A DEVICE SUITABLE FOR PREVENTING AND INTERCEPTING GAS

LEAKS

Technical field

The present invention concerns the technical field relative to safety devices that manage eventual gas leaks in plants.

In particular, the invention refers to an innovative safety device suitable for preventing and eventually blocking a gas leak deriving from a damaged civil or industrial plant.

Background art

Gas plants have ^' been known for decades and are widely used in ^' civil and industrial environments. In civil environments a gas plant is for example used for heating (gas stoves, burners, etc.) or for kitchens (hobs and ovens). In industries the applications are many, for example for gas welding.

In all cases there is a gas source, for example a gas bottle, that is connected to a gas conduit. The gas, in exit from the conduit, terminates in a burner or other instrument that triggers the lighting of the flame. The flame is therefore fed continuously through the gas that is provided.

In accordance with such a known art, unfortunately, it is known that there is a high risk and a high level of accidents, especially in domestic environments. Such types of accidents often have terrible causes, with explosions capable of making an entire neighborhood blow in the air. It is not rare to hear of cases of explosions or fires in civil environments due to gas leaks and that cause the death of many people. Last but not least, even if less frequent, there are also cases of death by asphyxia, especially during sleep hours.

Especially in kitchen gas plants of civil environments a connection of the pipes to the source gas (for example the gas bottle) is used with traditional bands that risk to damage the pipe. Moreover, although the use of certified pipes is mandatory, this does not exclude the risk of breakages and leaks.

There exist aid devices, for example the so-called electronic noses, which are particularly suitable for detecting an actual gas leak but not for preventing it. A specific electronics is in fact capable of detecting the presence of gas in the surrounding environment. Nevertheless, due to dust or dirt in general, such apparatus lose efficiency in time and result completely malfunctioning if regular maintenance is not performed.

Moreover, if such devices are useful to save a person from asphyxia, they are not completely sufficient to guarantee safety with regard to explosions. The electronic nose could in fact detect and indicate (for example through an acoustic signal or a phone text message) the gas leak when the quantity of gas in the air is sufficient to produce a dangerous accidental explosion. Further, they are structurally complex apparatuses and for this reason they are expensive, so they are not affordable for everyone.

In order to solve said technical problems, alternative solutions have been proposed.

One of these solutions is for example described in publication US2003/0037596.

Such a publication describes a device constituted by two coaxial pipes and with the space comprised between said two coaxial pipes filled with a polyurethane foam. In the central pipe the gas runs, while in the space defined by the circular crown a further small pipe is placed that runs longitudinally along the length of the circular crown and is trapped into the polyurethane foam. Such a small pipe is provided, along its length, with a series of opening holes. The small pipe is then connected to an aspiration system that creates a vacuum or depression state inside said small pipe. An apparatus for verifying the presence of gas connected to said small pipe as well is also foreseen.

In case there are gas leaks in the central conduit, due for example to a hole in the pipe, the gas exits from said conduit and circulates into the polyurethane foam to be then aspired by the small pipe previously placed into the crown through its holes placed along its length. In such a manner, the specific sensor can detect the presence of gas and therefore a leak due to the breakage of the central pipe.

This solution has the advantage of detecting the leak much before with respect to the use of a normal electronic nose placed in a pre-determined point in the environment. Nevertheless, it is certainly more complex since it requires not just the presence of an electronic nose, but also the presence of three pipelines and of which one of these is connected to said nose dedicated to detect the presence of gas. Further, it is necessary to fill the circular crown with a filler that allows the outflow of gas and into which at the same time the small aspiration pipe is trapped. The position of the small aspiration pipe has to vary according to the type of gas circulating in the central conduit since, according to the gas, there could be a flow circulating in one sense or in the opposite sense.

This solution, therefore, is not only complex but also poorly versatile and has to be adapted to the gases that are used. Moreover, in case of accidental breakdown of the sensor dedicated to recognize the presence of the gas, such a device results totally inefficient.

It is therefore felt the need for devices that are particularly simpler structurally, versatile and highly reliable, therefore not related to sensors of the electronic type dedicated to the recognition of the presence of gas and suitable to recognize a . gas leak immediately .

An example of such a solution is described in international publication WO83/02991.

