WO2014091254A1

WO2014091254A1 - Fire resistant structure

Info

Publication number: WO2014091254A1
Application number: PCT/GB2013/053310
Authority: WO
Inventors: Keith Murray
Original assignee: Darchem Engineering Limited
Priority date: 2012-12-14
Filing date: 2013-12-16
Publication date: 2014-06-19
Also published as: KR20200102555A; GB2510961B; EP2932569A1; KR20150116823A; GB2510961A; GB201322235D0

Abstract

A fire resistant structure is used for forming a duct and/or for protecting equipment. A first structural frame unit is connected to a second structural frame unit via a frame connection member. A first heat resistant panel attached to an outwardly-facing side of the first structural frame unit and a second heat resistant panel attached to an outwardly-facing side of the second structural frame unit. A heat resistant inter-panel member is positioned between the first heat resistant panel member and the second heat resistant panel member and covering the frame connection member, such that the first and second heat resistant panels and the heat resistant inter-panel member form a continuous covering of the first and second structural frame units. One or more removable fasteners are used to connect the heat resistant inter-panel member to the first and second heat resistant panels.

Description

Fire Resistant Structure

FIELD OF THE INVENTION

The present invention relates to a fire resistant structure for forming a duct and/or for protecting equipment (e.g. by encasing equipment), the present invention relates in particular, but not exclusively, to a fire resistant cable duct.

BACKGROUND OF THE INVENTION

A fire resistant structure is often provided to protect safety or critical electrical equipment and cables against a building fire, for example in nuclear power stations. Generally, such protection is provided by fire resistant boards fitted together to form a barrier around the electrical equipment and/or cables. The level of protection required can be optimised by altering the number of fire resistant boards.

The fire resistant boards are often connected together using a metallic wire fastener, for example lacing anchors, quilting pins or self-drilling self-tapping screws. The metallic wire fasteners are positioned on an outer surface of the boards, which means that in a fire situation the fasteners are affected by the heat of the fire and the structural integrity of the fire resistant structure can be compromised.

SUMMARY OF THE INVENTION

The present invention aims to address one or more problems associated with the prior art.

In a first aspect the invention provides a fire resistant structure for forming a fire resistant duct and/or for protecting equipment (e.g. by encasing equipment), the fire resistant structure comprising: a first structural frame unit connected to a second structural frame unit via a frame connection member; a first heat resistant panel attached to an outwardly-facing side of the first structural frame unit and a second heat resistant panel attached to an outwardly-facing side of the second structural frame unit; a heat resistant inter-panel member positioned between the first heat resistant panel member and the second heat resistant panel member and covering the frame connection member, such that the first and second heat resistant panels and the heat resistant inter-panel member form a continuous covering of the first and second structural frame units.

In the present application, an inwardly-facing side refers to a side facing towards a region defined by the fire resistant structure, e.g. in use towards another side of the fire resistant structure, towards an external structure to which the fire resistant structure is connected, or towards equipment to be protected and an outwardly-facing side refers to a side facing away from a region defined by the fire resistant structure, e.g. in use away from other sides of the fire resistant structure or equipment to be protected.

The panels used in the present invention may each be a single continuous panel or be composed to multiple panels to form a composite panel, e.g. with individual panel members arranged in side- to-side tessellation.

The fire resistant structure may define a cable duct or ventilation duct. Alternatively, the fire resistant structure may be used for the protection of junction boxes, raceways, cabinets or any other type of equipment that may require cladding with a fire resistant material to reduce heat transfer to the equipment in an event of a fire.

Provision of frame units to which the heat resistant panels are clad provides a structure that supports the heat resistant panels even in the event of a fire, such that the structural integrity of the structure is improved compared to the cladding methods of the prior art.

Further, when the fire resistant structure defines a cable duct, maintenance of structural integrity during a fire can remove the need for a cable tray because the frame itself can provide the same function as a cable tray. In exemplary embodiments, one or more removable fasteners are used to connect the heat resistant inter-panel member to the first and second heat resistant panels.

The use of removable fasteners to connect the fire resistant inter-panel members and/or spacers to adjacent heat resistant panels provides quick and easy access to a connection between adjacent frame units, which improves ease of access to equipment, e.g. cables, for maintenance.

The first and second frame units may be arranged substantially perpendicular to each other. An angled frame connection member (e.g. an L-shaped frame member) may connect two adjacent frame units positioned at an angle to each other (e.g. substantially 90 degrees to each other).

