WO2020074912A1

WO2020074912A1 - Flame arrester element

Info

Publication number: WO2020074912A1
Application number: PCT/GB2019/052890
Authority: WO
Inventors: Daomin Hong
Original assignee: Elmac Technologies Limited
Priority date: 2018-10-10
Filing date: 2019-10-10
Publication date: 2020-04-16
Also published as: EP3863735A1; GB201816489D0

Abstract

A flame arrester element (1A), the flame arrester element (1A) comprises a distinct first segment (11) and a distinct second segment (12), the distinct first segment (11) comprises a first flame arrester element portion and an outer periphery (11B), the distinct second segment (12) comprises an inner periphery (12A) and an outer periphery (12B) and a flame arrester element portion located therebetween, wherein the distinct first segment (11) and the distinct second segment (12) are located within one another, the outer periphery (11B) of the distinct first segment (11) and the inner periphery (12A) of the distinct second segment (12) being adjacent.

Description

FLAME ARRESTER ELEMENT

This invention relates generally to flame arrester elements. More specifically, although not exclusively, this invention relates to flame arrester elements and methods of manufacturing the same.

Flame arresters are widely used in the chemical and oil industry for preventing flame transmission, normally whilst minimising flow resistance. It is usual for conduits through which flammable gases or mixtures of vapours and gases are conveyed (or indeed conduits through which by-products or precursors of flammable gases are conveyed) and/or containers containing such species to be protected by flame arresters.

In general, flame arresters contain a flame arrester element. Flame arrester elements may comprise a porous matrix, which provides a means to cool the material that flows through the flame arrester to below its ignition temperature and/or to quench a flame to prevent ‘flashback’ or flame transmission to the unburnt flammable vapours and gases. In this way, combustion can be controlled, contained, attenuated and/or avoided. The porous material may be provided by parallel plates, a sintered material or a ceramic material, for example. However, as the diameter of the flame arrester element increases, it becomes increasingly difficult to manufacture and/or handle the flame arrester element due to its size and weight.

One example of a conventional design for a flame arrester element consists of a combination of a flat metal strip and a crimped or corrugated metal strip. During manufacture, the two metal strips are located adjacent one another and secured to a central mandrel or spindle. The pair of strips are wound repeatedly, in parallel, about the mandrel or spindle in a spiral configuration, until the desired diameter for the flame arrester element is reached. A flat metal band may be attached around the outer circumferential surface of the flame arrester element to secure the metal strips in place. The crimped metal strip bears against the flat metal strip within the spirals to create a matrix of channels. The size, shape, and uniformity of the channels within the matrix are key to its function.

An example of a flame arrester element formed by the winding method is shown in US7918664. The flame arrester element comprises a wound structure of a flat strip and a corrugated strip. At certain points along the helical winding of the flat strip the corrugated strip is not provided, thereby providing sections which are fluid impermeable and sections which are fluid permeable. This arrangement is said to improve the cooling performance of the flame arrester element.

The conventional manufacturing process described has a number of drawbacks. In particular, problems may well be experienced during the manufacture of flame arrester elements with a large diameter.

It is known that flame arrester elements comprising layers of crimped ribbon, and having a relatively small diameter, may be manufactured to within close tolerances. However, often the flame arrester element becomes increasingly difficult to manufacture and/or handle as the metal strip is wound around the central spindle to increase its diameter. The metal strip may‘telescope’, wherein some of the intermediate and/or outer spirals of metal strip slide out of the plane created by the top edges of the metal strip spirals, and/or away from the apex of the central spindle, so that the edges are no longer parallel. In addition, the layers of ribbon may spring apart, which is undesirable because such movement increases the channel size and may render the flame arrester element ineffective. This can damage the channel size and shape within the porous matrix, leading to a lack of uniformity.

In addition, it may become increasingly difficult to control the uniformity of the size and shape of the channels within the porous matrix as the diameter of the flame arrester element increases, e.g. the as-formed channels may be crushed or collapse. This is problematic because the flame extinguishing properties are particularly sensitive to the size of the channels, and non-uniformity compromises the performance of the flame arrester element.

It may also be challenging to control the structural rigidity and/or tension of the spiral within the flame arrester element as its diameter increases. As a consequence, the channels created between the spirals of metal strip may collapse under too much tension. Alternatively, the crimped metal strip may unwind from the spiral during manufacture under too little tension. The resulting flame arrester element may easily unravel. Therefore, this type of flame arrester element is easily damaged during manufacture, installation and maintenance.

The aforementioned problems may well cause damage to the channel size, shape, and/or uniformity of the porous matrix, which may result in a flame arrester element which is either partially or completely ineffective. A damaged flame arrester element may increase or decrease the pressure difference experienced by the fluid travelling through the flame arrester and will compromise its performance. Clearly, it is deleterious to use a damaged flame arrester element.

There have been attempts reported in the prior art to mitigate this problem. For example, US7955073 B2 describes a method for inserting fixing pins into a flame arrester element in an attempt to increase the stability of the flame arrester element. The fixing pins are inserted into radial bores, which are formed using spark erosion drilling whilst injecting cooling fluid to cool the metal and to remove the resulting waste material.

Another example of an attempt to mitigate the aforementioned problems with the method of manufacturing crimped metal strip flame arrester elements is provided in US8092213. This document describes a surface coating on the metal strip of the flame arrester element. The surface coating is applied wet from a coating solution after the metal strip of the flame arrester element has been wound in a spiral configuration. The surface coating fixes the two metal strips together in the desired configuration, wherein the freely accessible surfaces comprise the coating, and the contact points of the metal strip are free of the coating.

It is therefore a first non-exclusive object of the invention to provide a flame arrester element for use in a flame arrester, the flame arrester element having improved handleability during installation, maintenance, and repair whilst reducing post-formation operations.

Accordingly, a first aspect of the invention provides a flame arrester element, the flame arrester element comprising a distinct first segment and a distinct second segment, the distinct first segment comprising a first flame arrester element portion and an outer periphery, the distinct second segment comprising an inner periphery and an outer periphery and a second flame arrester element portion located therebetween, wherein the distinct first segment and the distinct second segment are located within one another, the outer periphery of the distinct first segment and the inner periphery of the distinct second segment being adjacent.

Advantageously, the flame arrester element of the invention is much easier to handle and manufacture. Moreover, the specifications of each distinct segment may be tailored such that each distinct segment comprises bespoke dimensions, channel sizes, shapes, strip thicknesses, and material selections. Accordingly, the flow paths through respective flame arrester element portions can be designed for bespoke conditions. Also, flame arresters with larger transverse dimensions can be provided without encountering the problems associated with the prior art, such as telescoping.

In embodiments the flame arrester element portion of a distinct first segment may be different or the same to that of a distinct second segment to allow the characteristics of the flame arrester to be configured for specific requirements. Moreover, even when the same material is used for successive flame arrester element portions (of successive distinct segments), the specific operating characteristics of the flame arrester element portions may be configured, as required. For example, the pore sizes of a first flame arrester element portion may be different to those of a second or successive flame arrester element portion. Because the distinct segments can be made in isolation from one another (rather than as a continuous winding, for example), it is possible to configure and/or tune the performance.

In embodiments, the flame arrester element may comprise a distinct first segment comprising an outer periphery (c2), a distinct second segment comprising an inner periphery (c3) and an outer periphery (c4), wherein c2<c3<c4. In embodiments, the distinct first segment and the distinct second segment may be located within one another, the outer periphery (c2) and the inner periphery (c3) being adjacent.

