Pressure vessel vented boss with sintered metal plug

A pressure vessel includes a shell, a liner, and a boss. The liner is positioned within the shell and defines the interior environment. The boss is located at a first interface between the shell and the liner. The boss includes a cavity and a venting structure located in the cavity. The cavity is located at a second interface between the liner and the boss, and the cavity is located at an interior surface of the boss in communication with the interior environment. A gas vent path is defined from the first interface, through the venting structure, and into the interior environment of the pressure vessel. The disclosure also describes a boss for a pressure vessel and a method of manufacturing the boss. The boss includes a port, a flange, a cavity and a gas venting structure. The cavity and gas venting structure are located on an interior of the flange.

BACKGROUND

Pressure vessels are commonly used for containing a variety of fluids under pressure, such as hydrogen, oxygen, natural gas, nitrogen, propane, methane and other fuels, for example. Generally, pressure vessels can be of any size or configuration. The vessels can be heavy or light, single-use (e.g., disposable), reusable, subjected to high pressures (greater than 50 psi, for example), low pressures (less than 50 psi, for example), or used for storing fluids at elevated or cryogenic temperatures, for example.

Suitable pressure vessel shell materials include metals, such as steel; or composites, which may include laminated layers of wound fiberglass filaments or other synthetic filaments bonded together by a thermal-setting or thermoplastic resin. The fiber may be fiberglass, aramid, carbon, graphite, or any other generally known fibrous reinforcing material. The resin material used may be epoxy, polyester, vinyl ester, thermoplastic, or any other suitable resinous material capable of providing fiber-to-fiber bonding, fiber layer-to-layer bonding, and the fragmentation resistance required for the particular application in which the vessel is to be used. The composite construction of the vessels provides numerous advantages such as lightness in weight and resistance to corrosion, fatigue and catastrophic failure. These attributes are due at least in part to the high specific strengths of the reinforcing fibers or filaments.

A polymeric or other non-metallic resilient liner or bladder is often disposed within a composite shell to seal the vessel and prevent internal fluids from contacting the composite material. The liner can be manufactured by compression molding, blow molding, injection molding, or any other generally known technique. Alternatively, the liner can be made of other materials, including steel, aluminum, nickel, titanium, platinum, gold, silver, stainless steel, and any alloys thereof. Such materials can be generally characterized as having a high modulus of elasticity. In one embodiment, liner20is formed of blow molded high density polyethylene (HDPE).

FIG. 1illustrates an elongated pressure vessel10, such as that disclosed in U.S. Pat. No. 5,476,189, entitled “Pressure vessel with damage mitigating system,” which is hereby incorporated by reference. Pressure vessel10has a main body section12and substantially hemispherical or dome-shaped end sections14. A boss16, typically constructed of aluminum, is provided at one or both ends of the pressure vessel10to provide a port for communication between the interior environment17of the pressure vessel10and the exterior environment19. As shown inFIG. 2, pressure vessel10is formed with liner20(such as an inner polymer liner) covered by a shell18. In an example, the shell18can be a filament-wound composite shell. The shell18resolves structural loads on the pressure vessel10, while liner20provides a gas barrier.

FIG. 2illustrates a partial cross-sectional view, taken along line2-2ofFIG. 1, of an end section14including boss16, such as that disclosed in U.S. Pat. No. 5,429,845, entitled “Boss for a filament wound pressure vessel,” which is hereby incorporated by reference. The boss16(shown separately inFIG. 3) includes neck22. The neck22includes an exterior surface23and a port26. The port26perpendicularly traverses the exterior surface23of the boss16and allows fluid communication between the exterior environment19and the interior environment17of pressure vessel10. The boss16also includes a flange24(depicted as an annular flange) extending radially outward from longitudinal axis36of port26. As shown,FIG. 2illustrates an interface60between the shell18and the liner20.FIG. 2also illustrates an interface62between the liner20and the boss16. In this disclosure, surfaces, directions, and elements facing interior environment17are referred to with the descriptor “interior,” and surfaces, directions, and elements facing exterior environment19are referred to with the descriptor “exterior.” It is to be understood that this non-limiting notation is provided merely for convenience and ease of comprehension; other descriptors may also be used and/or suitable.

Generally, flange24of boss16is contained between portions of liner20and/or is sandwiched between the liner20and the shell18. Typically, shell18abuts neck22. Flange24includes an exterior side38and an interior side37. Flange24may include at least one groove32(depicted as an annular groove) that is shaped to accept a tab34(such as an annular tab) of liner20. This construction secures the boss16to the pressure vessel10and provides a seal at interface62between the boss16and liner20.

