Rainproof flame arrester block

Abstract

A flame arrester block (230) is provided, comprising a plurality of first plates (305) each having an external perimeter and at least one opening in a region inside the external perimeter, the first plates (305) of said plurality being stacked on each other starting from a lower first plate of said plurality of first plates to an upper first plate of said plurality of first plates according to a stacking direction (X) with the openings of said first plates which are at least partially superimposed on each other so as to form a stack of plates defining an internal hollow space (402), said first plates (305) being mutually spaced along said stacking direction (X) so as to define, between adjacent plates in the stack of plates, a corresponding gap transversal to said stacking direction (X). The flame arrester block further comprises a closure plate (310) stacked above said upper first plate along said stacking direction (X), and a dam plate (380) defining together with a first plate (305) above said dam plate (380) along the stacking direction (X) a corresponding further gap, said dam plate (380) having an external perimeter and at least an opening (450) in a region inside the external perimeter of the dam plate, said opening (450) of the dam plate (380) being delimited by a barrier portion (385) of the dam plate which extends along the stacking direction (X) towards the closure plate (310), said barrier portion (385) being configured to confine liquid leaking into the internal hollow space (402) through said gap between adjacent plates, said dam plate (380) being configured to cause liquid confined by the barrier portion (385) be drained toward the outside of the flame arrester block (230) through said further gap.

Description

Technological background of the inventionTechnical Field of the invention

[0001] The present invention generally relates to devices for the protection against the propagation of flames in the presence of explosions and / or detonations caused by any source of ignition. Such protection devices are also known as flame arresters (or flame arrestors) or deflagration arresters or flame traps. In particular, the present invention relates to a rainproof flame arrester.Brief overview of the state of the art

[0002] Flame arresters are devices whose purpose is to extinguish the propagation of flames, for example in the presence of deflagration or detonation, generated by any cause of ignition.

[0003] Flame arresters are used as protection devices in various application fields, for example in the petrochemical, chemical, pharmaceutical industry fields, and, more generally, wherever in the presence of potentially explosive atmospheres.

[0004] A flame arrester is a device that, while stopping the propagation of flames, allows the passage of fluids (liquid or gases).

[0005] The operating principle on which flame arresters are based is the extinction of the combustion ("fire quenching" or "combustion quenching") due to the transfer of heat from the flame to a body of thermally conductive solid material at a lower temperature. This transfer of heat is made more efficient by forming, in the body of solid material, several narrow passages, through which the flame is forced to pass.

[0006] One type of commonly used flame arrester is called "Crimped Metal Ribbon" or CMR. A CMR flame arrester includes one or more flame arrester elements, each composed of layers of smooth and corrugated thin metal sheets alternated to each other, for example arranged in a generally coaxial way with a central mandrel to form a multilayer cylindrical body, the whole assembly being for example enclosed within an outer jacket. The spaces created between the corrugations of the corrugated metal sheets and the adjacent smooth metal sheets define a plurality of passages or channels for the fluid. Such passages, for example of approximately triangular section, extend generally parallel to the axis of the cylindrical body (or with a limited angle of inclination relative to the axis of the cylindrical body).

[0007] A CMR flame arrester is for example described in WO 94 / 00197.

[0008] Another type of flame arrester comprises a plurality of, e.g. metallic, plates, for example annulus-shaped, being coaxially stacked on each other and tightened to form a pack with an upper disc-shaped closure plate. The annulus-shaped plates and the closure plate are kept properly spaced apart from each other by means of corresponding spacers so as to define a plurality of radial passages or channels for the fluids.

[0009] A flame arrester of this type is for example described in EP 3082980.

[0010] When a flame arrester is mounted at an end of a vent duct of a tank intended to contain a flammable liquid, water generated by weather events, such as rain or snow, may disadvantageously penetrate inside the tank through the passages or channels for the fluids of the flame arrester.

[0011] For this reason, it is recommended to provide the flame arresters that are exposed to the external environment with an element adapted to act as protection against water infiltrations.