This solution is diametrically opposed to the preceding ones described since it does not use any electronic device of recognition of the gas. In particular, it describes a device for the prevention of gas leaks that foresees the use of a valve element through which the gas flow is allowed/impeded. The valve element is therefore mobile between an open position in which it allows the passage of the gas flow and a close position (therefore a safety position) in which it interrupts the passage of the gas. The open/close system of the valve is controlled through a mobile stalk that is pushed in the close position by a spring. The device comprises a double pipe, that is an internal pipe inside of which the main gas runs and a coaxial external pipe that covers the internal conduit. The external pipe and the internal pipe form a circular crown free of materials and inside of which a control gas is arranged at a pre-determined pressure. Such a circular crown is then communicating with a chamber where the spring is arranged through a mobile septum on which said spring rests.

This solution is therefore diametrically opposed with respect to US2003/0037596 since there is no filler present anymore into the circular crown or a further small aspiration pipe present into said crown. On the contrary, the circular crown is free and is subject to a control pressure through a gas in pressure.

The control of the opening/closure of the valve is therefore operated through the same control gas placed in the circular crown that acts on the septum to which the spring is fixed.

In normal operative conditions the pressure of the control gas pushes the septum towards the top, compressing the spring and therefore pushing the stalk in an open position that allows the normal outflow of the gas running in the central conduit through the valve.

As soon as there is a physical damage to the pipes (internal and/or external) there is a sudden fall of the control gas pressure and therefore a sudden fall of the pressure acting on the septum. In that sense, the spring beats the push force of the control gas acting on the septum and pushes the stalk in close position, thus interrupting the outflow of gas.

This solution, in a very simple way, allows the closure of the passage of the gas, without the need for sensors that can determine the presence of leaks.

Many other documents similar in the functioning are known, among which for example DE20110758, DE2911815, and BE627544. All these documents discuss solutions of devices in which there is a double coaxial pipeline with a control gas placed in the circular crown at a pre-determined pressure (superior or inferior with respect to the pressure with which the gas circulates in the central conduit or with respect to the external atmospheric pressure) . The breakage of the pipe implies a variation of pressure that, according to the case, controls a mechanical operation of a stalk, which moves in close position of the valve. Nevertheless, even if such devices result functioning, they are not exempt from defects.

The use of a control gas at a pre-determined pressure can create different technical inconveniences that can even harm the correct functionality of the device on the whole and result very dangerous .

In particular, the use of a control gas implies, in case for example of breakage of the internal conduit, a mix between the control gas itself and the gas that runs through the main conduit. Such a mix could for example result unstable and of an explosive nature, especially in the case the control gas used is air. It is in fact known that precisely the combination of some gases with the air is the cause of the formation of explosive mixes.

Also the use of inert gases, nevertheless, does not reduce pre-determined risks.

For example, in case of a hole in the internal conduit there is an interpenetration of the inert gas into the conduit where the main gas circulates that, for example, can feed a flame. The inert gas obviously is not combustible and its mix into the main conduit can create inert gas bubbles that could cause the extinction of the flame before the pressure fall reaches the threshold value that determines the closure of the valve. It is in fact clear that the pressure fall is progressive and can take also several seconds. In this lapse of time, before the intervention of closure of the valve, the inert gas bubbles could supervene the flame, causing the extinction thereof and therefore causing a free exit of the gas until the moment in which there is the reaching of the pressure condition that determines the closure of the valve. Even if the quantities of gas freed in the environment are not high, this is anyway a risk condition that has to be avoided. It is clear that with pipes long even hundreds of meters the quantity of gas that can be potentially emanated in such a situation becomes much more consistent and therefore dangerous.

Last but not least, the reactivity of closure of the valve through a gas in over-pressure or under-pressure is not high and a certain lapse of time is always required before the valve goes in close condition.

Disclosure of invention

It is therefore the aim of the present invention to provide a safety device to prevent and detect gas leaks that solves at least in part said technical inconveniences .

In particular, it is the aim of the present invention to provide an innovative safety device that is capable not only of blocking an actual leak but also of preventing it, impeding completely the exit of the gas.