A method of forming a pressure vessel10includes mounting a boss on a mandrel and allowing a fluid polymer material for liner20to flow around flange24and into groove32of boss16. The liner material then solidifies, thereby forming a portion of liner20adjacent to flange24and tab34received within groove32. Liner20is thereby mechanically interlocked with boss16. Accordingly, even under extreme pressure conditions, separation of liner20from boss16is prevented.

In an exemplary embodiment, shell18is formed from wound fibers and surrounds the liner20(and in some cases, also a portion of flange24of boss16). In an exemplary method, a dispensing head for the fibers moves in such a way as to wrap the fiber on the liner20in a desired pattern. If the pressure vessel10is cylindrical, rather than spherical, fiber winding is normally applied in both a substantially longitudinal (helical) and circumferential (hoop) wrap pattern. This winding process is defined by a number of factors, such as resin content, fiber configuration, winding tension, and the pattern of the wrap in relation to the axis of the liner20. Details relevant to the formation of an exemplary pressure vessel are disclosed in U.S. Pat. No. 4,838,971, entitled “Filament Winding Process and Apparatus,” which is incorporated herein by reference.

Although the liner20provides a gas barrier under typical operating conditions, the design of pressure vessel10of this type produces a phenomenon wherein gas diffuses into the liner20under pressurization of pressure vessel10. When depressurization of the pressure vessel10occurs, this gas diffuses out of the liner20, and in some cases into interface60between the liner20and the shell18, or even in some instances into interface62between the liner20and the boss16. A pocket of gas may be formed, forcing the liner20to bulge inward and possibly become stretched. Moreover, gas at the interface60between the liner20and the shell18can promote undesirable separation between the liner20and the shell18. Also, upon re-pressurization, the gas trapped between liner20and the shell18may be expelled abruptly through microcracks in the shell18at high pressures. The relatively sudden expulsion of gas can set off leak detectors, when, in actuality, pressure vessel10exhibits no steady leak. Additionally, the gas trapped between liner20and the shell18may move to interface62between the liner20and the boss16, thereby weakening the connection between the liner20and boss16.

SUMMARY

In one aspect, a pressure vessel having an interior environment is disclosed, the pressure vessel including a shell, a liner, and a boss. The liner is positioned within the shell and defines the interior environment. The boss is located at a first interface between the shell and the liner. The boss includes a cavity and a venting structure located in the cavity. The cavity is located at a second interface between the liner and the boss, and the cavity is located at an interior surface of the boss in communication with the interior environment. A gas vent path is defined from the first interface, through the venting structure, and into the interior environment of the pressure vessel.

In another aspect, the disclosure describes a boss for a pressure vessel including a port, a flange, a cavity and a gas venting structure. The port is configured to permit fluid communication between an exterior environment of the pressure vessel and an interior environment of the pressure vessel. The flange extends radially outward from the port, and the flange includes an exterior side and an interior side. The cavity is located on the interior side of the flange. The gas venting structure is located in the cavity.

In yet another aspect, a method of manufacturing a boss for use in a pressure vessel includes sintering a metal part such that it has a porosity that permits fluid to pass through the sintered metal part, but restricts molten polymer material from entering the sintered metal part; and inserting the sintered metal part into a corresponding cavity of the boss.

This disclosure, in its various combinations, either in apparatus or method form, may also be characterized by the following listing of items:

