This invention relates to a release valve for safety devices, in particular in fire-extinguishing systems, a relative fire-extinguishing system and a relative actuation method.

More specifically, the invention relates to a heat-activated extinguishing gas release valve for the release of fire-extinguishing gas of a gas fire-extinguishing system.

The invention also relates to a fire-extinguishing system comprising this valve.

As is known, gas systems, also known as "clean agent" systems, are among the systems for active fire protection. These systems use inert gas or gaseous extinguishing chemical substances to saturate the environment in which they are released and put out the fire. The inert gases extinguish the fire by reducing the concentration of oxygen in the environment, the gaseous extinguishing chemical substances through more complex mechanisms, including the development of endothermic reactions. Said inert gases and said gaseous extinguishing chemical substances will also be identified as a whole in the following description as extinguishing gases.

Gas fire-extinguishing systems were first used over a century ago when a first carbon tetrachloride fire-extinguishing system was invented. However, the greatest developments took place only in the years immediately following the Second World War, when “Halon” gases (for example Bromochlorodifluoromethane) were introduced and, in the early 1990s, with the introduction of its substitutes with a lower environmental impact, in part, still present on the market.

The inert gases most commonly used in gas fire-extinguishing systems are Argon Ar, Nitrogen N2, singly or in mixtures, which are both normally present in the atmosphere and with low environmental impact. The chemical substances most commonly used in gas fire-extinguishing systems are, on the other hand, HFC-227ea or 1 ,1 ,1 , 2, 3,3,3- Heptafluoropropane, HFC-125 or Pentafluoroethane and FK 5-1 -12 or Perfluoro (2-Methyl-3-Pentanone).

The gas systems can be advantageously used on objects and/or machinery of different types, including electronic and live ones, without irreparably damaging them and in areas normally manned by personnel, unlike what is provided for “traditional” systems (for example those using water, foam or powder).

Furthermore, the gas systems guarantee the total saturation of the environments in which these gases are released, also known as “total flooding”, allowing the formation of a homogeneous concentration of extinguishing agent within the room of interest in a very short time, usually within 10 seconds of release.

This feature makes it possible to quickly extinguish fires present in the most hidden and less accessible areas of the environments in question.

The characteristics and advantages of gas fire-extinguishing systems have favoured their widespread diffusion, especially in areas where the value of the capital protected is significant and where it is necessary to guarantee the safety of personnel, and in particular in the case of personnel assigned to supervise the protected environment even during the fire.

The gas fire-extinguishing systems must also follow specific safety regulations, such as the technical standard “Standard for Clean Agent Fire Extinguishing Systems - NFPA 2001” drawn up by the National Fire Protection Association (NFPA) for the United States, standard UNI EN 15004 “Fixed fire-extinguishing installations - Gaseous extinguishing systems” valid for Italy and based, together with other national standards, on ISO 14520 “Gaseous Fire-Extinguishing Systems ”, which define the reference standard.

Although the valve described in the patent is particularly suitable for use in gas systems that use chemical substances as extinguishing agents, it can be used as a discharge valve for other classes of extinguishing agents, including, by way of example, inert gases, water spray, fireextinguishing powder, fire-extinguishing foam.

Manually operated valves are often used in the prior art fire- extinguishing systems for the release of the extinguishing agent, in turn connected to the neck of the cylinder containing the extinguishing gas. These valves can also be indicated with the expression “shut-off valves” or “discharge” valves.

The actuation of these valves involves the displacement of one of their pistons and therefore the flow of the extinguishing agent (in the form of a compressed liquid) through the discharge port of the valve itself.

An example of such systems is described in European Patent No. EP 1 302 710 B1.

In the "traditional" valve there is often also a small rupture disc which performs the function of safety device, to prevent the fire-extinguishing system from exploding or being damaged due to an increase in the pressure difference between the cylinder and the outside environment, especially if caused in a relatively short period of time. Said safety device releases the extinguishing agent into the outside environment.

