EP2788265A1

EP2788265A1 - Method for controlling rate of gas escape from breached presssurized containment systems

Info

Publication number: EP2788265A1
Application number: EP11791551.2A
Authority: EP
Inventors: Francesco Nettis; Brian Spencer; Zachary SPENCER
Original assignee: Blue Wave Co SA
Current assignee: Blue Wave Co SA
Priority date: 2011-12-05
Filing date: 2011-12-05
Publication date: 2014-10-15
Also published as: WO2013083182A1; CN104254487A

Abstract

This invention is directed to a method of decreasing the rate of escape a gas from a breached containment system by introducing into the containment system a plurality of objects that create a tortuous path for the gas to get to the point of breach thereby substantially reducing the degree of damage done by the breach.

Description

METHOD FOR CONTROLLING RATE OF GAS ESCAPE FROM BREACHED PRESSSURIZED CONTAINMENT SYSTEMS

FIELD

This invention relates to a method of decreasing the rate of escape of a gas from a breached pressurized containment system such as a pressure vessel or a gas pipeline and thereby reducing both the damage due to the breach and the rate of propogation of said damage.

BACKGROUND

The detrimental effects of the burning of fossil fuels on the environment are becoming more and more of a concern and have spurred great interest in alternative energy sources. While progress is being made with solar, wind, nuclear, geothermal, and other energy sources, it is quite clear that the widespread availability of economical alternate energy sources, in particular for high energy use applications, remains an elusive target. In the meantime, fossil fuels are forecast to dominate the energy market for the foreseeable future. Among the fossil fuels, natural gas is the cleanest burning and therefore the clear choice for energy production. There is, therefore, a movement afoot to supplement or supplant, as much as possible, other fossil fuels such as coal and petroleum with natural gas as the world becomes more conscious of the environmental repercussions of burning fossil fuels.

Thus, natural gas is finding its way into such diverse areas as, without limitation, generation of electricity; domestic uses such as home heating and cooling, water heaters, clothes driers, ranges and ovens; transportation, where it replaces gasoline and diesel fuel; and even aircraft where experimentation with natural gas-powered jet aircraft has been on-going for over 30 years. While the benefits of natural gas are considerable, its use is not without a downside. The containment systems used to transport natural gas are susceptible to rupture, primarily due to external forces but also as the result of internal pressures that, for one reason or another, can be caused to exceed the normal operating pressures of the containment system.

In the case of a release, serious consequences are not a certainty: if escaping gas exits the containment system without destroying it and creating shrapnel and if it does not encounter an ignition source then the gas will simply dissipate into the environment. On the other hand, the potential for a catastrophic event, even if not great, is well worth preventing.

The problem to be solved is the reduction in the escape rate of gas from a ruptured pressurised gas containment system. It is the rapid movement of gas to and through a breach in a containment system that can result in an explosive event. Further, if the escaping gas encounters an ignition source, the rapid supply of fuel to the fire can turn a relatively controllable fire into a conflagration.

The present invention looks to provide a solution to this problem.

According to the present invention there is provided a method of reducing the rate of escape of pressurized fluids such as compressed natural gas from the systems used to contain and transport it, and systems and devices for achieving this, plus a method of reducing the rate of propagation of cracks within the wall of a pressure vessel for containing fluids such as compressed natural gas, and systems and devices for achieving this.

SUMMARY

According to the present invention there is provided a method of decreasing the rate of escape of a gas from a pressurized gas containment system when the system is breached, (or a system or apparatus for doing the same) comprising disposing therein a plurality of hollow objects within the volumetric space defined by the internal surface of the containment system, wherein: each hollow object comprises a surface that defines an object interior volume, the surface comprising one or more through-holes that fluidically couple the object interior volume with the volumetric space of the containment vessel; the plurality of hollow objects fill the volumetric space of the containment system; and when the containment system is pressurized with a gas, the gas also fills the interior volume of the objects.

As a result, the hollow objects create a tortuous route for the gas to travel to reach any breach, thus slowing the rate of escape compared to a design containing no such hollow objects.