Additionally or alternatively, the distinct first segment and/or the distinct second segment may comprise an inner and/or an outer periphery that are cooperatively shaped, for example protrusions on one periphery may engage with depressions or rebates on the other periphery. In one embodiment the inner and outer peripheries are stepped. For example, the distinct first segment may comprise a stepped outer periphery, and/or the distinct second segment may comprise a stepped inner periphery, e.g. sized such that the stepped outer periphery of the distinct first segment and the stepped inner periphery of the distinct second segment are capable of interlocking.

The outer periphery (c2) and the inner periphery (c3) may be shaped and sized such that a fluid tight seal is created between the outer periphery (c2) and the inner periphery (c3).

In alternative embodiments, the outer periphery of the distinct first segment and the inner periphery of the distinct second segment may be sized such that a gap is created therebetween, i.e. such that a fluid tight seal is not created therebetween. In these embodiments, the gap may be sized such that it is sufficiently small or narrow to prevent the passage of a flame. Preferably, the gap is sized to be of a similar width, e.g. the same width, as the width of the channels located within the distinct first and/or second segments, e.g. the channels created by a wound crimped ribbon, and/or the channels within a porous matrix. The width of these channels may be determined by the characteristics of the fluid travelling through the flame arrester element.

In embodiments where a gap is formed between the distinct first segment and the distinct second segment, this may be partially or completely sealed by a sealing means, for example formed from a resilient material. In an embodiment the sealing means may comprise an O-ring or an appropriately shaped gasket material. Advantageously, by using a sealing means to at least partially seal the gap between the distinct first and second segments, the distinct first and second segments do not have to be manufactured to high and/or exact tolerances.

The outer periphery (c2) of the distinct first segment and the inner periphery (c3) of the distinct second segment are sized such that a fluid tight seal may be created therebetween when the distinct first segment and the distinct second segment are located within one another.

The inner periphery (c3) may be of a greater size than the outer periphery (c2), and upon securing the distinct first segment to the distinct second segment, the inner periphery (c3) of the distinct second segment is adjacent to, and in intimate contact with, the outer periphery (c2) of the distinct first segment.

The distinct first segment may comprise a solid outer wall to provide the outer periphery (c2). The distinct first segment may comprise a solid inner wall. The solid inner wall may provide an inner periphery (d).

In embodiments, the solid inner wall and/or the solid outer wall may comprise or be provided by a sleeve, a pipe, or a ring.

Between the inner periphery and the outer periphery, for example between the solid inner wall and the solid outer wall, there may be provided a flame arrester element portion. The flame arrester element portion may be formed by a continuous winding of adjacent flat and corrugated material, e.g. strips. A strip is a length of material which is substantially longer than it is wide. The flat and corrugated material may be formed from the same or different materials. Preferably the flat and corrugated materials are both metal.

The distinct second segment may comprise a solid inner wall to provide the inner periphery (c3) and/or may comprise a solid outer wall to provide the outer periphery (c4). Between the solid inner wall and the solid outer wall there may be provided a flame arrester element portion. The flame arrester element portion may be formed by a continuous winding of adjacent flat and corrugated metal strips.

In an alternative embodiment, the flame arrester element portion of the distinct first and/or second segment may comprise a solid porous material, e.g. a sintered material, e.g. sintered metal or a sintered ceramic.

The flame arrester element may comprise any suitable number of distinct segments. For example, the flame arrester element may comprise a distinct third segment. The distinct third segment may comprise an inner periphery (c5) and an outer periphery (c6), wherein c3<c4<c5<c6. The distinct second segment and the distinct third segment may be secured e.g. removably secured, together, wherein the outer periphery (c4) and the inner periphery (c5) are sized such that a fluid tight seal is created between the distinct second segment and the distinct third segment.

In embodiments comprising a distinct third segment, the outer periphery (c4) of the distinct second segment and the inner periphery (c5) of the distinct third segment may be sized such that a fluid tight seal is created therebetween, i.e. the inner periphery (c5) is greater than the outer periphery (c4), and upon securing the distinct second segment to the distinct third segment, the inner periphery (c5) of the distinct third segment is adjacent to, and in intimate contact with, the outer periphery (c4) of the distinct second segment.

In alternative embodiments, the outer periphery (c4) of the distinct second segment and the inner periphery (c5) of the distinct third segment may be sized such that a gap is created therebetween, i.e. such that a fluid tight seal is not created therebetween. In these embodiments, the gap may be sized such that it is sufficiently small or narrow to prevent the passage of a flame. Preferably, the gap is sized to be of a similar width, e.g. the same width, as the width of the channels located within the distinct second and/or third segments, e.g. the channels created by a wound crimped ribbon, and/or the channels within a porous matrix. The width of these channels may be determined by the characteristics of the fluid travelling through the flame arrester element.

In embodiments where a gap is formed between the distinct second segment and the distinct third segment, this may be partially or completely sealed by a sealing means, for example formed from a resilient material. In an embodiment the sealing means may comprise an O-ring or an appropriately shaped gasket material. Advantageously, by using a sealing means to at least partially seal the gap between the distinct second and third segments, the distinct second and third segments do not have to be manufactured to high and/or exact tolerances.

The distinct third segment may comprise a solid inner wall to provide the inner periphery (c5) and/or may comprise a solid outer wall to provide the outer periphery (c6). Between the solid inner wall and the solid outer wall there may be provided a flame arrester element portion. The flame arrester element portion may be formed by a continuous winding of adjacent flat and corrugated metal strips. Alternatively, the flame arrester element portion may comprise a solid porous material, e.g. a sintered material, e.g. sintered metal or a sintered ceramic.

In embodiments, the flame arrester element comprises a distinct first, second, third, and an ... n^th segment. For example, n may be an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, 20, or more than 20, preferably, n = 2, 3, 4, 5, or 6.

In embodiments, the inner and/or outer periphery of the distinct first, second, third segment or ... n^th segment may be circular, e.g. substantially circular, and may represent a circumference.

The solid inner wall and/or the solid outer wall of each or all of the distinct first, second, third and/or ... n^th segments may comprise a metallic wall. For example, the solid inner wall and/or the solid outer wall of each or all of the distinct first, second, third and/or ... n^th segments may comprise a pipe, e.g. a metal pipe, a sleeve or a mandrel or spindle. Additionally or alternatively, the solid inner wall and/or the solid outer wall may comprise a flat metal strip, and/or a metallic flat metal strip, and/or a flat metal strip ring. Additionally or alternatively, the solid inner wall and/or the solid outer wall may include or comprise a resilient material that is resistant to an operating fluid media. Advantageously, this may provide corrosion resistance and thermal stability to the flame arrester element. The resilient material may be used as a seal between one or more of the distinct first, second, third, and/or n^th segments of the flame arrester element. The resilient material may be polymeric, e.g. the resilient material may comprise a polymer. In one embodiment the resilient material may comprise polytetrafluoroethylene (PTFE). The resilient material may be a sheet or tape. The resilient material may be applied to at least a portion of a periphery of a distinct segment. For example, the resilient material may be applied to a part of a segment which, in use, lies adjacent a second or further distinct segment. The resilient material may be a tape or sheet which is wound about a periphery (or at least a part of a periphery) of a distinct segment. The resilient material may be applied to each facing portions of adjacent distinct segments.

In embodiments where a gap is created between a solid inner wall and a solid outer wall of any of the distinct first, second, third and/or ... n^th segments, a flat metal strip, and/or a metallic flat metal strip, and/or a flat metal strip ring may fill the gap. Additionally or alternatively a resilient material that is resistant to an operating fluid media may at least partially, e.g. completely, fill the gap.

