U.S. patent number 3,612,333 [Application Number 05/015,040] was granted by the patent office on 1971-10-12 for securement system using loose keys for independent storage tanks.
This patent grant is currently assigned to Esso Research and Engineering Company. Invention is credited to Walter C. Cowles.
United States Patent |
3,612,333 |
Cowles |
October 12, 1971 |
SECUREMENT SYSTEM USING LOOSE KEYS FOR INDEPENDENT STORAGE
TANKS
Abstract
An arrangement for securing independent storage tanks or
containers in a tanker or other vehicle of transportation for
transporting cargoes below or above ambient temperature wherein the
arrangement comprises a system of key-keyway-bearer combinations
removed from the neutral axis of the container, preferably located
at the top and the bottom of the storage tank and utilizing loose
keys, or in other words, keys that are detached from the
surrounding keyway-bearer structure.
Inventors: |
Cowles; Walter C. (Stamford,
CT) |
Assignee: |
Esso Research and Engineering
Company (N/A)
|
Family
ID: |
21769218 |
Appl.
No.: |
05/015,040 |
Filed: |
February 27, 1970 |
Current U.S.
Class: |
220/560.11;
114/74A |
Current CPC
Class: |
F17C
13/082 (20130101); B65D 90/08 (20130101); B65D
90/12 (20130101); F17C 2203/014 (20130101); F17C
2203/0354 (20130101); F17C 2203/03 (20130101); F17C
2205/018 (20130101); F17C 2270/0105 (20130101); F17C
2260/015 (20130101); F17C 2221/033 (20130101); F17C
2223/033 (20130101); F17C 2203/0629 (20130101); F17C
2201/052 (20130101); F17C 2223/0161 (20130101); F17C
2201/0171 (20130101); F17C 2260/016 (20130101); F17C
2201/0166 (20130101); F17C 2203/0646 (20130101) |
Current International
Class: |
B65D
90/08 (20060101); B65D 90/12 (20060101); B65D
90/02 (20060101); F17C 13/08 (20060101); B65d
025/00 () |
Field of
Search: |
;220/9LG,15 ;114/74A
;62/45 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,293,275 |
|
Apr 1962 |
|
FR |
|
683,855 |
|
Dec 1952 |
|
GB |
|
Primary Examiner: Leclair; Joseph R.
Assistant Examiner: Garrett; James R.
Claims
Having thus set forth the nature of the invention, what I claim
herein is:
1. In the storage and transportation of a material having a
temperature differing widely from ambient temperature, a container
of large capacity formed of a material characterized by substantial
expansion and contraction due to temperature changes and which has
a substantially flat bottom, a supporting structure having a
relatively flat floor, means for mounting said container within
said supporting structure so that said flat bottom is disposed in
spaced relation relative to said flat floor and in a manner to
substantially stabilize the position of said container within said
supporting structure while permitting free expansion and
contraction thereof, said mounting means comprising a first and
second plurality of longitudinally and transversely arranged
elongated keyways provided on said flat bottom of said container
and one said flat floor respectively, corresponding ones of said
keyways of said first and second plurality being disposed in
vertically aligned matched relation thereby to define a composite
channel, an elongated key being slidably received in both of the
keyways of each of said composite channels, whereby said container
is stabilized against any undesirable movement relative to said
supporting structure.
2. An assembly according to claim 1 wherein the width of said first
plurality of keyways is greater than that of said second plurality
of keyways by a predetermined amount corresponding to the amount of
contraction of said container caused by the change from ambient
temperature to storage temperature.
3. An assembly according to claim 1 wherein bearing means are
operably associated with each of said keyways of said first and
second plurality whereby said bearing means assists in maintaining
said container in a stabilized position.
4. An assembly according to claim 3 wherein said bearing means for
each of said keyways comprises a pair of laterally spaced
horizontal bearing surfaces located on opposite sides of said
keyway, wherein said bearing surfaces of said corresponding ones of
said keyways are disposed in contact with each other.
5. An assembly according to claim 3 wherein said bearing means for
each of said keyways comprises a pair of opposing bearing members
extending laterally inward of each of said keyways for contact with
said key.