It is therefore the aim of the present invention to provide a device structured to intervene when there is a structural damage, but before such a damage causes a significant gas leak in the environment.

It is also the aim of the present invention to provide a device that results structurally simple, therefore economical and easy to install, which does not require frequent maintenance or results alterable in time by dust or other residues present in the air.

It is also the aim of the present invention to provide a device that results not only functional but also reactive and safe, annulling any risk of accidental explosion and/or that reduces to the minimum the risk of gas leaks also in the lapse of time necessary so that such a device enters in action interrupting the outflow of the gas .

These and other aims are therefore reached with the present device for preventing and/or interrupting gas leaks, in accordance with claim 1.

Such a device (1) comprises:

- A conduit (4', 4'') for the circulation of a gas and;

- Valve means (3) comprising opening/closing means (11, 12, 13, 15, 16; 211, 212) , mobile between an open position, to allow the circulation of the gas in the conduit (4', 4''), and a close position, to interrupt said circulation in the conduit (4', 4'');

In accordance with the invention, the conduit (4', 4'') forms an internal channel (300) which is in fluid communication with the valve means (3) in such a way as to make the gas outflow when said opening/closing means are in open position.

Therefore, in normal operative conditions, that is with the valve means open, there is a normal outflow of gas through the device described.

In addition, it is also foreseen an external chamber (600) that wraps the internal conduit (300) for at least a part of its entire length, the external chamber being placed at a pre-determined control pressure value ( P ) , obviously internal to the chamber 600, for example filling the chamber 600 with air, other gas or the vacuum (therefore zero pressure with respect to the acting external pressure) .

The external wrapping formed by the external chamber creates a protection of the internal conduit where the gas runs .

In order to prevent a leak, the external chamber (600) results placed in fluid communication with the opening/closing means (11, 12, 13, 15, 16) which are configured in such a way as to assume an open or close position on the basis of a specific control pressure value ( P ) acting on them through said fluid communication with the external chamber.

In accordance with the invention the creation of a vacuum condition into the external chamber (600) is therefore foreseen. In that sense, the open/close means are therefore configured to remain in open position in correspondence of the creation and the maintenance of said vacuum condition in the external chamber (600) and switch to close position in correspondence of a variation of said vacuum condition, in particular an increase in the pressure .

The opening/closing means are therefore set in such a way as to remain in open condition when the control pressure in the external chamber is the one originally set, that is vacuum condition. In case of damage of the external chamber, for example a hole, there is a variation of pressure, in particular an increase in the pressure control. For example, the opening of a hole in the internal conduit allows the inlet of the circulating gas in the chamber 600 with a sudden increase in the pressure. Likewise, a hole on the external conduit puts in communication the chamber 600 with the external environment (atmospheric pressure) , determining a sudden increase in pressure also in this case.

The increase in pressure, that is the deviation from the vacuum condition, takes to a closure of the opening/closing means.

Said opening/closing means are therefore set in such a way as to be positioned in a close condition, obstructing the passage of the gas towards the internal conduit 300, as soon as a control pressure variation is detected with respect to the pre-set original value, in particular an increase in the pressure with respect to the vacuum condition initially set.

The use of the vacuum into the chamber 600 (therefore the absence of any gas, including air) solves all said technical inconveniences.

In particular, a vacuum condition annuls totally the risks of potentially dangerous mixes between circulating gas and control gas, mixes that could precisely cause accidental explosions, especially if the control gas is air .

By creating the vacuum into the external chamber (600) there is not the risk anymore of formation of inert gas bubbles that could take to the extinction of the flame in the lapse of time necessary for the valve to close.

Further, the vacuum condition, in the case of breakages, results to be extremely more reactive than in the case of use of gas at pre-determined pressures. In that sense, the time necessary for the valve to perceive an increase in pressure in the control chamber 600 is certainly much lower with respect to the case of use of gas in over or under-pressure . In that sense, this solution results above all much more reactive.

The external chamber 600, by wrapping the internal pipe for almost all or all its length, in fact forms a protective sheath which, almost certainly, will be damaged before the internal pipe will. The pressure variation, in such a way, allows to modify the position of the opening/closing means from an open position into a close position before an actual gas leak takes place, therefore preventing a potential damage.

