Note: Descriptions are shown in the official language in which they were submitted.
212.5 63~
BI~C~GRO~ND OF THE lNV ~ ION
FIELD OF THE ll.vl!ihllON:
This invention relates to pressure vessels used for the
storage of gases, particularly compressed natural gas (CNG) above
ground.
DE8CRIPTION OF THE RBLATED ART:
Pressure vessels used for the storage of gases have
traditionally been expensive due to the time and labor intensive
manufacturing processes. Conventional methods of manufacture have
been by welding component parts together or forging of the vessel.
Both of these methods are expensive and time consuming. As a
result, a very costly pressure vessel is produced requiring long
lead times for manufacture. In addition, pressure vessels of
conventional construction are extremely heavy, thereby causing
difficulties and added cost in handling and transportation.
Welding of component parts of a pressure vessel is
accomplished by obtaining a piece of pipe of desired length and
specifications and welding a forged hemispherical section on each
end. Each hemispherical section would have an opening therein to
allow for gas access. Welding produces a pressure vessel with
seams that are a line of reduced strength of the vessel. In
addition, welding is a very labor intensive process.
Difficulties arise in the welding process when two sections of
- differing thicknesses are welded together. Joining of this type
may require additional machining of the pieces to produce a taper
in order for a satisfactory weld to be obtained.
A pressure vessel may also be constructed by welding sections
of differing shapes to one another. An example of this is
disclosed in the Watter patent, USPN 3,024,938. Such construction
also produces a vessel containing seams therein.
An alternative conventional method of construction of pressure
vessels is accomplished through forging at high temperatures. Such
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methods of manufacture are equally as labor intensive and time
consuming as those that are welded.
In using the forging method, a section of pipe of a desired
length is obtained. In this method, in order to produce the
hemisphe~ical heads of the pressure vessel, the pipe is forged at
extremely high ~emperature and the ends of the pipe are swaged
closed. Once this is comp~eted, the en~ire vessel is heat treated.
After heat treatment, the swaged closed ends of the pipe are
machined. The resultant pressure vessel is then cleaned and tested
according to applicable specifications. This manufacturing process
produces a seamless vessel, however, the cost of such production
are high due to the heating and machining require~ents.
Therefore, a need in the industry exists for a pressure vessel
that is capable of storage of compressed gases, such as compressed
natural gas which requires no expensive forging or welding. A need
also exists for a pressure vessel where the manufacture time is
expedited over conventional methods. A further need in the
industry exists which conforms to ASME specifications yet is not as
heavy as conventional vessels.
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8~MMARY OF TH lNv~N~lON
It is the purpose of the present invention to obtain a
pressure vessel capable of above ground compressed storage of
gases, such as compressed natural gas meeting ASME specifications.
An additional purpose is to provide an apparatus for storage
of compressed gases which is constructed without the requirement of
forging or welding. Such construction facilitates and expedites
the manufacturing process resulting in significant cost savings
over traditional designs. The pressure vessels of this invention
are capable of use in a plurality while taking up minimal ground
space.
An apparatus to accomplish this purpose is comprised of a
seamless cylinder or tube requiring no hot or cold forming or
welding. This seamless tube is rolled to American Society of
Mechanical Engineers (ASME) or American Petroleum Institute (API)
standards. Electric Resistance Weld tubes, butt weld tubes, or
common oilfield casing could be used instead of seamless tubes.
Once a desired length of tube is obtained, threads are machined on
each end. A head or cap with threads machined on its inner surface
is constructed. The threads of the cap mate the threads of the
tube and a cap is screwed onto each end of the tube. Since both
the tube and cap are threaded so that the threads of the tube
receive the threads of the cap, no welding, or re-heat treating is
required to produce the necessary seal in order to create the
pressure vessel. Therefore, this design is very effective for use
as a pressure vessel while also being easy to manufacture at
minimal cost. The tubular gas storage vessels of this invention
may be designed to meet ASME or DOT specifications.
A cap is screwed on each end of the tube. Each cap contains
a passage which is threaded to mate a reducing bushing. The
threaded reducing bushing is screwed inside the passage of the cap
to allow access of a gas port of required diameter. In order to
provide this access, at least a partially t~readed central passage
is machined into the reducing bushing.