6. An assembly according to claim 3 wherein additional bearing
means are provided adjacent the periphery of said flat bottom of
said container and support means for said bearing means are
provided on said flat floor for further supporting said container
within said supporting structure.
7. An assembly according to claim 1 wherein said container includes
a relatively flat top portion and said supporting structure has a
top wall, a third and forth plurality of longitudinally arranged
elongated keyways provided on said flat top portion and on said top
wall, respectively, corresponding ones of said keyways of said
third and fourth plurality being disposed in vertically aligned
matched relation.
8. An assembly according to claim 7 wherein the width of said
keyways comprising said first and third plurality is greater than
that of said keyways comprising said second and fourth plurality by
a predetermined amount corresponding to the amount of contraction
of said container caused by a change from ambient temperature to
storage temperature.
9. An assembly according to claim 7 wherein bearing means are
operably associated with said third and fourth plurality of said
bearing means comprising a pair of opposing bearing members
extending laterally inward of each of said keyways disposed for
contact with said key.
10. In the storage and transportation in the cargo hold of a tanker
of a material having a temperature differing widely from ambient
temperature, a tank of large capacity formed of a material
characterized by substantial expansion and contraction due to
temperature changes, said tank having top and bottom walls, said
cargo hold having a deck and a floor, means for securing said tank
within said cargo hold so that said bottom wall is spaced from said
floor, said securing means comprising a first and second plurality
of opposing longitudinal and transverse keyways operably secured to
said bottom wall and said floor respectively, a third and fourth
plurality of opposing longitudinal keyways operably secured to said
top and said deck respectively, key means separate from said
keyways being slidably and removably disposed in opposing ones of
said keyways thereby to stabilize and effectively isolate said tank
from any movement transmitted by said tanker.
11. In the assembly of claim 10 wherein girders extend downward
from said deck in a transversely spaced arrangement thereby to
define a plurality of bays, said fourth plurality of keyways being
secured to said deck in alternate bays between said girders,
thereby to facilitate insertion of said key means into its
corresponding keyways.
12. A tank of relatively large capacity for use in the storage and
transportation of material having a temperature differing widely
from ambient temperature and being formed of a material
characterized by substantial expansion and contraction caused by
temperature changes, said tank being adapted for securement within
a cargo containing structure and having top, bottom and sidewalls,
means adapted to securely position said tank within said enclosed
area, said means comprising a first plurality of longitudinal and
transverse extending elongated channels formed on said bottom of
said tank and a second plurality of longitudinal extending
elongated channels formed on said top of said tank, each of said
channels being adapted to match with an opposing channel formed
with the cargo containing structure thereby to form a composite
keyway capable of slidably receiving a slidable and removable key,
whereby said tank will be secured in position when placed within
said cargo containing structure.
Description
BACKGROUND OF THE INVENTION
The present invention relates in the broadest sense to the storage
and transportation of liquids such as liquefied natural gas,
hereinafter referred to as LNG, at extremely low temperatures well
below ambient temperature and at essentially atmospheric pressure.
More particularly, the present invention is concerned with a novel
and improved system for securing storage tanks carrying LNG or the
like in large quantities within a moving vehicle such as a tanker
and wherein the system uses loose keys.
It is well know in the art that the transportation of gasses, such
as natural gas and the like, to locations remote from its source of
origin may best and most efficiently be accomplished by reducing
the volume of the gas through its conversion into the liquid state.
Such a conversion enables the storage volume requirements to be
greatly reduced (e.g., approximately six-hundredfold for a given
quantity of methane gas and, as will be appreciated by those
skilled in the art, enables the most efficient and orderly transfer
of the gas to the remote area.
In order to transfer LNG in a practical and economically feasible
manner in relatively large volumes, it is necessary to store the
liquefied natural gas at approximately atmospheric pressure, since
large containers built to withstand superatmospheric pressures
would be impractical, if not impossible, to construct for use on
seagoing tankers or vessels and the like. The LNG now is kept in
storage containers having exceptionally large capacities and these
containers when transported by tanker are confined within the cargo
hold space of the tanker. To prevent heat losses which would lead
to excessive volatilization of the stored liquified gas, it is
essential to provide proper thermal insulation for the containers.