1. A pressure vessel having an interior environment, the pressure vessel including:

a shell;a liner positioned within the shell and defining the interior environment;a boss located at a first interface between the shell and the liner, the boss including:a cavity at a second interface between the liner and the boss, the cavity located at an interior surface of the boss in communication with the interior environment; anda venting structure located in the cavity, wherein a gas vent path is defined from the first interface, through the venting structure, and into the interior environment of the pressure vessel.
2. The pressure vessel of item 1, wherein the venting structure includes a sintered metal.
3. The pressure vessel of any of items 1-2, wherein the venting structure has a porosity that allows gas to pass through the venting structure while inhibiting material of the liner from entering the venting structure.
4. The pressure vessel of any of items 1-3, wherein the venting structure has an annular shape.
5. The pressure vessel of item 4, wherein the cavity includes a complementary annular shape corresponding to the annular shape of the venting structure.
6. The pressure vessel of any of items 1-5, wherein the venting structure is one of a set of venting structures.
7. The pressure vessel of item 6, wherein the cavity is one of a set of cavities, and wherein each cavity of the set of cavities is configured to correspond to a shape of one of the venting structures of the set of the venting structures.
8. The pressure vessel of item 7, wherein the cavities of the set of cavities are circumferentially spaced apart from each other equally.
9. A boss for a pressure vessel, including:a port configured to permit fluid communication between an exterior environment of the pressure vessel and an interior environment of the pressure vessel;a flange extending radially outward from the port, the flange including an exterior side and an interior side;a cavity located on the interior side of the flange; anda gas venting structure located in the cavity.
10. The boss of item 9, wherein the gas venting structure includes a sintered metal.
11. The boss of any of items 9-10, wherein the gas venting structure has a porosity that allows gas to pass through the gas venting structure while inhibiting molten polymer material from entering the gas venting structure.
12. The boss of any of items 9-11, wherein the gas venting structure has an annular shape.
13. The boss of item 12, wherein the cavity includes a complementary annular shape corresponding to the annular shape of the gas venting structure.
14. The boss of any of items 9-13, wherein the venting structure is one of a set of venting structures.
15. The boss of item 14, wherein the cavity is one of a set of cavities, and wherein each cavity of the set of cavities is configured to correspond to a shape of one of the venting structures of the set of the venting structures.
16. The boss of item 15, wherein the cavities of the set of cavities are circumferentially spaced apart from each other equally.
17. A method of manufacturing a boss for use in a pressure vessel, including:sintering a metal part such that it has a porosity that permits gas to pass through the sintered metal part, but restricts molten polymer material from entering the sintered metal part; andinserting the sintered metal part into a corresponding cavity of the boss.
18. The method of item 17, further including machining the corresponding cavity.
19. The method of item 18, wherein the boss includes a port connecting an exterior side of the boss and an interior side of the boss, and wherein the machining includes machining a surface on the interior side of the boss.
20. The method of item 19, wherein the boss includes a flange extending radially outward from the port, the flange including an exterior side and an interior side, and wherein the machining includes machining a surface on the interior side of the flange.

This summary is provided to introduce concepts in simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the disclosed or claimed subject matter and is not intended to describe each disclosed embodiment or every implementation of the disclosed or claimed subject matter. Specifically, features disclosed herein with respect to one embodiment may be equally applicable to another. Further, this summary is not intended to be used as an aid in determining the scope of the claimed subject matter. Many other novel advantages, features, and relationships will become apparent as this description proceeds. The figures and the description that follow more particularly exemplify illustrative embodiments.

While the above-identified figures set forth one or more embodiments of the disclosed subject matter, other embodiments are also contemplated, as noted in the disclosure. In all cases, this disclosure presents the disclosed subject matter by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope of the principles of this disclosure.

The figures may not be drawn to scale. In particular, some features may be enlarged relative to other features for clarity. Moreover, where terms such as interior, exterior, above, below, over, under, top, bottom, side, right, left, etc., are used, it is to be understood that they are used only for ease of understanding the description. It is contemplated that structures may be oriented otherwise.

DETAILED DESCRIPTION

The present disclosure describes exemplary gas venting structures, and methods for generating such venting structures, for use in a pressure vessel. The gas venting structures can be embedded in a boss of a pressure vessel, such that the exemplary structures prevent separation of the liner from the boss and/or the liner from the shell under pressure. The gas venting structures allow venting of gas trapped between the liner and the shell (or the boss), such as gas trapped between the liner and an interior surface of the shell that interfaces the liner. This disclosure relates, in one aspect, to combining at least one of the exemplary gas venting structures with boss16of pressure vessel10. In some embodiments, the venting structure is configured as a plug or insert positioned in a corresponding cavity of the boss. Each of the exemplary gas venting structures has features to allow gas that accumulates between liner20and shell18(or boss16) to vent to the interior environment17of the pressure vessel10. If a port of boss16is open (such as port26), gas from the interior environment17of pressure vessel10can then vent to exterior environment19outside of the pressure vessel10. For example, as shown inFIGS. 4A and 5, first exemplary venting structure28aprovides a path54through which gas may vent from interface60between shell18and liner20to the environment17internal to pressure vessel10. Thus, damage to liner20and unwanted venting through shell18is prevented.

