
used in supporting the inner container 16 and contents thereof
relative to the circumjacent heat shield 17. That is to say, all of
the spokes 34 and 45 may be quite narrow since the majority of the
spokes in each case are under tension and a much smaller cross
sectional area is required to enable a support to carry a weight in
tension than is required for a support to carry the same weight in
compression.
This same minimization or reduction in the paths of heat migration
between the heat shield 17 and outer jacket 18 is defined by the
spokes 38 adjacent the flexible end of the vessel and by the
hangers 50 and 51 adjacent the fixed end thereof. Analogously, the
paths of heat migration along the longitudinal support structures
are quite restricted and constitute essentially only the restricted
cross sectional solid or metal areas of the cylindrical pipe 57 and
of the tubular rod 63 and the restricted areas of interconnection
thereof with the intermediate heat shield. Continuing with the
longitudinal support structure, the interconnection of the heat
shield 17 with the outer jacket 18 is also defined through a
restricted thermal flow path largely defined as to its
heat-transmitting capacity by the restricted physical
interconnection of the hollow tubular rod 75 at each end thereof
with the connectors 74 and 76.
It may also be noted that the inner and outer radial or transverse
support components are isolated from each other so that no single
continuous flow paths are defined radially outwardly through the
support components from the inner container 16 to the outer jacket
18. A somewhat similar discontinuity pertains as to the inner and
outer longitudinal support structures although there is a
restricted serial interconnection thereof established at the shell
67.
The structural assembly described at the fixed or right end of the
vessel 15 as it is shown in FIG. 1 largely prevents significant
displacements of one container relative to the other. However, at
the opposite or flexible end of the vessel, the radial spokes 34
and 38 which respectively connect the inner and intermediate
containers and intermediate and outer containers permits relative
displacements of all of the containers particularly in axial or
longitudinal directions. Enabling such relative movement
accommodates temperature differentials and changes, and
displacements owing to static and dynamic loads that may be
imparted to the vessel differentially as respects the various
containers thereof.
The bipartite cooling system which provides a temperature barrier
restricting the inward migration of heat from the outer container
18 to the inner container 16 is illustrated in FIGS. 11 through 14
to which particular reference will now be made. The cooling system
constitutes two separate and substantially independent cooling
arrangements, one of which utilizes withdrawal of the contents of
the inner container 16 as a means for providing the temperature
barrier and the other of which utilizes a separate cooling media
confined within the reservoir 26. The temperature barrier is
associated with the intermediate heat shield container 17, and it
includes first and second flow conduits 84 and 85 respectively
formed or configurated into coils that are wound about and are
welded or otherwise fixedly secured to the heat shield container,
as illustrated best in FIGS. 11, 12 and 13.
The flow conduit 84 is connected at one end thereof via a conduit
section 86 to the lower end of the reservoir 26, and at its other
end the conduit 84 is vented to atmosphere through an outlet
section 87 having control and regulator elements located therealong
as is shown diagrammatically in FIG. 14. In this respect, the
cooling fluid contained within the reservoir 26 and flowing through
the conduit 84 is a low temperature cryogenic fluid such as
nitrogen, and a trap 88 is interposed in the line 87 so as to
retain liquid nitrogen in the conduit 84 and permit only gaseous
nitrogen to be vented to atmosphere. A pressure relief valve 89 is
disposed in the line which vents at 90 so as to establish the
pressure at which venting occurs. A valve-equipped drain line 91
communicates with the line 87 at the juncture of the trap 88 and
relief valve 89 to enable the line to be drained. Generally, the
conduit 84 is filled with liquid nitrogen and as it absorbs heat
tending to migrate through the heat shield container 17 toward the
inner container 16, the resultant expansion of parts of the liquid
nitrogen and conversion thereof into the gaseous phase is followed
by the escape of the heated gas to atmosphere, thereby forming a
temperature barrier restricting the inward migration of heat from
the outer container 18 to the inner container 16.