In this way, all said technical inconveniences are solved since, in a simple and functional manner, it is possible to obtain not only the interruption but even the prevention of leaks with a device that does not require particular maintenance and is not subject to malfunctioning due to dust or other residues.

Further advantages can be deduced from the dependent claims .

Brief description of drawings

Further features and advantages of the present device, according to the invention, will result clearer with the following description of some embodiments, made to illustrate but not to limit, with reference to the annexed drawings, wherein:

- Figure 1 shows a view in an overall section of a gas plant comprising the safety device in accordance with the invention in a configuration that allows the normal circulation of the gas;

- Figure 2 shows a view in section of the valve used for the interruption of the circulation of the gas represented in an open configuration;

- Figure 3 shows a view in section of the plant of figure 1 but in a close configuration;

- Figure 4 shows a view in section of the single valve in a close configuration;

- Figures from 5 to 8 represent a variant of the invention in which the pipes of the device work in vacuum conditions ;

- Figures 9 and 10 show a further variant in which the system of aspiration to create the vacuum is integrated in the valve body.

Description of a preferred embodiment

Figure 1 describes in section a plant 1 in accordance with the present invention. The plant naturally foresees a gas source 100, for example in the shape of a gas bottle, and a burning device 200 from which the flame emanates as a consequence of the combustion of the gas (for example the cooker of a kitchen or the burner of a stove) .

The plant therefore comprises a safety device 2 which is formed by a valve element 3 and a conduit 4 that connects the valve element to the burner 200. The valve element, naturally, is placed between the conduit 4 and the gas source 100 in order to interrupt, if necessary, the passage of the gas.

As therefore shown in the enlarged view of figure 2, the conduit 4 making part of the present safety device foresees a circular external sheath 4' and a circular internal sheath 4'' of inferior diameter with respect to the external sheath and positioned coaxially to the external sheath. In such a manner, a circular crown is formed that forms a watertight close chamber 600 which wraps an internal conduit 300 where the gas circulates. In particular, the space interposed between the external sheath 4' and the internal sheath 4'' forms a chamber 600 in which a fluid 500 is present at a pre-determined control pressure value (P) . The circular section formed by the internal sheath 4'' forms in fact the normal conduit 300 in which the gas coming from the source runs.

The chamber 600, composed by the space delimited by the external sheath and the internal sheath, runs preferably for all or almost all the length of the internal sheath 4'' and, as shown in figure 1, terminates on the burner in such a way as to connect to it in a watertight-like manner (that is without pressure losses) . As a matter of fact, the fluid 500 contained does not have a way to be dispersed and its internal pressure remains always constant.

As clarified below, the advantage of having an external sheath that runs substantially for all the length of the internal sheath is that such a device is capable of preventing the leaks since the chamber that is formed forms a sort of external protection for the pipe into which the gas runs.

As shown in figure 2, the conduit 4 foresees a ramification 5 that puts in fluid communication the chamber 600 and the valve element 3. In such a manner, the fluid in pressure that is stored in the circular crown formed by the external sheath 4' and the internal sheath A'' further flows to the valve element 3. In fact, therefore, a single continuous chamber 600 is formed, formed not only by the rectilinear part between external and internal sheath (circular crown), but also by the ramification 5 and by the space 10 (chamber 10) at the head of the valve element.

The valve element operates between an open position, in which it allows the passage of the gas coming from the source along the conduit 4, precisely along the conduit 300 formed by the internal sheath 4'', and a close position in which it impedes such a passage. The control between the open or close positions is made through the fluid 500 stored in the circular crown comprised between the two sheaths 4'' and 4', that is in the chamber 600 and more precisely through the internal control pressure to which it is exposed.

To that aim, the valve element comprises the chamber 10 communicating with the conduit 5 and, for that reason, where the fluid 500 in pressure is present. The fluid pressure is calibrated in such a way as to push on a piston 11 which, through a spring 12, moves a lock 13. The lock 13 is integral to the piston 11, therefore it follows the motion of the piston itself. The lock, further, is guided in its rectilinear translation motion through a circular channel obtained in a fixed support 15, obviously inside the valve element. The lock terminates with a needle 16 which, according to its position, obstructs or frees the passage of the gas obtained always into the valve element. The passage for the gas, from the source to the conduit 300, is formed by the parts 20, 30, 40 internal to the valve element.