The solid inner wall and the flame arrester element portion may be connected and/or integrally formed. The solid outer wall and the flame arrester element portion may be connected and/or integrally formed. In embodiments, the solid inner wall may be connected and/or integrally formed with the solid outer wall. For example, the solid inner wall may be formed from a flat metal strip that has been wound around a central mandrel or spindle to form one or more layers, e.g. two, three, four, five, six, seven, eight, nine, ten, twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety, one hundred, two hundred, three hundred, four hundred, five hundred, or more layers. The solid outer wall may be formed from a flat metal strip that has been wound around the flame arrester element portion to form one or more layers, e.g. two, three, four, five, six, seven, eight, nine, ten, twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety, one hundred, two hundred, three hundred, four hundred, five hundred, or more layers. For example, there may be 10 to 200, say 15 to 150 layers. In one embodiment there may be 10 to 40 layers. Preferably, there will be fewer than 100 layers (e.g. 100 layers of 0.05mm thick shim or 50 layers of 0.2mm thick shim). Preferably the solid outer wall will be formed of fewer layers than the solid inner wall. The flat metal strip is preferably from 0.01 mm to 0.3 mm thick, more preferably from 0.04 to 0.25 mm thick. Upon completion of the solid inner wall, the flat metal strip of the solid inner wall may be combined with a crimped and/or corrugated metal strip, i.e. a crimped metal strip may be placed adjacent the flat metal strip, so as to be integrally formed with the flame arrester element portion, of a distinct segment. Additionally or alternatively, upon completion of the flame arrester element portion, the crimped metal strip of the flame arrester element portion may be removed before formation of the solid outer wall, so that the flame arrester element portion is integrally formed with the solid outer wall of a distinct segment.

In an embodiment, the outer periphery of one of the distinct segments may be formed from a solid wall, such as a pipe, sleeve or a ring. A successive flame arrester element portion, for example formed from a wound strip, may be secured to the outer periphery.

In an embodiment, the inner periphery of one of the distinct segments may be formed from a solid wall, such as a pipe, sleeve or a ring. A successive flame arrester element portion, for example formed from a wound strip, may be secured to the inner periphery. By way of example, a wound strip may be secured to the inner periphery and wound around the solid wall of the inner periphery, to form the flame arrester element portion.

In one embodiment a distinct segment may be provided with an inner periphery formed from a solid pipe and an outer periphery formed from successive windings of flat metal strip.

If the inner and/or outer periphery of a distinct segment is made from a solid ring, a ring of material holes, for example through-holes or blind holes, may be provided therein. If the inner and/or outer periphery of a distinct segment is made from a wound strip, holes, for example through-holes, may be provided therein. Blind holes in the inner and/or outer periphery of a distinct segment (or plural distinct segments) made from a solid ring may be threaded. Through-holes in the inner and/or outer periphery of a distinct segment (or plural distinct segments) may be threaded. The flame arrester element portion will typically radiate out from the inner periphery thereof, conveniently we call this a radial direction (although it need not imply that the flame arrester element and/or flame arrester element portion is circular). The through-holes may extend through the inner periphery and/or outer periphery in a direction transverse to the radial direction, which conveniently we call the axial direction. By such through-holes the distinct segment (or plural distinct segments) can be secured to a winding table to facilitate winding of, say, a laminate of corrugated/flat metal strip about the inner periphery. Once used, the through-holes can be used to secure to the flame arrester element support bars or the like. Additionally or alternatively, the inner and/or outer periphery of a distinct segment may comprise apertures therethrough extending in the radial direction. The apertures in the radial direction may allow the passage of pins, screws, bolts and the like to secure the flame arrester element portion to the respective periphery/peripheries and/or to secure adjacent distinct segments and/or to secure successive windings together. The holes, through-holes and/or the apertures may be countersunk.

In embodiments, the layers formed from winding a flat metal strip may be spot welded, e.g. to secure the layers together.

In embodiments, the solid inner wall and the flame arrester element portion may be secured together, e.g. by welding. In plan, the surface area of the flame arrester element which is provided by the various solid portions (i.e. the solid inner periphery and/or solid outer periphery) provides less than 33% of the flame arrester element, the remainder being the porous flow portion. By minimising the solid portion to, preferably less than 30%, say less than 25 or 20% or 15% or 10%, the pressure drop across the flame arrester element is minimised.

Each of the distinct segments of the flame arrester element, i.e. the distinct first, second, third, and/or ... n^th segment, have a height. The height of each distinct segment is the dimension perpendicular to the major transverse dimension, e.g. the diameter. The height of each distinct segment may be equal to one another within a flame arrester element. For example, the distinct first segment has a height H1 , and the distinct second segment has a height H2. In embodiments, the height H1 of the distinct first segment is equal to the height H2 of the distinct second segment, i.e. H1 = H2. Additionally or alternatively, wherein the distinct third segment has a height H3, and the distinct fourth segment has a height H4, in embodiments, the height H1 of the distinct first segment may be equal to the heights of the distinct second, third, and fourth segments, i.e. H1 = H2 = H3 = H4. Alternatively, the heights of each distinct segment may be unequal within the flame arrester element. For example, the height H1 of the distinct first segment, and the height H2 of the distinct second segment may not be equal, e.g. H1 may be larger than H2, i.e. H1 >H2. In alternative embodiments, H1 may be smaller than H2, i.e. H1<H2.

The flame arrester element may comprise one or more of support bars, a ring, or a spacer member. The support bars, ring and/or spacer member may be affixed to the solid inner wall and/or the solid outer wall of the flame arrester element. The support bars, ring, and/or spacer members may be secured to the distinct segments by any suitable means, e.g. welding, and/or a screw connection via threaded holes.

In embodiments, the support bars and/or spacer members may comprise countersunk clearance holes that are aligned with corresponding holes within the solid inner wall and/or the solid outer wall of the flame arrester element, such that the support bars or spacer members and the flame arrester element may be secured together using screws or pins. Advantageously, this avoids the need for welding, which is known to damage the flame arrester element and may adversely affect its performance.

Advantageously, securing the support bars, ring and/or spacer members to the solid inner periphery and/or the solid outer periphery (for example, one or both of the axial faces of each of the inner and/or outer periphery) of the distinct first, second, third, and/or ... n^th segments of the flame arrester element enables the flame arrester element portion(s) to be exposed, meaning that the full capacity of flow rate and flame quenching is achieved across the entire surface area of the major face of the flame arrester element. If the support bars were to be secured to the flame arrester element portion(s), e.g. the wound crimped metal strips, then the risk of damage to the flame arrester element would be increased, and the capacity and/or performance of the flame arrester element would be reduced. The flame arrester element of the present invention at least partially mitigates this problem. Furthermore, by securing the support bars, ring and/or spacer members to the solid inner periphery and/or the solid outer periphery of the distinct first, second, third, and/or ... n^th segments of the flame arrester element, greater mechanical integrity of the flame arrester element is provided. By increasing the mechanical integrity of the flame arrester element the thickness of the support bars can be reduced. A further aspect of the invention comprises a method of forming a flame arrester element, the method comprising providing a distinct first flame arrester element segment having a first flame arrester element portion and a first outermost peripheral solid wall, providing a distinct second flame arrester element segment having a second flame arrester element portion, a second innermost peripheral solid wall and securing the first outermost peripheral solid wall to the second innermost peripheral solid wall.

In embodiments, the innermost peripheral solid wall or solid inner wall may be between 2 to 20 mm thick, e.g. between any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, or 19 mm to any one of 20, 19, 18, 17, 16, 15, 14, 13, 12, 1 1 , 10, 9, 8, 7, 6, 5, 4, 3, 2 mm thick. In some embodiments, the innermost peripheral solid wall or solid inner wall is between 5 to 15 mm thick, e.g. 6, 7 or 10 mm thick.