Also, the containers must be of sufficient strength to withstand
the internal stresses that may be induced therein by large
temperature gradients through the walls of the container. In using
containers having such large capacity in a moving vehicle, it is
desirable to maintain absolute control of the movements of the
containers so as to avoid bumping or shifting movements thereof in
response to the erratic movements of the transportation vehicle,
such as the pitch and roll movements of a seagoing tanker. The
problem of properly securing the containers in the cargo hold space
provided therefor in the tanker further is increased by the need to
compensate for movement of the storage containers caused by the
expansion or contraction thereof that comes about due to the
storage of the containers at a temperature well below that of
ambient temperature. This change in temperature naturally will
result in considerable contraction in the dimensions of the
containers when filled with a material such as liquefied gas or the
like, and in a corresponding expansion when the containers are
emptied and allowed to rise in temperature. Heretofore, the
solution to the problem of properly securing the containers in the
tanker's cargo hold space has been the use of key-keyway systems
employing keys formed integral with the tanker's hull.
The prior art securement arrangements have been found to be
unsatisfactory in many respects. Frequently, prior art securement
systems for mounting containers in a tanker have relied upon
vertically disposed key-keyway arrangements. These prior art
arrangements have not only been relatively complex and costly to
construct, but have been ineffective in providing an equalized
distribution of stress concentrations along the entire key-keyway
structure. This is because the key-keyway is located at the
vertical center of the container sidewalls and therefore, the
stress is concentrated at one or two localized points which
normally are at either end of the key. Thus, the possibility of
local failure where greater stress concentrations occur is greatly
increased. Since these arrangements are structurally inefficient
the consequence is a substantial increase in the cost. Other prior
art systems have used top and/or bottom key-keyway arrangements
wherein the key is formed integral with the tanker's hull or the
container. Since the key and key-way constructions are formed as an
integral part of the container or the tanker's hull, the
construction of the container is substantially more complicated
and, also, it is substantially more difficult to inspect and repair
the keys and the keyways. Further, the keys do not always properly
mate with the keyways thereby requiring further modification at the
site of the tanker or other vehicle of transportation.
SUMMARY OF THE INVENTION
The present invention overcomes both these and other prior art
deficiencies by providing a novel and improved arrangement for
securing independent storage tanks or containers in position in a
tanker or vehicle of transportation, while allowing for contraction
or expansion of the container caused by the loading of the cargoes,
such as LNG, at lower than ambient temperature. The system
comprises essentially an arrangement of keys, keyways and bearer
supports located at the bottom of the container in directions
corresponding to and along the longitudinal and transverse
centerlines of the tank. Specifically, a lower keyway and container
support pedestal are secured to the inner bottom wall of the
tanker's hull. A matching keyway and container bearing member are
secured to the underside of the container. A loose key, preferably
made of fabricated steel, is fitted into the channel formed between
the keyways to secure the container from undesirable lateral and
longitudinal movement relative to the ship. The container's bottom
or lower keyways are designed so that its width is wider than they
key at ambient temperature by an amount carefully calculated to
correspond to the amount of thermal contraction that occurs when
the container is cooled to the temperature of the cargo. Thus, at
operating temperature the key will fit neatly in the keyway. The
containers may be further supported by additional bearer members
and support pedestals located near the outboard sides of the
container. To further secure the containers against any upsetting
force that may result from the motion of the transportation
vehicle, there is provided a second key and keyway system located
at the top of the container extending in a direction on the
longitudinal centerline thereof. As with the lower container
keyways, the keyways secured to the top of the container are
constructed to suit the dimension of the key when the container is
cold. Matching keyways are secured to the underside of the deck and
these upper keyways are fitted only in alternate bays formed
between adjacent deck girders. The keys are designed to be shorter
than the distance between the adjacent girders to facilitate their
insertion into the keyway. Thus, installation of the containers,
deck structure and keyways can be accomplished prior to the final
fitting and insertion of the keys. The container securement of the
present invention is more effective than that proposed by the prior
art, since forces and therefore stress concentrations are equally
distributed along the container, bearing areas are substantially
reduced, and the key support structure can be less extensive than
required heretofore. The use of a common structure for slidably
mounting the keys and providing bearer support substantially
reduces the construction costs and minimizes thermal losses. A
significant feature of the present invention comprises the use of
loose keys which permits the keys and keyways to be machine
finished under workshop conditions prior to final installation.