[0012] For example, a proper cover (rain cover) may be mounted above the flame arrester in such a way to intercept the rain before it reaches the passages or channels for the fluids of the flame arrester.

[0013] DE942916 discloses a protection device against flames and explosions for combustible liquid containers. The protection device comprises a plurality of stacked hollow conical elements covered by a hood element.

[0014] WO2020011881 discloses an explosion protection valve to be mounted to a wall opening of a closed working space. A first end face forming a first sealing area and a second, opposite end face forming a second sealing area are provided on a sealing element. In the closed state of the explosion protection valve, a valve plate contacts the first end face in a sealing manner and the second end face is exposed at least in part, in order, in the assembled state of the explosion protection valve, to contact the wall directly in a sealing manner or a fastening flange arranged on the wall. An inner, continuous sealing inner peripheral area is provided on the sealing element which connects the first end face and the second end face. The sealing element, having an outer sealing outer peripheral area, opposite the sealing inner peripheral area, which connects the first end face and the second end face, is arranged on the valve seat element. The sealing inner peripheral area peripherally delimits the valve seat opening.

[0015] GB 2549784 discloses a flame arrester which includes a stack of spaced plates which include an end plate and a plurality of intermediate plates, a first flow passage defined at least in part by an aperture in each intermediate plate and a second flow passage defined between adjacent plates. At least a portion of the periphery of the intermediate plates tapers.

[0016] US3903646A discloses a flame arrestor for the air intake of an internal combustion engine having improved resistance to the ingress of moisture into the air intake and including a plurality of arcuate fin elements which have a generally inverted V-shaped cross secton and which are stacked in vertically spaced relationship to form an annular assembly, a base having a barrel section adapted to be received by the air intake and an annular ledge extending radially from the barrel section for supporting the fin element assembly, and a cover overlying the fin element assembly and the base. The cover includes an outer portion which extends radially beyond the outer edges of the fin elements and the base to prevent impingement of water draining from the cover onto the fin elements. Moisture collecting on the base ledge is prevented from draining into the air intake by an integral annular raised portion which is located adjacent to the inside edges of the bottommost fin elements to act as a barrier or dam. One or more openings are provided in the outer perimeter of the ledge to afford overboard drainage of moisture from the ledge and the fin elements.Summary of the Invention

[0017] The Applicant observed that the known solutions providing for using a rain cover mounted above the flame arrester, such as the hood element disclosed in DE942916, are not efficient for the following reasons.

[0018] First of all, the presence itself of an additional element (the rain cover) implies a cost increase.

[0019] In order to be effective, the rain cover should be sufficiently large to cover the exposed upper portion of the flame arrester, implying a further increase of the volumes.

[0020] Moreover, since flame arresters require a continuous maintenance, providing for cleaning the passages or channels for the fluids of the flame arrester, such rain cover should be unmounted / mounted from / to the flame arrester at each cleaning operation.

[0021] The applicant has also noticed that although the presence of an upper disc-shaped closure plate in the flame arresters comprising stacked annulus-shaped plates (such as in the flame arrester described in EP 3082980) can intercept rain, water infiltration through the passages or channels for the fluids between the plates may however occurs because of capillarity.

[0022] This drawback of water infiltration for capillarity affects also the solutions disclosed in DE942916, WO2020011881, GB 2549784.

[0023] In the solution disclosed in DE942916, water leaking for capillarity through the passages between adjacent hollow conical elements may easily reach the internal hollow space of the protection device, and then flow outside the protection device through the central bottom opening of the latter, reaching the underlying liquid container.

[0024] In the solution disclosed in WO2020011881, water leaking for capillarity through the passages between adjacent metal plates may easily reach the internal portion of the valve seat, possibly reach the continuous sealing inner peripheral area delimiting the valve seat opening, and then flow down into the underlying working space.