A gage network is also associated with the reservoir 26, as shown
in FIG. 14, and it includes a liquid level gage 92 and a pressure
gage 94. The liquid level gage 92 is connected to the bottom of the
reservoir 26 via a conduit 95 which has a pressure equalizing valve
96 interposed therealong. At its lower end, the conduit 95 may
communicate directly with a fill or supply line 97 which has a fill
valve 98 disposed therealong. The pressure gage 94 is connected by
a line 99 having a vapor-to-gage valve 100 located therealong to
the upper end of the reservoir 26 through a branch conduit 101. The
branch conduit 101 has a vent valve 102 therein by means of which
the reservoir 26 at its upper end is vented to atmosphere. The
conduits 95 and 99 which respectively connect with the gages 92 and
94 are interconnected by a gage equalizing valve 104, and the line
99 is also connected directly to the liquid level gage 92 by a line
105. A liquid block valve 106 connects the line 99 intermediate to
gage 94 and valve 100 to atmosphere. A bursting disc 107 and relief
valve 108 vent the line 101 to atmosphere, as shown at 109.
Thus, the portion of the bipartite cooling system that comprises
the reservoir 26 and flow conduit 84 constitutes a complete and
independent system flow-isolated from the interior of the
fluid-receiving container 16 and flow system connected therewith.
Liquid nitrogen or other comparable cooling media is supplied to
the reservoir 26 through the valve 98 and supply line 97, and since
the flow conduit 84 is in open communication with the reservoir 26
adjacent the lower end thereof, the conduit and cooling coil
defined thereby is ordinarily filled with the liquid fluid. As heat
is absorbed by the liquid within the conduit 84 and portions of the
liquid are thereby converted to the gaseous phase, the gaseous
components are vented to atmosphere at 90 through the trap 88 and
relief valve 89. The liquid level and pressure within the reservoir
26 are made evident by tha gages 92 and 94, and the pressure within
the reservoir is prevented from exceeding some predetermined value
by the relief valve 108 through which the reservoir is vented to
atmosphere at 109. In the event of malfunction of the valve 108,
the bursting disc 107 will rupture, if necessary, to limit the
pressure of the fluid within the reservoir 26. The various valve,
regulator, gage, and safety components within the nitrogen cooling
system are standard items well-known in the art, and for this
reason no further description thereof is included.
The conduit 85 is connected at one end thereof to the interior of
the fluid-receiving inner container 16, and such connection is made
adjacent the upper end of the container through a conduit section
110. Adjacent its other end, the flow conduit 85 is vented to
atmosphere at 111 through a pressure release valve 112 that defines
the maximum permissible gaseous pressure within the conduit 85. A
cooling valve 114 is also connected to the line 85 and is manually
operable and is used to permit sufficient escape of the gaseous
fluid (i.e., helium) from the conduit 85 so as to cool the same and
the heat shield container 17 about which it is coiled. The valve
114 vents to atmosphere at 115. It should be observed that the vent
115 can be connected to a delivery system by means of which the
helium gas otherwise venting to atmosphere can be conducted to a
compressor or otherwise retained for use. It will be appreciated
that a complete delivery and withdrawal system is associated with
the inner container 16 which will also have a pressure gage, liquid
level gage, safety devices, and vent means, but such details have
been omitted because they are not germane to the present invention.
Accordingly, in FIG. 14 only the general connections with the
container 16 are shown and they include the fill and drain line
116, vapor return line 117 which communicates with the vent line
118, and the lines 119 and 120 which respectively communicate with
a liquid level gage and pressure gage neither of which is shown.
For a complete disclosure concerning the details of an entire
system associated with a cryogenic storage and transport vessel,
reference may be made to the copending application of Robert S.
Hampton, Ser. No. 808,765, filed Mar. 20, 1969now U.S. Pat. No.
3,602,003, and entitled Method of and Apparatus for Transporting
Cryogenic Liquids.
The bipartite cooling system evidently constitutes a liquid
nitrogen cooling arrangement that comprises the flow conduit 84 and
a gaseous helium cooling arrangement that comprises the conduit 85.
