EP0698761A1

EP0698761A1 - A sealed protective container for the underground installation of reservoirs containing liquefied gases under pressure

Info

Publication number: EP0698761A1
Application number: EP94830406A
Authority: EP
Inventors: Giovanni Poilucci
Original assignee: Walter Tosto Serbatoi SpA
Current assignee: Walter Tosto Serbatoi SpA
Priority date: 1994-08-23
Filing date: 1994-08-23
Publication date: 1996-02-28
Anticipated expiration: 2014-08-23
Also published as: DK0698761T3; ATE180556T1; DE69418708T2; EP0698761B1; DE69418708D1; SI0698761T1; GR3030905T3; ES2133523T3

Abstract

A sealed protective container (1,2) for the underground installation of a cylindrical reservoir (11) containing gas under pressure, with the cylinder axis lying horizontally, comprising a housing shell (1,2) for the reservoir (11) with the formation of an interspace (53) between the shell and the reservoir, an upper hatch (26) for access to the interspace and means (8,9) of supporting the reservoir adapted to allow rotation of the reservoir (11) about the cylinder axis, so that the inspection of the reservoir lower surface can take place through the hatch as the reservoir is rotated. As a possible alternative, the shell is formed of two tightly coupled half-shells, an upper one and a lower one, and the inspection of the whole surface of the reservoir can take place by removing the upper half-shell.

Description

The present invention relates to a sealed protective container for the underground installation of reservoirs containing liquefied gases under pressure, usually fuel gases.
The invention also relates to the underground installation as implemented using said sealed protective container.
As is known, reservoirs containing liquefied gases under pressure are mainly installed above ground in the proximities of the gas utilization sites, which may be factories, restaurants, or homes.
In the latter case, and especially in the presence of a garden, the above-ground installation of the reservoirs represents an unsightly point which cannot always be suitably disguised.
In addition, safety regulations require that an area be left clear around the reservoir, and suitably fenced off if necessary, wherein the use of free flames should be avoided, as should unauthorized access or access with vehicles which could impair the system integrity.
To obviate this drawback, it has been known to have recourse to underground installation of the reservoirs.
In this case, the burying is not carried out directly, but rather in a suitably waterproofed concrete ditch to which access by personnel or inspection instruments should be allowed to ascertain the state of the reservoir.
Recently, to obviate the cost and time for the completion of the masonry work, the underground installation of the reservoirs in fabricated sealed chambers comprising a plastics shell, preferably of high-density polyethylene, has been proposed.
The interspace between the reservoir and the shell may be pressurized or filled with inert substances and ensures at all events a more effective protection against corrosion of the reservoir, despite it being painted, as may be due to stray currents, water beds, rainwater impregnating the soil, and humic acids.
Despite the protection afforded by the plastics shell, the sealed housing, and the thermal insulation afforded by underground installation, which limits the thermal excursions to which the reservoir is subjected and prevents direct exposure to electromagnetic radiation, in particular solar radiation, its deterioration and corrosion cannot be ruled out completely.
The regulations of the various countries, therefore, enforce the requirement that in these installations the reservoir should be surveyable periodically on a many year basis.
To meet this requirement the technology of underground installation within a plastics shell provides, in connection with the shape of the reservoirs which is typically a cylindrical one, two types of installations and solutions:

Installation of the reservoir with the cylinder axis horizontal housed within a sealed plastics shell provided with a hatch for introducing into the interspace between the shell and the reservoir miniaturized remote inspection instruments (TV cameras and the like) guided along suitable tracks laid inside the shell for checking the surface state of the lower portion of the reservoir which, absent at the moment adequate experimental ascertainments, is considered to be the reservoir portion which is more exposed to the risk of corrosion.
It is evident that this solution meets the requirement for surveyability only in part.
Installation of the reservoir with the cylinder axis vertical housed in a well-like shell having a top closure cover, removable with a minimum of earthmoving to permit of periodical removal and inspection of the reservoir.