[0025] In the solution disclosed in GB 2549784, water leaking for capillarity through the passages between adjacent plates may easily reach the inner hollow space of the flame arrester defined by the central apertures of the stacked plates and then flow outside the flame arrester from the central aperture of the bottom plate of the stack, reaching the underlying container the flame arrester is attached to.

[0026] The applicant has therefore faced the problem of solving these and other drawbacks of the state of the art.

[0027] The invention is defined by the appended claims. According to an embodiment of the present invention, a flame arrester block is provided.

[0028] The flame arrester block comprises a plurality of first plates each having an external perimeter and at least one opening in a region inside the external perimeter.

[0029] The first plates of said plurality are stacked on each other starting from a lower first plate of said plurality of first plates to an upper first plate of said plurality of first plates according to a stacking direction with the openings of said first plates which are at least partially superimposed on each other so as to form a stack of plates defining an internal hollow space.

[0030] Said first plates are mutually spaced along said stacking direction so as to define, between adjacent plates in the stack of plates, a corresponding gap transversal to said stacking direction.

[0031] The flame arrester block comprises a closure plate stacked above said upper first plate along said stacking direction.

[0032] The flame arrester block comprises a dam plate defining together with a first plate above said dam plate along the stacking direction (X) a corresponding further gap.

[0033] Said dam plate has an external perimeter and at least an opening in a region inside the external perimeter of the dam plate.

[0034] Said opening of the dam plate is delimited by a barrier portion of the dam plate which extends along the stacking direction towards the closure plate.

[0035] Said barrier portion is configured to confine liquid leaking into the internal hollow space through said gap between adjacent plates.

[0036] Said dam plate is configured to cause liquid confined by the barrier portion be drained toward the outside of the flame arrester block through said further gap.

[0037] According to an embodiment of the present invention, the barrier portion of said dam plate comprises one of: a portion curved towards the closure plate, a vertical wall extending towards the closure plate, and a linear ramp extending towards the closure plate.

[0038] According to an embodiment of the present invention, each one of said first plates extends along a plane substantially perpendicular to the stacking direction.

[0039] According to an embodiment of the present invention, the dam plate comprises a peripheral portion between the external perimeter and the barrier portion, said peripheral portion extending along a plane substantially perpendicular to the stacking direction.

[0040] According to an embodiment of the present invention, each of said first plates has the shape of a quadrangular frame, particularly square or rectangular or rhomboidal, an ellipsoidal frame, a star-shaped frame, a quadrangular with lobes frame, or has an annulus shape.

[0041] According to an embodiment of the present invention, said dam plate has a shape corresponding to the shape of said first plates.

[0042] According to an embodiment of the present invention, each of said first plates and said dam plate have an annulus shape.

[0043] According to an embodiment of the present invention, each first plate has an internal radius greater than a inner radius of the dam plate.

[0044] According to an embodiment of the present invention, said dam plate is located below said lower first plate according to said stacking direction.

[0045] According to an embodiment of the present invention, said at least one first plate and said dam plate are tightened to form a pack.

[0046] According to an embodiment of the present invention, the flame arrester block comprises at least one further dam plate.

[0047] According to an embodiment of the present invention, each of said at least one further dam plate is positioned between a corresponding pair of first plates in the stack of plates.

[0048] Another aspect of the present invention provides for a protection device against flames and / or explosions, comprising at least one flame arrester.Brief description of the appended drawings

[0049] These and other features and advantages of the present invention will be made apparent by the following detailed description of possible exemplifying and not restrictive embodiments of the present invention, description that will be carried out referring to the accompanying drawings. In the drawings: Figure 1 schematizes a possible application of a flame arrester block according to an embodiment of the solution proposed in the present invention; Figure 2 shows, partly in section, an end-of-line protection device with a flame arrester block according to an embodiment of the present invention; Figure 3 shows, in section, a detail of the flame arrester block of Figure 2; Figures 4 and 5 show, respectively, in plan view from below and in section, a part of the flame arrester block of Figure 2; Figure 6 shows, in section, a detail of the flame arrester block according to a further embodiment of the present invention. Detailed description of exemplary embodiments of the invention

[0050] With reference to the drawings, sharing the same reference system identified by the three orthogonal directions X, Y, Z, Figure 1 schematically shows a possible application of a flame arrester block according to an embodiment of the present invention.