In embodiments, the outermost peripheral solid wall or solid outer wall may be between 0.5 to 20 mm thick, e.g. between any one of 0.5, 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, or 19 mm to any one of 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 , 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 , 0.5 mm thick. In some embodiments, the outermost peripheral solid wall or solid outer wall is between 2 to 10 mm thick.

For example, it is possible to use, as the inner periphery of a distinct segment, a standard pipe. For example, an inner periphery may be formed from a standard 30” pipe, for example to from a 48” flame arrester element. The wall thickness of a standard 30” pipe is 9.5 mm or 12.7 mm, the larger thicknesses being used for extra strength. Of course, other standard pipe sizes can be used. The wall thickness of the standard pipe may be reduced (e.g. by machining) for use of the standard pipe as the inner periphery of the distinct segment.

In embodiments, the distinct first flame arrester element segment comprises an outer periphery (c2), the distinct second segment comprising an inner periphery (c3) and an outer periphery (c4), wherein c2<c3<c4, the outer periphery (c2) and the inner periphery (c3) are sized such that a fluid tight seal is created between the outer periphery (c2) and the inner periphery (c3).

In embodiments, the peripheries of the distinct segments, e.g. the outer periphery of the distinct first segment, and the inner periphery of the distinct second segment, may comprise a resilient material to provide a fluid tight seal therebetween. The resilient material may be a polymer, for example PTFE or expanded PTFE. The resilient material may be shaped according to the geometry of the gap, e.g. manufactured to at least partially, e.g. completely, fill the gap.

In embodiments, the outer periphery of the distinct first segment and the inner periphery of the distinct second segment may be sized such that a gap is created therebetween, i.e. such that a fluid tight seal is not created therebetween. In these embodiments, the gap is sized such that it is sufficiently small or narrow to prevent the passage of a flame. Preferably, the gap is sized to be of a similar width, e.g. the same width, as the width of the channels located within the distinct first and/or second segments, e.g. the channels created by a wound crimped ribbon, and/or the channels within a porous matrix.

In embodiments, the distinct first flame arrester element segment further comprises an inner periphery (d). The inner periphery (d) represents the centre of the flame arrester element. The method may comprise securing the distinct first flame arrester element segment within the distinct second flame arrester element segment, e.g. in a concentric arrangement or in another suitable geometric arrangement, for example, in a square arrangement.

The first and/or second flame arrester element portion may be fabricated by a continuous winding of adjacent flat and corrugated metal strips. Alternatively, the flame arrester element portion may be fabricated from a solid porous material, e.g. a sintered material, a sintered metal or a sintered ceramic.

The method may further comprise a method of manufacturing one or more of the distinct first and/or second flame arrester element segments prior to securing a distinct first segment within a distinct second segment, e.g. in a concentric arrangement.

In embodiments wherein the first and/or second flame arrester element portion is/are fabricated by a continuous winding of adjacent flat and corrugated metal strips, the method may further comprise locating a central mandrel or spindle, securing a metal sheet, e.g. a metal strip, to the central mandrel or spindle, winding said metal strip around the central mandrel or spindle in a spiral configuration to create a distinct segment, e.g. a distinct first segment, a distinct second segment, a distinct third segment, and/or a distinct ... n^th segment. In embodiments, the central mandrel or spindle may comprise a solid inner wall, e.g. fabricated from a pipe or a sleeve, of a distinct n^th segment.

For example, the method may further comprise locating a first central mandrel or spindle, securing a corrugated metal strip and an adjacent flat metal strip to the first central mandrel or spindle, winding said corrugated metal strip and said adjacent flat metal strip around the first central mandrel or spindle in a spiral configuration to create a distinct first segment.

The method may further comprise locating a second central mandrel or spindle, securing a corrugated metal strip and an adjacent flat metal strip to the second central mandrel or spindle, winding said corrugated metal strip and said adjacent flat metal strip around the second central mandrel or spindle in a spiral configuration to create a distinct second segment.

Additionally or alternatively, the method may further comprise locating a central mandrel or spindle, securing a flat metal strip to the central mandrel or spindle, winding said flat metal strip around the central mandrel or spindle in a spiral configuration to create a solid inner wall. The method may further comprise locating a corrugated metal strip adjacent, proximate to or on the flat metal strip, winding said flat metal strip and said corrugated metal strip around the central mandrel or spindle in a spiral configuration to create a flame arrester element portion. The method may further comprise locating the flat metal strip on the flame arrester element portion, and winding said flat metal strip around the flame arrester element portion in a spiral configuration to create a solid outer wall.

In embodiments, a flat metal strip of a different thickness, e.g. thicker than the flat metal strip used to construct the solid inner wall and/or the flame arrester element portion, may be used to fabricate the solid outer wall. The solid outer wall may be secured by spot welding.

The solid inner wall, the flame arrester element portion, and the solid outer wall may be integrally formed such that the flat metal strip comprises one continuous length, i.e. an unbroken length. Wherein the metal strip comprises one continuous length, the method may comprise locating a central mandrel or spindle, securing a flat metal strip to the central mandrel or spindle, winding said flat metal strip around the central mandrel or spindle in a spiral configuration to create a solid inner wall, locating the corrugated metal strip proximate to or on the flat metal strip, winding said flat metal strip and said corrugated metal strip around the central mandrel or spindle in a spiral configuration to create a flame arrester element portion, removing said corrugated metal strip, and winding said flat metal strip around the flame arrester element portion in a spiral configuration to create a solid outer wall. In an alternate embodiment, a thicker flat metal strip may be used to form the outer wall, for example by connecting (e.g. spot welding) the thicker flat metal strip to the flat metal strip used to form the flame arrester element portion.

In alternative embodiments, the solid inner wall and/or solid outer wall may be provided by a pipe section or a ring.

The flame arrester element of the present invention may be secured into any suitable housing for use as a flame arrester. In embodiments, a plurality, e.g. 2, 3, 4, 5, 6, 7, 8, 9, or

10 of the flame arrester elements, for example flame arrester elements according to the invention may be secured together in parallel relations for location in a suitable housing for use as a flame arrester. Where plural flame arrester elements are installed, the adjacent flame arrester elements may abut one another or may be separated by a flame arrester element spacer. The flame arrester element spacer may be a tube of material, for example an annulus, against opposed faces of which the adjacent flame arrester elements bear. The flame arrester element spacer may have a wall thickness of 1 , 2, 3, 4 or 5 mm, for example between 2 mm and 3 mm. The flame arrester element spacer may otherwise be a metal gauze, wire mesh or a perforated plate. The use of plural flame arrester elements may be particularly advantageous for use in in-line detonation or deflagration flame arresters. For in-line detonation flame arresters it may be useful to use up to say 2, 3, 4, 5, 6, 7, 8, 9, 10,

1 1 or 12 flame arrester elements, say from 4 to 10. Otherwise, for in-line detonation flame arresters it may be useful to use any number of flame arrester elements, say more than 12. For in-line deflagration flame arresters 2, 3, 4, 5, 6, 7, 8, 9, 10 flame arrester elements may be used, say from 1 to 8 flame arrester elements, or 2 to 5 flame arrester elements. Otherwise, for in-line deflagration flame arresters it may be useful to use any number of flame arrester elements, say more than 10.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention. The number of distinct segments within the flame arrester element of the present invention is not limited to two, three, or four distinct segments. There may be any suitable number of distinct segments in the flame arrester element of the present invention. The height of each distinct segment may be equal in the flame arrester element. Alternatively, the height of each distinct segment may be variable, so that the height of the distinct first segment need not be equal to the height H2 of the distinct second segment, and/or the height H3 of the distinct third segment, and/or the height Hn of the distinct n^th segment.