This solution, which appears to be most promising, affords the indisputed advantage that it allows the reservoir to be thoroughly inspected, but in relation to the weight of the same which may be in the 300 to 1000 kg range even when empty, requires the intervention of suitable hoisting and handling means and accordingly entails a high cost of the inspection operations.
In addition, it requires the use of reservoirs with outlet plug, inlet plug and measurement accessories located on one end whereas the reservoirs currently available commercially are designed for installation with the cylider axis horizontal and outlet, inlet and measurement arrangements laid on a generatrix line of the cylinder.
Thus, these reservoirs cannot be used in vertical axis installations.
These limitations and drawbacks are removed by the use of the sealed protective container and the underground installation forming the subject-matter of the present invention, wherein the essentially cylindrical plastics shell designed for underground installation and to enclose the reservoir with the cylinder axis horizontal is provided with means of supporting the reservoir which allow for its rotation about its axis.
In this way, the inspection of the entire surface of the reservoir is permitted in an integral and reliable fashion by the technician directly or occasionally with the aid of simple instruments, such as mirrors and endoscopes, and can be readily supplemented with more sophisticated checks such as ultrasound testing, without the reservoir having to be removed from its housing by just the rotation of the reservoir about its axis.
This type of installation allows inter alia reservoirs already installed above ground to be regenerated and re-used, without modifications to the same, excepting for the possible removal of their rest feet, where integral with the reservoir.
It also allows replacement of the underground reservoirs when made necessary by safety considerations after inspection, without a fresh installation under ground having to be arranged for, thereby saving the installation investment made already.
The features and advantages of the invention will be more clearly apparent from the following description, given with reference to non-limitative examples of practical implementation illustrated by the accompanying drawings, in which:

Figure 1 is a diametrical section view of a first form of the sealed protective container according to the invention, as inserted into a ditch dug in the ground;
Figure 2 is a sectional view of the container taken along section line A-A in Figure 1;
Figure 3 is a sectional view of the container taken along line B-B in Figure 1;
Figure 4 is a sectional view of a construction detail of the container;
Figure 5 shows in section a first variation of the construction detail in Figure 4;
Figure 6 shows in section a second variation of the construction detail in Figure 4;
Figure 7 shows in section a third variation of the construction detail in Figure 4;
Figure 8 shows in section a variation of the container construction in Figure 1;
Figure 9 is a sectional view of the container in Figure 8 taken along line C-C in said figure;
Figure 10 is a sectional view of the container in Figure 8 taken along line D-D in said figure.