[0051] Reference 105 indicates a reservoir, for example a tank of a petrochemical plant (or a chemical plant, a pharmaceutical plant, etc.). The tank 105 is intended to contain a flammable liquid 110, for example oil (petroleum) or a liquid derived from petroleum refining, exhaling flammable vapours 115.

[0052] The tank 105 is provided with a vent duct 125 for venting the flammable vapours 115 which develop internally to the tank 105. At the end of the vent duct 125 an end-of-line protection device 130 is mounted, provided with a flame arrester block to stop the potential propagation of flames along the vent duct 125 and within the reservoir 105 in the presence of deflagrations that trigger the combustion of the flammable vapours 115, for example deflagrations triggered by electrical discharges, for example due to atmospheric events such as lightnings 135 from storm clouds.

[0053] Figure 2 shows, partly in section, the end-of-line protection device 130 of Figure 1 according to an embodiment of the present invention, according to a view parallel to directions X and Y. Figure 3 shows, in section, a detail of the flame arrester block equipped by the end-of-line protection device 130 of Figure 2 according to an embodiment of the present invention, according to view parallel to directions X and Y. Figure 4 shows the flame arrester block according to an embodiment of the present invention, according to a plan view from below parallel to directions Z and Y. Figure 5 shows a section of the flame arrester block according to an embodiment of the present invention, according to the section plane V - V parallel to directions X and Z shown in Figure 4.

[0054] The end-of-line protection device 130 of the embodiment of the invention of Figure 2 comprises a hollow body 205 having an inner hole whose longitudinal axis x, corresponding to the longitudinal axis of the end-of-line protection device 130, is parallel to direction X. The hollow body 205 comprises a first end flange 210 for mounting, for example, to the vent duct 125 shown in Figure 1. The hollow body 205 comprises, starting from the first end flange 210 and proceeding along a direction parallel to direction X, a first portion 215, for example substantially cylindrical, followed by a second portion 220, for example conical, terminating in a second end flange 225.

[0055] On the second end flange 225 there is mounted a flame arrester block 230 according to embodiments of the present invention.

[0056] The flame arrester block 230 comprises a plurality of plates 305, for example metallic plates, preferably made of carbon steel or stainless steel or special steel, for example having the shape of a circular crown (annulus shape), stacked along a direction parallel to the direction X, i.e., parallel to the longitudinal axis x of the end-of-line protection device 130, with the openings of each annulus-shaped plate 305 that are superimposed on each other.

[0057] Each annulus-shaped plate 305 extends along a plane substantially perpendicular to the longitudinal axis x of the end-of-line protection device 130, i.e., on a plane parallel to directions Y and Z. The annulus-shaped plates 305 are stacked on each other (along direction X) in such a way to define a substantially hollow cylinder structure, which defines an internal hollow space (identified in the figures with reference 402) extending along direction X with a longitudinal axis aligned with the longitudinal axis x of the end-of-line protection device 130.

[0058] Preferably, but not necessarily, the annulus-shaped plates 305 are of equal radius, both internal and external, in such a way to define an internal hollow space 402 having a substantially cylindrical shape, having a circular lower opening 403 having a radius corresponding to the internal radius of the annulus-shaped plates 305. In the case the annulus-shaped plates 305 do not have all a same internal radius, the size of the lower opening 403 of the internal hollow space 402 depends on the internal radius of the lowest annulus-shaped plate 305 of the stack of annulus-shaped plates 305.

[0059] The lower opening 403 of the internal hollow space 402 defined by the stack of plates 305 is configured to be superimposed on the internal hole of the hollow body 205 when the flame arrester block 230 is mounted to the second end flange 225 of the hollow body 205.