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A gas port with threads mating those of the partially threaded
central passage of the reducing bushing can then be screwed into
the reducing bushing to provide gas flow as required.
Depending upon the particular application of the pressure
S vessel, the other end of the tube with a second cap screwed thereon
may be fitted with a second reducing bushing and gas port or may be
sealed by screwing a threaded plug into the reducing bushing to
prevent the escape of the contents of the vessel. When the vessel
is fit with this reducing bushing with a second gas port, a
plurality of vessels may be connected together, or in any other
manner as required.
An alternative cap assembly includes a cap which is not
threaded to be screwed onto the end of the tube but rather designed
to fit inside. This cap contains a shoulder portion of reduced
diameter onto which a packing assembly is attached. The packing
assembly consists of alternating series of chevron rings stacked
against one another in wood chip or teflon chip type packing
material known in the art and moldable around the cap. This
packing assembly seals the end of the tube to prevent the escape of
gas stored in the tube.
The cap is secured in the tube by a retainer ring having a
diameter larger than the inner diameter of the tube. The retainer
ring fits into a groove cut in the inner diameter and is
constructed in three sections to facilitate installation. The cap
assembly is secured in the tube by a washer and a plurality of
bolts that extend through the washer and retA; n; ng ring to screw
into the cap. Passages are drilled partially through the cap which
intersect with its shoulder so that the packing assembly can be
energized to provide a proper seal in the tube. Fittings secure the
passages once the packing assembly is energized. A drain is drilled
through the cap and is sealed by a drain plug. A partially threaded
passage extends through the cap, ret~ining ring, and washer into
which a gas port may be inserted. The other end of the tube would
be closed by the same cap assembly which may be closed by a plug
screwed into the partially threaded center passage of the cap or
2125633
another gas port could be inserted into the partially threaded
central passage in order to connect a plurality of tubes together
or in any manner as required.
A plurality of pressure vessels may be stacked vertically to
form a cascade. A cascade provides increased storage capability
while taking up a minimal amount of ground space, or footprint.
This support consists of a pair of vertical vessel clamps which
conform to the outer diameter of the tubular pressure vessels.
When two such vessel clamps are clamped onto a plurality of vessels
and secured together, the vessels are retained at a pre-determined
distance from one another.
A second, identical set of vessel clamps are secured a
distance from the first set in order to support the entire lengths
of the tubular pressure vessels.
lS Multiple pressure vessels are then positioned vertically by
securing them to a support base designed to receive the support
brackets. The base receives the support brackets so that they are
perpendicular to the ground. When secured, the tubular pressure
vessels are secured in a vertical-parallel arrangement by the
support ~tructure.
In constructing a threaded tubular pressure vessel of this
design, the manufacturing process may be expedited in comparison
with traditional arrangements since no forging or welding is
required. As a result, a tubular above ground gas storage vessel
suitable for storage of compressed gases may be manufactured at
significant savings in cost and labor.
Other features and advantages of the invention will become
apparent in view of the drawings and following detailed
description.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an isometric view of the tubular above ground gas
storage vessel of this invention where three tubular vessels are
secured, or stacked, in a cascade by the support structure.
Figure 2 is a cross-section taken along line 2-2 of Figure 1.
Figure 3 is an isometric view of a support bracket for a
plurality of above ground gas storage vessels of this invention.
Figure 4 is an isometric view of a support base for a cascade
of tubular above ground gas storage vessels of this invention.
Figure 5 is an end view of the tubular above ground gas
storage vessel of this invention depicting an alternative means of
securing the caps to the tube.
Figure 6 is a view taken along line 6-6 of Figure 5.
Figure 7 is a view taken along line 7-7 of Figure 6.
Figure 8 is a view taken along line 8-8 of Figure 5.
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, (
~ETAILED DESCRIPTION OF THE PREFE~RED EMBODIMENT
Referring now to the drawings, where identical or
corresponding parts were referred to by the same reference numerals
throughout the several views, Figure 1 is an isometric view of a
preferred embodiment of the invention. In Figure 1, a cascade of
three tubular above ground gas storage vessels, numerically 10, 12,
and 14, are viewed as they are supported by a pair of support
structures, 20 and 22.