The porous matrix of the flame arrester element portion need not be provided by a metal strip, e.g. a crimped metal strip. Other porous matrices may be used to provide the flame arrester element portion. The distinct segments of the flame arrester element may comprise more than one type of porous matrix. For example, the distinct first segment may comprise a sintered material and the distinct second segment may comprise a combination of a flat metal strip and a crimped metal strip wound together in a spiral configuration.

As stated above, there may be further provided a second flame arrester element. The second flame arrester element may be in facing relations with the flame arrester element, for example to provide serial flow through the flame arrester element and the second flame arrester element. The flame arrester element and the second flame arrester element may be adjacent, proximate or abutting.

The second flame arrester element may comprise a distinct first segment and a distinct second segment, the distinct first segment comprising a first flame arrester element portion and an outer periphery, the distinct second segment comprising an inner periphery and an outer periphery and a second flame arrester element portion located therebetween, wherein the distinct first segment and the distinct second segment are located within one another, the outer periphery of the distinct first segment and the inner periphery of the distinct second segment being adjacent.

In embodiments there may be a third, fourth or fifth or n^th flame arrester element. Each of the further flame arrester elements may comprise a distinct first segment and a distinct second segment, the distinct first segment comprising a first flame arrester element portion and an outer periphery, the distinct second segment comprising an inner periphery and an outer periphery and a second flame arrester element portion located therebetween, wherein the distinct first segment and the distinct second segment are located within one another. One or more of the further flame arrester elements may be in facing relations. For example, each flame arrester element may be adjacent, proximate or abutting a preceding or succeeding flame arrester element. By way of a further example, each flame arrester element may be spaced from a preceding or succeeding flame arrester element, and spacers may be provided therebetween. The spacing between a flame arrester element and a preceding or succeeding flame arrester element may be between 2 and 5 mm, for example between 2 and 3 mm.

All of the flame arrester elements may be located in a common housing.

Advantageously, the use of successive flame arrester elements allows for the entire flame arrester construction to have tailored flow both across the flame arrester element construction (i.e. in a direction across or transverse the principal flow axis) and through the flame arrester element construction (i.e. in a direction through or parallel to the principal flow axis).

In embodiments, successive flame arrester elements may be located in distinct housings to provide flame arrester element and distinct housing assemblies. Each flame arrester element and distinct housing assembly may be assembled in facing relations with a preceding or succeeding flame arrester element and distinct housing assembly. The distinct housings may contain support bars and/or sealing means. Additionally or alternatively spacers and/or sealing means may be provided between successive flame arrester element and distinct housing assemblies. Successive flame arrester element and distinct housing assemblies may be secured together using securing means located on the distinct housing or may all be located in a further housing. The flame arrester element and distinct housing assemblies may be usable individually as flame arresters.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and, in particular, the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. For the avoidance of doubt, the terms“may”,“and/or”,“e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1A is a schematic view of a flame arrester element in plan view, according to a first embodiment of the invention;

Figure 1 B is the flame arrester element of Figure 1A, in a disassembled state;

Figure 1C is an isometric view of the flame arrester element of Figure 1A;

Figure 2 is a front elevation view of a flame arrester element, according to a further embodiment of the invention;

Figure 3 is a schematic view of a flame arrester comprising a flame arrester element, according to an embodiment of the invention;

Figure 4 is a flame arrester comprising a flame arrester element, according to a further embodiment of the invention;

Figure 5A is a sectional view of a portion of a flame arrester element according to a further embodiment of the invention;

Figure 5B is a sectional view of a portion of a flame arrester element according to a yet further embodiment of the invention.

Figure 6 is a perspective view of a housing for a flame arrester element.

Figure 7A is an exploded view of a segmented flame arrester element inside of the housing, according to a further embodiment of the invention;

Figures 7B to 7D are sequential perspective views of the housing with segments of the segmented flame arrester element therein, according to the embodiment shown in Figure 7A;

Figure 8 is a sectional view of assembled flame arrester element layers;

Figure 8A is an enlarged view of section A in Figure 8; and

Figure 9 is an exploded view of segmented flame arrester element layers, according to a further embodiment of the invention. Referring to Figure 1A, there is shown a schematic view of a flame arrester element 1A in plan view, according to a first embodiment of the invention. Referring also to Figure 1 B, there is shown the flame arrester element 1A of Figure 1A in a disassembled state 1 B. Referring also to Figure 1 C, there is shown an isometric view 1 C of the flame arrester element 1A.

The flame arrester element 1A comprises a first segment 1 1 , a second segment 12, a third segment 13, and a fourth segment 14.

Each of the first, second, third and fourth segments 1 1 , 12, 13 and 14 comprise a solid inner wall 1 1 A, 12A, 13A, 14A respectively, a solid outer wall 11 B, 12B, 13B, 14B respectively, and a flame arrester element portion 1 1 C, 12C, 13C, 14C respectively. For example, the first segment 11 comprises a solid inner wall 11 A, a solid outer wall 11 B, and a flame arrester element portion 11 C and so on.

The first, second, third, and fourth segments 11 , 12, 13, 14 are distinct or individual, i.e. the segments are separate or separable from one another, and not integrally formed or connected with one another, as is clearly demonstrated in the disassembled state 1 B (shown in Figure 1 B).

The first segment 1 1 has an inner diameter d1 and an outer diameter d2. The solid inner wall 1 1 A defines an inner circumference (d), and the solid outer wall 1 1 B defines an outer circumference (c2) of the first segment 1 1.

The second segment 12 has an inner diameter d3 and an outer diameter d4. The solid inner wall 12A defines an inner circumference (c3), and the solid outer wall 12B defines an outer circumference (c4) of the second segment 12.

The third segment 13 has an inner diameter d5 and an outer diameter d6. The solid inner wall 13A defines an inner circumference (c5), and the solid outer wall 13B defines an outer circumference (c6) of the third segment 13.

The fourth segment 14 has an inner diameter d7 and an outer diameter d8. The solid inner wall 14A defines an inner circumference (cl), and the solid outer wall 14B defines an outer circumference (c8) of the fourth segment 14. The segments 11 , 12, 13, 14 are sized such that d<c2<c3<c4<c5<c6<c7<c8, and d1<d2<d3<d4<d5<d6<d7<d8. The flame arrester element 1A has a height H (shown in Figure 1C). In this embodiment, the height H of the flame arrester element 1A is equal to the height of each of the first, second, third, and fourth segments 11 , 12, 13, 14.

The flame arrester element 1A is assembled in a sequential and concentric manner, i.e. the first segment 11 is located concentrically within the second segment 12, the second segment 12 is located concentrically within the third segment 13, and the third segment 13 is located concentrically within the fourth segment 14. The order of steps may be reversed, i.e. the second segment is located around the first segment and so on. In this embodiment, a fluid tight seal may be created between the concentrically arranged segments 11 , 12, 13, and 14, i.e. the solid outer wall H B of the first segment 11 contacts the solid inner wall 12A of the second segment 12 and is shaped and sized so as to create a fluid-tight seal between the solid outer wall 11 B of the first segment 11 and the solid inner wall 12A of the second segment 12. Similarly, the solid outer wall 12B of the second segment 12 contacts the solid inner wall 13A of the third segment 13 is shaped and sized so as to create a fluid-tight seal between the solid outer wall 12B of the second segment 12 and the solid inner wall 13A of the third segment 13. Finally, the solid outer wall 13B of the third segment 13 contacts the solid inner wall 14A of the fourth segment 14 so as to create a fluid-tight seal between the solid outer wall 13B of the third segment 13 and the solid inner wall 14A of the fourth segment 14. In this embodiment, the fourth segment 14 forms the outermost segment.