The heat resistant inter-panel member may comprise a heat resistant corner member arranged so as to form a hollow region between the heat resistant corner member and the angled frame member.

The first and second frame units may be connected so as to be co-planar.

The fire resistant structure may comprise: a third structural frame unit connected to the second structural frame unit via a planar frame connection member so as to be coplanar with the second structural frame unit. The fire resistant structure may comprise a third heat resistant panel connected to an outwardly-facing side of the third structural frame unit. The fire resistant structure may comprise a further heat resistant inter-panel member between the second and third heat resistant panels. A further removable fastener may connect the heat resistant inter-panel member to the second and third heat resistant panels. The removable fastener may comprise a series of lacing anchors positioned on the first and second heat resistant panels and wire lacing between the anchors on the first and second heat resistant panels to secure the heat resistant inter-panel member to the first and second heat resistant panels.

The further heat resistant panels may be attached to an inwardly-facing side of the first structural frame unit and the second structural frame unit.

The first, second, and further heat resistant panels may be made from the same material. The first, second, and further heat resistant panels have the same thickness to provide a similar barrier to heat transfer. The present inventor has found that it is beneficial to provide a fire structure with symmetrical heat resistant properties, so that there is no preferential direction for heat transfer. This has been found to be particularly beneficial when the fire structure is used to protect electrical equipment and/or electrical cables. The fire resistant structure may comprise further frame units connected together to form a three-sided or four-sided structure.

The fire resistant structure may comprise a plurality of structural frame units arranged to define a straight, bent, curved or T-shaped channel.

The fire resistant structure may define a cable duct. Further heat resistant panels may be attached to an inwardly-facing side of the first structural frame unit and the second structural frame unit. The first frame unit and the second frame unit may each define a void so as to form a hollow region between the first and second heat resistant panels and the further heat resistant panels.

The first frame unit and the second frame unit may comprise a plurality of holes along a side face for providing a position of attachment to another frame unit, a frame connection member, or an external structure, and/or for reducing heat build-up in the frame unit. The provision of holes in the frame units advantageously reduces the weight of the fire resistant structure. Reduced weight is particularly desirable when the fire resistant structure defines cable ducting or ventilation ducting. The holes also reduce transfer of heat through the frame from one side to the other. The holes also allow bolting or connection points without the use of additional angles which would otherwise be exposed to fire.

Each frame unit may comprise a series of holes on a perimeter of a front and/or rear face, and one or more of said holes may receive a fastener to attach one of the heat resistant panels to said frame unit.

In a second aspect the invention provides a fire resistant assembly comprising the fire resistant structure according to the first aspect and a cable tray. In a third aspect the invention provides a fire resistant structure for protection of ducts and/or equipment, the fire resistant structure comprising: a plurality of frame units attached together to form a substructure of the fire resistant structure; and a plurality of heat resistant panels arranged to clad the substructure so as to cover an outward- facing side of the substructure for reducing heat transfer through the fire resistant structure.

A plurality of fire resistant panels may be arranged to clad an inward-facing side of the substructure. Such an arrangement prevents a fire at the duct or equipment protected by the fire structure from spreading, this is particularly beneficial when the fire structure is used for protecting electrical equipment, for example cable ducts.

The same type of fire resistant panels may be positioned on the inward-facing side of the substructure as on the outward-facing side of the substructure. The fire resistant panels on the inward-facing side of the substructure may provide the same thickness of cladding as the fire resistant panels on the outward-facing side. The present inventor has found that it is beneficial to provide a fire structure with symmetrical heat resistant properties, so that there is no preferential direction for heat transfer. This has been found to be particularly beneficial when the fire structure is used to protect electrical equipment and/or electrical cables.

A heat resistant spacer member and/or heat resistant corner member may be positioned between two or more heat resistant panels on an outwardly-facing side of the substructure.

The heat resistant spacer member and/or heat resistant corner member may be connected to the adjacent panels via a removable fastener.

The removable fastener may comprise a series of lacing anchors and wire lacing between at least two lacing anchors. The lacing anchors and wire may be made from a metallic alloy.

The heat resistant spacer and/or heat resistant corner member may be positioned in a region of attachment between two frame units to cover a connection between the two frame units. Two or more frame units may be arranged substantially perpendicular to each other.