FIG. 3shows a conventional boss16without one of the exemplary venting structures embedded in boss16. Boss16includes neck22having port26(which may have been bored) that allows fluid communication between the interior environment17of pressure vessel10and the environment19exterior to pressure vessel10. Port26has longitudinal axis36. Boss16can have flange24(depicted as an annular flange) extending radially outwardly from port26and terminating at distal edge46. In an exemplary embodiment, flange24has groove32(depicted as an annular groove) to accept a tab34of liner20, which has a cooperating and complementary configuration. Mechanical inter-locks (i.e., elements that are structurally inhibited from separation) are shown, but it is contemplated that other methods of mechanically, frictionally, or chemically (e.g., by the use of adhesives) securing liner20to boss16may be used. It is noted that in some embodiments, a portion35of liner20extends over an exterior side38of flange24to aid in connecting liner20and boss16, as illustrated inFIGS. 1, 10 and 11.

FIG. 4Ais a perspective radial cross-sectional view of first exemplary boss16awith first exemplary venting structure28afitted into venting-structure-receiving cavity27aof boss16a.FIG. 4Bis an interior end view of first exemplary boss16a.FIG. 5is a partial cross-sectional view of a pressure vessel10aincluding first exemplary boss16a, taken along line5-5ofFIG. 4B, liner20and shell18.

The liner20serves as a gas barrier and defines interior environment17. However, as discussed above, in some high pressure applications, the gas can undesirably diffuse through liner20and to an interface60between liner20and shell18. In an exemplary embodiment, first exemplary venting structure28a—and any other of the exemplary venting structures described herein—can have microscopic vent channels to fluidly connect the interior environment17of vessel10to the interface60between liner20and shell18. The exemplary venting structures are configured to prevent gas that has permeated through liner20and into at least interface60between liner20and shell18from becoming trapped, by providing a vent path54. Vent path54defines a path of least gas flow resistance from interface60. As shown inFIG. 5, the gas in pocket50more easily moves along interface60than through the materials of either liner20or shell18. Thus, gas travels from pocket50and along interface60to interface62between liner20and boss16a. Cavity27a, which contains venting structure28a, is positioned at a location along interface62and at interior surface31of boss16a. Cavity27a, and therefore venting structure28a, is located at interior surface31of boss16ain communication with interior environment17. Because a material bond strength between liner20and boss16ais typically weaker than a material bond strength between shell18and boss16a, the gas generally travels along the illustrated path54at the interface62. Upon reaching venting structure28a, which has higher gas permeability compared to the materials of either liner20or boss16a, the gas flows in path54through venting structure28aand out interior surface30a, into interior environment17of pressure vessel10a. Thus, vent path54is defined from interface60, though venting structure28a, and into the interior environment17of pressure vessel10a.

First exemplary venting structure28a—and any other of the exemplary venting structures described herein—may be formed of a metallic or non-metallic material, or a combination thereof, such as, for example, aluminum, steel, iron, bronze, brass, or a polymer or composite material. A metallic material may be sintered so that the venting structure28includes sintered metallic material. An exemplary venting structure28has a porosity and/or density that allows gas to pass through it while inhibiting material of liner20from entering the venting structure during manufacturing of the vessel. While there may be some permeation of the liner material onto venting structure28at liner interface surface29, significant penetration of the liner material into the venting structure28is prevented. Any of the venting structures28described herein may be formed by machining a sintered material blank into the desired shape for the structure28. In an alternative example, the venting structure28may be formed in a desired shape, such as by filling a die or mold with metal powder, and then sintering. In one method, the cavity27in the boss serves as at least part of the die or mold for the material powder, and the venting structure28is formed by sintering the material in situ in the boss cavity27. Sintering forms microscopic vent channels in the venting structure by the generation of pores in the sintered material. Suitable processes include, for example, powder forging, hot or cold isostatic pressing, metal injection molding, electric current assisted sintering, and additive manufacturing. The microscopic vent channels can include diameters in the range of 0.1 to 1 micrometers, for example, due to the sintering process. Exemplary venting structures28have a porosity of about 5% to about 15%. Exemplary venting structures28have a density of about 5.2 grams/cubic centimeter to about 7.9 grams/cubic centimeter.

In an exemplary embodiment of manufacturing of the vessel10a, the boss16aIncludes—or is provided with—a venting-structure-receiving cavity27afor receiving the first exemplary venting structure28a. The cavity27acan include surface56a. The surface56acan be adhered to surface58aof the first exemplary venting structure28aby a high temperature resistant adhesive or by other means, including welding the surface58ato the surface56a, for example. In an exemplary embodiment, venting structure28ais shaped to fill the recess or cavity27aso that boss16awith venting structure28ahas substantially the same configuration as boss16ofFIG. 3.