When constructed according to this invention, tubular gas
storage vessels 10, 12 and 14 are usable for storage of any
compressed gas, however, they are particularly suited for storage
of compressed natural gas. Such gas storage may either be
stationary or mobile as required. Stationary storage of compressed
natural gas is required to meet motor vehicle fuel requirements at
a fueling station.
Tubular gas storage vessels 10, 12 and 14 may be constructed
from any suitable materials such as 9 5/8" OD common seamless tubes
which require no forging or welding. Tubular casings 16, 17 and 18
of tubular gas storage vessels 10, 12 and 14, respectively, are
seamless and rolled to American Society of Mechanical Engineers
(ASME) or American Petroleum Institute (API) standards. It should
be understood, however, that these tubes are not limited to these
standards. Where permitted common oilfield casing milled to API
standards could be used. It should also be understood that
construction is not -limited to seamless tubes as Electric
Resistance Weld (ERW) or butt weld tubes can also be used.
Seamless welds are preferred because presently ASME de-rates the
working pressure of ERW tubes, therefore, seamless tu~es provide
more storage per dollar.
Tubular casings 16, 17 and 18 can be cut at any length
required by particular gas storage requirements. When used for the
storage of compressed natural gas, suitable standard lengths of 21'
and 42' are possible with the pressure rating (4:1) of 4,340 psi.
In such configurations, the tubular gas storage vessels will hold
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~ 1 2563~
2,277 SCF in the 21' version and 4,554 SCF in the 42' model (each
tube). The preferred tubular gas storage vessels of this invention
are designed according to Section VIII, Div. 1 of the ASME Code.
Both ends of each tubular casing 16, 17 and 18 terminate with
5 a cap. Each tubular gas storage vessel lo, 12 and 14 are identical
in configuration. For the purpose of exemplification, this
description and accompanying reference numerals will be limited to
tubular gas storage vessel 10. It is understood that tubular gas
storage vessels 12 and 14 are configured in the same manner as
vessel 10. Both ends of tubular casing 16 of tubular gas storage
vessel 10 are threaded to mate with threads machined on the inner
circumference of caps 24 and 26.
Figure 2, a view taken along line 2-2 of Figure 1, depicts a
cross-sectional view of the manner in which tubular casing 16 is
sealed by cap 26 on a first end to form a tubular gas storage
vessel 10. Tubular casing 16 is machined to terminate with a
threaded portion 28. Cap 26 is threaded on its inner circumference
30 so that the threads of the threaded portion 28 of tubular casing
16 mate with the threads of the inner circumference 30 of cap 26.
Cap 26 is then screwed onto the end of tubular casing 16. Since
both the tube and cap are threaded so that the threads of the tube
receive the threads of the cap, no welding, or re-heat treating is
required to produce the necessary seal to create gas storage vessel
10, therefore making this design very effective for use as a gas
storage vessel while also being easy to manufacture at minimal
cost.
In order to help prevent the leakage of the contents of
tubular gas storage vessel lo, the inside of cap 26 may be grooved
to receive a gasket, or o-ring 40.
An annular passage 32 is drilled in cap 26 in order to provide
for the flow of gas to tùbular pressure vessel 10. The wall of
annular passage 32 within cap 26 is machined to have threads 34
therein. A reducing bushing 36 having the same outer diameter 38
as the diameter of passage 32 is threaded to mate threads 34 of
passage 32. Reducing bushing 36 is screwed into passage 32 of cap
2~63~ (--
26. A groove may be cut in reducing bushing 36 in order to receive
a gasket or o-ring 42 to help prevent the escape of the contents of
tubular pressure vessel 10.
A central passage 44 is drilled in reducing bushing 36.
Central passage 44 is at least partially threaded to receive a gas
port to inject gas into tubular gas storage vessel lo. Reducing
bushing 36 provides the ability for vessel 10 to receive gas ports
of various diameters.
