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(11) | EP 2 075 204 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Tank-cavern for containment of liquids |
| (57) Tank-cavern or large underground cistern for the containment of liquids comprising
a metallic structure (2) and a static structure of covering (3) aimed at separating
the metallic structure from the surrounding ground, this metallic structure being
supported inside the static covering by means of U-bolts (also insulating) (4) fixed
to said external covering, where between the metallic structure and the static structure
at least one layer of filler material (5) is envisaged, where said metallic structure
comprising a plurality of metallic elements joined one to the other by their transversal
and longitudinal edges (7) which have suitable profiles aimed at forming the transversal
and longitudinal ducts for recovery and location of any possible leaks, such that
these ducts, both longitudinal and transversal, converge below the tank in a single
collector duct for collection of the leaks which in turn is arranged in such way as
to have a termination in correspondence with a monitoring chamber (C).
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[0001] This invention concerns a tunnel-tank or large underground cistern for the containment of liquids of any kind.
[0002] Such tanks are generally cylindrical in shape with a horizontal or vertical axis and envisage an internal metallic structure for containment, apart from and anchored to the static structure in simple or reinforced concrete, and a filler material interposed between the two structures, the metallic one for containment and the static one.
[0003] The construction of large underground tanks is carried out, as well known, by means of calendered metallic elements known as "rings" of considerable size and presented on the transversal edges with a suitable L-shaped profiles, aimed at creating directly, with the juxtaposition of the rings and with the covering of the profiles with flat sections, the formation of transversal and longitudinal ducts for monitoring, recovery and location of any possible leaks.
[0004] The transversal ducts may, instead, be created from omega and flat sections for coverage, welded to the edges of the rings, which in this case do not have L-shaped profiles and the latter solution is generally preferred in that the calendering of the rings that are stiffened by profiles is difficult.
[0005] Such metallic elements, of large dimensions, allow an easier and more economical assembly of the metallic structure, (placed away from the intrados surface of the static concrete structure that protects it from the exterior, to which it is anchored) in that both the handling and the placing of the elements themselves are considerably easier and rationalised, compared to previous assembly techniques.
[0006] The metallic structure for containment is supported apart from the static reinforced or unreinforced concrete structure, by means of suitable U-bolts anchored to the same static structure and in the resulting interspace a filler material is poured or injected.
[0007] The system described above allows one to obtain, in the preparation of large underground or buried tanks, the best conditions of stability, in that the system made up of the set of a metallic containment structure, static structure, filler material and the surrounding ground, results integral as a single interactive structural complex, in such way that the set of the three structural components intervenes directly and unanimously on the stability of said tanks, said structural complex being configured according to the scheme of a tunnel-tank.
[0008] In order to guarantee the best structural stability of the set of the three structural elements making up the tank (the static structure, the metallic plating and the filler material), as filler a particular oxidised bitumen is used and injected or poured hot at a temperature of about 200÷220°C into the interspace constructively created between the static structure and the metallic containment structure, by means of which the necessary structural continuity of the whole is ensured.
[0009] To this end one also creates on the external surface of the individual rings of the metallic plating, means aimed at increasing the adherence between the metallic plating and the oxidised bitumen that is poured or injected hot, means generally made up of sections of various kinds welded externally on the rings.
[0010] The transversal and longitudinal ducts created, on the perimeter of the rings, for recovery and location of any possible leaks, both longitudinal and transversal, are made to converge under the tank in a single duct, with the function of collector of the possible leaks which in turn is located below and outside the tank itself, in such way as to have a termination in correspondence with a collecting vessel.
[0011] This vessel normally allows one to check any possible leaks from the tank, referred to the unit of time taken into consideration and therefore its degree of hermetic sealing, as well as the longitudinal location of the leak. That in as much as said leak turns out to be relative to the band of rings whose ducts converge in the collector duct connected with that vessel.
[0012] The purpose of this invention is to supply a more accurate monitoring system which allows one to continuously monitor the degree of hermetic sealing of the tunnel tank or the underground tank, and easily locates in a longitudinal sense the breakage from which any possible leak results. In particular, the ducts are previously pressurised and on the termination of the collector duct for collection of leaks, as well as the aforesaid collecting vessel, a pressure detecting device is installed, which is particularly sensitive and able to monitor even a minimal variation of the pressure gradient exercised inside the duct of the tank in the case in which a break is found with leakage of inert gas. The drop in pressure, revealed by the aforesaid device, will therefore signal the presence of a leak from the tank that will easily be located.
[0013] Furthermore, downstream from the pressure device, in the collector duct for collection of leaks the insertion of a valve is arranged which has a dual function: when closed, the valve allows one to read the value of the relative pressure of the gas inside the monitoring duct; when open, the valve allows one to recover the leak and to measure the consistency of the same in the unit of time considered.
[0014] The subject of this invention is formed by a tank-cavern or large underground cistern for the containment of liquids having the features of the attached claim 1.
[0015] In the following this invention will be illustrated with reference to a form of exemplary realisation illustrated in the attached figures in which
in figure 1 one illustrates schematically a cross-section of an example of an underground tank,
in figure 2 one illustrates in a perspective view a ring of the metallic structure,
in figure 3 one illustrates schematically a cross-section of a cistern with vertical axis.