The coil defined by the conduit 84 is ordinarily filled with liquid
nitrogen, but as the nitrogen absorbs heat migrating inwardly from
the outer container 18 toward the intermediate heat shield 17,
portions of the liquid nitrogen are converted into gas and bubble
outwardly along the conduit to the vent 90. However, since the coil
defined by the conduit 84 extends longitudinally about the heat
shield container 17 there is a temperature differential as between
the bulk head 23 at the flexible end of the vessel and the bulk
head 25 at the fixed end thereof because of the reservoir 26 and
storage therewithin of the low temperature nitrogen. Therefore, as
gaseous nitrogen circulates along the conduit 84, it is reliquified
each time it circulates through those portions of the conduit which
are adjacent the reservoir 26. In any event, the liquid nitrogen
cooling arrangement forms a temperature barrier tending to maintain
the intermediate heat shield container 17 at a relatively uniform
temperature which, for example, may be of the order of
-300.degree.F.
The temperature barrier defined by the liquid nitrogen cooling
arrangement is very effective and absorbs substantially all of the
heat migrating inwardly toward the heat shield container 17. It has
been calculated that the shield is effective to absorb well over 90
percent of the heat migrating inwardly, and in many instances it is
believed that the heat absorption may approach 99 percent of the
total inward migration of heat. Thus, for example, the outer
container 18 may have a temperature of about +70.degree.F, the
intermediate container 17 may be maintained at a temperature of
about -300.degree.F, and the inner container 16 will maintain a
helium temperature of about -452.degree.F.
As helium gas is admitted into the conduit 85, it may have a
temperature of about -400.degree.F, and as the helium gas emerges
from the conduit 85 it will be at a much higher temperature which
may approach that of the nitrogen say, for example, about
300.degree.F. As explained hereinbefore, this helium gas can either
be vented to atmosphere or, desirably, is carried by a delivery
system to a compressor or other place of implant use. The helium
gas admitted to the conduit 85 is the normal boil off gas from the
container 16, and by admitting it into the conduit 85, it will
reduce the evaporation rate within the container 16 because more
heat is taken from the gas than would be normally vented.
Consequently, by using the gaseous helium cooling arrangement, the
boil off rate from the container 16 is markedly reduced. It might
be mentioned that the liquid nitrogen cooling arrangement is
advantageously used during transport of the cryogenic vessel, and
that the gaseous helium cooling system is advantageously used when
the vessel is located at a storage facility at a point of use, at
which time the boil off helium can be effectively utilized in the
plant facility. It would not be necessary at this time to use the
nitrogen cooling system.
In one specific embodiment of the invention, the rate of helium
boil off is limited to the order of 0.5 percent per day, and the
support system has a maximum heat leak therethrough of about 2 BTUs
per hour. The insulation provided between the spaced containers has
a heat leak of about 22 BTUs per hour.
Although the heat conductivity of stainless steel is about 12 times
less efficient than that of cooper, the arrangements heretofore
described enable steel containers to be used throughout, thereby
permitting the higher strength of steel to be used. For example,
and referring to FIG. 1, the supports 34 at the flexible end of the
vessel move toward the right, as viewed in FIG. 1, when the shield
17 first cools, and the difference in longitudinal movement of the
shield 17 and inner vessel 16 results in a net longitudinal
movement of the support 34. Thus, the supports 34 will tend to have
a more nearly vertical orientation, but because the supports shrink
owing to the difference in temperature between the liquid helium
within the inner container and the temperature of the shield
established by the liquid nitrogen, the two movements tend to
compensate each other and the supports 34 operate effeciently with
the stress level therein being due essentially to the load carried
by the inner container 16. Since the supports 34 are of thin steel,
they are highly flexible and any bending stresses are
negligible.
More particularly, and referring to FIG. 15, stress of significance
will develop in the supports 34 (in the absence of means to prevent
the same) when there are substantial temperature differences
between the containers such as the inner container 16 being cold
and the heat shield 17 being warm, and vice versa. Considering the
case of the inner container 16 becoming cold, it will shrink
longitudinally through a distance d1, and correspondingly, each
support 34 will necessarily swing through an angle d0 toward a more
nearly vertical orientation.