The pressurized containment system usually comprises a pressure vessel. However, it might be a pressurised fluid distribution pipe, or some other pressurised containment system.

The pressure vessel may be, for example, spherical, oblate spheroidal, toroidal or cylindrical with domed end sections.

The objects may each comprise a three-dimensional geometric shape.

A maximum internal dimension of each hollow object within the pressurised containment system's internal volumetric space may be from 1/100 to 1/10 of the transverse cross-sectional diameter of the volumetric space, e.g. at its widest point. The number and diameter of through-holes in each object surface may be provided to permit loss of no more than one-half of the volume of contained gas in the object in no less than 30 seconds.

The objects may be spherical.

The objects may be designed to hold their shape when placed within the volumetric space. Alternatively they may be adapted to compress and squeeze together to form an internal structure, like a honeycomb or open cell foam.

The objects may each comprise a length of pipe sealed at both ends, the length of the pipe being less than one or more of the following: the diameter of the sphere if the pressure vessel is spherical; the diameter along the minor axis of an ellipse that defines the spheroid if the pressure vessel is an oblate spheroid; the diameter of the torus if the pressure vessel is toroidal; or the length of the cylindrical section of the cylinder with domed end sections.

This is so that the pipe can fit within the volumetric space of the vessel.

The pipe might be straight or curved. If curved, it might be longer than that defined above, e.g. if coiled or curved to fit within the volumetric space.

The diameter of each pipe may be from 1/100 to 1/10 of the transverse cross- sectional diameter of the volumetric space accommodating it, e.g. at its widest point.

The pressurized gas containment system, as mentioned above, may comprise a pressurized pipeline. The objects may then comprise lengths of pipe open at both ends, the length being determined either by the length of a section of the pipeline as the pipeline is being assembled or by the length of unobstructed passage through the pipeline.

The pipes may each have a diameter that is from 1/100 to 1/10 of the transverse cross-sectional diameter of internal space within the pipeline.

The pipes might be inserted into a pipeline that is already in place, i.e. a retro-fit.

The pipes may be inserted into segments of a pipeline during construction. According to a further aspect of the present invention there is provided a method , apparatus or system for reducing the rate of propagation of cracks within the wall of a pressurized gas containment system for containing fluids such as compressed natural gas, comprising a skeleton arrangement within the pressurized gas containment system, the skeleton arrangement being attached to the internal wall of the pressurized gas containment system, and being open-celled to allow gas to flow through openings therein, albeit not without an increased resistance. The skeleton arrangement may be a spiral coil within the pressurized gas containment system, or it may be a series of hoops. Alternatively it may be a scaffold arrangement or cob-web arrangement.

The arrangement may have members or arms, e.g. radially extending from a central column or multiple columns.

The arrangement may have a webbing arranged at the ends of any such arms, or it may be arranged to be attached to or to rest against the inside of the wall(s) of the pressurized gas containment system.

The skeletal members of these arrangements may be hollow and may have porous walls, e.g. like the hollow objects described above.

DETAILED DESCRIPTION

Brief description of the figures

These figures are provided for illustrative purposes only and are not intended nor should they be construed as limiting this invention in any manner whatsoever.

Figures 1 A to 1 E show isometric projections of various types of pressure vessel.

Figure 1A shows a spherical pressure vessel.

Figure 1 B shows and oblate spheroid, sometimes referred to as a "near sphere," pressure vessel.

Figure 1C shows a toroidal pressure vessel.

Figure 1 D shows a pressure vessel with a cylindrical center section and one domed end section.

Figure 1 E shows a pressure vessel with a cylindrical center section and two domed end sections. Figure 2 shows a pressure vessel suffering from two breaches through the composite wall of the pressure vessel;

Figure 3 shows a pressure vessel containing spherical devices that control gas escape from the vessel if breached. Figure 4 shows a pressure vessel containing a skeleton arrangement in the form of a plurality of arms, braces and webs.

Figure 5 shows a pressure vessel containing coils that control gas escape from the vessel if breached.

Figure 6 shows a pressure vessel containing pipe-like devices that control gas escape from the vessel if breached. Coiled pipes (not shown) may fill the dome portion, although usually the pipes will have closed ends, and they will extend into the dome portions. The closed ends may have a porous nature, like the sides of the pipes.