Also, the material forming the exemplary venting structure may be formed to fit the venting-structure-receiving cavity of the boss instead of the cavity being formed to fit the venting structure. In another exemplary embodiment of manufacturing the boss, a portion of the boss can be treated with heat and/or a chemical(s) such that the portion of the boss becomes the first exemplary venting structure28a. In this last example, a venting-structure-receiving cavity is not machined into the boss.

First exemplary venting structure28a—and any other of the exemplary venting Structures—may include liner interface surface29aand interior surface30a(facing the interior17of pressure vessel10a). In an exemplary embodiment, liner interface surface29ais in groove32, such that liner interface surface29contacts tab34of liner20. Liner interface surface29acan be configured such that gas trapped between liner20and liner interface surface29acan enter first exemplary venting structure28a. After entering the venting structure28a, the gas can move through microscopic vent channels in the venting structure28a. The gas exits the venting structure28aat interior surface30ato vent to interior environment17of pressure vessel10. The venting structure28athereby fluidly connects the interior environment17to the interface60between liner20and shell18.

In an exemplary embodiment, interior surface30aof venting structure28ais flush with the interior surface31of first exemplary boss16a. The interior surface30afaces the interior environment17of pressure vessel10. In an exemplary embodiment, the interior surface30ais spaced from bore surface41of port26. Interior surface30acan be configured such that gas can—without resistance from liner20—exit interior surface30aafter the addition of liner20to the vessel (as shown inFIG. 5by the path of gas travel54).

In an exemplary embodiment, as shown inFIG. 4A, first exemplary venting structure28acorresponds to an annular shape of venting-structure-receiving cavity27aof boss16a. As shown, the first exemplary venting structure28a—and of any other of the exemplary venting structures—can at least partially abut groove32. As shown, the first exemplary venting structure28adefines an inner surface42of the groove32and at least part of an exterior portion44and interior portion45of the groove32. Also, the venting structure28amay wrap around all the way to outer surface43of groove32, as shown inFIG. 10. The surface of first exemplary venting structure28aat exterior portion44of groove32, inner surface42, and interior portion45of groove32defines liner interface surface29a. While venting structure28aat least partially includes inner surface42, exterior portion44and interior portion45of groove32, other exemplary venting structures may have other configurations. Some exemplary embodiments are illustrated herein, but it is contemplated that many other variations are possible.

As show inFIGS. 4A and 4B, the interior surface31of first exemplary boss16ahas a circular shape with undulating surface contours, including interior surfaces of flange24, groove32and inner portion40. The interior view ofFIG. 4Bshows that each of the aforementioned features of first exemplary boss16aat their respective interior ends have circular shapes, where the interior end of flange24encircles the interior end of groove32, which in turn encircles inner portion40a, which encircles the port26. It is contemplated that vent structures28can also be provided on an interior surface31of a boss16having no groove32.

In the exemplary embodiment shown inFIG. 5, gas pocket50is formed at interface60between liner20and shell18, causing a deformation52of liner20(which is greatly exaggerated in the illustration for purposes of discussion). As shown by path of gas travel54, the gas follows a path of least resistance from gas pocket50along the interface60between liner20and shell18to interface62between liner20and first exemplary boss16a. The gas then can travel to an interface29abetween first exemplary venting structure28aand liner20. The gas enters channels of venting structure28avia liner interface surface29aand travels through the channels to an interior environment17of the vessel, as indicated by path54. While path54is shown only on a portion of vessel10a, it is to be understood that such vent paths may be located from gas pockets located anywhere at interface60through any radial portion of venting structure28a.

Deformation52depicts a bulge or bubble, but is shown as such merely for discussion purposes. Moreover, the size of deformation52is exaggerated for purposes of illustration. Different amounts of gas may exist anywhere in the interface60between liner20and shell18, and/or in the interface62between boss16and liner20, causing various deformations52of liner20if not allowed to vent. While the drawing figures show deformation52for discussion purposes, it is contemplated that the provision of venting structure28on pressure vessels10would actually prevent the formation of such deformations52.

FIG. 6Ais a perspective radial cross-sectional view of second exemplary boss16bwith second exemplary venting structure28b.FIG. 6Bis an interior side view of second exemplary boss16b.FIG. 7is a perspective cross-sectional view of a pressure vessel including second exemplary boss16b, taken along line7-7ofFIG. 6B, liner20, and shell18. Second exemplary boss16billustrated inFIGS. 6A-7is similar to first exemplary boss16aillustrated inFIGS. 4A-5, except for structural differences due to the shape of second exemplary venting structure28bdiffering from the shape of first exemplary venting structure28a.