With reference to Figures 1 to 7, the protective container consists of two flanged half-shells, a lower one 1 and upper one 2, respectively, having a generally semicyclindrical shape, preferably with annular stiffening rib formations 51 for the semicylindrical section which impart at the same time increased flexibility to the half-shells in the axial direction and an easier coupling of the flanges with the recovery of any deformations induced by the manufacturing process.
The two half-shells are preferably but not necessarily made of plastics, specifically high-density polyethylene and formed by the spin molding technique as one piece which is then cut into the two half-shells at the coupling flanges 3, 4.
Clearly the two half-shells can also be made of another material or by another technology, for example of glass-reinforced resin or sheet metal and in the extreme pre-fabricated of a suitably waterproofed reinforced concrete.
However, the spin molding technique is preferable because it allows, by the same shell forming operation and using low-cost molds, all of the more appropriate construction details for the application to be obtained.
For example, Figure 4 shows in section the construction detail of the flanges 3 and 4 of the two half-shells which can be readily obtained as solid elements of greater thickness than, up to twice as thick as, the half shells 1, 2 and illustratively 14-16 mm thick.
The coupling of the two half-shells, following the interposition of a resilient sealing gasket 13, is obtained by bolting the flanges 3, 4 with bolts such as 12 distributed over the spread of the flanges.
The bolt seats can also be obtained in the course of the spin molding process, as can be the overlapping lip 14 in the two half-shells (which may also be integral with the lower half-shell and oriented upwards) and a possible ear 15 for closing exteriorly the joint, which ear protects, with the container under ground, from water and dirt seepage through the joint.
In one or both of the flanges a gasket receiving seat 13 may also be formed.
The spin molding technique also allows, as shown in Figure 5, hollow flanges to be obtained with a thickness more than twice the thickness of the half-shells, with bolt seats pre-formed and not communicated to the interior of the container which stiffen the flanges locally in the compression stressed areas.
As illustrated by Figure 6, the sealed coupling of the flanges may also be obtained, instead of by bolting, by thermoplastic welding of the joint, with the possible contribution of thermoplastic material (having a lower plasticization temperature or higher plasticity) in the form of a tape 21 laid between the two flanges 3, 4.
Also possible, as illustrated by Figure 7, is the coupling with a plurality of metal or plastics snap-on straddlers 52 or a continual C-shaped band forced gradually onto the edge of the flanges, suitably raised to ensure stable holding for the hitch.
Formed in the lower half-shell 1 are four or more shaft supports 5, 6, 7 for four or more rubber tired wheels or rollers 8, 9, 10 which form one or more pairs of saddles on which a cylindrical reservoir 11 rests free to rotate about its own axis and separated from the hollow formed by the half- shells 1 and 2 by an interspace 53.
Since the surface of the reservoir 11 is protected by a protective coating, usually paint, a plastics jacket, epoxy resin and the like, even in combination, the number of the rollers, their dimensions and the coating material thereof are selected to provide a convenient surface of contact with the reservoir such as to avoid contact pressures which could damage the protective coating of the reservoir.
The shaft supports 5, 6, 7 can easily be formed as particularly strong rest forks in the same manner as the flanges 3, 4 of Figures 4, 5 are formed or occasionally also as solid ribs extending internally and bored after the forming operation.
Also in the lower half-shell 1, there are formed, preferably by the same technique as previously described, anchoring eyebolts 16, 17, 18 through which metal clamps 19, 20 are passed and embedded into a foundation slab 52 of reinforced concrete.
The slab external of the container, functions to provide the container with an adequate and rigid supporting foundation which by anchoring to the container also ensures compensation for any hydrostatic thrusts exerted on the container by a sodden soil.
Reservoirs for liquefied gases under pressure are provided, on a generatrix of the cylinder, with at least one fill fitting 22, a safety valve 23 and a pressure gauge 24 which have a certain radial bulk external of the reservoir cylindrical surface.
To permit of full rotation of the reservoir through an arc of 360° about its cylinder axis, the container formed of the half- shells 1, 2 is clearly dimensioned with a greater inside radius than this radial bulk, at least at the sections corresponding to the axial positions of the accessories on the reservoir surface.
The gas tapping can take place through the pressure gauge fitting 24, or a further outlet fitting 25, via a pressure reliever installed of preference directly on the fitting and not shown, which produces a first pressure drop stage at the outlet, e.g. from 17.5 bar to 1.5 bar.
A liquid phase tap fitting may also be provided.
The container is provided with at least one tower-type hatch 26 which allows the accessories to be accessed for the application of load and tap connections and possible inspection.
The hatch tower is closed by one or more screw-on or hinge cover lids 27, 28 (or even bayonet or plain rest-on types) which constitute the single part not under ground and are preferably made, as described in European Patent Application No. 9383024.9 by this applicant, with a treadable and fire-resisting structure.
Expediently, the turret 26 is provided with tight unions 29 for passing a gas tapping underground pipe 30.
In liquefied gas reservoirs buried under ground it is essential to avoid that any gas leakage past the fittings affect the whole free interspace between the container and the outer surface of the reservoir and any leakout must be confined within as reduced a volume as possible such as that of the hatch.
This is the more important with the container described wherein the container diameter is comparatively larger, at least at the axial position of the accessories than the reservoir diameter.
The separation of the two volumes is obtained by a resilient torus or doughnut 31, e.g. of foamed rubber covered with an impervious sheath or preferably consisting of an air bladder of the automotive kind, inflatable through a valve to a suitable pressure.
The torus 31 is partway received in a toroidal seat 32 formed in the upper half-shell 2 around a fitting between the half-shell and the hatch 26 wall.
Expediently, formed in the half-shell at the upper portion of the upper half-shell 2 is a rectilinear channel 33 which, while breaking the continuity of the various ribs, extends for the full length of the half-shell and ensures a constant and adequate passage section for inspection instruments, such as endoscopes or simple mirrors mounted on telescopic arms and associated with light sources.