A drain 46 may be drilled into cap 26 at any suitable
location. Drain 46 allows access to vessel 10 without disturbing
any other fittings. Drain 46 may receive a probe to monitor the
pressure in vessel 10 or a plug to provide for the removal of
condensation which may result from compression of the gas within
vessel 10.
Reducing bushing 36 may receive a gas port but it may be
plugged depending upon operational requirements. Referring to
Figure 1, the second end 29 of tubular casing 16 depicts~ a second
cap 24 and a second reducing bushing 48. Reducing bushing 48 in
Figure 1 is sealed with a plug 50.
In ~ preferred embodiment, the first end of tubular casing 16
will have a reducing bushing, such as 36 of Figure 2, which
receives a gas port to allow the flow of gas into and out of vessel
10. As shown in Figure 1, the second end of tubular casing 16 will
then have a second reducing bushing 48 which is sealed with plug 50
to allow compressed gas to be storèd within vessel 10. It is
- understood, however, that the second reducing bushing 48 could also
receive a gas port, or be configured so that tubular gas storage
vessels 10, 12 and 14 are connected to one another (not shown).
Figure 5 is an end view of the above-ground storage vessel of
this invention depicting an alternative assembly for closing the
ends of the tube. In this embodiment, the ends of the tube are not
threaded to receive the cap but rather the cap is secured into the
ends of the tube in order to seal the pressure vessel.
Referring to Figure 6, a view taken along line 6-6 of Figure
5, a first end 82 of a tube 83 with this alternative embodiment can
212~633
be seen. Tubes of this design can be substituted for those shown
in Figure 1. In order to receive the cap assembly, generally 84 of
this embodiment, the inner diameter of each end of the tube 83 is
slightly enlarged. In Figure 5, first end 82 of tube 83 has an
5enlarged section 86. This enlarged section 86 of first end 82 is
of a length sufficient to receive the entire cap assembly 84.~
Cap assembly 84 includes cap 88 of a diameter that equals the
internal diameter of the enlar~ed section 86 of the first end 82.
A central passage 89 is drilled into cap 88. Central passa~e 89 is
10at least partially threaded to receive a gas port so that the gas
being stored in tube 83 may be injected or released as required.
Cap 88 contains an annular shoulder 90 of reduced diameter
which is inserted into first end 82 of tube 83. Shoulder 90 has a
reduced diameter as compared with t~e rest of cap 88 so that
15packing 92 may be inserted between cap 88 and enlarged section 86.
Reference is now made to Figure 8, a view taken along line-8-8
of Figure 5. Prior to inserting cap 88 into first end 82 of tube
83, packing is placed around cap 88 on shoulder 90. Packing 92
consists of a series of chevron rings 94 fit against one another in
20a stacked arrangement. A material 96 is inserted as a part of
packing 92 against chevron rings 94. Material 96 is injectable
packing used in the art for high pressure applications. This
injectable packing material 96 is moldable by hand, formed into a
wad ring and inserted against chevron rings 94. Once material 96
25is inserted, a second set of chevron rings 98 are inserted against
material 96. Following rings 96 is a metal support ring 100 which
prevents packing 92 from extruding into the interior of the tube.
A snap ring 102,is fit over cap 88 into a snap ring groove 104
cut into cap 88. The function of snap ring 102 is to hold packing
3092 in place, both before and after cap 88 is inserted into first
end 82 of tube 83. After packing 92 is secured to cap 88, cap 88
is inserted into first end 82.
Referring to Figure 6, once cap 88 including packing 92 is
inserted into first end 82, a retainer plate 106 is secured.
35Retainer plate 106 has a diameter ~reater than the inside diameter
11
~2563~
of enlar~ed section 86 of first end 82. A retainer plate groove
108 is cut inside first end 82 to receive retainer plate 106.
Referring to Figure 7, a view taken along line 7-7 of Figure
6, retainer plate 106 consists of three segments, 110, 112 and 114.
These segments, 110, 112 and 114, enable retainer plate 106 to be
fit inside retainer plate groove 108 of Figure 6. Retainer plate
106 contains a central passage 116 to allow a gas port to be
inserted through. Holes 111, 113 and 115 are drilled in segments
110, 112 and 114 respectively of retainer plate 106 to allow bolts
to be inserted there through.