In the illustrated embodiment, venting structure28bis one of a set of similar venting structures28b, each one of which is configured as a wedged-shaped body. Each venting structure28bis located in a cavity27bhaving a shape that corresponds to the shape of its respective venting structure28b. Each cavity27bis one of a set of cavities27b, each one of which contains a venting structure28b. In an exemplary embodiment, each of the venting structures28bis substantially in the form of a triangular prism. Such a shape provides liner interface surface29bon at least two sides of groove32while simultaneously reducing the presence of venting structure28bat bore surface41of port26. Accordingly, the strength of boss16bproximate port26is maintained. Moreover, a relatively large venting interior surface30bof venting structure28bis provided.

Venting structures28bare shown positioned in corresponding venting-structure-receiving cavities27bof boss16b. While four venting structures28bare shown, it is contemplated that more or fewer wedge shaped bodies can be used. In an exemplary embodiment, a substantially triangular shape is bounded by three surfaces including liner interface surface29b, interior surface30b, and a surface58b, which may be substantially a hypotenuse with respect to liner interface surface29band interior surface30b. The cavity27bcan include surface56b. The surface56bcan be adhered to surface58bof the second exemplary venting structure28bby a high temperature resistant adhesive or by welding the surface58bto the surface56b, for example.

As shown inFIG. 7, gas in pocket50between liner20and shell18flows along vent path54to exhaust into interior environment17. Path54begins at pocket50at interface60between liner20and shell18and continues to interface62between liner20and boss16b. The gas then can travel to an interface29bbetween venting structure28band liner20. The gas enters channels of venting structure28bvia liner interface surface29band travels through the channels to an interior environment17of the vessel10b.

FIG. 8Ais a perspective radial cross-sectional view of third exemplary boss16cwith third exemplary venting structure28c.FIG. 8Bis an interior side view of third exemplary boss16c.FIG. 9is a perspective cross-sectional view of pressure vessel10cincluding a third exemplary boss16c, taken along line9-9ofFIG. 8B, liner20and shell18. Third exemplary boss16cillustrated inFIG. 8Ais similar to first and second exemplary bosses16a,16bexcept for structural differences due to the shape of third exemplary venting structure28cdiffering from the shape of venting structures28a,28b. Third exemplary venting structure28cfits into venting-structure-receiving cavity27cof boss16c. The third exemplary venting structure28cis one of multiple cylindrical shaped bodies, each having at least two opposing ends and one cylindrical surface. While four venting structures28bare shown, it is contemplated that more or fewer cylindrical shaped bodies can be used. One of the opposing ends facing the inner environment of the vessel includes interior surface30c. The cylindrical surface includes a portion that includes liner interface surface29c. The cavity27ccan include surface56c. The surface56ccan be adhered to surface58cof the third exemplary venting structure28cby a high temperature resistant adhesive or by welding the surface58cto the surface56c, for example.

As shown inFIG. 9, gas in pocket50between liner20and shell18flows along vent path54to exhaust into interior environment17. Path54begins at pocket50at interface60between liner20and shell18and continues to interface62between liner20and boss16c. The gas then can travel to an interface29cbetween venting structure28cand liner20. The gas enters channels of venting structure28cvia liner interface surface29cand travels through the channels to an interior environment17of the vessel10c.

FIG. 10is a partial radial cross-sectional view of a top half of a pressure vessel including a fourth exemplary boss16dof the present disclosure with a fourth exemplary venting structure28d, liner20dand shell18. Fourth exemplary boss16dis similar to first exemplary boss16aexcept that fourth exemplary venting structure28ddiffers from the shape of venting structures28a; venting structure28dwraps around groove32of boss16d, including outer surface43of groove32. Fourth exemplary venting structure28dfits into venting-structure-receiving cavity27dof boss16d.

Fourth exemplary venting structure28din one embodiment is an annular structure. However, it is contemplated that the concept illustrated therein can also be applied to the multiple venting structures28band variations thereof. Thus, with reference toFIGS. 6A-7, it is contemplated that a variation of venting structure28bmay wrap around groove32of boss16b, including outer surface43of groove32.

As shown inFIG. 10, gas in pocket50between liner20dand flange24of boss16dexhausts to interior environment17by flowing along vent path54, which begins at pocket50at interface62between liner20dand boss16. The gas then can travel to an interface29dbetween venting structure28dand liner20d. The gas enters channels of venting structure28dvia liner interface surface29dand travels through the channels to an interior environment17of the vessel10d.