The spring 12 is a compression spring calibrated on the basis of the pressure selected of the fluid 500 (for example air or other gas) .

As indicated in figure 2, the arrow addressed towards the bottom on the piston represents the pressure exerted by the gas in the chamber 600 on the piston 11. Such a pressure is selected in such a way so that the spring 12 compresses of such a quantity that the needle 16 frees the passage 20, 30, 40 towards the conduit 300.

In use, therefore, when there is a sufficient pressure value of the fluid stored in the chamber 600, the piston 11 beats the force of the spring and translates in a position towards the support 15, thus compressing the spring. The conformation of the lock is such that, in this position frees the passage for the gas, that is frees the path (20, 30, 40) . The lock has in fact the shape of a needle with a narrow part which does not obstruct the throat of passage of the gas in the part 30, and a widened part that instead obstructs the throat 30 as per figure 4. When there is a pressure variation, in this case a pressure fall in the chamber 600, then there is a pressure reduction in the chamber 10 and the spring takes the piston 11 back in lifted position, beating the residue pressure acting on the piston 11. Consequently, the needle 13 goes back to the lifted position, obstructing the passage, that is obstructing the throat 30 and interrupting the passage of the gas as per figure 4.

As schematically shown in figure 3, the sudden pressure fall of the fluid stored in the chamber 600 cannot exist if not as a consequence of a damage present on the external sheath 4', so the closure of the circulation of the gas is obtained already before a real and true gas leak can take place. Such a system is therefore efficiently preventive since, foreseeing two coaxial conduits, it foresees a closure of circulation of the gas as soon as a damage is present on the external sheath. The gas stored in the chamber (obviously innocuous gas for human health, like air) serves to control the damage and collaborates with the valve that operates the closure on the basis of a leak thereof, that is a pressure fall.

From here it. is clear that, naturally, the more the internal sheath is covered by the external sheath along its length, the greater is the protection that is obtained. The system would also be efficient with an external sheath 4' that runs only for a part of the length of the internal sheath but this would increase the statistical risk of a damage present on the internal sheath in the part that is not covered by the external sheath .

The system works efficiently also in the case of an initial hole in the single internal sheath 4'' since the fluid pressure 500 into the chamber 600 can be calibrated in such a way as to be superior to the pressure of circulation of the gas into the conduit 300. In this way there is an interpenetration of the fluid 600 into the conduit of the gas 300 in case of damage and therefore, as in the preceding case, there is anyway a pressure fall that controls in closure the valve.

A trenching of both the sheaths, naturally, causes a pressure fall anyway and therefore always the closure of the valve, even if in this case a minimum gas leak in the environment would be present and inevitable. In any case, the interruption of the feeding of gas would be immediate and obviously much faster than in the case in which electronic noses are used and that require a certain quantity of gas in the environment before they detect the gas and intervene. It is also to be considered that the electronic noses, in very wide environments, diminish their efficiency if they are not placed correctly in strategic positions.

A further variant of the invention is shown in figures from 5 to 8.

In this case, remaining as it is all that has already been said, the fluid 500 into the chamber 600 is substituted by the vacuum and therefore with a valve system that. works in the inverse sense with respect to the preceding case. Naturally, being the control pressure null into the chamber 600, the pipe has to have a certain rigidity so as not to collapse totally under the action of the atmospheric external pressure acting on it.

In this case, as shown in figure 6, the valve is open since the spring 212 (of compression) keeps the needle in lifted position.

At the moment of a damage, that is of a hole in the external sheath, there is a sudden increase in pressure in the chamber 600 and therefore, as shown in figure 8, there is a force that acts on the piston 211 directed towards the bottom and that pushes the lock in a closing position, beating the force of the spring.

The condition of vacuum into the chamber 600 can be obtained in many equivalent ways.

For example, a system of aspiration can be foreseen that connects in a pre-determined point of the external conduit and that aspirates the air inside it up to create a vacuum condition. The external conduit can therefore foresee a specific attachment to which to connect such an aspiration device.