However, such traditional valves usually have high head losses, as illustrated in more detail below.

The aim of the invention is therefore to provide a discharge valve in which the head losses are considerably reduced with respect to valves of the "traditional" type.

It is, in fact, well known that the efficiency of a valve is directly correlated to the “head loss" that the fluid undergoes, whether in the gaseous, liquid or mixed phase (fluid in biphasic conditions), during the passage through the valve itself. The head loss, often also incorrectly referred to as "pressure loss", is equivalent to the total loss of energy possessed by the fluid as it passes through the device.

The head loss for a given fluid in a given phase depends exclusively on the characteristics of the valve in terms of the tortuosity of the free passages (paths travelled by the fluid) and on the shape of the "wet" parts of the valve itself (that is, the parts in contact with the fluid). In other words, the most efficient valves, that is to say, those which induce less energy loss on the fluid during their passage, are those that allow a sufficiently regular path for the fluid, with limited abrupt changes of direction and narrowings and with rounded internal shapes.

In a fire-extinguishing system, a lower head loss of the discharge valve translates into a series of advantages that directly and indirectly reflect on the efficiency and cost-effectiveness of the entire system. With the same diameter of the discharge valve, cylinder capacity, operating pressure and, obviously, the type of extinguishing agent, a system equipped with a discharge valve with reduced or limited head loss allows, by virtue of the greater energy possessed by the fluid downstream of the valve, improvement of the transfer of the fluid from the cylinder to the nozzles and therefore to the environment to be protected, with the possibility of covering greater distances and therefore of placing the cylinders in more remote points than the place to be protected, or transferring a greater quantity of fluid per unit of time. The possibility of locating the cylinders in remote places with respect to the risk to be protected in particular could be useful, when not essential, in inconvenient and/or inaccessible places and/or with modest spaces available to position the cylinders in the vicinity of the environment to be protected and in any case to the advantage of a greater flexibility of installation of the system.

Moreover, a discharge valve with reduced head loss allows, for the same considerations of an energy nature, a reduction in the quantity and pressure of the pressurisation gas (propellant, generally nitrogen) necessary for the correct operation of the system (the pressurisation gas, in fact, constitutes an accumulation of potential energy which moves the extinguishing gas during the discharge).

A reduced quantity of propellant has the dual advantage of freeing up space in the cylinder for the extinguishing agent, which translates into the possibility of using a cylinder of lower capacity and therefore of lower cost (higher extinguishing mass/propellant mass ratio), that is to say, by virtue of the lower operating pressure, to reduce the thickness of the cylinder itself, with a further reduction in cost.

Another characteristic of the discharge valve according to the invention is the practical possibility of making a device having a diameter greater than that typical of the "traditional" valve. The constructive and functional simplicity of the invention is directly reflected not only in its cost but also in the possibility of producing valves with a significant diameter.

In fact, the “traditional” valve commonly used has considerable constructive complexities, with extensive use of mechanical parts and with significant weights; such constructive complexity does not normally allow devices to be made with a nominal diameter sufficient to be installed on cylinders with dimensions greater than 350 litres of capacity. By way of example, cylinders with a maximum capacity of 343 litres are currently marketed coupled with valves with a nominal diameter of 3” (88.9 mm). Said 3” valve has a weight of 18.82 kg (without considering the actuation devices), a length of 241 mm and a diameter of 129 mm. This sometimes requires system configurations consisting of numerous cylinders in parallel. A valve manufactured according to the prior art with a diameter equal to or greater than 5” would entail insurmountable technical difficulties and, in any case, prohibitive weights and dimensions.

According to the prior art, shut-off valves operated automatically, both mechanically and by heat, are also known.

Examples of such valves for fire-extinguishing systems are described in patent documents EP 3 460 300 A1 , US 6 394 188 B1 and US 2016 102 773 A1 .