As a result of the angular change d0, any support 34 will tend to
displace the mounting plate 32 radially through a distance dr; but
since the plate cannot be so displaced because it is constrained by
all of the supports 34, each support will tend to be compressed. At
the same time, however, the decreasing temperature of the container
16 which appears in gradient form along each support 34 will cause
the same to shrinks, thereby tending to decrease the distance
between the mounting plate 32 and outer welded end 35 of each
support. Evidently, if the amount of the radial shrinkage can be
made equal to the radial distance dr, no stress would be developed
in the supports 34 as a consequence of the temperature change
noted.
It is difficult to achieve the pure form of this desirable result,
but proper selection of the angular disposition of each support 34
from the vertical (i.e., essentially the angle d0) will approximate
the same such that each support has a limited tensile force
therealong at substantially all times and is never stressed beyond
about 70 percent of its yield strength including the load-induced
stress when the inner container 16 is filled. As a specific
example, is the aforementioned vessel for liquid helium in which
the inner container 16 has a length of about 450 inches and is
cooled to approximately -452.degree.F. and the slightly longer
container 17 is cooled to about -320.degree.F., supports 34 having
a length of approximately 40 inches may have an angular disposition
of 7.degree..
In such vessel, thermally induced relative longitudinal movement
between the inner vessel 16 and heat shield 17 of 0.124 inches
induced negligible stress; and in the same vessel such relative
movement between the heat shield 17 and outer jacket 18 of 1.160
inches resulted in negligible stress in the supports 38 when the
angular disposition thereof was about 1 1/2.degree.. Thus, the
desired relationship is one in which thermally induced radial
shrinkage of each radial support is effectively compensated by the
radial decrease in the distance between the ends of the support
resulting from the arc through which it swings as a consequence of
thermally induced relative longitudinal shrinkage of the containers
to which the support is attached.
Considering the supports 45 at the fixed end of the vessel, as the
intermediate container 17 cools the supports 45 become shorter, but
the diameter of the inner storage container 16 shrinks or
decreases. Consequently, there is an increasing stress within the
supports 45 as they tend to become shorter. However, because the
two functions are generally concurrent, the stress is not
materially increased and the supports are well able to withstand
the load imparted thereto by the liquid helium within the inner
container 16. The angular spacing between the supports adjacent
each end of the vessel affords a proper G-loading along their
respective axes.
The attachment of the inner container 16 to the shield 17 and
attachment of the shield 17 to the outer container 18 as heretofore
described affords a double heat barrier length. The various
supports operate effectively because of this length, and the
intermediate points along the supports (i.e., at the intermediate
container 17) are at a substantially fixed temperature which is
that of the intermediate container, and is about -300.degree.F when
the liquid nitrogen cooling system dominates and about
-360.degree.F when the gaseous helium system is effective.
The aforementioned bipartite cooling system comprising the two
coils 84 and 85 could be converted into a single-coil system
selectively connected to the nitrogen storage supply or to the
inner helium container 16. In such cases, it would be most
convenient to provide a vacuum-jacketed valve and conduit (neither
being shown) exteriorly of the outer container 18 to permit such
selective interconnection of the coil. With an arrangement of this
type, the cooling coil could be connected with the nitrogen storage
chamber 26 and nitrogen circulated through the coil to cool the
heat shield 17, as heretofore described; and this same coil could
then be evacuated and connected to the gaseous side of the helium
container 16 to permit helium to circulate through the coil, as
previously explained, to absorb heat and cool the shield.
The cooling function of the nitrogen system can be automatically
controlled and regulated to a predetermined discharge temperature
by means of a temperature-responsive solenoid-operated valve in the
nitrogen line, and the valve 89 is such a valve. The trap 88 allows
only gaseous nitrogen to be vented through the valve 89, as set
forth hereinbefore.
While in the foregoing specification an embodiment of the invention
has been set forth in considerable detail for purposes of making a
complete disclosure thereof, it will be apparent to those skilled
in the art that numerous changes may be made in such details
without departing from the spirit and principles of the
invention.
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