In alternative embodiments, a gap may be present between each of the segments 11 , 12, 13, 14 such that a fluid tight seal is not created therebetween. In these embodiments, the gap is sized such that it is sufficiently small or narrow to prevent the passage of a flame.

In other embodiments these gaps may be fitted with a resilient material, e.g. polytetrafluoroethylene (PTFE) or expanded PTFE. The solid inner walls 11 A, 12A, 13A, and 14A, and the solid outer walls 11 B, 12B, 13B, and 14B, may be formed from any suitable material, e.g. metal. In this embodiment, the inner and solid outer walls 1 1A, 12A, 13A, and 14A, 11 B, 12B, 13B, and 14B are formed from a flat metal strip or shim.

In embodiments, the solid inner walls 11 A, 12A, 13A and 14A are formed from a pipe, pipe section or portion or a solid ring, and the solid outer walls 1 1 B, 12B, 13B and 14B are formed from flat metal shim/strip, which are secured using securements (e.g. welds or bolts) and/or spot-welded. The solid inner walls 1 1A, 12A, 13A, 14A and the solid outer walls 11 B, 12B, 13B may also be provided with or fixed with a resilient material, e.g., polytetrafluoroethylene (PTFE) or expanded PTFE.

In this embodiment, each of the solid inner wall 11 A, 12A, 13A, 14A comprises a pipe section or a solid ring. The cross-sectional area of the pipe section is a small fraction of the corresponding flame arrester element portion, for example 5% ~ 15%, say 10% and preferably less than 20%.

The flame arrester element portion 1 1 C, 12C, 13C, 14C of each segment 11 , 12, 13, and 14, is formed from a metal strip (not shown) comprising a crimped metal strip and a flat metal strip, which are wound in a spiral configuration to create pores in the spaces formed between the crimped metal strip and the flat metal strip (not shown). In other embodiments, the flame arrester element portion 1 1 C, 12C, 13C, 14C may be formed from another porous media, e.g. a sintered material such as a sintered metal or ceramic, and/or may have the same pore size or a different pore size. Additionally, each of the flame arrester element portion 1 1 C, 12C, 13C, 14C may each be formed using a different porous media, e.g. with different pore sizes.

In embodiments, the transverse dimension, i.e. in the radial direction, of the flame arrester element portion 1 1 C, 12C, 13C, 14C need not be the same size. Preferably, when measured along a radius from the centre of the flame arrester element, the element portions 1 1C, 12C, 13C, 14C provide a decreasing contribution to the length of the radius.

In the embodiment shown in Figures 1A and 1 B, there are four distinct segments 1 1 , 12, 13 and 14. However, in other embodiments there may be less than four segments, or there may be more than four segments. The flame arrester element 1A comprises multiple distinct segments. This confers several advantages because the distinct segments 11 , 12, 13, 14 may each be manufactured, assembled, maintained, repaired and replaced separately. Additionally, in embodiments, the flame arrester element 1A may be produced up to any desired size, for example, the flame arrester element 1A may comprise a nominal pipe size of DN800, DN900, DN1000, DN1200, DN1400, DN1500, DN1600, DN1800, DN2000 or larger.

For example, the flame arrester element 1A has improved handleability, and each distinct segment is easily produced with the conventional manufacture technology. The weight of each segment is less than the total weight of the flame arrester element, which enables each segment to be transported and handled separately before assembling into the final flame arrester element 1A. Otherwise, the flame arrester element is very difficult to be manufactured and handled.

The performance of the flame arrester element is also improved. Each distinct segment has greater structural rigidity in comparison to the flame arrester elements of the prior art. In embodiments, wherein the flame arrester element portion is provided by a wound crimped metal strip, the hoop stress within each distinct segment provides structural rigidity by means of interwinding friction, which prevents collapse by telescoping. The distinct segments each comprise fewer layers of wound metal strip, and as a consequence, the probability and risk of the metal strip‘telescoping’ is reduced. Therefore, the pore size and flame arrester element portion are more consistent, and is easier to control, which leads to improved flame arrester performance.

Additionally, maintenance and repair of the flame arrester element is improved. Each individual distinct segment may be repaired or replaced separately or on an individual basis, which is more cost effective by reducing the need to replace the entire flame arrester element.

Referring now to Figure 2, there is shown an isometric view of a flame arrester element 2A, according to a further embodiment of the invention. The flame arrester element 2A comprises a first segment 1 T, a second segment 12’, and a third segment 13’. Each of the first, second, and third segments 1 1’, 12’, 13’ has a height H1 , H2, H3 respectively. In this embodiment, the first segment 1 1’ and the second segment 12’ are equal in height, i.e. H1=H2. The height H3 of the third segment is less than the height H1 of the first segment 1 T and the height H2 of the second segment 12’, i.e.H1 >H3 and H2>H3.

The first, second and third segments 1 T, 12’, 13’ are distinct or individual, i.e. the segments are separate or separable from one another, and not integrally formed or connected with one another.

In this embodiment, the first segment 1 T comprises a porous matrix formed from a wound crimped metal strip (not shown). The second segment 12’ comprises a porous matrix formed from a porous ceramic material (not shown). The third segment 13’ comprises a porous matrix formed from a wound crimped metal strip (not shown). In this way, the materials used for the porous matrix in each segment may be adapted and changed to suit the requirements of the specific application and the flame quenching performance. Of course, different materials for the flame arrester element portion (different matrix materials) can be used, tailored to suit the specific requirements and the relative sizes of the different matrix materials can be configured as appropriate. In embodiments all of the materials for the flame arrester element portions are the same.

In other embodiments, different types of porous media may be employed in different segments, for example, the first segment 1 T and the second segment 12’ both comprise a porous matrix formed from a wound crimped metal strip (not shown) while the third segment 13’ comprises a porous matrix formed from a sintered metal (not shown).

Referring now to Figure 3, there is shown a cross-sectional view of a flame arrester 3 comprising the flame arrester element 1A of Figure 1A and a housing 31. The flow path F of fluid flowing through the flame arrester 3 is shown. Although flow path F is shown, it will be appreciated by the skilled person that the flow path in flame arrester 3 could also be in the opposite direction to flow path F.

It should be noted that any element rings and/or support bars and/or bolts and/or nuts as well as any connection flanges are not shown. The flame arrester element 1A comprises a first segment 1 1 , a second segment 12, a third segment 13, and a fourth segment 14. Fluid is able to flow along the flow path F through the housing 31 and through the flame arrester element 1A, which quenches the flame (not shown). As explained previously, the height H of the first, second, third, and fourth segments 11 , 12, 13, 14 are equal.

Referring now to Figure 4, there is shown a cross-sectional view of a flame arrester 4 comprising a flame arrester element 4A”. The flame arrester 4 comprises the flame arrester element 4A” and a housing 41. The flow path F’ of fluid flowing through the flame arrester 4 is shown. Although flow path F’ is shown, it will be appreciated by the skilled person that the flow path in flame arrester 4 could also be in the opposite direction to flow path F’.

The flame arrester element 4A” comprises a first segment 11”, a second segment 12”, and a third segment 13”. The first segment 11” has a height H1”, the second segment 12” has a height H2”, and the third segment 13” has a height H3”.

The first, second and third segments 1 1”, 12”, 13” are distinct or individual, i.e. the segments are separate or separable from one another, and not integrally formed or connected with one another.