In particular, patent document EP 3 460 300 A1 describes a valve for the release of pressurised fluids, said valve is activated by the opening of a reverse acting rupture disc, in turn operated by a mechanical device which regulates its opening without perforating the disc.

Patent document US 6 394 188 B1 on the other hand describes a valve for the release of extinguishing gas comprising an inflatable membrane which separates said extinguishing gas from the outlet of the valve and which opens following the explosion of an explosive charge placed inside the system, wherein this explosive charge is activated by a heat sensor.

Patent document US 2016 102 773 A1 on the other hand describes a valve for the release of extinguishing gas comprising a breakable diaphragm operated through the expansion of a fluid following the administration of heat, an actuator regulated by a heat sensor.

However, each of the solutions proposed in the prior art has significant operating limits.

The valve described in patent document EP 3 460 300 A1 consists of a rupture disc, of the reverse acting type, the opening of which is caused by an external device by the un-stabilisation of the dome. In particular, said un-stabilisation is induced by means of a strut (with either electric, pneumatic or squib drive) which, by striking the top of the dome as necessary, destabilises it causing the disc to break. This solution, although of undoubted effectiveness, is rather complicated, expensive and subject to malfunctions.

The device described in US 6 394 188 B1 provides for actuation by means of an explosive charge, with all the contraindications of the case, including the prohibition which is in force in many countries to use this type of system for the actuation of the fire-extinguishing system as well as the authorisations necessary for their handling.

The device described in US 2016 102 773 A1 provides for the use of a fluid which has the characteristic of expanding when a certain amount of thermal energy is transferred to it; however, the fracturing of the diaphragm must take place simultaneously on both sides (cylinder side and valve outlet side) in order to correctly achieve the purpose of actuating the system. Other drawbacks of the system described are that the auxiliary fluid must be dispersed in the environment to be protected as well as the risk of fragmentation of the diaphragm and consequent clogging of the pipes downstream of the valve.

In particular, the rupture discs of the prior art valves have the sole function of preventing any accidental overpressures which may be created inside the extinguisher cylinder from leading to the collapse of the same cylinder.

In fact, these rupture discs only ensure their opening at a predetermined pressure, at ambient temperature.

The aim of the invention is therefore to overcome the drawbacks of the prior art. Moreover, an aim of the invention is to provide a gas release valve for fire-extinguishing systems which is more efficient than a traditional valve and which minimises the head losses of the extinguishing fluid passing through it.

A further aim of the invention is that this valve is simple and economical, if compared to the prior art valves.

Moreover, an aim of the invention is to provide a gas release valve which is simple and reliable, both in terms of production and of operation.

The aim of the invention is also that such valves are safer, if compared to the prior art valves.

Finally, an aim of the invention is that this valve guarantees the release of a greater quantity of extinguishing gases, within the discharge time of 10 seconds prescribed by the technical standards, compared to a “traditional” valve having the same diameter.

The object of the invention is therefore a release valve for fireextinguishing systems, consisting of a tubular body with a first end and a second end and which comprises: means for coupling with a source of an extinguishing gas at a working pressure, positioned at said first end; an outlet, positioned at said second end; a rupture disc, positioned in a position between said coupling means and said outlet, wherein said rupture disc is made of metallic material subject to mechanical degradation when heated, being configured to ensure the seal of said release valve) at said working pressure when subjected to temperatures lower than a predetermined temperature and to open at said working pressure when said predetermined temperature is reached; heating means, designed to heat said rupture disc to said predetermined temperature and actuator means connected to said heating means, to activate the heating of said rupture disc at said predetermined temperature by means of said heating means and the consequent opening of said rupture disc with the release of extinguishing gas towards said outlet.

According to the invention, the rupture disc can be cut with a perimeter incision near its outer edge in such a way as to be able to open at said working pressure along said perimeter incision, when heated to said predetermined temperature.