[0060] In the exemplary but not limitative embodiment of the invention illustrated in the figures, the internal radius of the annulus-shaped plates 305 is (slightly) larger than the internal radius of the second end flange 225, while the external radius of the annulus-shaped plates 305 corresponds to the external radius of the second end flange 225. The internal and external radiuses of the annulus-shaped plates 305 may be however different.

[0061] At the top (according to the orientation of Figure 2 and according to direction X), the flame arrester block 230 is closed by a closure plate 310 having the shape of a disc (or disk) having a radius preferably equal to the external radius of the annulus-shaped plates 305. The disc-shaped plate 310 too may be a metallic plate, preferably made of carbon steel or stainless steel or special steel.

[0062] The disc-shaped closure plate 310 and the annulus-shaped plates 305 are tightened to form a pack, at least the latter being properly spaced apart from each other by means of spacers 315, for example washers. For clamping in a pack the disc-shaped closure plate 310 and the annulus-shaped plates 305 with interposed the respective spacers 315, bolts or tie rods 320 may be used (as in the example shown), inserted in through holes 400 formed in circumferential succession and in corresponding positions: in the vicinity of the perimeter of the disc-shaped closure plate 310, in the vicinity of the external perimeter of the annulus-shaped plates 305, and advantageously in the second end flange 225.

[0063] The flame arrester block 230 thus formed gives rise to a plurality of radial passages for aeriform fluids (vapours or gases), said passages being transverse, for example substantially orthogonal, to the direction X, and being defined by the interspaces (gaps), created by the spacers 315, between the various pairs of adjacent annulus-shaped plates 305 (and possibly by the interspace between the last annulus-shaped plate 305 of the stack and the disc-shaped closure plate 310). In this way, the aeriform fluids (vapours or gases) coming from the tank, go back up crossing the internal hole of the hollow body 205, reach the internal hollow space 402 defined by the stack of annulus-shaped plates 305 through the lower opening 403, and go out in the external environment through said radial passages between the annulus-shaped plates 305.

[0064] The thickness of the spacers 305, and thus the distance between two adjacent annulus-shaped plates 305 (and, possibly, between the last annulus-shaped plate 305 of the stack and the disc-shaped closure plate 310), are designed such that a possible flame 330 that generates outside the flame arrester block 230 does not propagate inside the hollow body 205 thanks to the action of extinction ("quenching") determined by the transfer of heat from the flame to the plates 305, 310 of the flame arrester block 230.

[0065] By making reference to the figures, the thickness of the annulus-shaped plates 305 is identified with s, the distance between annulus-shaped plates 305 adjacent in the stack (and possibly the distance between the last annulus-shaped plate 305 of the stack and the disc-shaped closure plate 310) is identified with d, the width (to be intended as the difference between external radius and internal radius) of the annulus of each plate 305 is identified with L, the external radius of the annulus-shaped plates 305 is identified with R, and the internal radius of the annulus-shaped plates 305 is identified with r. In the embodiment of the invention, illustrated in the figures, the lower opening 403 of the internal hollow space 402 has a radius corresponding to the radius r of the annulus-shaped plates 305.

[0066] Such construction variables, together with the number N of the annulus-shaped plates 305 stacked to form the pack and the material of the annulus-shaped plates 305, have values that depend on the fluid of depends on the fluid of the specific application of interest and the operating conditions of the fluid itself in the considered application (for example, pressure and temperature inside the tank 105).

[0067] In particular, the distance between the adjacent annulus-shaped plates 305, and possibly between the last annulus-shaped plate 305 of the stack and the disc-shaped closure plate 310 may be of the order of magnitude of the value of the parameter known as MESG ("Maximum Experimental Safe Gap") related to the particular fluid of interest for the specific application from time to time considered. The MESG parameter is defined in ISO 16852, which is the reference standard for the test of flame arresters. For example, the reference standard establishes that the value of the MESG for class IIA fluids (e.g., propane) is 0.9 mm, the value of the MESG for class IIB3 fluids (e.g., ethylene) is 0.65 mm, and the value of the MESG for class IIC fluids (e.g., hydrogen) is 0.5 mm. Given the specific fluid of the application of interest, the distance between the adjacent annulus-shaped plates 305, and possibly between the last annulus-shaped plate 305 of the stack and the disc-shaped closure plate 405) is advantageously chosen so as to be less than or at most equal to the value of the MESG established by the standard for that fluid.

