Technical field of application

The present invention relates to the industrial field of gas storage plants, and more in particular concerns a modular element adapted to be used for the construction of an anchoring base for a membrane gasometer, of hemispherical or spherical dome type, utilizable in particular for storing biogas generated by sludge or slurry digestion.

The invention also concerns a polygonal shaped anchoring base for a membrane gasometer produced with a plurality of said modular elements.

Background art

Membrane gasometers for storing biogas normally comprise a first closed-bag impermeable flexible membrane, adapted to delimit a first variable volume gas storage chamber, and a second membrane, adapted to create a pressurization chamber, substantially in the shape of a hemisphere or % of a sphere, generally containing air, above said gas storage chamber.

Hemispherical membrane gasometers are anchored, by means of a metal flange, to a reinforced concrete slab platform or, alternatively to a ring-shaped platform, again made of reinforced concrete, having a centreline with the same circumference as the hemisphere and as the metal flange. Said anchoring flange produces the gas-tightness of the pressurization chamber of the gasometer; at the same time, the anchoring point of the metal flange on the reinforced concrete platform is the place in which the tensile stresses exerted by the pressurized membranes are transferred.

The reinforced concrete platform, whether a slab or ring-shaped, performs a function of anchoring base for the gasometer and is the first structure to be produced for subsequent installation of the gasometer.

In order to produce semi-circular membrane gasometers supported on a reinforced concrete platform as described above, the installation site must be easily accessible for a cement mixer.

Unfortunately, in many countries, for example in countries in South East Asia, such as Malaysia, Indonesia, Thailand, Vietnam, etc., biogas plants requiring gasometers are located in uninhabited areas that can only be reached by light vehicles travelling over rough roads. Concrete mixing plants are very far from the construction sites and, due to their size and weight, it is not easy for cement mixers to reach these sites.

Even more unfortunately, in many countries in which civil buildings use other materials, (iron, wood, prefabricated materials), the high cost of works in reinforced concrete has a significant impact on the overall cost of producing the gasometer.

Moreover, to produce the reinforced concrete platform, structural calculations and the use of specialized labour are necessary. Each installation is different and must be calculated and designed based on the surrounding conditions, in particular the conditions of the ground on which the gasometer will stand.

Presentation of the invention

The object of the present invention is to eliminate the drawbacks and the disadvantages described above, producing an anchoring base system for a membrane gasometer that is alternative to the existing reinforced concrete systems.

Another object of the invention is to produce a standard prefabricated modular element, applicable in series for the construction of an anchoring base of a membrane gasometer even on unstable ground, inexpensive to produce and to transport.

Yet another object of the invention is to produce an anchoring base of a membrane gasometer that is inexpensive, does not require calculations based on obligatory geological surveys of the ground on which the gasometer is to be installed and that eliminates the need to use reinforced concrete.

The objects are achieved with a modular element adapted to be used for the construction of an anchoring base for a membrane gasometer, particularly on unstable ground, characterized by the fact that said modular element is in the shape of an upside down T and comprises:

- a first and a second L-shaped semi-module, each comprising a vertical wall and a supporting foot, adapted to be associated with each other by means of screw connection means at respective vertical walls;

- an edge beam, adapted to be associated with at least one of said semi-modules by means of screw connection means, where said first and second semi-module and said edge beam are made of sheet metal cut and bent and without any welds.

Advantageously, said first and second semi-module are identical as regards material, shape and size.

According to a first aspect of the invention, said first and second semi-module comprise gusset plates, arranged between the respective vertical wall and the respective supporting foot, and associated therewith by means of screw connection means.

In particular, said gusset plates comprise folded edges comprising holes, said semi-modules comprise corresponding holes, and said screw connection means comprise bolts adapted to engage said holes.

According to a preferred embodiment, each of said first and second semi-module is obtained from a metal sheet.

Advantageously, said vertical wall of each semi-module comprises shaped openings, where the material obtained from said openings is adapted to produce said gusset plates.

According to a further aspect of the invention, said supporting foot of each semi-module is trapezoidal in shape.

In a possible variant, said edge beam comprises slots, at least one of said semi-modules comprises holes, and said screw connection means comprise bolts adapted to engage said slots and said holes. Moreover, said modular element comprises:

- angled plate connection elements for joining said vertical wall of adjacent modular elements by means of screw connection means;

- arch shaped connectors for joining said supporting foot of adjacent modular elements by means of screw connection means.

The subject of the invention is also an anchoring base for a membrane gasometer characterized by the fact that it comprises a plurality of modular elements according to the invention, where said base is polygonal in shape and each modular element is adapted to produced one side of said polygonal shaped base.