Discussion It is understood that, with regard to this description and the appended claims, reference to any aspect of this invention made in the singular includes the plural and vice versa unless it is expressly stated or unambiguously clear from the context that such is not intended. For instance, a reference to a "dome" is to be construed as referring to one dome or two domes and reference to "domes" is to be construed as referring to one dome as well as two domes.

As used herein, any term of approximation such as, without limitation, near, about, approximately, substantially, essentially, appreciably and the like, mean that the word or phrase modified by the term of approximation need not be exactly that which is written but may vary from that written description to some extent. The extent to which the description may vary will depend on how great a change can be instituted and have one of ordinary skill in the art recognize the modified version as still having the properties, characteristics and capabilities of the word or phrase unmodified by the term of approximation. In general, but with the preceding discussion in mind, a numerical value herein that is modified by a word of approximation may vary from the stated value by ±10%, unless expressly stated otherwise. As used herein, the use of "preferred," "preferably," or "more preferred," and the like refers to preferences as they existed at the time of filing of this patent application.

As used herein, "pressurized" and "compressed" are used interchangeably and simply refer to a fluid that is in an enclosed environment wherein the pressure is higher than that of the external environment.

As used herein, a "pressurized containment system" refers to all the interrelated elements required to transport a pressurized or compressed fluid from point A to point B. Non-limiting examples include, for instance, a ship laden with a plurality of pressure vessels, a truck carrying a pressure vessel, a railroad train that includes a railcar or railcars carrying pressure vessels and a pipeline comprising the piping itself and ancillary pressure regulating devices such as pump stations, block valve stations and the like.

As used herein, a "pressure vessel" refers to a closed container designed to hold fluids at a pressure substantially different from ambient pressure. In particular at present, it refers to such containers used to hold and transport compressed natural gas, CNG. Pressure vessels may take a variety of shapes but most often seen in actual use are spherical, oblate spheroidal, toroidal and cylindrical center section vessels with domed end sections at either or both ends. Non-limiting illustrations of such vessel are shown in Figs. 1A to 1 E. Although these shapes are not new, the contents or structure of these pressure vessels are new. As used herein, a "pipeline" refers to the commonly recognized system for overland or off-shore transport of fluids such as oil (e.g., the Trans-Alaska and Pan- European pipelines) and gas (TransCanada PipeLines LP and the contemplated Alaskan Natural Gas Pipeline) water (Morgan-Whyalla pipeline in Western Australia).

As used herein, a "breach" of a pressurized fluid containment system, such as, without limitation, a pressure vessel or pipeline, refers to any damage to the system that permits release of the contained fluid to the environment. See, for example, Figure 2, where two large breaches 10 are illustrated. They are each aligned with one of the winding lines 12, of which there are many different ones, since the winding process for forming the composite structure of this pressure vessel involved multiple layers of windings designed not to overlie each other in parallel, but instead to cross over oneanother. The cause of damage leading to a breach 10 may be one or more of many things.

For example, without limitation, a projectile impact, such as a bullet or stone, may case a breach, as may a tine of a mechanized pay-loader, or even damage arising from a fall, e.g. if dropped, or a crash - e.g. if banged into something.

As used herein, a "hollow object" refers to any manner of construct comprising a shell that defines and fully encloses an object interior volume. Typically it involves a porous-walled object

The "surface" of a containment system refers to the shell of the system that defines and fully encloses a volumetric space. The volumetric space is defined by an inside wall of that shell. Without limitation, a pressure vessel may comprise an outer shell that defines and encloses a volumetric space of 0.1 of a cubic meter or 100 cubic meters. Smaller and much larger vessels are also contemplated.

A pipeline comprises the wall of the pipe that defines and encloses, without limitation, the entire length of the pipelines that is under pressure or any segment of the pipeline that is under pressure but that is separated from the rest of the pipeline by a pressure value and the like.

A through-hole refers to an aperture that extends completely through a wall or a shell such that the environments on either side of the wall or shell are fluidically coupled, that is, a fluid in one of the environments is capable of moving into the other environment via the through-hole. This can be achieved vie a porosity of the wall, or by it being open- celled.