An angled frame member, e.g. an L-shaped frame member may connect two adjacent frame units positioned substantially perpendicular to each other.

A fire resistant corner member may be clad to the angled frame member so as to form a hollow region between the fire resistant board and the L-shaped frame member.

The substructure may define a two-sided, three-sided or four-sided structure.

The substructure may define a straight, bent, curved or T-shaped channel through which cables can extend.

The fire resistant structure may define a cable duct. Each frame unit may define a void such that when a fire resistant panel is clad to an inwardly-facing and an outwardly facing side of the frame unit, a hollow region is formed therebetween.

The frame units may comprise a plurality of holes along a side face for providing a position of attachment to another frame unit or external structure, and/or for reducing heat build-up in the frame unit. The provision holes in the frame units advantageously reduces the weight of the fire resistant structure. Reduced weight is particularly desirable when the fire resistant structure defines cable ducting or ventilation ducting.

The frame units may comprise a series of larger diameter holes and a series of smaller diameter holes along a side face. One or more of the larger diameter holes may be intended for attachment to an external structure. The larger holes may be dimensioned for attachment to an external structure using a plurality of plates and bolts. For example, the fire resistant structure may comprise a plurality of plates and fasteners, the plates being dimensioned to have a width greater than the diameter of the larger hole, the fastener and plates being used to attach the fire resistant structure to an external structure. Use of the larger diameter holes for attachment in such a way means that the accuracy required for connection of the fire resistant structure to an external structure is significantly reduced, compared to using a simple bolt and hole arrangement. The larger holes may be axially aligned. The smaller holes may be interspaced between the larger holes, for example, four smaller holes may surround each larger hole.

One of the plurality of fire resistant panels may be positioned coincident to one of the frame units and clad thereto. The fire resistant panels may be clad to the substructure using a fastener, e.g. a threaded fastener. Such an arrangement of frame units and fire resistant panels eases access to equipment for maintenance, compared to removing the fire resistant material from the cladding systems of the prior art.

Each frame unit may comprise a series of holes on a perimeter of a front and/or rear face, and one or more of said holes receives a fastener to attach one of the fire resistant panels to said frame unit. The fastener may be threaded fastener. A ferrule may be positioned through the fire resistant panel at a position coincident with the fastener so as to reduce or prevent direct contact of the fastener with the fire resistant panel.

The frame unit may be square, rectangular, or trapezoidal in shape. The frame unit may include a corner brace at each corner of the frame unit to improve the stability of the frame unit.

The frame unit may be formed from two or more frame members folded from a flat- pack configuration.

Each frame member may be folded to form two sides of a frame unit, such that two frame members when fastened together (e.g. by screws or bolts) may form a frame unit. Alternatively, each frame member may form one side, three sides or four sides of a frame unit. The frame member may comprise two sides that can be folded to form a perimeter, or a portion of a perimeter, of two sides (e.g. fire facing sides) of the frame unit. The frame member may be an elongate member that can be folded to an L-shape. The frame member may have four side flaps that can be folded substantially perpendicular to a central region of the elongate member to form a perimeter of two sides of a frame unit (e.g. fire facing sides). The elongate member may comprise a flap at a longitudinal extent that can be folded to ease connection of the elongate frame member to a further frame member, when folded to an L-shape. The fire resistant structure may comprise a cover panel positioned over the fire resistant panels to cover an outwardly-facing side of the fire resistant structure. Alternatively, a fire resistant fabric cover may cover the fire resistant panels.

The fire resistant structure may comprise a gasket (e.g. an expandable gasket) positioned between adjacent heat resistant panels and/or between adjacent frame units (e.g. along one or more sides of each frame unit).

The frame units may be made from metal, e.g. steel.

Each of the plurality of fire resistant panels may comprise an endothermic-reactive insulating fibrous material. This type of fire resistant panel has been found to be particularly beneficial for reducing heat transfer. Further, when the fire resistant structure is used for protecting electrical equipment and/or electrical cables, this type of material is beneficial because the material is breathable under normal (non-fire) conditions, which means that the fire resistant panel has a limited effect on electrical current. The insulating fibrous material may include: (i) an inorganic endothermic filler which undergoes multiple endothermic reactions between the range of 100°C and 750°C; (ii) inorganic fiber material; and (iii) an inorganic polymer binder.