[0068] The number of annulus-shaped plates 305 to be stacked to form the flame arrester block 230 depends instead on the maximum acceptable pressure drop. By increasing the number of annulus-shaped plates 305 in the stack, the pressure drop decreases.

[0069] For example, using annulus-shaped first plates 305 having an internal radius r of 100 mm for a class IIA fluid, about 60 annulus-shaped plates 305 spaced apart by about 0.9 mm can be provided, if it is desired to have full flow, that is, without reduction of the flow section of the gas. By doubling the number of annulus-shaped plates 305, the pressure drop is halved.

[0070] According to an embodiment of the present invention, the flame arrester block 230 comprises one or more dam plates configured to avoid that water leaked - for example, for capillarity - into the internal hollow space 402 through the radial passaged between adjacent plates 305 may penetrate inside the hollow body 205, up to reaching the tank 105. In the example illustrated in Figures 2- 5, a single dam plate is provided, identified with reference 380.

[0071] According to an embodiment of the present invention the dam plate 380 is located in the lower portion of the flame arrester block 230, i.e., the portion thereof that is opposite - with respect the direction X - to the disc-shaped closure plate 310. According to an embodiment of the present invention, the dam plate 380 is located at the lower opening 403 of the internal hollow space 402.

[0072] According to an embodiment of the present invention illustrated in Figures 2 - 5, the dam plate 380 is located below - along direction X - the stack of plates 305.

[0073] According to an embodiment of the present invention, the dam plate 380 is positioned coaxial with the plates 305.

[0074] According to an embodiment of the present invention the dam plate 380 has an internal radius ra smaller than the internal radius r of the plates 305.

[0075] According to an embodiment of the present invention, the dam plate 380 comprises an internal opening 450 concentric with the lower opening 403 of the internal hollow space 420 defined by the stack of annulus-shaped plates 305, and having a lower amplitude.

[0076] In other words, the lower opening 403 of the internal hollow space 402 defined by the plates 305 entirely encircles, according to a plan view parallel to directions Z and Y, the internal opening 450 of the dam plate 380.

[0077] According to an embodiment of the present invention, the internal opening 450 of the dam plate 380 has a radius ra smaller than the radius r of said lower opening 403.

[0078] According to an embodiment of the present invention, the dam plate 380 comprises a barrier portion 385 delimiting the internal opening 450 of the dam plate 380 and that extends (along direction X) toward the internal hollow space 402, i.e., toward the disc-shaped closure plate 310.

[0079] According to the embodiments of the invention illustrated in the figures, the dam plate 380 comprises a peripheral portion between the external perimeter of the dam plate 380 and the barrier portion 385. According to the embodiments of the invention illustrated in the figures, said peripheral portion of the dam plate 380 extends along a plane substantially perpendicular to direction X.

[0080] In this way, water (or other liquid) that leaks into the internal hollow space 402 through the radial passaged between adjacent plates 305 cannot reach the underlying hollow body, because it is confined by the barrier portion 385.

[0081] According to an embodiment of the present invention illustrated in Figures 2 - 5, the barrier portion comprises a portion bended upward along direction X. Similar consideration apply in case the barrier portion 385 of the barrier portion 380 has a different shape, such as a vertical wall extending upward along direction X (i.e., toward the disc-shaped closure plate 310), or a linear ramp or piecewise linear extending upward along direction X (i.e., toward the disc-shaped closure plate 310).