As used herein, a "three-dimensional geometric shape" has the meaning generally would be associated with it by those skilled in the art. Examples of geometric shapes include, without limitation, spheres, cones, cylinders, pyramids and prisms. Also included in three-dimensional geometric shapes are randomly shaped objects that do not fit within any of the generally understood categories of such shapes but that still enclose an internal volume.

As used herein, the "maximum internal dimension" of an object refers to the distance from one point on a wall or shell to another point on the wall or shell of a three- dimensional geometric object as measured along a straight line. For example, without limitation, the maximum internal dimension of a sphere is the diameter of the sphere and the maximum internal dimension of a cube is the distance from a corner, through the point of symmetry of the cube to the opposite corner. With regard to an oblate spheroid, the maximum internal diameter is the major axis of the ellipse that defines the spheroid. Based on these examples those skilled in the art will easily be able to determine the maximum internal dimension of any three-dimensional object.

For the purpose of this invention, the maximum internal dimension of objects used to fill the volumetric space of a pressurized containment system should be from 1/100 to 1/10 of the cross-sectional diameter of the containment system. The containment systems of this invention have well-defined cross-sections. For example, without limitation, the cross-sectional diameter of a sphere is simply the diameter of the sphere. The cross-section diameter of a torus is the diameter of the tubular construct that forms the torus and the cross-sectional diameter of a cylindrical pressure vessel with domed ends is simply the distance as measured along a line perpendicular to the longitudinal axis of symmetry of the vessel. The cross-section diameter of an oblate spheroid, for the purpose of this invention will be the length of the major axis of the associated ellipse.

Where in the spectrum of 1/100 to 1/10 of the cross-sectional diameter of the containment system the maximum internal dimension of objects used to fill the containment system should fall depends on the cross-sectional diameter of the containment system. For smaller cross section systems, such as without limitation, those systems with a cross-sectional diameter up to about one meters, the 1/10 ratio should work very well but as the cross-sectional diameter of the containment system increases, the size of the objects becomes unwieldy and likely unworkable. For example, a vessel with a cross-sectional diameter of 6 meters would require objects with a maximum internal dimension of 0.6 meters, which would quite obviously be too large to be useful. Thus, the ratio of maximum internal dimension to cross-sectional diameter should be reduced accordingly. In general a maximum "maximum internal dimension" of an object of this invention used fill a containment system would be about 5 centimeters.

As a non-limiting example of this invention, consider a cylindrical pressure vessel with one domed end, the walls of which vessel define a volumetric space. The cylindrical portion of the vessel has a cross-sectional diameter. Spherical objects, referred to herein for the sake or simplicity as "balls," are then selected that have a diameter that is about one-tenth of the cross-sectional diameter of the cylindrical portion of the vessel. The balls may be made of any material known to be inert to the compressed gas to be contained in the pressure vessel, i.e., materials such as steel, aluminum, polymers, ceramics and the like. The thickness of the wall of the ball must be determined so as to avoid having the balls themselves destruct when the pressure vessel is breached. Such determination is well within the ability of those skilled in the art based on the disclosure herein. Factors such as the inherent strength of the material used to fabricate the balls, the intended operating pressure of the vessel in which the balls will be placed and the maximum ΔΡ, that is, the expected maximum difference between the pressure in the balls and that outside the balls when the vessel ruptures. For objects other than balls, the geometry of the object would also be taken into account. Of course, thicknesses can be determined empirically, that is, by making balls of various thicknesses and subjecting them to the anticipated conditions that they will encounter. Once the proper ball dimensions have been established, the size and number of through-holes must be determined. The determination is based on the requirement that no more than 50% of the gas, which is at the initial operating pressure of the pressure vessel, can escape from the interior of a ball in no less than 30 seconds. Again, this determination may best be made empirically but such experimentation would be relatively easily performed by those skilled in the art without undue effort. The completely characterized ball being in hand, they are then simply poured into the pressure vessel until it is close to full. By "close to full" is meant that not every iota of the volumetric space of the vessel must be filled with balls nor is it necessary that the balls pack with mathematical precision, but effort should be taken to get as many as possible into the vessel. The vessel is then ready for filling with a compressed gas.