The inorganic endothermic filler may be an hydrated compound and at least one endothermic reaction may comprise dehydration. The hydrated inorganic compound may be in combination with a fibrous component and the ratio of inorganic endothermic component to fibre may be between 0.25 and 3.0.

The endothermic inorganic compound may dehydrate in a first endothermic reaction and then may emit an inert gas on further heating in a second endothermic reaction. The inert gas can increase the insulating effect of the heat resistant panel, i.e. the material can be breathable when required (i.e. in non-fire situations) and then in fire situations reactions can occur to provide the necessary insulating effect.

The dehydration reaction may release water vapour. The inorganic compound may be a hydrated carbonate. In such embodiments, the inorganic compound may react firstly to release the water of hydration, and secondly to release carbon dioxide as in the following chemical equations for a bivalent metallic element M:

MC0₃.nH₂0 ^Heat ) MC0₃ + nH₂0 MC0₃ ^Heat ) MO + C0₂ The carbon dioxide released in the second endothermic mechanism is inert and therefore will tend to further stifle any fire which may exist.

The endothermic reactions may continue to absorb heat from the surroundings up to 750°C. The endothermically reactive inorganic compound may be Magnesium Carbonate-Hydrate optionally in combination with Magnesium Calcium Carbonate. This may be supplemented with 1-2% hydrated Zinc Borate or Zinc Stanate, 3-5% crude Vermiculite.

The weight ratio of endothermic filler of part (i) to the inorganic fibre of part (ii) may be in the range of 0.25 to 3.0. The filler may have a particle top size of >150 micrometers. The weight ratio of organic to inorganic constituents is may be less than 0.2.

In a fourth aspect the invention provides a method of fire proofing a component (e.g. a cables, a ventilation system, electrical equipment or machinery), the method comprising: providing a plurality of frame units; connecting the plurality of frame units to form a substructure; and cladding a plurality of heat resistant panels to an outward-facing side of the substructure.

Each of the plurality of frame units may be provided with a heat resistant panel clad to one side. The frame units may be connected together to form a substructure with the heat resistant panels facing inwardly. The plurality of heat resistant panels may then be clad to an outward-facing side of the substructure so as to form a fire resistant structure having both an inwardly-facing and an outwardly facing side clad with a plurality of heat resistant panels.

Two or more frame units may connect together to form a two-sided, three-sided or four-sided structure. The method may comprise configuring one or more flat-pack frame members to form one of said frame units.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of a section of a three sided fire resistant cable duct connected to a concrete wall;

Figure 2 shows an exploded view of a frame unit of the cable duct of Figure 1;

Figure 3 shows a frame member of the frame unit of Figure 2; Figure 4 shows a perspective view of an initial stage of assembly of the cable duct of Figure 1;

Figure 5 shows a perspective view of the cable duct of Figure 1 at a subsequent step of assembly to that shown in Figure 4;

Figure 6 shows a perspective view of a corner section of the cable duct of Figure 1 at a subsequent step of assembly to that shown in Figure 5;

Figure 7 shows a perspective exploded view of a fastener used to connect the cable duct of Figure 6 to a concrete wall;

Figures 8 to 13 shows a perspective view of sequential assembly steps of the cable duct of Figure 1 ; Figure 14 shows a perspective view of a two sided fire resistant cable duct connected to a concrete wall;

Figure 15 shows a perspective view of a three sided fire resistant cable duct forming a curved corner region;

Figure 16 shows a perspective view of a three sided T-shaped fire resistant cable duct; Figure 17 shows a perspective view of a three sided fire resistant cable duct having a horizontal and a vertical section;

Figure 18 shows a perspective view of a four sided fire resistant cable duct; and

Figure 19 shows a perspective view of a three sided fire resistant structure for protecting a wider region of cables or equipment.

DETAILED DESCRIPTION OF EMBODIMENT(S)

Referring to Figure 1, a section of fire resistant structure, in this embodiment a cable duct for protecting cable, is indicated generally 10. The cable duct 10 is connected to a concrete wall 8. In the present embodiment, the cable duct is a three-sided structure extending along the concrete wall 8 and defining a channel 11 of rectangular cross section through which cables and/or a cable tray can extend (no cable or cable tray is shown in Figure 1, but a cable tray is indicate at 6 in Figure 10).