Moreover, according to the invention, said heating means can be arranged in contact with said perimeter incision of said rupture disc. In particular, said heating means can be immersed in said rupture disc, especially in the case of multilayer type rupture discs.

According to the invention, said heating means can be an electrical resistance arranged at said rupture disc.

In particular, said electrical resistance can be electrically insulated from said rupture disc.

According to the invention, said electrical resistance can be a resistance with a rectangular section.

Further, according to the invention, said perimeter incision and said heating means can have a substantially ring shape.

Moreover, according to the invention, the rupture disc is preferably made of aluminium.

Again according to the invention, the rupture disc can be of the non- breakable type.

Furthermore, according to the invention, said predetermined temperature can be greater than or equal to 150 °C, preferably between 150 °C and 400 °C when the rupture disc is made of aluminium.

Moreover, according to the invention, the release valve can comprise a filling port arranged in a position between said coupling means and said rupture disc.

Furthermore, according to the invention, said tubular body can comprise a housing, arranged in a position between said first end and said rupture disc, for housing a safety disc.

Again according to the invention, said tubular body can comprise a pressure gauge, arranged between said first end and said rupture disc.

Finally, according to the invention, said rupture disc can be of the flat type, forward acting or reverse acting.

The invention also relates to a fire-extinguishing system comprising a source of extinguishing gas coupled to a release valve according to the invention by means of said coupling means of said release valve. According to the invention, said system can comprise a circuit of a fire-extinguishing system connected to a release valve according to the invention, through said outlet of said release valve.

Finally, the object of the invention is a method of actuating a fireextinguishing system according to the invention, wherein said actuation means are activated to actuate said heating means so as to heat said rupture disc to said predetermined temperature, causing the rupture of said rupture disc and allowing the flow of extinguishing gas through said release valve, from said extinguishing gas source towards said outlet of the release valve.

The invention is now described, by way of example and without limiting the scope of the invention, with particular reference to the accompanying drawings, wherein:

Figure 1 shows a release valve for fire-extinguishing systems according to the invention.

With particular reference to Figure 1 , a release valve 100 according to the invention, for the release of an extinguishing fluid, in particular gas, comprises: a tubular body 1 having a first end 1 ‘ and a second end 1 ", comprising

- coupling means 10 arranged on said first end 1 ', for coupling the tubular body 1 with a source for filling extinguishing gas and the fluid connection with said extinguishing gas source, for example a cylinder or a system containing such extinguishing gas at a working pressure;

- an outlet 11 , for the extinguishing gas outlet from said release valve 100, arranged on said second end 1 ", in which said outlet can be connected to a downstream hydraulic system, such as the pipes of a fire-extinguishing system, for example by means of a threaded surface 1 1

- a rupture disc 2, arranged downstream of said coupling means 10 and upstream of said outlet 11 , wherein said rupture disc 2 is configured to maintain the seal at said working pressure, and to open once a predetermined temperature induced on the rupture disc 2 is exceeded, said rupture disc 2 being made of material subject to mechanical degradation when heated, as illustrated in more detail below; - heating means 3, in particular a resistance 3, designed to heat said rupture disc 2 to said predetermined temperature, being for example in direct contact with it; and

- actuator means (not shown in the drawings), connected to said heating means 3, so as to actuate them to allow the opening of the rupture disc 2.

According to the embodiment shown in Figure 1 , the coupling means 10 are a threaded surface 10 arranged at said first end 1 ’ of said tubular body 1 and which can be screwed onto said extinguishing gas cylinder, for fluid connection therewith.

According to alternative embodiments (not shown), the coupling means 10 can be different from those shown. By way of example, these coupling means can alternatively be constituted by a bolted coupling flange or by an externally threaded portion, of the male type, coupled to the source for filling extinguishing gas, in place of the threaded portion 10, of the female type, shown in Figure 1 .