A schematic representation of a pressure vessel containing balls as set forth above is shown in Fig. 3. Pressure vessel 1 has polar opening at its top through which spherical objects, i.e. balls 22, each of which has one or more through-hole or pore in it, or a porous wall characteristic. The balls are typically round, although the shape is unimportant. In particular, it is to be noted that the balls need not all have the same diameter. It is nevertheless preferred that the limitations on object diameter as set forth elsewhere herein is adhered to. It is also noted that the balls are not perfectly packed into the vessel. Such a packing is unnecessary although it is preferred that the balls are closely packed together so that approximately the whole pressure vessel is loaded with balls.

If and when the vessel is breached, compressed gas within the pressure vessel that is not also confined within the interior volume of the balls is quickly, for all intents and purposes instantaneously, released form the vessel. The gas in the balls, however, which can comprise a majority of the gas that was put in the pressure vessel to begin with, is released according to the above-described formula. This substantially slower release of the gas not only prevents the build-up of extreme pressures, shock waves and the like that accompany explosions but also will drastically reduce the fuel being provided to a fire caused by contact of the initially released gas with an ignition source.

Depending on the size of the breach and the size of the balls, the balls may or may not remain in the vessel. Whether they do or don't is of little relevance to this invention. The key factor is the exceedingly slower release of the fluid from the balls compared to that of the fluid in the pressure vessel but not in the balls. That is, if the balls remain in the vessel because the breach is too small for them to exit through it, then the above description pertains but even if the breach is large and the balls are ejected from the pressure vessel, balls fabricated as described herein should still maintain their integrity and therefore will continue to slowly release the fluid contained in them even if they themselves are at a distant from the pressure vessel. The above description will readily be modified based on the description herein to accommodate any hollow object, in particular, any 3-dimensional geometric shape object that it might be desired to use.

With regard to the use of pipes, the procedure is very similar to the above. The pipe material can be selected in the same manner as the ball material. The pipe is sealed at the ends to provide an interior volume similar to the interior volume of the balls. The size and number of through-holes in each pipe would likewise be determined in the same manner and to the same end as those in the balls - no more than 50% of the gas, which is at the initial operating pressure of the pressure vessel, can escape from the interior of the ball in no less than 30 seconds.

The only difference between pipes and balls lies in the length of the pipe and the manner of loading them into the pressure vessel. The length is easily determined: it should be such that each pipe fits completely within the pressure vessel and extends from the fill end to the opposite end of the vessel as closely as possible. That is, it is possible to use different length pipes so as to accommodate the additional length of a cylindrical vessel in the region of its domed end sections. This, however, is not necessary. Pipes of a single length that is determined by the length of the cylindrical center section of the pressure vessel will suffice.

Figure 6 shows a pressure vessel having polar opening at its top into which pipes, each containing one or more through-holes, pores or a porous wall characteristic, have been inserted. It is noted that the pipes as shown all have the same length, and have aligned tops. Therefore they do not fully fill the pressure vessel. That is, the lengths do not extend into the domes, as shown through the virtual window 36 (shown for reference only). The pipe lengths, however can be different so as to fill out into the domes. Alternatively the domes can be filled with balls or coiled pipes, or other porous elements.

This loading of the pressure vessel with pipes of the same length is the simplest approach to using piping as to fabricate pipes with constant lengths is simple. However, different lengths that will more closely follow the contours of the particular vessel into which the pipes are being placed would simplify the filling of the contours of the pipe - without having to resort to other forms of object.

As mentioned above, the ends of the pipes are sealed so that the pipes operate in the same manner as the balls described above. That is, if the pressure vessel is breached, gas contained the pipes will be released at a much slower rate than the gas that is only contained by the pressure vessel walls and is not also contained in the pipes, which gas is released immediately upon breach.