The functionality of the container described and the manner of its installation are evident.
Once an underground installation ditch is prepared with a level, and occasionally consolidated with mortar bed, rest surface, the lower half-shell 1, provided with anchoring clamps fitted through the eyebolts 16, 17, 18 and forming the frame for the uniform mat, is laid into the ditch.
The uniform mat is then completed by the casting of a suitable volume of concrete mix.
Subsequently, the reservoir 11 is laid onto the supporting rollers and the upper half-shell 2 is coupled to the lower one 1 by tightening the bolts or welding the joint in situ.
Alternatively, the assembling of the container with the incorporated reservoir may be carried out at factory.
In this case, the installation can take place using suitable removable slings or using as hoisting eyebolts the very eyebolts arranged for anchoring on the uniform mat.
It is also suitable that removable anchors be provided between the reservoir and the container for transport.
Once the resilient doughnut 31 is disposed in its seat, if not already there, the connection can be made of the reservoir to the gas tapping pipe (or pipes) and after closing the hatch the container can be covered with earth, leaving the hatch cover flush with the ground level.
By opening the hatch, without removing earth, it is possible to proceed with periodical refilling of the reservoir and periodical checking for gas leaks.
Also by opening the hatch and without removing earth, it is possible to perform, with the periodicity enforced by law, checks on the state of the reservoir.
This operation is preferably carried out with the reservoir empty.
After removing the resilient doughnut 31 from its seat it becomes possible, with a minimum of effort, to rotate the reservoir on the supporting rollers so as to bring the various generatrix lines of the reservoir one after another to the inspection channel 33 in the upper half-shell and visually check, occasionally with the aid of an endoscope or periscope, the state of the whole reservoir surface and in particular its lower surface and rest areas, which are those more likely to be affected by ageing and the risk of corrosion.
If necessary, with the visual inspection there may be associated more sophisticated forms of checking, such as the acoustic and mechanical response of the reservoir protective coating to striking or ultrasonic checking of the thickness and the integrity of the sheet metal comprising the reservoir.
Corrosion may indeed be internal of the reservoir and due to progressive buildup in the reservoir of gas contaminants of higher specific density and lower volatility, such as water.
To facilitate the reservoir rotation, a band provided with handgrips or equivalent means (also for the purpose of static balancing) may be associated with the reservoir.
Advantageously, the band may also be provided with a toothing co-operating with drive members which may be installed, either permanently or on the occasion of the inspections, in the hatch, as purposely provided with suitable supports for anchoring the motor.
It should be noted that if the inspection reveals a need for replacement of the reservoir, this can be done by removing a limited volume of the covering earth and removing the upper half-shell alone.
In this way, the investment made for the underground installation can be largely saved because the removal of the lower half-shell, fresh digging operation for burying the lower half-shell, and fresh casting of a uniform mat, are now unnecessary.
Also in the case of the half-shells being welded to each other it is possible to perform in situ an operation of cutting and separating the upper half-shell to remove the reservoir and replace it.
The coupling flange of the lower half-shell can then be re-finished and welded to the upper half-shell, occasionally with the replacement of just the latter, if the cutting operation has impaired its integrity beyond recovery.
Figures 1 to 7 only show a preferred embodiment of the container according to the invention and it is apparent that many changes may be made thereunto.
For example, the two half-shells, instead of being coupled by flanges disposed in a plane containing the axis of the cylindrical reservoir, may be coupled along a different section, preferably at a higher level, provided that the section opening is sufficiently broad to allow for the introduction of the reservoir into the lower half-shell to rest on the supports.
In this case the lower half-shell forms a reservoir containing tray, whereas the upper half-shell forms a tray closing cover.
The rotary support for the reservoir by means of wheeled saddles is also but a preferred embodiment and may be formed by end supports in the lower half-shell cooperating with pins disposed axially at the reservoir end.
In this case suitable stiffening ribs are conveniently provided in the lower half-shell or a possible outer framework may be provided.
As a further variation which affords the possibility of a still easier full inspection of the reservoir, without removing it and the advantage of a smaller installation bulk and less volume of the interspace between the reservoir and the container, for the benefit of safety in the event of gas leakouts, at the sole expense of limited earthmoving work for carrying out the checking inspections, the container may be made as shown in the sectional views of Figures 8, 9, 10.
In this case the container is formed by a lower containment tray 34 and an upper half-shell with a cover 35 coupled removably to the tray by a tight joint with flanges clamped down by bolts or another equivalent means.
The half-shell 35 is provided with a hatch 36 covered by one or more screw caps or hinge covers (or another type of lid).
The hatch walls merge with the upper half-shell in the vicinity of the surface of the reservoir 37 to form a toroidal housing 38 for a resilient sealing gasket 39, preferably an O-ring which isolates the reservoir housing volume from the hatch volume.
As for the other aspects and possible variations, the container is quite identical of that previously described with reference to Figures 1 to 7.
In this case, however, no inspection channel is provided in the upper half-shell 35 because unnecessary.
In fact, the reservoir inspection can be carried out in this case by removing a minimum earth volume, sufficient to uncover the half-shell 35.
The removal of the half-shell which, even in the case of containers for gas reservoirs with the maximum commercial capacity provided of 5000 liters may have a curtailed weight on the order of 50-60 kg, poses no difficulty and requires no hoisting equipment.
With the half-shell removed, the rotation of the reservoir on its supports allows it to be fully inspected with no need for the reservoir to be removed from the container by means of adequate hoisting equipment for its weight which, even when empty, may vary, according to the capacities provided commercially (1000-5000 liters) from 300 kg to upward of one tonne.