In general, a rupture disc 2 is a device configured to open at a predetermined, and is non-reclosable pressure, such as to protect a pressure vessel, equipment or system from potentially damaging overpressure or vacuum conditions. The rupture discs 2 must meet safety requirements established by current legislation (for example UNI EN 12094.4: 2004 regarding the use of rupture discs in fire-extinguishing devices), and in particular be produced with standardised procedures.

Compared to the common safety valves, the rupture discs guarantee a watertight seal, with reduced dimensions, and a repeatability of performance levels. Moreover, the rupture discs have low production costs and are easy to maintain.

Regarding repeatability in performance level, the rupture discs are configured to provide an instant response in a predetermined response time (with response times in the order of milliseconds) to an increase or decrease in pressure.

Moreover, the rupture discs are usually designed to always open in the same way, so as to substantially guarantee the same opening area or free space. If this were not the case, the fire-extinguishing system could not be designed correctly.

In fact, the reliability of the rupture discs makes it possible to carry out a sizing of the pipes of a system comprising a rupture disc 2, for example through the use of a sizing software, by carrying out a plurality of experimental tests, such as to verify that

- the mass of the extinguishing agent discharged following the opening of a rupture disc 2 is equal to ±10% of that expected, with a standard deviation of less than 5%;

- the discharge time is equal to 10s ± 1 s;

- the pressure at the discharge nozzle shows a variation equal to ±10%.

This could not be achieved with normal release valves, which do not guarantee a repeatable opening.

According to the embodiment described, the rupture disc 2 is cut with a perimeter incision near its outer edge (or outer circumference), in such a way as to ensure the seal at said working pressure when subjected to lower temperatures than said predetermined temperature, and being able to open at said working pressure along said perimeter incision when heated to said predetermined temperature, for the release of said extinguishing gas towards said outlet 11 . This characteristic makes it possible to improve the reliability of the rupture disc 2, since it is guaranteed that, once opened, the rupture disc always has the same opening area.

According to the embodiment shown in Figure 1 , the perimeter incision of the rupture disc has a substantially circular shape. In this way, the uniform rupture of the rupture disc 2 is favoured.

According to an embodiment, the rupture disc 2 is a multi-layer type rupture disc.

In use, once the rupture disc 2 is brought to said predetermined temperature by means of said heating means 3, the mechanical resistance of the rupture disc 2 at the perimeter incision decreases causing it to open along said outer circumference.

Preferably, the heating means 3 act directly on said perimeter incision, as explained in more detail below.

This predetermined temperature is chosen according to the material with which said rupture disc 2 is made. Preferably, this predetermined temperature is greater than or equal to 150 °C. In the case of an aluminium rupture disc, this predetermined temperature is between 150 °C and 400 °C.

In particular, the rupture disc 2 is preferably made of aluminium or other metallic material whose mechanical resistance characteristics decrease with the increase in temperature.

It is in fact known that metals can undergo different forms of mechanical degradation when subjected to high heat sources.

For this reason, the rupture discs 2 made of metallic materials inside the valve 100 can also undergo such mechanical degradation.

More preferably, the rupture disc 2 is made using a metal having a high thermal conductivity, so as to ensure that the disc 2 is heated by the heating means 3 in the shortest possible time. For this reason, preferably, the rupture disc 2 is not made of materials with low thermal conductivity, such as ceramic materials or cellulose.

The rupture disc 2 is also of the non-breakable type, to prevent the rupture fragments from obstructing the piping of the system to which said valve 100 is associated.

The rupture disc 2 is preferably a flat, forward acting or reverse acting rupture disc, configured to open at a predetermined rupture pressure, higher than said working pressure.

Finally, preferably, this rupture disc has a diameter of between 2.5 cm and 20 cm, depending on the size of the tubular body 1 of the valve 100. Rupture discs with smaller diameter are used for smaller valves.

The heating means 3 are preferably a resistance 3, in particular a resistance 3 of the circular type, such as to follow the shape of said perimeter incision.