The situation when the pressurized containment system is a pipeline is somewhat different. Here, open-ended pipes are used because it would be undesirable to use piping sealed at both ends in that such would impede the natural flow of the gas through the pipeline. Thus the material of which the piping is made is of less importance in that the piping will not be subjected to the extreme pressures that the balls and piping of the pressure vessel would since gas would flow freely through the open-ended piping. The diameter of the pipe would, however, be determined on the same basis as that of balls and pipes in pressure vessels, that is, the pipes should have a diameter no greater than about one-tenth of the cross-sectional diameter of the pipeline. The length of the pipes is a function of the length of the pipeline and its construction segments. For example, without limitation, it would be possible to after-fit an existing pipeline with the rate reducing piping of this invention by simply inserting lengths of flexible piping from a roll of the piping at any point along the length of the pipeline including its inception point. Numerous lengths of piping would be inserted such that the pipeline is essentially filled with the piping. The piping could be advanced into the pipeline as far as the pipeline is unobstructed by ancillary pipeline internal paraphernalia that would hinder further advancement. In some cases, the piping might only advance a matter of a few hundred feet or less while in other cases it might be possible to advance the piping for miles within the pipeline. Once gas that is not contained in the protective piping has exited through the breach, the protective piping decreases the release rate of the remainder of the gas in the pipeline through the breach by forcing gas to traverse the length of the protective piping and then return to the breach. This would in essence have the same effect as the reduced release rate of pressurize gas from the balls or piping in a pressure vessel.

It is also possible to insert the piping of this invention into a pipeline during the construction of the pipeline. In this case, the length of each of the inserted pipes would confirm to the length of each segment of pipeline put in place. For example, without limitation, pipeline segments 33 feet in length are often used. In this case, the length of each piece of piping of this invention would likewise be about 33 feet in length. For compressed natural gas pipelines, pipeline segments of about 50 feet are possible; in this case the piping of this invention would be 50 feet in length.

Figure 3 shows a pressure vessel 20 filled with balls 22, with each ball being porous such that they fill with the pressurised fluid. Figure 4 also shows a pressure vessel 20, but this time it has a skeletal arrangement within it formed of numerous porous, hollow arms 24, each radiating from a central spine 30. Cross braces 26 and webs 28 are also provided to give added strength to the skeletal structure. The webs serve to give the walls structural rigidity, whereby crack propogation is slowed - segments of wall cannot pull apart so easily. Further, the arms provide impact rigidity such that impacts will not cause localised compression of the vessel 20, although when under pressure from the compressed fluid, localised deformation is typically difficult to achieve anyway.

By being hollow and porous-walled, the balls/arms/braces/webs, although occupying a large amount of the space within the pressure vessel 20, do not greatly reduce the volumetric storage capacity of the pressure vessel.

Referring finally to Figures 5 and 6, two further arrangments are shown. Figure 5 has a series of coiled, hollow, members, all having a porous wall, whereby they can contain the compressed fluid and form a reduced flow-rate through any breaches. Figure 6, on the other hand, comprises a series of tubular members within the pressure vessel, as visible through the imaginary window 36.

In general, all containment systems such as pressure vessels and pipelines used to contain and transport virtually any fluid can benefit from this invention. It is an express embodiment of this invention, however, that the containment system be used for the containment and transport of compressed natural gas, either in the pure state or as "raw gas," which refers to natural gas as it comes directly from the well. It is to be remembered though that the pressure vessels of this invention can carry a variety of gases, such as raw gas straight from a bore well, including raw natural gas, e.g. when compressed - raw CNG or RCNG, or H2, or C02 or processed natural gas (methane), or raw or part processed natural gas, e.g. with C02 allowances of up to 14% molar, H2S allowances of up to 1 ,000 ppm, or H2 and C02 gas impurities, or other impurities or corrosive species. The preferred use, however, is CNG transportation, be that raw CNG, part processed CNG or clean CNG - processed to a standard deliverable to the end user, e.g. commercial, industrial or residential.

Storage/transportation pressures for CNG can be anything up to say 400bar, but usually up to 300 bar, and normally in excess of 100 bar.