Also, the use of loose keys permits the withdrawal of the keys for
inspection and repair if required. By virtue of the fact that the
present arrangement provides for equal distribution of forces, the
stress concentrations are evenly distributed on the container and
consequently the possibilities of failure associated therewith are
substantially reduced. Further, the use of loose keys as compared
to integral formed male tenons simplifies and expedites
construction of the storage containers.
Accordingly, it is a primary object of the present invention to
provide a novel and improved system for securing storage containers
in a transportation vehicle, such as a tanker, which is low in
cost, economical in construction, and reliable in operation.
Another object of this invention is to provide a novel and improved
system for securing independent storage container and which uses
loose keys.
A further object of this invention is to provide a novel and
improved key-keyway system for securing a storage container in a
cargo hold of a vehicle and wherein there is equal distribution of
stress concentrations along the container.
Having in mind the above and other objects that will be evident
from an understanding of this disclosure, the invention comprises
the devices, combinations construction, arrangements of parts as
illustrated in the presently preferred embodiment of the invention
which is hereinafter set forth in such detail as to enable those
skilled in the art readily to understand the function, operation,
construction, and advantages of it when read in conjunction with
the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a transverse cross-sectional view taken substantially
along the line 1--1 in FIG. 2 of a tanker in which the new and
improved system for mounting a storage container according to the
principles of the present invention has been installed;
FIG. 2 is a bottom plan view taken substantially along the line
2--2 in FIG. 1 of the storage container partially broken away;
FIG. 3 is a top plan view taken substantially along the line 3--3
in FIG. 1 illustrating a portion of the top of the storage
container embodying the features of the present invention;
FIG. 4 is a enlarged cross-sectional view taken substantially along
the line 4--4 in FIG. 3 showing details of construction of a top
key-keyway arrangement constructed in accordance with the present
invention;
FIG. 5 is an enlarged cross-sectional view taken substantially on
the line 5--5 in FIG. 2 illustrating details of construction of a
bottom key-keyway-bearer arrangement constructed in accordance with
the present invention; and
FIG. 6 is an exploded perspective view illustrating a bottom
key-keyway-bearer arrangement embodying the principles of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is disclosed in combination with a cryogenic
storage container for storing liquefied natural gas (LNG) or the
like at atmospheric pressure, such as disclosed in the U.S. Pat. of
Clarke et al., No. 3,319,431, issued May 16, 1967, and assigned to
the assignee of the present invention, wherein the container is
fully disclosed and to which reference may be had for a more
complete understanding thereof.
Referring now to the drawings, there is illustrated in FIG. 1 a
storage container 10 which is installed in a double-hulled tanker
11 (although a single-hulled tanker may be suitable) having an
outer hull 12 and an inner hull 13 which are maintained in
separated spaced relationship by structural members 14 and which
defines a cargo hold space 15. The container 10 includes an inner
tank 16 which constitutes a primary barrier having the general
shape of the cargo hold 15 and which is fabricated from aluminum,
stainless steel, high nickel steel, aluminum alloy or a like
material which is capable of withstanding the thermal stresses
induced by the cryogenic cargoes. The inner tank 16 is enclosed by
a similarly shaped and designed outer tank 17 which constitutes an
outer or secondary barrier and also, as with the inner tank 16, is
fabricated from a material such as aluminum or the like which is
not deleteriously affected by the extremely cold temperatures of
the cryogenic cargoes. The tanks 16 and 17 are maintained in space
relation by means of rigid spacing members 18 secured
therebetween.
The double-walled tank or storage container 10 is provided about
its outer surface with an exterior layer of thermal insulation 19.
It will be understood by those skilled in the art that for purposes
of the present invention the layer of insulation 10 may be located
otherwise than as illustrated. For example, it may be situated
along the inner hull of the tanker 11. Briefly referring to the
internal construction of the tank 10, there is illustrated as
impervious longitudinal bulkhead 20 that is effective to prevent
sloshing of the LNG cargo from side-to-side within the tank. The
tank also includes horizontal flats 21 and 22 which include a
plurality of apertures 23 and 24, respectively, to permit drainage
and circulation.