The modular element according to the present invention advantageously allows the construction of an anchoring base for a membrane gasometer with a modular system of prefabricated metal parts that avoids the use of reinforced concrete, the use of cement mixers or other ad hoc means of transport, and the use of specialized and costly local labour.

Even more advantageously, the total elimination of reinforced concrete and its transport costs translates into a lower environmental impact.

The weight transferred from the backfill to each supporting foot acts as resistance force to the vertical component of the tensile force exerted on the anchoring flange by the membranes pressurized by the gas present in the gasometer.

In the same way, the backfill of the base exerts on the vertical wall a counter-force to the horizontal component of the same tensile force exerted on the anchoring flange.

All the components of the modular elements, i.e., the semimodules, the edge beam, the angled plate connection elements and the arch shaped connectors, are sized and shaped to be perfectly stackable and superimposable, in order to reduce their volume during transport, so as to be easily transportable even with trucks with normal load dimensions.

The use of special transport vehicles, which would have difficulty in accessing the isolated areas in which gasometers are normally positioned, is not required.

Even more advantageously, the single components of which the modular element is produced can be easily assembled with only screw connection means: therefore, assembly of the modular element can take place directly on site, further simplifying the transport step.

For the same reason, when no longer required, the entire base of the invention can be dismantled and reassembled in other sites without requiring onerous and costly disposal works. The reusability of the base allows a gasometer to be installed in a given site even for brief periods of time.

As the entire base is made of sheet metal, it can also be completely recycled, or sold as scrap.

Sheet metal has proved to the best choice as base for constructing an anchoring base solution comprising prefabricated modular elements.

The lightness of the modular elements allows them to be positioned manually in the excavation, or by means of a small excavator machine.

The sheet metal modular elements allow the insertion of flanges for coupling or fixing underground gas inlet and outlet pipes, again made of steel, serving the gasometer.

The modular elements can be installed directly in an excavation on unstable ground: all the modular elements are equipped with elements for adjusting the height that allow vertical alignment of the entire base without requiring excessive precision from those who carry out the excavation works.

The excavated soil can be reutilized to fill the base, thus without requiring movement and disposal of material.

To prevent the type of ground from influencing the capacity of resistance of the base, the modular elements are designed and sized based on ground with deteriorating characteristics, i.e., with lower density and lack of mechanical stability.

The cost of an anchoring base thus produced is very low, much lower than a reinforced concrete platform the larger the gasometer to be installed is.

Even more advantageously, besides the costs of materials and works, there is also a saving on the cost of design by a specialized technician.

Brief description of the drawings

These and other advantages will be more apparent from the description of the invention, set forth below with the aid of the drawings, which represent an example of embodiment thereof, wherein:

- Fig. 1 illustrates, in an axonometric view, a modular element adapted to be used for the construction of an anchoring base for a membrane gasometer according to the invention;

- Fig. 2 illustrates, in a partially exploded cross section along a vertical plane, the modular element of Fig. 1 ;

- Figs. 3-6 illustrate, in axonometric views, different components of the modular element of Fig. 1 ;

- Fig. 7 illustrates, in a plan view from above, a metal sheet from which the components of the modular element of Fig. 1 are obtained;

- Fig. 8 illustrates, in a plan view from above, two modular elements of Fig. 1 side by side during the assembly of an anchoring base;

- Fig. 9 illustrates, in a plan view from above, a polygonal anchoring base for a membrane gasometer comprising a plurality of modular elements as in Fig. 1 .

Detailed description of a preferred embodiment of the invention

With reference to Figs. 1 and 2, there is illustrated a modular element 100 adapted to be used for the construction of an anchoring base F (Fig. 8) for a membrane gasometer on unstable ground.

Said modular element 100 is of prefabricated type and is in the shape of an upside down T.

Said modular element 100 comprises a first 1 and a second 2 L- shaped semi-module, each comprising a vertical wall 11 , 21 and a supporting foot 12, 22.

As is apparent from Fig. 2, said first 1 and second 2 semi-module are identical as regards shape and size, and are associated with each other at the respective vertical wall 11 , 21 to produce together the upside down T shape of the modular element 100.

Stable coupling of the two semi-modules 1 , 2 takes place by means of screw connection means: each semi-module 1 , 2 comprises holes 14, 24 and said screw coupling means comprise bolts 15 that simultaneously engage the holes 14, 24 of the two semi-modules 1 , 2.

With particular reference to Fig. 3, which illustrates a single semimodule 1 , as, as mentioned above, said semi-modules are identical as regards shape and size, the description below regarding the first semi-module 1 is also valid for the second semi-module 2.