CNG can include various potential component parts in a variable mixture of ratios, some in their gas phase and others in a liquid phase, or a mix of both. Those component parts will typically comprise one or more of the following compounds: C2H6, C3H8, C4H10, C5H12, C6H14, C7H16, C8H18, C9+ hydrocarbons, C02 and H2S, plus potentially toluene, diesel and octane in a liquid state, and other impurities/species.

The invention has been described above purely by way of example. Variations in detail with respect to the above-illustrated embodiments are possible within the scope of the present invention as defined in the appended claims.

Claims

What is claimed:

1 . A method of decreasing the rate of escape of a gas from a pressurized gas containment system when the system is breached, comprising disposing a plurality of hollow objects within the volumetric space defined by the surface of the containment system, wherein each hollow object comprises a surface that defines an object interior volume, the surface comprising one or more through-holes that fluidically couple the object interior volume with the volumetric space of the containment vessel wherein:

The plurality of hollow objects fills the volumetric space of the containment system; when the containment system is pressurized with a gas, the gas also fills the interior volume of the objects, and the objects create a tortuous route for the gas to travel to reach the breach.

2. The method of claim 1 , wherein the pressurized containment system comprises a pressure vessel.

3. The method of claim 2, wherein the pressure vessel is spherical, oblate spheroidal, toroidal or cylindrical with domed end sections.

4. The method of any of claims 1 -3, wherein the objects each comprise a three- dimensional geometric shape.

5. The method of claim 4, wherein a maximum internal dimension of each object is from 1/100 to 1/10 of the cross-sectional diameter of the containment vessel at its widest point.

6. The method of any of claims 1-5, wherein the number and diameter of through- holes in each object surface permits loss of no more than one-half of the volume of contained gas in the object in no less than 30 seconds.

7. The method of claims 1 -6, wherein the objects are spherical.

8. The method of any of claims 1 -4 and 6, wherein the objects each comprise a length of pipe sealed at both ends, the length of the pipe being less than: the diameter of the sphere if the pressure vessel is spherical; the diameter along the minor axis of an ellipse that defines the spheroid if the pressure vessel is an oblate spheroid; the diameter of the torus if the pressure vessel is toroidal; or the length of the cylindrical section of the cylinder with domed end sections. such that the pipe can fit within the volumetric space of the vessel.

9. The method of claim 8, wherein the diameter of each pipe is from 1/100 to 1/10 of the cross-sectional diameter of the pressure vessel at its widest point.

10. The method of claim 1 , wherein the pressurized gas containment system comprises a pressurized pipeline.

1 1 . The method of claim 10, wherein the objects comprise lengths of pipe open at both ends, the length being determined either by the length of a section of the pipeline as the pipeline is being assembled or by the length of unobstructed passage through the pipeline.

12. The method of claim 1 1 , wherein the pipes each have a diameter that is from 1/100 to 1/10 of the cross-sectional diameter of the pipeline.

13. The method of any of claims 10-12, wherein the pipes are inserted into a pipeline that is already in place.

14. The method of any of claims 10-12, wherein the piles are inserted into segments of a pipeline during construction.

15. A method for reducing the rate of propagation of cracks within the wall of a pressurized gas containment system for containing fluids such as compressed natural gas, comprising providing a skeleton arrangement within the pressurized gas containment system, the skeleton arrangement being attached to or arranged to engage against the internal wall of the pressurized gas containment system, and being open- celled to allow gas to flow through openings therein.

16. The method of claim 15, wherein the skeleton arrangement is a spiral coil within the pressurized gas containment system.

17. The method of claim 15, wherein the skeleton arrangement is a series of hoops.

18. The method of claim 15, wherein the skeleton arrangement is a scaffold arrangement.

19. The method of claim 15, wherein the skeleton arrangement is a cob-web arrangement.

20. The method of any one of claims 15 to 19, wherein the arrangement has members or arms radially extending from either a central column or multiple columns.

21 . The method of any one of claims 15 to 20, wherein the arrangement has a webbing arranged to be attached to or to rest against an inside wall of the pressurized gas containment system.

22. The method of any one of claims 15 to 21 , wherein the skeleton arrangement comprises hollow members with porous walls.

23. A pressure vessel adapted by the method of any one of the preceding claims.