As shown in FIG. 1, the tank 10 properly is secured in position
within the cargo hold 15 of the double-hulled tanker 11 by means of
a bottom key-keyway-bearer system generally designated 25 and a top
key-keyway system generally designated 26. Also, to further provide
support for the tank 10 there is provided at the tank bottom a
plurality of bearer/support arrangements generally designated 27
situated near the outboard sides of the tank. At the bottom of the
tank 10 the system 25 comprises a plurality of keyway-bearer means
28, one pair being longitudinally disposed and a second pair being
transversely or laterally disposed keyways, each of the pairs
located along lines corresponding to the respective centerlines of
the tank 10 as best illustrated in FIG. 2. Since each of these
keyway-bearer means 28 are identical in their construction and
arrangement, only one need be described for purposes of
understanding the present invention. The keyway-bearer 28 comprises
a lower keyway or elongated channel 29 secured to the underside of
the tank 10. See FIGS. 2 and 5. The keyway 29 is formed by a pair
of laterally spaced keyway vertical bearing members 30, which are
made of balsa wood, fir or other suitable material, which extend
the length of the members 30 and are located adjacent to tank
bottom, and that properly are secured in place by means of support
brackets 31 which are suitably fastened at one end to the bottom of
tank 10 and at the other end to the vertical bearing member 30.
These brackets 31 comprise the same material as that for the tank
which may be made of aluminum, 9 percent nickel steel or any other
suitable material. As shown in FIG. 5, at the lower end of the
inner surface of each of the bearing members 30 there is provided a
lateral bearing block 32, which is made of wood, laminated phenolic
(micarta) or any other suitable material and has an outer contact
bearing surface 33. At the bottom of each of the vertical bearing
members 30 there is secured a contact bearing surface 34 made of a
material such as micarta, stainless steel, or the like, to
vertically provide support for the tank 10 and any cargo contained
therein. To the inner bottom of the tanker and disposed for
alignment with the foregoing keyway-bearer means 28 there are
provided a pair of keyway-bearer support means 28', comprising a
pair of laterally spaced elongated hollow keyway support stools 35,
which comprise preferably 9 percent nickel steel or some other
suitable material such as aluminum, etc. At the top or upper
surface of each of the support stools 35 there is secured vertical
contact bearing surfaces 36, which are similar to the bearing
surfaces 34 described heretofore. The support stools 35 are
properly secured in place adjacent the inner bottom of the tanker
by means of support brackets 37, which are similar to the support
brackets 31 for the bearer members 30. The support stools 35 are
disposed such that when the tank 10 is mounted in the tanker's
cargo hold 15 the bearing surfaces 36 of the stools 35 will align
in contact with the corresponding bearing surfaces 34 of the
vertical bearing member 30. On the inner surface at the upper end
and extending the length of the support stools 35 there are
provided a pair of opposing lateral bearing blocks 38, having outer
contact surfaces 39, which are similar to the lateral bearing
members 32. The spacing between the lateral bearing blocks 38--38,
as illustrated in FIG. 5, defines an elongated channel or keyway 40
having a width that is slightly smaller than that between the
lateral bearing blocks 32--32 for reasons to be described
hereinafter. Also, disposed adjacent the inner bottom of the tanker
are a pair of spaced support blocks 41 of suitable wood material
which are located between opposing inner faces of the support
stools 35 inwardly of the lateral contact surfaces 39. These blocks
41 provide vertical support for elongated hollow steel key 42
having a rectangular end cross section and which is to be slidably
inserted into the channel formed by the keyways 29 and 40 upon
mounting the tank 10 in the tanker's cargo hold 14. Once the tank
10 has been mounted with its bearer members 30 properly located
relative to the support stools 35, as shown in FIG. 5, the loose
key 42, made preferably of fabricated steel, is fitted into each of
the channels thereby to secure the tank from lateral and
longitudinal movement relative to the tank top. The spacing between
lateral bearing blocks 38--38 is such as to provide a relatively
close fit for the key 42. However, the keyway width defined between
the lateral bearing blocks 32--32 secured to the tank 10 is such
that it is wider than the corresponding key width at ambient
temperature by an amount carefully calculated to correspond to the
thermal contraction when the tank 10 is cooled to the temperature
of the cryogenic cargo. Thus, when the tank 10 is at operating
temperature the key 42 will fit neatly in the keyway 29 defined