Moreover, the resistance 3 has a square or rectangular section (also called micro-tubular heater), preferably comprising an external steel casing, so as to ensure a better contact with the rupture disc 2 and heat said rupture disc 2 in a uniform manner. In particular, the resistance 3 is preferably in direct contact with the incision of the rupture disc 2, so as to guarantee the heating of the incision, and the consequent opening of the rupture disc 2 along said incision, in the shortest possible time. However, the rupture disc 2 is electrically isolated from the resistance 3. This allows the incision to receive heat by conduction from the resistance, guaranteeing that the heat is initially concentrated at the incision, whilst simultaneously avoiding the establishment of a Joule effect inside the rupture disc 2 itself. This feature has the further advantage of increasing the safety of the rupture disc 2. According to an embodiment, the resistance 3 is embedded inside the rupture disc 2.

In particular, if the rupture disc 2 is of the multilayer type, comprising a plurality of layers, the resistance can be included in said plurality of layers. In such a case, all the layers may comprise said incision.

The actuator means can be any element capable of activating the heating of the heating means 3, such as for example a switch to be operated manually/semi-automatically, capable of connecting/disconnecting the heating means 3 to electrical power supply means, or a control unit connected to a smoke detector or the like, capable of operating the release valve 100 automatically.

The release valve 100 further comprises:

- a filling port 12 or pressurisation port 12, for the unidirectional entry into the release valve 100 of extinguishing gas at said working pressure, wherein said filling port 12 is arranged between said first end T and said second end 1 ” and can be connected to a respective outlet of said source for filling extinguishing gas; and

- a housing 13, arranged approximately at the height of said filling port 12, for housing a calibrated safety disc (not shown in the drawings).

The calibrated safety disc (not shown) is calibrated to a burst pressure higher than said working pressure and lower than the rupture pressure of the rupture disc 2, to preserve the rupture disc 2 in the event of any accidental overpressure.

The calibrated safety disc is therefore arranged in the housing 13 with the purpose of preserving the release valve 100 from any accidental overpressures. In this way, any accidental overpressure which might occur in the cylinder of extinguishing gas (for example due to accidental overheating of the cylinder) would cause the safety disc to burst instead of the rupture disc 2, thus preventing accidental activation of the fireextinguishing system.

According to an embodiment(not shown), only the filling port 12 or the housing 13 with safety disc may be present, or neither of the two elements.

The release valve 100 shown in Figure 1 also comprises a pressure gauge 4 arranged inside the tubular body 1 , at said filling port 12, for measuring said working pressure. However, other positions of this pressure gauge are possible, provided they are upstream of the rupture disc 2.

Moreover, preferably, said pressure gauge 4 is an analogue pressure gauge, equipped with a pressure transducer (also called “pressure gaugepressure switch"). According to an embodiment (not shown), such a pressure gauge 4 may also not be present.

Finally, the valve 100 comprises sealing means 5, 6, 7, 8 to ensure the sealing of the elements arranged inside it.

In particular, the valve 100 shown in Figure 1 comprises

- a counter-stop ring 5, in particular made of steel, brass or other similar material, immediately upstream of which to install said rupture disc 2,

- an O-ring 6, for the watertight coupling of the sealing disc 5, and therefore of the rupture disc 2, with the tubular body 1 , and

- two further lower O-rings 7, 8, to ensure the seal of the gas cylinder when screwed onto said threaded surface 10.

According to alternative embodiments (not shown), these sealing means may be different from the sealing means 5, 6, 7, 8 described with reference to Figure 1 , but in any case shaped in such a way as to perform the sealing functions described above.

In particular, if said coupling means 10 between the source for filling extinguishing gas and the release valve according to the invention is made through bolted flanging, the O-rings 7 and 8 can be replaced by a gasket placed between the flanges themselves.

During the operation of the valve 100, the actuator means make current flow in the resistance 3, which heats the rupture disc 2 up to said predetermined temperature, thus resulting in its rupture.