Claims

A sealed protective container for the underground installation of a cylindrical reservoir (11) for gas under pressure, with the cylinder axis lying horizontally, comprising a shell (1,2,34,35) for housing said reservoir (11) with the formation of an interspace (53) between said shell (1,2,34,35) and said reservoir (11) and a hatch (26,36) for accessing said interspace covered by an openable cover forming with said hatch an inner hatch volume,
said container being characterized in that it comprises means (8,9) for supporting said reservoir, internal of said shell (1,2), adapted to allow rotation of said reservoir (11) about said axis, such that, by said rotation, inspection of the surface of said reservoir is enabled.
The container of Claim 1, wherein said supporting means comprises a plurality of saddles with supporting rollers (8,9,10).
The container of Claim 2, wherein said supporting rollers comprise a resilient rest surface.
The container of either Claim 1 or 2 or 3, comprising resilient means (31,39) in contact with said shell (1,2) and said reservoir (11) to isolate said
The container of Claim 4, wherein said resilient means comprise a resilient inflatable torus (31).
The container of the preceding claims, wherein said shell is formed of a lower half-shell (1,34) and an upper half-shell (2,35) coupled by a tight joint, along a section of said shell with an opening effective to allow for the insertion and housing of said reservoir in said lower half-shell on said supporting means (8,9).
The container of Claim 6, wherein said tight joint is formed by a pair of flanges (3,4) clamped down by bolts (12) with an intervening resilient gasket (13).
The container of Claim 6, wherein said tight joint is formed by a pair of welded flanges.
The container of the preceding claims, comprising an inspection channel (33) formed in said upper half-shell (2).
An underground installation of a cylindrical reservoir (11) for gas under pressure, with the cylinder axis lying horizontally, comprising a sealed underground container (1,2) housing said reservoir with the formation of an interspace (53), said container (1,2) being provided with an open top access hatch (26), characterized in that said container comprises means (8,9) for supporting said reservoir adapted to allow rotation of said reservoir about said axis, such that said rotation enables inspection of the surface of said reservoir.
The installation of Claim 10, comprising a foundation slab (52) of reinforced concrete and means (19,20) of anchoring said container on said foundation slab.