In the illustrated embodiment of pressure vessel10d, liner20dis formed to also abut an exterior surface of flange24of boss16d, thereby having portion35on the exterior surface of the flange24. Another vent path for gas trapped at interface60between liner20and shell18travels around liner portion35and continues to interface62between liner20and boss16c. The gas then travels through the channels of venting structure28dto the interior environment17of the vessel10c.

FIG. 11is a partial radial cross-sectional view of a top half of a pressure vessel including a fifth exemplary boss16eof the present disclosure with a fifth exemplary venting structure28e, liner20eand shell18. Fifth exemplary boss16eis similar to third exemplary boss16cexcept that fifth exemplary venting structure28eis located in differently placed substantially cylindrical venting-structure-receiving cavities27eof boss16e, compared to the locations of venting-structure-receiving cavities27cof boss16c. In the illustrated embodiment, venting-structure-receiving cavities27eof boss16eare located to intercept outer surface43of groove32. In an exemplary method of forming pressure vessel10e, liner20emay be formed around flange24before creating venting-structure-receiving cavities27e. The cavities27ein an exemplary embodiment are provided not only in boss16ebut in a portion of liner20eas well. Accordingly, interior surface30eof venting structure28eis configured to be flush with inner portion surface40eof flange16eand in fluid communication with interior environment17.

As shown inFIG. 11, gas in pocket50between liner20eand flange24of boss16eexhausts to interior environment17by flowing along vent path54, which begins at pocket50at interface62between liner20eand boss16. The gas then can travel to an interface29ebetween venting structure28eand liner20e. The gas enters channels of venting structure28evia liner interface surface29eand travels through the channels to an interior environment17of the vessel10e.

In the illustrated embodiment of pressure vessel10e, liner20eis formed to also abut an exterior surface of flange24of boss16e, thereby having portion35on the exterior surface of the flange24. Another vent path for gas trapped at interface60between liner20eand shell18travels around liner portion35and continues to interface62between liner20and boss16e. The gas then travels through the channels of venting structure28eto the interior environment17of the vessel10e.

The fifth exemplary venting structure28eis one of multiple cylindrical shaped bodies, each having at least two opposing ends and one cylindrical surface. While four venting structures28eare contemplated (similar to the arrangement of venting structures28cshown inFIG. 8Bbut located farther out radially from axis36), it is to be understood that more or fewer cylindrical shaped bodies can be used. One of the opposing ends facing the inner environment17of the vessel includes interior surface30e. The one cylindrical surface includes a portion that includes liner interface surface29e.

In an exemplary embodiment, multiple bodies of an exemplary venting structure of this disclosure—whether wedge shaped, cylindrical, other another shape—can be inserted into corresponding cavities of an exemplary boss of this disclosure. While four venting structures28b,28c,28d,28eare shown in each of the respective bosses16b,16c,16d,16eit is contemplated that more or fewer can be used. Moreover, cavities27may be located differently than illustrated on interior surface31of the boss16. Also, the cavities27may or may not be equally spaced apart about a circumference about port26of the boss16.

FIG. 12illustrates an exemplary method100of manufacturing a pressure vessel10. In the manufacturing of the vessel10, manufacturing of the boss16may be completed separately from the manufacturing of the vessel liner20and shell18. For example, a boss with a venting structure(s)28may be pre-fabricated prior to other steps of manufacturing a pressure vessel. In an exemplary embodiment, the manufacture of a pressure vessel10a,10b,10c,10d,10ewith the boss16a,16b,16c,16d,16ehaving a venting structure28a,28b,28c,28d,28emay be similar to the manufacture of a pressure vessel10with a conventional boss16not having the venting structure28. The exemplary bosses16a,16b,16c,16d,16edescribed herein can be pre-fabricated to be compatible with known and foreseeable processes for manufacturing pressure vessels.

An exemplary method100includes step102of forming a cavity (such as venting-structure-receiving cavity27a,27b,27c,27d, or27e) on an interior side (such as including a portion of interior surface31) of a boss16a,16b,16c,16d,16e. For example, the cavity can be formed, such as by machining, at a location between edge46and port26at the interior surface31of the boss16a,16b,16c,16d,16e. The cavity can be formed to receive a correspondingly shaped venting structure. For example, an annular cavity27amay be formed for receiving an annular structure such as first exemplary venting structure28a. Also or alternatively, for example, the cavity may be formed for receiving a wedge shaped structure such as second exemplary venting structure28bor a cylindrical shaped structure such as exemplary venting structure28c,28e. Also, the cavity may be replicated along the interior end portion of the boss such that a set of cavities are circumferentially, preferably evenly, spaced apart from each other (such as shown inFIGS. 6A, 6B, 8A, and 8B).