After retainer plate 106 is secured in retainer groove 108, a
washer 118 is mounted inside first end 82. Washer 118 is mounted
flush with the end of first end 82 of tube 83. Washer 118 has a
plurality of holes drilled through it so that a series of bolts,
fittings and a plug may be inserted. After the entirety of cap
- assembly 84 is inserted into first end 82, bolt 120 is inserted
through washer 118, retainer plate 106 and screwed into cap 88.
Two additional bolts (not shown) are screwed into cap 88 in the
same manner as bolt 120. Figure 5 shows these bolts 120, 122 and
124 which are spaced approximately 120 around a circumference of
washer 118. Although bolts 120, 122 and 124 are used in this
embodiment, it is understood that any number can be used to secure
cap assembly 84 in first end 82. Washer 118 has a central passage
126 in order to allow insertion of a gas port to be screwed into
cap 88.
Referring to Figure 8, a view taken along line 8-8 of Figure
5, in order to energize packing 92, a plurality of passages are
drilled into cap 88. Two horizontal passages. 128 and 130 are
drilled in cap 88 prior to insertion into tube 83 and prior to
installation of packing 92. In addition, horizontal passages 128
and 130 are drilled only a part of the way through cap 88. Two
vertical passages 132 and 134 are drilled in cap 88 from shoulder
90 to intersect with horizontaI passages 128 and 130. Vertical
passages 132 and 134 are positioned to intersect with material ~6
of packin~ 92.
12
2 l 256~3
In order to energize packing 92, vertical passage 132 and
horizontal passage 128 are filled with the same packing material as
96. An injection fitting 136 with threads mating the threads of
horizontal passage 128 is screwed into horizontal passage t28.
Injection fitting 136 is available commercially and consists of a
body, a check valve, and an injection screw. Fitting 136 is filled
with packing material which is forced into horizontal passage 128
by the screw in fitting 136. This, in turn, forces the packing
material inside the horizontal passage 128 into vertical passage
132 and out into shoulder 90 and compresses material 96.
Additional packing may be added as required. While packing 92 is
being energized, horizontal passage 130 and vertical passage 134
are left open to allow air to escape which was previously trapped
in pockets inside material 96. In addition, excess material 96 can
also escape. Once the packing has been energized J plug 138 is
screwed into horizontal passage 130.
Once the tube has been pressurized, additional packing
material 96 may be added to seal leaks should they develop without
removing cap assembly 84. This provides a feature not previously
known in the art.
As shown in Figure 6, a third partially threaded horizontal
passage 140 is drilled through cap 88. Horizontal passage 140 is
distinct from horizontal passages 128 and 130 of Figure 8 in that
it continues entirely through cap 88. Horizontal passage 140
serves as a drain for the removal of condensation from tube 83 or
may receive a probe to monitor the gas pressure within tube 83.
Tube 83 is positioned for use so that horizontal passage 140 is
located at the bottom of tube 83. Horizontal passage 140 is sealed
by a plug 142. Plug 142 has threads mating the threads in
horizontal passage 140 so that plug 142 is screwed into horizonta~
passage 140.
Figure 5 shows bolts 120, 122 and 124 spaced approximately
120 around washer 118. Fitting 136, and plugs 138 and 142 are,
likewise spaced 120 around the circumference of washer 118. In a
preferred embodiment, therefore, bolts 120, 122 and 124, fitting
13
212~6~
136,and plugs 138 and 142 are spaced 60 from each other as shown
in Figure 5. It is understood that any suitable configuration
could be an alternative to this arrangement.
Holes 144, 146 and 148 are drilled through washer 118 and are
of a diameter to allow fitting 136, and plugs 138 and 142 to be
inset. In Figure 7 it can be seen that plate segments 110, 112 and
114 of retainer plate 106 are spaced to allow fitting 136, and
plugs 138 and 142 to be screwed flush with cap 88 in order to
obtain a proper seal.