A plurality of structural frame units 12 define a substructure of the cable duct. In the present embodiment, the substructure includes a series of side frame units and connecting frame units joined together to form a three-sided substructure. In the present embodiment the frame units are rectangular in shape. The side frame units are joined to the connecting frame units via a frame connection member, in this embodiment an L-shaped frame member 13, i.e. a side of a connecting frame unit connects to one side of the L-shaped frame member 13, and a side of a side frame unit connects to the other side of the L-shaped frame member 13. The frame units and L- shaped frame members are connected together using fasteners 18, e.g. a bolt and nut.

Heat resistant panels 14b are clad to the frame units 12 on an inward-facing side of the substructure formed by the frame units 12. Heat resistant panels 14a are clad to the frame units 12 on an outward-facing side of the substructure. In the present embodiment each of the heat resistant panels 14a, 14b are clad to be coincident with one of the frame units 12. A fire-resistant inter-panel member is positioned between the side heat resistant panels clad to the side frame units and the connecting frame unit. In the present embodiment, the fire resistant inter-panel member is a fire resistant corner member 40 positioned along each corner of the substructure. In the present embodiment, the corner members 40 are substantially L-shaped and are arranged so as to form a substantially square shaped channel with the L-shaped frame member 13.

The heat resistant panels 14a, 14b are connected to the frame units 12 using fasteners 38, which in this embodiment are threaded fasteners. The connection between the heat resistant panels and the frame units is such that it is possible to remove one of the connecting frame units with the fire resistant boards attached from the cable duct 10 when maintenance is required.

The fire resistant corner members 40 are secured in place via wire lacing. A series of wire anchors, in this embodiment J hooks 44, are provided on the heat resistant panels 14a near a junction with a respective fire resistant corner member 40, and on each side thereof. A wire 46 loops around two J hooks, one on either side of the fire resistant member 40, to secure the fire resistant member in place. In this embodiment, the wire and J hooks are made from a metallic alloy. The cable duct 10 is connected to the concrete wall 8 using a plurality of L-shaped frame members 48, shown in more detail in Figure 6. One side of the L-shaped frame member fastens to a side of a respective frame unit, and the other side of the L-shaped member connects to the concrete wall 8.

The individual components of the cable duct 10 will now be described in more detail. Referring to Figure 2, each frame unit 12 is formed using two frame members 20. Each frame member 20 is substantially L-shaped and the frame members 20 connect together to form a frame unit 12. One of the frame members 20 is shown in an unfolded ("flat-pack") configuration in Figure 3.

The frame member 20 includes a side face 22 that connects to another frame unit 12 or an L-shaped frame member 13 or 48. A flap 24 of the flat-pack frame member 20 folds substantially perpendicularly to the side face 22 to form a portion of a perimeter around the frame unit 12 to which the heat resistant panel 14a, 14b can be attached. In this embodiment, a flap 24 is positioned on two opposing sides of the side face 22 so as to create a perimeter on both of the outwardly-facing and inwardly-facing sides of the frame unit 12. A flap 26 at one longitudinal end of the flat-pack frame member 20 is folded substantially perpendicularly to the side 22 so as to form a surface to which the other frame member 22 can connect to form the frame unit 20.

A series of holes are provided along the side 22 of the frame member 20 of the frame unit 12. The holes are of two sizes, namely axially aligned larger diameter holes 30 and axially aligned smaller diameter holes 32. The smaller diameter holes 32 are positioned to surround the larger diameter holes 30 with equal spacing.

A series of holes 27 are provided along the perimeter 24 of the frame unit 12 (not shown in Figure 5 for clarity) for receiving the fastener 38 for connection of the heat resistant panels 14a, 14b to the frame unit 12.

In this embodiment the frame members 20 are manufactured from galvanised carbon steel. However, in alternative embodiments any suitable metal or material may be used.

Referring to Figures 4 and 5, the L- shaped member 13 used to connect frame units 12 together comprises smaller and larger diameter holes sized and arranged to be coincident with the respective smaller and larger diameter holes of the respective sides of the frame units 12 to be connected. The frame units 12 are connected to the reshaped frame member using a fastener 18 received through the smaller diameter holes 32 (only one labelled for clarity). In this embodiment, the position of the fasteners 18 is at each longitudinal end of the frame units 12 on either side of one of the larger diameter holes 30. The holes 32 not used for attachment contribute to reducing heat build-up in the frame unit 12 during a fire situation.