The first segment 11” and the second segment 12” have equal heights H1” and H2”. However, the third segment 13” has a smaller relative height H3”. In this case, in the flow path F’ directions, the centre-most segments 1 1”, 12” protrude to either side of the outer most segment 13”. The flame arrester 4 and flame arrester element 4A” is symmetrical in a flow sense and thus may be installed either way around. Although in this embodiment the centre-most segments 1 1”, 12” protrude to either side of the outer-most segment 13”, the centre-most segments 1 1”, 12” may only protrude on one side of the outer-most segment 13” and be substantially flush with the other side of the outer-most segment 13”.

It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. For example, the number of segments in the flame arrester element may vary between 2 to 4 or more, for example more than 5, or 6 to 8, or 9 or more, for example, 10, 15 or 20. The number and size of each segment may be selected depending on the application. Advantageously, the flame arrester element 1A, 2A, 4A” may be assembled using different sized segments, which perform different functions. For example, the height of the first segment may be larger than the height of the second segment to enable greater quenching performance to be achieved in the centre of the flame arrester element. Different sized distinct segments may also be used to improve flow distribution through the flame arrester element, or to design the flame arrester element for specific functions and/or purposes. Additionally, the flame arrester element portion of each segment of the flame arrester element of the invention need not be provided by the same type of material. The material used to form the porous matrices of the flame arrester element portions of the distinct segments may be selected depending on the performance requirements and operating conditions of the flame arrester element. Moreover, in embodiments when the same material is used for successive flame arrester element portions (of successive segments), the specific operating characteristics of the flame arrester element portions may be configured, as required. For example, the pore sizes of a first flame arrester element portion may be different to those of a second or successive flame arrester element portion. Because the segments can be made in isolation from one another (rather than as a continuous winding, for example), it is possible to configure and/or tune the performance.

In other embodiments, there may be provided more than one flame arrester element 1A within a housing, for example, two, three or more flame arrester element 1A used for a flame arrester. In a further embodiment, a plurality of individual flame arrester elements similar to flame arrester element 1A (according to the invention) may be employed while the segment number and/or construction/configuration of each individual flame arrester may be different from one another. Different flame arrester elements may be located sequentially in a housing with or without flame arrester element spacers to maintain the spacing between adjacent, successive flame arrester elements.

Whilst the above embodiments have shown flame arrester elements 1A, 2A, 4A” with distinct segments, the outer periphery and inner periphery being planar, it is also possible to provide the distinct segments with facing outer/inner peripheries that co-operate. Figure 5A shows a portion of a further flame arrester element 100 comprising a distinct first segment 11 1 and a distinct second segment 1 12. Each segment 1 1 1 , 1 12 may comprise an outer periphery and an inner periphery and a flame arrester element portion therebetween. In this case it is crimped ribbon, but other materials may of course be used. The first segment 1 1 1 has an outer periphery 1 1 1 B and the second segment 1 12 has an inner periphery 1 12A, each having a respective extension portion 11 1 C, 112C which co operates to ensure that the passage between the distinct segments 11 1 , 112 is tortuous. Other or alternate cooperating portions may be provided. For example, the co-operating portions may comprise male/female members, aligned castellations and so on. Preferably, the cooperation between adjacent distinct segments will provide a tortuous passageway between the segments 1 11 , 112 from one side of the flame arrester element to another. In this fashion even if the segments are not so closely matched as to generate a fluid tight seal (as indicated in Figure 5A), the tortuous passageway will inhibit (if not prohibit) the flow of fluid between the distinct segments and/or will prevent passage of a detonation or deflagration front. Additionally or alternatively, the gap between successive segments (whether provided with mutually cooperating portions or not) may have a resilient material located therein, to inhibit or prohibit flow between successive segments. Figure 5B shows a portion of a further flame arrester element 100’ with closely matched successive segments 1 11’, 1 12’, whereby a fluid tight engagement is provided between the segments 11 1’, 112’.

Figure 6 shows a housing 61 for use with a flame arrester element. The housing 61 has a side wall 61 a for radial containment of the flame arrester element, and support bars 61 b for axial containment of the flame arrester element. A cover, typically in the form of further support bars (not shown) can be received on a shoulder 61 d which is provided on the side wall 61 a opposite to the support bars 61 b, if required. The housing 61 can receive a flame arrester element, for example the flame arrester elements disclosed herein. The support bars 61 b provide spaces therebetween to allow for the flow of fluid through the housing 61. Any number and pattern of support bars 61 b may be provided. The housing 61 contains a central aperture 61 c for receiving fixing means for securing a flame arrester element to the housing 61. The cover also contains a central aperture for securing it to the housing. Said fixing means may extend through the flame arrester element, for example through the aperture formed by the solid inner wall 1 1 A shown in Figure 1 A.

Referring to Figure 7 A there is provided an exploded view of a segmented flame arrester element according to the invention, and its corresponding housing. Figures 7B to 7D show the sequential insertion of concentric distinct flame arrester element segments 71 1 , 712, 713 into the housing 61. Figure 7B shows the outer distinct flame arrester element segment 713 installed within the housing 61. Figure 7C shows the outer distinct flame arrester segment 713 and the central distinct flame arrester element segment 712 installed within the housing 61. Figure 7D shows the outer distinct flame arrester element segment 713, the central distinct flame arrester element segment 712, and the inner distinct flame arrester element segment 71 1 installed within the housing 61. The inner distinct flame arrester element segment 71 1 contains a central aperture 711 a for receiving a securing means, such as a bolt or rivet, and corresponds with the central aperture 61 c in the housing 61.

As is visible in Figures 7B-7D, the space defined by the housing 61 is not filled in the axial direction by distinct flame arrester element segments. In Figure 8 there is provided a plurality of distinct flame arrester element segments arranged in layers 81 in the axial direction within the housing 61. In this embodiment each flame arrester element layer 81 comprises an outer, central and inner distinct flame arrester element segment and each distinct flame arrester element segment is the same size in each flame arrester element layer 81. However, the distinct segments may vary in size throughout the layers. Further, the number of distinct segments in each layer may vary throughout the layers. An element ring 85 is also provided and the flame arrester element layers 81 are contained within the space created by the housing 61 and the element ring 85. The element ring 85 is received on the shoulders 61d of the housing 61. The element ring 85 contains support bars 85a to provide gaps for the flow of fluid therethrough. Any number and pattern of support bars 85a may be provided. The element ring 85 and flame arrester element layers 81 are secured in place by a threaded insert 84 which is received in the central aperture 61 c of the housing 61 , and in a central aperture 85b of the element ring 85. In this embodiment eight flame arrester element layers 81 are provided. However, any number of flame arrester element layers 81 are envisaged. Although in this embodiment each flame arrester element layer 81 contains three concentric distinct flame arrester element segments, the flame arrester element layers 81 may contain a single flame arrester element, or any number of distinct flame arrester element segments.

Figure 8A shows an enlarged view of section A of Figure 8.

In a further embodiment of the invention, the stacked flame arrester elements contained within a housing, as shown in Figure 8, are separated by intermediate layers (not shown) in the form of support bars or spacer members. The intermediate layers are present between adjacent flame arrester element layers. These intermediate layers allow flame arrester element layers to be handled separately from adjacent flame arrester element layers more easily. In Figure 9 there is provided a plurality of distinct flame arrester element segments arranged in layers 91. Each layer comprises a flame arrester element according to the embodiment shown in Figure 1A, with the exception that there are three distinct segments 911 ; 912; 913 instead of the five shown in Figure 1A. Accordingly, like features are denoted with a preceding‘9’ in Figure 9. Although three distinct flame arrester element segments 911 ; 912; 913 are shown for each layer 91 , any number of distinct flame arrester element segments are envisaged in each layer 91. Similarly, although three flame arrester element layers 91 are shown, any number of layers are envisaged. Upon stacking the flame arrester element layers 91 , the solid inner peripheries 911 A; 912A; 913A and the solid outer peripheries 911 B; 912B; 913B of each layer abut that of the preceding and/or succeeding layer.