Said vertical wall 11 comprises shaped openings 6.

Said supporting foot 12 is trapezoidal in shape.

The oblique sides of said supporting foot 12 are inclined by an angle a necessary, as will be seen below, to prevent, during construction of the anchoring base F, partial overlapping with the supporting feet 12 of adjacent modular elements (Fig. 8).

Said first 1 and second 2 semi-module comprise gusset plates 4, arranged between the respective vertical wall 11 , 21 and the respective supporting foot 12, 22, and associated therewith by means of screw connection means.

Said gusset plates 4, illustrated in detail in Fig. 4, comprise folded edges 41 comprising holes 42; said semi-modules 1 , 2 comprise corresponding holes 13, 23, and said screw connection means between semi-module 1 , 2 and gusset plates 4 comprise bolts 5 adapted to engage said holes 42, 13, 23.

Each modular element 100 comprises angled plate connection elements 10 and arch shaped connectors 25, illustrated in the detail of Fig. 5 and in the detail of Fig. 8, respectively, for joining adjacent modular elements 100, again by means of screw connection means, in order to produce a continuous anchoring base F. Said screw connection means comprise suitable holes 16, 17 obtained on said semi-modules 1 , 2, corresponding slotted holes 18, 19 obtained on said angled plate connection elements 10 and on said arch shaped connectors 25, respectively, and screws 20 adapted to engage said holes 16, 17 and said slotted holes 18, 19.

Said first 1 and second 2 semi-module, said gusset plates 4, said angled plate connection elements 10 and said arch shaped connectors 25 are all made of sheet metal cut and bent and without any welds.

Said sheet metal is preferably a galvanized carbon steel sheet, and once cut and bent to produce the single components, is coated with an epoxy powder paint. Alternatively, it is possible to use an ungalvanized S232 (black iron) carbon steel, again coated with epoxy powder paint, or stainless steel sheet.

Advantageously, each semi-module 1 , 2, the respective gusset plates 4 and the respective angled plate connection elements 10 and arch shaped connectors 25 are all obtained from a single sheet 200 of sheet metal, according to a precise cutting pattern, as illustrated in Fig. 7.

In particular, shaped openings 6 are obtained in the portion of sheet metal that forms the vertical wall 11 of the semi-module 1 , which, besides lightening the semi-module 1 with advantages for transportability, provide the material to produce said gusset plates 4.

Said modular element 100 further comprises an edge beam 3, illustrated in detail in Fig. 6, adapted to be associated with at least one of said semi-modules 1 , 2 by means of screw connection means.

Said edge beam 3 is adapted to cooperate with a flange (not illustrated) for clamping the membranes that produce the gasometer, optionally also with the interposition of gaskets.

Said edge beam 3 is also made of sheet metal cut and bent and without any welds; in particular said edge beam 3 is made of AISI 304 steel.

Said edge beam 3 is L-shaped and thus comprises a vertical edge 31 , adapted to cooperate with the vertical wall 1 1 , 21 of at least one semi-module 1 , 2, and a cantilevered wing 32 adapted to cooperate with said fixing flange of the membranes.

To guarantee the gas-tightness of the entire gasometer, it is fundamental that the fixing flange of the membranes, according to prior art, cooperates with a perfectly flat surface so that any gaskets interposed also operate correctly producing a seal.

As the excavation in which the base F is placed might not have a flat and uniform surface, the height of each modular element 100 must be adjusted, so that the cantilevered wings 32 of each edge beam 3 are all coplanar.

For this purpose, said modular elements 100 comprise elements for adjusting their height, in particular means for adjusting the fixing height of the edge beams 3 to the respective semi-modules 1 , 2.

In detail, said edge beam 3 comprises slots 7, at least one of said semi-modules 1 , 2 comprises holes 8, and said screw connection means comprise bolts 9 adapted to engage said slots 7 and said holes 8.

Said slots 7 thus offer different possible fixing heights of the edge beam 3 to the semi-module 1 , 2.

With particular reference to Fig. 9, there is illustrated an anchoring base F for a membrane gasometer produced by means of a plurality of modular elements 100.

Said base F is polygonal in shape and each modular element 100 produces one side of said polygonal shaped base F.

Advantageously, at least one modular element 100 of said anchoring base F is technological and comprises fixing flanges (not illustrated) for steel gas inlet and outlet pipes and/or for a pipe of an overpressure safety valve.

Moreover, to preserve the epoxy paint of the sheet metal, after being laid in the base excavation, each modular element can be covered with a geotextile layer (not illustrated).