Frame units 12 that are connected together in a coincident plane are connected in a similar way, and the fasteners may either directly connect the frame units 12 together, or the frame units 12 may be connected together via, for example a frame connection member of square cross section (see for example feature 60 in Figure 9). When a frame connection member is used, a heat resistant inter-panel member, e.g. a heat resistant spacer, is positioned between adjacent heat resistant panels, to fill a gap corresponding to the position of the frame connection member. It can be seen from the exploded view shown in Figure 2, that a central region of the frame unit 12 defines a void. This creates a series of hollow regions 40 between the inward-facing and outward-facing sides of the cable duct. Such a hollow region reduces heat flow through the cable duct. Referring again to Figure 2, ferrules 36 are positioned through each heat resistant panel 14a, 14b. A fastener 38 extends through the frame unit 12, and the ferrule 36 to clad the heat resistant panel 14a, 14b to a respective frame unit 12.

In this embodiment, the material and thickness of the heat resistant panels on both the inwardly-facing side and the outwardly-facing side of the frame units is the same. This creates symmetrical thermodynamic properties through a wall of the cable duct formed by the frame units 12 and the heat resistant panels 14a, 14b.

In this embodiment, the heat resistant panels are formed using the fire protection material described in US5834120, and the following is a brief summary of the material. The heat resistant panel includes organic fibres, inorganic endothermic material and organic binder. The inorganic fibres are refractory materials which combine high strength together with good thermal resistance and the ability to withstand thermal shock. The fibres form a matrix for retaining high levels of the endothermic filler in interstices between fibres. Suitable fibres for this purpose are silica, alumino- silicate and glass fibre or other fibres often classified as MMVF, in this embodiment the fibre is aluminosilicate. The mean fibre diameter should be in the range 1 to 8 micrometers with a full range of 0.5 to 12 micrometers and an original maximum fibre length of up to 150 mm. The fibre content may be 20-40%.

The inorganic endothermic material is in the form of a powder with a topside >250 micrometers. The endothermic material filler is able to provide multiple endothermic reactions across a temperature spectrum from 100°C to 750°C, and includes hydrated magnesium carbonate. The loss on ignition for the endothermic material should be >50% by weight. The weight ratio of endothermic filler to inorganic fibre is in the range 0.25 to 3.0 and the endothermic material includes 50-75%. The hydrated magnesium carbonate is Ultracarb HFD. The amount of organic binder is less than 20%, about 4.5% in this embodiment. The binder is selected from various polymers and elastomers in latex form: a suitable binder being an acrylic resin type which provides excellent heat resistance, ongoing properties and non-corrosive combustion products. The material may also include Vermiculite- sodium silicate or other suitable filler material.

The heat resistant panels 14a, 14b may be layered, and the number of heat resistant panels in a layer can be varied depending on the fire protection required. In the present embodiment, the heat resistant panels 14a, 14b are coincident with the frame units 12. However, in alternative embodiments the heat resistant panels may be clad to the frame units using any appropriate configuration. Cladding the heat resistant panels to be coincident with the frame units eases assembly of the cable duct and access for maintenance of the cables.

In the present embodiment, a fire resistant cloth (e.g. made of a similar material to the heat resistant panels) is used to cover the fire resistant panels. However, in alternative embodiments, no cloth may be provided or a cover panel may be positioned over each of the heat resistant panels 14a. The cover panel may be made from a powder coated carbon steel, but in alternative embodiments any suitable material may be used.

An expandable gasket 17 is positioned between each of the heat resistant panels and at an interface between the cable duct and the concrete wall 8. The expandable gasket restricts heat leakage at the point of abutment of the heat resistant panels.

To assemble the cable duct 10, first the required number of frame members 20 are bent to form the required number of frame units 12. That is, the flaps 24 and 26 of the frame member 20 are bent perpendicular to the side 22. A first portion of the frame member 21a is then bent substantially perpendicular to a second portion 21b of the frame member 20. Two bent frame members are then bolted together via the end flaps 26. The required number of frame units 12 are assembled in the same manner.

A heat resistant panel 14b is then fastened to one side of each of the frame members using fasteners 38. It is intended that in some applications, the frame units will be supplied assembled with a heat resistant panel 14b attached to one side. The expandable gasket is then connected to the fire resistant panels using, for example, staples and/or glue.

Referring to Figures 4 and 5, the frame units 12 are then bolted together. Frame units positioned substantially perpendicular to each other are bolted together via the L- shaped frame member 13, as previously discussed. Frame units positioned in substantially the same plane are bolted directly together or via a frame connection member 60 using the smaller holes 32, as discussed previously.