[0082] Advantageously, according to an embodiment of the present invention, the dam plate 380 is tightened to form a pack together with the annulus-shaped plates 305 and with the closure plate 310, and kept properly spaced from the pack of annulus-shaped plates 305 by means of spacer elements similar to the spacers 315, for example washers. In the same way as what described above, the dam plate 380 too is provided with through holes 400 (aligned with the through holes 400 of the plates 305 and 310), at the external perimeter and adapted to receive the bolts or tie rods 320.

[0083] According to an embodiment of the present invention, the dam plate 380 is made of the same material of the plates 305. For example, the dam plate 380 may be a metallic plate, preferably made of carbon steel or stainless steel or special steel.

[0084] Since the dam plate 380 according to the embodiments of the invention described herein defines, together with the annulus-shaped plate 305 just thereabove, a further transversal radial passage, for example substantially orthogonal to direction X, such dam plate 380 is advantageously configured to carry out the following functions: avoiding that water reaches the underlying hollow body 205; draining the water confined by the barrier portion 385 toward the outside of the flame arrester block 230 through such further radial passage; allowing aeriform fluids (vapours or gases) be vent out through such further radial passage; and contributing - together with the plates 305, 310 - to the action of extinction ("quenching") of possible flames 330.

[0085] According to an embodiment of the present invention, further dam plates may be provided in addition to the dam plate 380, each positioned for example between a respective pair of plates 305 adjacent in the stack, and comprising a corresponding barrier portion.

[0086] In the example illustrated in Figure 6, in addition to the dam plate 380 positioned below - along direction X - the stack of plates 305, a further dam plate is provided (identified in figure 6 with reference 380' ) positioned between a pair of plates 305 in the stack and comprising a respective barrier portion (identified in Figure 6 with reference 385'). The dam barrier 380' is thus positioned above - along direction X - the dam plate 380, i.e., the dam plate 380' is located between the dam plate 380 and the closure plate 310.

[0087] Thanks to the presence of more dam plates that are superimposed - along direction X - on each other, the dam action against the infiltration of water through the radial passages between adjacent plates is increased without compromising the operation of the flame arrester block 230.

[0088] Indeed, if the amount of water (or other liquid) leaked into the internal hollow space 402 through the radial passages between adjacent plated became excessive (for example in presence of strong and / or prolonged rain), a single dam plate 380 could not be sufficient for damming such amount of water, which could anyway go beyond the corresponding barrier portion 385. By providing more dam plates 380, 380', the total amount of water to be dammed would be therefore distributed across the plurality of dam plates 380, 380'.

[0089] According to an embodiment of the present invention, the dam plate 380' has a shape similar to those of the dam plate 380, and it is positioned coaxial with the plates 305.

[0090] In this way, water that leaks into the internal hollow space 402 through the radial passages between adjacent plates 305 above the dam plate 380' cannot reach the underlying hollow body 205, because it is confined by the barrier portion 385' and immediately drained outside through the radial passage defined by the dam barrier 380' itself and the annulus-shaped plate 305 just thereabove, while water that leaks into the internal hollow space 402 through the radial passages between adjacent plates 305 between the dam plate 380' and the dam plate 380 cannot reach the underlying hollow body 205, because it is confined by the barrier portion 385 and immediately drained outside through the radial passage defined by the dam barrier 380 itself and the annulus-shaped plate 305 just thereabove.

[0091] According to an embodiment of the present invention, the dam barrier 380' has the shape of an annulus and has an internal radius ra' smaller than the internal radius r, in such a way to avoid that water leaked through the radial passages reaches the underlying hollow body 205.

[0092] According to an embodiment of the present invention, the internal radius ra' of the dam barrier 380' is at the same time larger than the internal radius ra of the dam barrier 380, in such a way to guarantee that possible water overflows from the dam plate 380' are anyway collected and dammed by the underlying dam plate 380.

[0093] Generalizing, according to an embodiment of the present invention, when a plurality of dam plates 380 is provided, the internal radiuses ra of each dam plate 380 are all smaller than the internal radius r of the internal hollow space 402, and the internal radius ra of a generic dam plate 380 may be advantageously larger than internal radius ra of the underlying dam plates 380.