It can also be foreseen an internal valve so that, when the device detaches once the vacuum has been created, the valve is configured in close position impeding the inlet of air and keeping such a vacuum condition.

Another solution is described with reference to figures 9 and 10.

In that case, the system that generates the vacuum is integrated in the body of the valve itself.

The same components will be indicated with the same numbering .

Figure 9 shows an opening condition of the valve so that the gas can freely outflow along the conduit 300 since the lock component 313 is in lifted position and allows the free outflow of the gas through the passage (20, 30, 40) .

The figure shows the same interspace 600 formed by the two coaxial pipes, where the vacuum is created, and which channels into the valve body through the conduit 50 in such a way as to be placed in communication with the lock 313.

In this way the system, as also in the preceding case, is configured in such a way that the lock 313 remains in open position ^, if the vacuum condition is kept to then switch right afterwards into close position if the vacuum condition is altered (that is there is an increase in pressure ) .

In this case, to the classical lock 313 a system for the realization of the vacuum right afterwards described is coupled.

As it can be understood from figure 10 (and equally from figure 9) , a flexible membrane element 316 is foreseen, for example a deformable sheet in rubber, connected to the lock 313 in such a way as to define a chamber 314 that on one side is communicating with the conduit 50 and on the other side is communicating with an overlying chamber 319 through a hole 318. A separating septum 405, fixed, separates the chamber 319 from the chamber 314, the two chambers being between them in fluid communication through the hole 318.

The lock has a compression spring 406 that on one side is fixed to the septum 405 and on the opposite side is fixed to the surface of the lock.

The lock is therefore mounted in a translatable way into its chamber 314 with a stop that is obviously limited superiorly by the compression of the spring 406 and interiorly by the position that brings the lock in position of closure of the valve.

The alternate translation motion can be manually realized through a pivot 515 that brings a stalk 516 that is in contrast against the lock.

A spring 517 tends to take the stalk 516 back in a detached position from the lock (see figure 10).

The chamber 319 foresees a fixed stalk 543 on which a spring 544 is mounted coaxially that pushes a block 545 that closes the opening 318. The chamber 319 has a vent hole 321 in contact with the exterior.

The system works in the following way.

Through an alternate movement of the pivot 515, as of double direction of arrow of figure 9, an alternate motion of the lock is realized that from the close position of figure 10 is taken to the open position of figure 9 and vice-versa.

In particular, switching 'from the position of figure 10 to that of figure 9, the lock reduces the volume of the chamber 314 into which it is inserted and pushes the air both in its chamber 314 and in the chamber 600 with which the chamber 314 is placed in communication. Such air is pushed in pressure through the hole _. 318, causing the lifting of the block 545 ad the compression of the spring 544 to which the block 545 is connected.

In this way, as per figure 9, the passage 318 opens and the air is removed from the chamber 314 to outflow outside through the hole 312 of the chamber 319.

When the spring 517 takes the pivot 515 back in lowered position, the lock 313 tends to go back towards i the close position of the valve (position of figure 10) pushed by the action of the compression spring 406 to which it is connected. Contextually, the compression spring 544 pushes the block 545 in close position of the opening 318 in such a way that during said return motion

) the lock does not cause an aspiration of air into its chamber 314.

Going on with this operation for a certain number of times, progressively the total or almost total exit of air from the chamber 314 and from the interspace 600 will take

< place, creating in fact a vacuum condition. Once said vacuum condition has been reached, the depression in the chamber 314 will beat the force of the spring 406, keeping the lock in open position, while the spring 517 will take the stalk in lowered position, becoming spaced from the

I lock.

The user will have the feeling of reaching such a condition since the action on the pivot 515 will take place without presenting the due resistance, because the pivot does not push anymore on the lock that has remained bound in the open position.

A sudden increase in pressure, for example due to a hole in the external or internal sheath, will permit the spring to take the lock back in close position since the vacuum condition will be altered.

It is clear that the spring 406 can be calibrated at different values in such a way as to set on the basis of it different vacuum values (in the sense of values next to the zero pressure value) .

The pivot 315 can be operated manually or mechanically in an automatic way through a specific machinery .

In the present description with the term vacuum it is intended not just pressure value equal exactly to zero but also pressure values that are next to the zero value.