Referring to Figure 6, the assembled frame units 12 are connected to the concrete wall 8 via the L-shaped frame members 48, as previously described. The L-shaped frame member is secured to the concrete wall 8 using, in this embodiment, a plurality of two part fasteners 50, 52 (illustrated in Figure 7), and a plurality of plates 54 (illustrated in Figure 7) dimensioned to be of greater width than the diameter of the larger hole 30 of the frame unit 12. A threaded portion 52 of the two part fastener passes through the plate 54, through one of the larger holes 30, and into the external structure 8. A head 50 of the two part fastener secures the plate against the frame unit 12 so as to attach the frame unit to the external structure 8. In alternative embodiments, any other suitable method of attachment may be used.

Referring to Figures 8 to 13, the heat resistant panels 14a are then connected to the outward facing sides of the frame units 12 using fasteners 38. The section of the cable duct 10 shown in Figure 8 is a corner section. In the corner region a square frame unit is provided. A frame connection member 60 connects the square frame unit of the corner region to a rectangular frame unit along a side of the cable duct 10. A heat resistant inter-panel member, in this embodiment a heat resistant spacer 58, is positioned in gaps formed between the heat resistant panels due to the frame connection member. The heat resistant spacers are secured to the heat resistant panels 14a using a series of J hooks 44 and wire 46, as described previously.

The heat resistant corner members are then positioned on the corners of the substructure using J hooks 44 and wire 46, as previously discussed. Advantageously, providing heat resistant panels 14a, 14b on both an inward-facing side and an outward-facing side of the substructure means that the cable duct provides protection against both a fire outside the cable duct and a fire inside the cable duct. Cladding the frame units 12 with the heat resistant panels 14a, 14b means that there is no or reduced compromise to the integrity of the substructure during a fire compared to cladding systems of the prior art.

The present inventors have also found it to be particularly advantageous to provide the same thickness (and type) of heat resistant panels on the inwardly-facing side of the substructure as on the outwardly-facing side of the substructure. I.e. so that the heat resistance is symmetrical on both sides of the frame resistant structure.

The heat resistant corner members 40 can be easily and quickly removed because of the laced connection to the heat resistant panels 14a. This permits quick and easy access to the fasteners securing the top frame unit to the side frame units, to remove the top frame, e.g. for maintenance. The holes 30, 32 provided in the frame units 12 and L-shaped members 13, 48 reduce the weight of the frame units and L-shaped members and also help to reduce heat build-up in the substructure.

As will be appreciated, cable ducts may have alternative configurations to that of the previously described embodiment. Alternative embodiments will now be discussed with like features having the same reference numeral but different prefix to distinguish between embodiments.

Referring to Figure 14, the cable duct 110 may be two-sided. Such a cable duct is suitable, for example, when cables extend along a corner of an external structure e.g. concrete wall. The two sided cable duct further comprises a hinge 170 which enables the two sided cable duct to be opened for inspections or adding/removing cables to/from the duct via the hinged panel whilst allowing for both sides of the two sided cable duct to remain anchored to the concrete 108.

An example of the cable duct extending around a squared corner has previously been described, but referring to Figure 15, it can be seen that the cable duct can also be assembled to extend around a curved corner. In such embodiments, the top frame units 212 and heat resistant panels 214a are trapezoidal in shape.

Referring to Figure 16, the cable duct may also be assembled to form a T-shaped cable duct. In such embodiments, the arrangement of frame units 312 and heat resistant panels 314a is similar to that previously described, but in addition a square top frame unit 312 and heat resistant panel 314a may be provided at the T-junction.

Referring to Figure 17, the cable duct 410 may have a horizontal section 462 and vertical section 462. In such embodiments, the assembly is as previously described, but a square side frame unit 412 and heat resistant panel 414a, 414b may be provided at the junction 466 between the horizontal and vertical sections.

Referring to Figure 18, the cable duct 510 may be a four sided cable duct. In this embodiment, the ends of the cable duct 510 are bolted to an external structure using the holes 30 in the frame, in a similar manner to that described for the L-shaped members (i.e. using two part fasteners and a plate). In the case of large spans, or ducts with a large cross section and therefore weight, additional stiffener plates may be used to provide extra rigidity in the connection region.