between lateral bearing blocks 32--32. In addition to the foregoing
described combined bearing-support arrangements located at each of
the key-keyway means 28, the tank 10 further is supported
vertically by additional bearing members 43 (similar to bearing
members 30) and support pedestals 44 (similar to support stools 35)
which extend longitudinally near the outboard sides of the tank, as
best illustrated in FIG. 2. Each of the bearing members 43 is
suitably secured to the underside of the tank 10 and is provided
with a contact bearing surface 45 that is similar to the bearing
surfaced 34, and each of the support stools or pedestals 44 is
provided with a contact bearing surface 46 which is similar to the
bearing surfaces 36. As shown in FIG. 6, it is clearly apparent
that by using an arrangement including a loose key 42, that is, one
structurally separate from the surrounding keyway defining
structure, the installation and repair of the keys and/or the
keyways is greatly simplified. A modification of the foregoing
described construction and arrangement that is within the scope of
this invention may include making the bottom keys 42 in multiple
lengths so that complete withdrawal thereof for purposes of
inspection or otherwise is permitted. Thus, in the event of
pitching or rolling movement of the tanker, the longitudinal and
transverse key-keyway combinations properly will secure the tank in
place in the cargo hold while permitting thermal expansion and
contraction.
The tank 10 further is secured from undesirable movement by means
of the longitudinal extending top key-keyway means 47 (secured to
the tank) and 47' (secured to the deck 49) which comprise the
system 26. The top or deck keyway 47' comprises a pair of laterally
spaced support stools or pedestals 48 fastened adjacent the
underside of the deck 49. Each inner surface of the support stools
48 at its bottom end is provided with a lateral bearing block 50
having an outer bearing contact surface 51, similar to the lateral
bearing blocks 32 and 38. The stools 48 are secured to the
underside of the deck 49 by means of metal support brackets 52 in a
manner similar to that for the lower bearing and support members.
The bearing blocks 50 define elongated channels or keyways 53. The
keyways 53 may be located in alternate bays (see FIG. 3) formed
between the downward extending transverse deck girders 54 so as to
facilitate insertion and removal of the keys 42 therefrom. This is
best illustrated in FIG. 3, wherein the key is shown in dotted
lines prior to insertion into its keyway. At the top of the tank 10
there is secured the matching keyway 47 comprising a second pair of
support stools 55 which are held in spaced relation by means of
support brackets 56. A lateral bearing member 57 having a bearing
contact surface 58 is secured to the inner surface at the upper end
of each of the support stools 55. These members 55 extend
longitudinally the length of the stools and define an upper tank
keyway 59. Located and secured to the tank top wall between the
opposing inner faces of the support stools 55 inwardly of the
bearing members 57 are a pair of spaced support blocks 60,
preferably of a wood material, which function in a manner similar
to the support blocks 41. As with the lower tank keyways 29, the
top tank keyway 59 is constructed to suit the dimension of the key
42 when the tank 10 is cold. Thus, as shown in FIG. 4, the spacing
between the lateral bearing blocks 50 is less than the width
between the lateral bearing members 57 so that when the key 42
slidably is inserted into register with the keyways 53 and 59 and
the tank is cooled, the space between the upper tank bearing
members 57 will contract laterally with corresponding contraction
of the tank thereby to form a neat fit for the loose key 42. It is
to be noted that when using a construction where the girders extend
down, the keys 42 are shorter than the distance between adjacent
deck girders 54 so that installation is made easier. It is apparent
from the foregoing description that installation of the tanks, deck
structure and keyways can be completed before final fitting and
insertion of the keys into their corresponding keyways.
As an alternate arrangement to the above, both the top and bottom
tank keyways may be recessed into the tank structure (that is, the
top and bottom tank walls), thereby permitting an increase in the
size of the tanks relative to their capacity.
Further numerous alterations of the structure herein disclosed will
suggest themselves to those skilled in the art. However, it is to
be understood that the present disclosure relates to a preferred
embodiment of my invention which is for purpose of illustration
only and is not to be construed as a limitation of the invention.
All such modifications which do not depart from the spirit of the
invention are intended to be included within the scope of the
appended claims.
* * * * *