[0094] However, the concepts of the present invention may be also applied to the case in which the sizes of the dam plates 380 are all equal.

[0095] Different modifications may be applied to the embodiments of flame arrester block 230 previously described.

[0096] For example, the spacers 315, instead of being parts which are separated from the plates 305, 310, 380, 380', may be formed in a single piece with the plates 305 and / or 310 and / or 380 and / or 380' , providing for a thickness increase of the material, for example at the holes 400.

[0097] The plates 305, 310, 380, 380' and / or the spacers 315 may be realized in such a way to define, once stacked, gaps generically transversals, also not strictly orthogonal to direction X. Particularly, the plates 305 do not necessarily have a plane surface.

[0098] Moreover, the annulus-shaped plates 305, 380, and / or 380' may have different shapes, for example ellipsoidal, square, rectangular, rhomboidal, star-shaped, lobed, or generally any shape in plan, having an external perimeter and at least one opening in the region inside the perimeter.

Claims

1. Flame arrester block (230) comprising: - a plurality of first plates (305) each having an external perimeter and at least one opening in a region inside the external perimeter, the first plates (305) of said plurality being stacked on each other starting from a lower first plate of said plurality of first plates to an upper first plate of said plurality of first plates according to a stacking direction (X) with the openings of said first plates which are at least partially superimposed on each other so as to form a stack of plates defining an internal hollow space (402), said first plates (305) being mutually spaced along said stacking direction (X) so as to define, between adjacent plates in the stack of plates, a corresponding gap transversal to said stacking direction (X), - a closure plate (310) stacked above said upper first plate along said stacking direction (X), and - a dam plate (380) defining together with a first plate (305) above said dam plate (380) along the stacking direction (X) a corresponding further gap, said dam plate (380) having an external perimeter and at least an opening (450) in a region inside the external perimeter of the dam plate, said opening (450) of the dam plate (380) being delimited by a barrier portion (385) of the dam plate which extends along the stacking direction (X) towards the closure plate (310), said barrier portion (385) being configured to confine liquid leaking into the internal hollow space (402) through said gap between adjacent plates, said dam plate (380) being configured to cause liquid confined by the barrier portion (385) be drained toward the outside of the flame arrester block (230) through said further gap.

2. Flame arrester block (230) according to claim 1, wherein the barrier portion (385) of said dam plate (380) comprises one of: - a portion curved towards the closure plate (310), - a vertical wall extending towards the closure plate (310), and - a linear ramp extending towards the closure plate (310).

3. Flame arrester block (230) according to any of the preceding claims, wherein: - each one of said first plates (305) extends along a plane substantially perpendicular to the stacking direction (X); - the dam plate (380) comprises a peripheral portion between the external perimeter and the barrier portion (385), said peripheral portion extending along a plane substantially perpendicular to the stacking direction (X).

4. Flame arrester block (230) according to any one of the preceding claims, wherein each of said first plates (305) has the shape of a quadrangular frame, particularly square or rectangular or rhomboidal, an ellipsoidal frame, a star-shaped frame, a quadrangular with lobes frame, or has an annulus shape.

5. Flame arrester block according to claim 4, wherein said dam plate (380) has a shape corresponding to the shape of said first plates.

6. Flame arrester block according to any of the preceding claims, wherein each of said first plates (305) and said dam plate (380) have an annulus shape, each first plate (305) having an internal radius greater than a inner radius of the dam plate (380).

7. Flame arrester block according to any of the preceding claims, wherein said dam plate (380) is located below said lower first plate according to said stacking direction.

8. Flame arrester block according to any one of the preceding claims, wherein said at least one first plate (305) and said dam plate (380) are tightened to form a pack.

9. Flame arrester block according to any of the preceding claims, comprising at least one further dam plate (380'), each of said at least one further dam plate (380') being positioned between a corresponding pair of first plates (305) in the stack of plates.

10. Protection device against flames and / or explosions, comprising at least one flame arrester according to any one of the preceding claims.

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