The flame arrester element layers 91 of Figure 9 may be secured together. This may be achieved using securing means (not shown) located at the periphery of each layer. Otherwise, the layers 91 may be secured by fixing means extending through inner and/or outer peripheries 911A; 911 B; 912A; 912B; 913A; 913B of each layer (not shown). The fixing means may be screws, bolts or pins. The assembled flame arrester element layers 91 may be then installed into a housing, such as housing 61 shown in Figure 6, to form a flame arrester. Successive flame arrester element layers 91 may be separated by intermediate layers such as spacers.

Otherwise, the inner and/or outer peripheries 911 A; 911 B; 912A; 912B; 913A; 913B of each layer may extend, in the axial direction, beyond the remainder of the flame arrester element layer 911 ; 912; 913 (e.g. beyond the crimped ribbon of the flame arrester element layer 911 ; 912; 913). In this way, the section of each flame arrester element layer 91 which is not the inner or outer periphery 911A; 911 B; 912A; 912B; 913A; 913B (e.g. the crimped ribbon section) may be spaced from that of preceding and/or succeeding layers.

Each or plural flame arrester element layer(s) may be provided in one or more housings. Plural housing may be secured together. Successive housings may be separated by intermediate layers such as spacers

The flame arrester element layers have improved handleability, and each distinct layer is easily produced with the conventional manufacture technology. The weight of each layer is less than the total weight of the flame arrester element, which enables each layer to be transported and handled separately before assembling into the final flame arrester element. Otherwise, the flame arrester element is very difficult to be manufactured and handled.

The performance of the flame arrester element is also improved. In embodiments, wherein the flame arrester element layer is provided by a wound crimped metal strip, the hoop stress within each distinct segment provides structural rigidity by means of interwinding friction, which prevents collapse by telescoping. When flame arrester elements are provided in series each layer comprises narrower metal strips, so the weight to overcome the interwinding friction to cause telescoping is reduced. Therefore, the pore size of each flame arrester element portion is more consistent, and is easier to control, which leads to improved flame arrester element performance.

Furthermore, the performance of the flame arrester is increased as the pore size is variable in the fluid-flow direction of the flame arrester.

Additionally, maintenance and repair of the flame arrester element is improved. Each individual distinct layer and segment may be repaired or replaced separately or on an individual basis, which is more cost effective by reducing the need to replace the entire flame arrester element.

The flame arrester elements are described as being circular, in plan. Other shapes may be deployed. Further, each distinct flame arrester element segment is described as being circular or annular in plan, but other shapes may be deployed. It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

1. A flame arrester element, the flame arrester element comprising a distinct first segment and a distinct second segment, the distinct first segment comprising a first flame arrester element portion and an outer periphery, the distinct second segment comprising an inner periphery and an outer periphery and a flame arrester element portion located therebetween, wherein the distinct first segment and the distinct second segment are located within one another, the outer periphery of the distinct first segment and the inner periphery of the distinct second segment being adjacent.

2. A flame arrester element according to Claim 1 , wherein the distinct first segment comprises an inner periphery.

3. A flame arrester element according to any of Claims 1 or 2, wherein the distinct first segment comprises a solid inner wall and/or wherein the distinct second segment comprises a solid inner wall to provide its inner periphery.

4. A flame arrester element according to any preceding Claim, wherein the distinct first segment comprises a solid outer wall to provide its outer periphery and/or wherein the distinct second segment comprises a solid outer wall to provide its outer periphery.

5. A flame arrester element according to Claim 3 or Claim 4, wherein the solid inner wall of the distinct first segment and/or the solid inner wall of the distinct second segment and/or the solid outer wall of the distinct first segment and/or the solid outer wall of the distinct second segment is formed from a solid annulus, e.g. a pipe section or a ring, and/or is formed from successive windings of thin strip material.

6. A flame arrester element according to any preceding Claim, wherein the distinct first segment and/or the distinct second segment comprises a continuous winding of flat strip material.

7. A flame arrester element according to any preceding Claim, further comprising one or more further distinct segments.

8. A flame arrester element according to Claim 7, wherein each of said first and second distinct segments and said one or more further distinct segments are located sequentially within one another.

9. A flame arrester element according to any preceding Claim, wherein the distinct first segment and the distinct second segment each have a thickness and the thickness of the distinct first segment is the same or different to the thickness of the distinct second segment.

10. A flame arrester element according to any preceding Claim, wherein the distinct first and/or distinct second segment and/or at least one of a or said one or more further distinct segments comprise a flame arrester element portion.

11. A flame arrester element according to Claim 10, wherein the flame arrester element portion is provided between the or a respective inner periphery and the or a respective outer periphery.

12. A flame arrester element according to Claim 10 or 11 , wherein the flame arrester element portion comprises or is formed by a continuous winding of adjacent flat and corrugated material, e.g. strips.

13. A flame arrester element according to any one of Claims 10 to 12, wherein the flame arrester element portion is connected to an inner periphery and/or outer periphery of the respective segment.

14. A flame arrester element according to any preceding Claim, further comprising support bars and/or a flame arrester element spacer member.

15. A flame arrester element according to Claim 14, wherein the support bars and/or the flame arrester element spacer member are affixed to the inner periphery of the first distinct segment and/or to the inner and/or outer periphery of the second distinct segment.

16. A flame arrester element according to any preceding Claim, wherein the outer periphery of the first distinct segment and the inner periphery of the second distinct segment have cooperating facing portions.

17. A flame arrester element according to Claim 16, wherein the cooperating facing portions together define a tortuous passageway.

18. A flame arrester element according to any of Claims 1 to 17, wherein the outer periphery of the distinct first segment and the inner periphery of the distinct second segment are shaped and sized such that a substantially fluid-tight engagement is created therebetween.

19. A method of forming a flame arrester element, the method comprising providing a distinct first flame arrester segment having a first flame arrester element portion and an outer peripheral solid wall, providing a distinct second flame arrester segment having a second flame arrester element portion, an inner peripheral solid wall and locating the outer peripheral solid wall of the distinct first flame arrester segment adjacent the inner peripheral solid wall of the distinct second flame arrester segment.

20. A method according to claim 19, wherein said first and second flame arrester segments are located such that a gap is formed between the outer peripheral solid wall of the distinct first flame arrester segment and the inner peripheral solid wall of the distinct second flame arrester segment.

21. A method according to claim 20, comprising locating a resilient material in the gap between the outer peripheral solid wall of the distinct first flame arrester segment and the inner peripheral solid wall of the distinct second flame arrester segment.

22. A method according to Claim 19, 20 or 21 , comprising securing the distinct first flame arrester segment within the distinct second flame arrester segment, e.g. in a concentric arrangement.

23. A method according to any of Claims 19 to 22, comprising providing the distinct first flame arrester segment and/or distinct second flame arrester segment by continuous winding of a flat strip.

24. A method according to Claim 23, further comprising continuously winding a corrugated strip with the flat strip to form a respective flame arrester element portion.

25. A method according to any of Claims 19 to 24, comprising locating the flame arrester element within a housing.

26. A flame arrester comprising one or more flame arrester elements of any of Claims 1 to 18.

27. A flame arrester according to claim 26, wherein the said one or more flame arrester elements are located within one or more respective housings.

28. A flame arrester according to claim 27, comprising plural flame arrester elements each having a respective housing, and wherein said housings are secured together.