In Figure 1, a plurality of tubular gas storage vessels, 10,
12 and 14 are supported in vertical-parallel fashion by support
structures 20 and 22. Support structures 20 and 22 allow tubular
pressure vessels 10, 1~ and 14 to be arranged in a cascade
providing increased storage capability while taking up a minimum of
ground space, or footprint. Although a cascade of three to fiYe
tubular gas storage vessels would be most practical, it should be
understood that any number of`any size tubular gas storage vessels
may be in a cascade. Several such cascades could be positioned
next to one another making the tubular gas storage vessels of this
invention versatile to meet any gas storage requirements.
Support structures 20 and 22 provide rigid, vertical-parallel
support for a cascade of vessels 10, 12 and 14. Since support
structures 20 and 22 are identical, for the purpose of
exemplification, this description and accompanying reference
numerals will be limited to support structure 20.
Support structure 20 includes two vessel clamps 52 and 54 and
support base 56. Figure 3 illustrates vessel clamp 52 of support
structure 20. Vessel clamp 52 includes a vessel cradle 58, a plate
60 and a contoured spacer 62. Vessel cradle 58 contains a number
of semi-circular concave portions 64, 66 and 68. A number of semi-
circular concave portions of vessel cradle 58 would equal the
number of tubular gas storage vessels in the cascade. Concave
portions 64, 66 and 68 are semi-circular in order to conform to the
circular-outer circumference of tubular gas storage vessels 10, 12
and 14, such that when vessel clamps ~2 and 54 of Figure 1 are
14
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212~63~ ,
secured together, the vessel cradles 58 and 70 will match up to
conform to the outer diameter of the tubular gas storage vessels
10, 12 and 14.
Referring to Figure 3, contoured spacer 62 connects vessel
5 cradle 58 with plate 60. Contoured spacer 62 is contoured so as to
follow semi-circular concave portion 64, 66 and 68 and provide a
flat, linear surface onto which plate 60 may be attached.
Contoured spacer 62 may be fixed to vessel cradle 58 and plate 60
by any suitable fashion known in the art.
Referring to Figure 4, support base 56 includes a horizontal
foot 72 upon which two vertical channels 74 and 76 are secured
perpendicular to horizontal foot 72. Vertical channel 74 and 76
are secured a distance from the distal ends of horizontal foot 72.
Braces 78 and 80 extend from horizontal foot 72 and are secured to
vertical channels 74 and 76 respectively. Braces 78 and 80
maintain vertical channel 74 and 76 in their perpendicular
association with horizontal foot 72. Plate 6~ of Figure 3 provides
a flat surface which is received by vertical channel 74 of Figure
4.
As seen in Figure 1, vessel clamps 52 and 54 are secured to
one another such that tubular gas storage vessels 10, 12 and 14 are
clamped in a vertical-parallel arrangement, or cascade. Plate 60
is received by vertical channel 74 such that vessel clamp 52 and 54
are maintained perpendicular to horizontal foot 72.
Vessel clamps 52 and 54 are secured together by any suitable
means. In a preferred embodiment, vessel clamps 52 and 54 are
bolted to one another. Likewise, plate 60 is secured ~o vertical
channel 74 by any suitable manner. In a preferred embodimer,t,
plate 60 is bolted irto vertical channel 74. It is understood that
vessel clamp 54 is secured into support base 56 in the same manner
as vessel clamp 52.
A plurality of tubular gas storage vessels may be supported in
a cascade in Figure 1 by support structures 20 and 22. The number
of such support structures is dependent upon the length of the
tubular gas storage vessels requiring support. The length of
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tubular gas storage vessels is, likswise, dependent upon gas
storage requirements. This invention, therefore, provides a
lightweight pressure vessel that is economical to construct,
lightweight in desi~n, and highly versatile in use.
While the invention has been described with a certain degree
of particularity, it is manifest that many changes may be made in
the details of construction without departing from the spirit and
scope of this disclosure. It is understood that the invention is
not limited to the embodiment set forth herein for purposes of
exemplification, but is to be limited only by the scope of the
attached clai~ or claims, including the full range of equivalency
to which each element thereof is entitled.
16