Referring to Figure 19, two or more top frame units 612 and heat resistant panels 614a, 614b may be provided so as to surround a wider region of cables, or surround equipment, electrical or otherwise. Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

For example, because the cable duct maintains structural integrity in the event of a fire, in some applications this means there is no need for a cable tray because the fire resistant structure itself provides the cable tray.

The overall shape of the fire resistant structure may be different to that shown in the embodiments described, i.e. the overall shape of the fire resistant structure may be modified for a particular application e.g. to match the shape of the equipment or machinery to be protected.

The fire resistant structure may form a ventilation duct. In such embodiments, an steel sheet or composite type sheet may be applied to an inwardly-facing side of the internal fire resistant panels.

Claims

A fire resistant structure for forming a duct and/or for protecting equipment, the fire resistant structure comprising:

a first structural frame unit connected to a second structural frame unit via a frame connection member;

a first heat resistant panel attached to an outwardly-facing side of the first structural frame unit and a second heat resistant panel attached to an outwardly-facing side of the second structural frame unit;

a heat resistant inter-panel member positioned between the first heat resistant panel member and the second heat resistant panel member and covering the frame connection member, such that the first and second heat resistant panels and the heat resistant inter-panel member form a continuous covering of the first and second structural frame units.

A fire resistant structure according to claim 1 or claim 2, further comprising one or more removable fasteners for connecting the heat resistant inter-panel member to the first and second heat resistant panels.

The fire resistant structure according to claim 1 or claim 2, wherein the first and second frame units are arranged substantially perpendicular to each other.

The fire resistant structure according to claim 3, wherein an angled frame connection member connects two adjacent frame units positioned at an angle to each other.

The fire resistant structure according to claim 4, wherein the heat resistant inter-panel member comprises a heat resistant corner member arranged so as to form a hollow region between the heat resistant corner member and the angled frame member.

6. The fire resistant structure according to claim 1, wherein the first and second frame units are arranged to be co-planar.

7. The fire resistant structure according to any one of the previous claims, comprising: a third structural frame unit connected to the second structural frame unit via a planar frame connection member so as to be coplanar with the second structural frame unit; a third heat resistant panel connected to an outwardly-facing side of the third structural frame unit; a further heat resistant inter-panel member between the second and third heat resistant panels.

8. The fire resistant structure according to claim 7 wherein one or more further removable fasteners are provided for connecting the heat resistant inter-panel member to the second and third heat resistant panels.

9. The fire resistant structure according to any one of the previous claims,

wherein the removable fasteners comprise anchors positioned on the heat resistant panels and wire lacing extending between the anchors.

10. The fire resistant structure according to any one of the previous claims,

wherein further heat resistant panels are attached to an inwardly-facing side of the first structural frame unit and the second structural frame unit.

11. The fire resistant structure according to any preceding claim wherein the first and second heat resistant panels are made from the same material.

12. The fire resistant structure according to claim 11 wherein the first and second, heat resistant panels have the same thickness.

13. The fire resistant structure according to any one of the previous claims,

comprising one or two further frame units connected together, in order to produce a three-sided or four-sided structure, respectively.

14. The fire resistant structure according to any one of the previous claims,

wherein the structural frame units are arranged to define any one of a straight, bent, curved or T-shaped channel.

15. The fire resistant structure according to any preceding claim, wherein at least one of said structural frame units incorporates a hinge to enable opening of the fire resistant structure.

16. The fire resistant structure according to claim 15 wherein each heat resistant panel associated with the structural frame unit incorporates said hinge is modified to allow the hinge to open and close.

17. The fire resistant structure according to any one of the previous claims,

wherein the fire resistant structure defines a cable duct.

18. The fire resistant structure according to any one of the previous claims,

wherein further heat resistant panels are attached to an inwardly-facing side of the first structural frame unit and the second structural frame unit, and wherein the first frame unit and the second frame unit each define a void so as to form a hollow region between the first and second heat resistant panels and the further heat resistant panels.

19. The fire resistant structure according to any one of the previous claims,

wherein the first frame unit and the second frame unit comprise a plurality of holes along a side face for providing a position of attachment to another frame unit, a frame connection member, or an external structure, and/or for reducing heat build-up in the frame unit.

20. The fire resistant structure according to any one of the previous claims,

wherein each frame unit comprises a series of holes on a perimeter of a front and/or rear face, and one or more of said holes receives a fastener to attach one of the heat resistant panels to said frame unit.