[0016] With reference to the mentioned figures, the tank, according to this invention, includes a metallic structure 2 and a static structure of covering 3, the latter aimed at separating the metallic structure from the surrounding ground, realised, for instance, in simple or reinforced concrete. The metallic structure is supported inside the static structure of covering 3 by means of U-bolts (also insulating) 4 fixed to said static structure 3.
[0017] Between the metallic structure and the static structure at least one layer of filler material 5 is envisaged, which may for example be poured or injected hot through suitable closable traps on the metallic structure.
[0018] Once solidified, said filler material must transmit the solicitations of the metallic structure to the static face and vice versa, and, for this purpose, oxidised bitumen has proved useful made liquid through heating and having the following average features:
- penetration at 25°C 20-30 dmm
- softening point 80-115°C
- Fraas breaking point -5 - +12° C
- ductility at 25°C 3 cm min
- flash point 240 - 260° C min
- specific weight at 25/25°C 1.01 - 1.05 g/cc
[0019] When cold, said oxidised bitumen presents the necessary plasticity to transmit the solicitations, without permanent deformations and without breakage, between the components of the tank. This bitumen is poured in the interspace constructively realised between the static structure and the metallic structure of containment at a temperature of about 200-220 °C in such way as to completely fill the aforesaid interspace.
[0020] As mentioned, with the adoption of this filler material, it is possible to guarantee the stability of the whole of the tank with the metallic structure and static structure, calculated with smaller resistant cross-sections compared to tanks not having such a layer of filler.
[0021] Advantageously, to guarantee or exalt the effect of adherence between the metallic structure and the filler of hot oxidised bitumen fixed sections are present, for example, by means of welding to the external surface of the plates 6 made up of round bars suitably separated and intersected with one another.
[0022] This arrangement is indicative and exemplar, in that said sections may be of any type whatsoever (flat sections, L-shaped, Z-shaped, etc.) and may be placed with any horizontal and transversal orientation as indicated in the drawings or even oblique. Prominent elements may also be envisaged externally but located on the plating. Naturally, what has been expressed with reference to the longitudinal body of the tank, is also valid for the heads of the tank itself both with a flat and a convex surface. Furthermore, what has been described with regard to cylindrical tanks with a horizontal axis is also valid for tanks with any other shape and arrangement (vertical, subvertical, spherical tanks etc.).
[0023] The metallic structure is made up of a plurality of metallic elements or rings joined to one another by the transversal edges 7 which have suitable L-shaped profiles or equivalent, aimed at creating, directly with the placing side by side of said elements, the containment structure of the tank and with the help of flat sections, the formation of the transversal and longitudinal ducts for recovery and location of any possible leaks.
[0024] These transversal monitoring ducts may instead be created from omega and flat sections, welded to these elements, which in this case do not have the L-shaped profile.
[0025] According to this invention these monitoring ducts, both longitudinal and transversal, are made to converge below the tank in a single collector duct for collection of any possible leak, a channel which, in turn, is arranged so as to have a termination in correspondence with a monitoring chamber C in which a collector vessel may be envisaged. This vessel normally supplies an indication of the level of the leakage from the tank and therefore of its degree of hermetic sealing. In particular, on the termination of the collection channel a pressure detection device is installed, particularly sensitive even to the minimum pressure gradient, suitable to constantly monitor the pressure that is exerted from the inside of the tank monitoring ducts.
1. Tank-cavern or large underground cistern for the containment of liquids comprising
a metallic structure (2) and a static structure of covering (3) aimed at separating
the metallic structure from the surrounding ground, this metallic structure being
supported inside the static covering by means of U-bolts (also insulating) (4) fixed
to said external covering,
between the metallic structure and the static structure at least one layer of filler material (5) is envisaged,
said metallic structure comprising a plurality of metallic elements joined one to the other by their transversal and longitudinal edges (7) which have suitable profiles aimed at forming the transversal and longitudinal ducts for recovery and location of any possible leaks,
characterised by the fact that
these ducts both longitudinal and transversal converge below the tank in a single collector duct for collection of the leaks which in turn is arranged in such way as to have a termination in correspondence with a monitoring chamber (C).
between the metallic structure and the static structure at least one layer of filler material (5) is envisaged,
said metallic structure comprising a plurality of metallic elements joined one to the other by their transversal and longitudinal edges (7) which have suitable profiles aimed at forming the transversal and longitudinal ducts for recovery and location of any possible leaks,
characterised by the fact that
these ducts both longitudinal and transversal converge below the tank in a single collector duct for collection of the leaks which in turn is arranged in such way as to have a termination in correspondence with a monitoring chamber (C).
2. Tank-cavern or large underground cistern according to claim 1, characterised by the fact that in said monitoring chamber a collector vessel for liquids is envisaged.
3. Tank-cavern or large underground cistern according to claim 1, characterised by the fact that in said monitoring chamber, on the termination of the collector ducts
for collection of any possible leaks, which converge in it, previously pressurised,
a pressure detection device is envisaged, sensitive even to the minimum pressure gradient
of the same, able to monitor the pressure that is exerted inside the monitoring duct
of the tank by the inert gas contained therein, should a leak occur from a welded
joint with the subsequent leaking of the gas contained therein and the following leakage
of the liquid from the tank itself into the duct.