Alternatively, in another embodiment, a portion of an interior side of a flange of a boss can be treated, such as by heat, pressure, and/or chemicals, to take on venting qualities. This can occur at a location on the interior surface31of the boss in lieu of forming a cavity for receiving a separate venting structure.

While particular exemplary shapes for venting structure28are shown in the illustrated embodiments, it is contemplated that many other configurations may also be suitable. Particularly suitable configurations provide a path from interface62between liner20and boss16to interior environment17of the pressure vessel10. An advantage of venting to the interior environment17of the pressure vessel10, rather than the exterior environment19, is that such interior venting does not potentially create false alerts from leak detectors. In an exemplary embodiment, the exemplary venting structure28is configured to provide an efficient vent path54while maintaining the structural integrity of the boss16. Because the material of venting structure28may be less dense, more porous, and not as strong as the primary material of boss16, venting structures28are spaced from port26and/or spaced from other venting structures28in some embodiments. Such arrangements allow the stronger material of boss16to surround the venting structures28. It is contemplated that the number, shape, and location of the venting structures28can be different than shown. Moreover, in the embodiments having multiple discrete venting structures28, the illustrated embodiments show that each of the venting structures28of a particular boss16is identical to each of the other venting structures28in the respective boss16. However, it is contemplated that venting structures28of different configurations can be used in a single boss16if desired.

Referring toFIG. 10, the method100includes step104of sintering a venting structure such that it has a porosity and/or density that permits gas to pass through the sintered structure, but restricts liner material from entering the sintered structure. Such sintering can occur before or after the venting structure is embedded into a corresponding cavity of the boss.

In exemplary embodiments, sintering of one of the venting structures28described herein can include a process of compacting metal or other material in powder form into a die, mold or cavity and forming a solid mass of material by heat and/or pressure without melting the material to the point of liquefaction. In some embodiments, the venting structure28can be formed in a mold shaped to complement a corresponding cavity27, for example. In other embodiments, the cavity27may serve as the die into which material power is placed for sintering and thereby forming the venting structure28in situ in the boss16itself. The sintering may include using metals, ceramics, plastics, and other materials. The atoms in the materials diffuse across the boundaries of the particles, fusing the particles together and creating a solid yet porous piece. The sintering can occur under atmospheric pressure by using a protective gas, such as an endothermic gas. The sintering with metal can include subsequent reworking to produce a desired range of material properties. Changes in density, alloying, or heat treatments can alter the physical characteristics of the venting structure28. Bronze and stainless steel are particularly suitable in applications requiring high temperature resistance.

Advantages of using powder, such as a metal power, include the benefit of being able to control levels of purity and uniformity in starting materials (which can reduce steps in the fabrication process). Benefits also including being able to control grain size of the starting material. These advantages allow for the manufacture of the venting part to control porosity of the part and the final shape of the venting structure28. The use of powders, especially metal powders for sintering, allows for the fabrication of high-strength material that can withstand high pressures and a wide range of temperatures.

Referring back toFIG. 10, the method100can include a step106of inserting the sintered venting structure28into a corresponding cavity27of the boss, in a method where in the venting structure is not formed in situ. In an exemplary embodiment, the insertion occurs after the sintering of the venting part28and the forming of the cavity27. Further, the venting structure28may be machined to fit into a pre-fabricated cavity27on the boss, or vice versa. In other words, the cavity27may be machined to receive a pre-fabricated venting structure28as well.

The method100also includes step108of providing a liner20for a pressure vessel such that it contacts at least a portion of the venting structure28. In an exemplary method, boss16a,16b,16c,16d,16eis mounted on a mandrel. Such a mandrel is typically provided with a shaped form about which the liner20is manufactured. The molten liner material may be applied to and shaped over the form. After the liner material is placed, it is cured, such as by cooling in some embodiments. The liner20along with the shell18secures the boss16a,16b,16c,16d,16eon the vessel10a,10b,10c. By providing a sintered venting part28prior to forming the liner20, gas trapped between the liner20, the shell18, and/or the boss16a,16b,16c,16d,16eduring the manufacturing of the vessel10a,10b,10ccan escape via the venting structure28into an interior environment17of the vessel.

Although the subject of this disclosure has been described with reference to several embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the disclosure. In addition, any feature or description disclosed with respect to one embodiment is applicable to and may be incorporated in another embodiment, and vice-versa.