By way of example, said resistance 3 can be connected to a battery, in particular a lithium ion battery or other similar technology, having an adequate supply power to ensure efficient and rapid heating of said resistance 3.

Some illustrative but non-limiting examples of valves 100 according to the invention are now described.

Example 1

A prototype of the valve 100 was made wherein the tubular body 1 has a diameter of 6.35 cm at said threaded surface 10 and said outlet 11 .

The rupture disc 2 inserted inside the tubular body 1 is a flat rupture disc 2, made of aluminium, pre-incised along the external circumference, non-breakable, with a rated failure pressure equal to 40 bar (4 10 ⁶ Pa) at ambient temperature.

The heating means 3 are a micro-tubular heater 3 with a square section, approximately 5x5 mm in size.

These heating means 3 are connected to an electric power supply wire, coming out of the tubular body 1 , in turn connected to a lithium ion battery.

The threaded surface 10 has been screwed to an extinguishing gas cylinder with suction tube, having a capacity of 50 litres and equipped with a suction tube.

The suction tube was in turn connected to said filling port 12.

Through said filling port 12, the assembly, consisting of the cylinder with suction tube and the valve 100, was filled with 20 kg of extinguishing agent FK 5-1 -12, pressurised with nitrogen N2 until the said working pressure was reached, which in the case in the example is equal to 25 bar (2.5 10 ⁶ Pa) at 21 °C.

The outlet 11 was connected to a pipe with a diameter of 6.35 cm and a length of 10 m, which simulates the route of the pipes of a fire- extinguishing system.

Finally, inside the tubular body 1 , in particular through further inlets, the analogue pressure gauge and the safety disc calibrated at a pressure of 32 bar (3.2 10 ⁶ Pa) were respectively applied.

Once electrical energy was supplied to the heating means 3, these reached a temperature of 500 °C in approximately 80 milliseconds, causing the mechanical degradation of the rupture disc and therefore its opening, making the extinguishing agent FK 5-1 -12 flow out inside the pipe.

Example 2

A prototype of valve 100 was made having a tubular body 1 with a diameter of 12.7 cm at said threaded surface 10 and said outlet 1 1 .

The rupture disc 2 inserted inside the tubular body 1 is a rupture disc 2 of the reverse acting type having a failure pressure of 55 bar (5.5 10 ⁶ Pa) at ambient temperature, made of aluminium.

The heating means 3 are a resistance 3 with characteristics similar to those of the previous example 1 .

These heating means 3 are connected to an electric power supply wire, coming out of the tubular body 1 , in turn connected to a lithium ion battery.

The threaded surface 10 of the tubular body 1 was screwed to a cylinder for containing the extinguishing gas, having a capacity of 200 litres, equipped with a suction tube.

The suction tube was in turn connected to said filling port 12.

Through said filling port 12, the assembly consisting of the cylinder with cylinder and the valve 100 was filled with 100 kg of extinguishing agent FK 5-1 -12, pressurised with nitrogen up to a pressure of 30 bar at 21 °C.

The threaded portion 1 T of the outlet 1 1 was in turn connected to a pipe with a diameter of 6.35 cm and a length of 10 m, which simulates the route of the pipes of a fire-extinguishing system.

Finally, inside the tubular body 1 , in particular through further inlets, the analogue pressure gauge and the safety disc calibrated at a pressure of 40 bar (4 10 ⁶ Pa) were respectively applied.

Once electrical energy was supplied to the heating means 3, these reached a temperature of 500 °C in approximately 75 milliseconds, causing the mechanical degradation of the rupture disc 2 and therefore its opening, making the extinguishing agent FK 5-1 -12 flow out inside the pipe.

The preferred embodiments have been described above and variants to the invention have been suggested, but it shall be understood that the invention may be modified and/or adapted by experts in the field without thereby departing from the scope of the inventive concept, as defined in the claims herein.