FIELD OF THE INVENTION

The present invention relates to a fire resistant structure, in particular, a firewall and/or a fire resistant ceiling, a kit of parts for forming a fire resistant structure, a fire door and/or a method of assembly and/or modification of a fire resistant structure.

BACKGROUND OF THE INVENTION

Fire resistant structures such as firewalls and fire resistant ceilings are required in many buildings to restrict the spread of fire. There are generally two types of firewalls; concrete firewalls and composite firewalls. Concrete firewalls may be found, for example, in a nuclear power station. Composite firewalls generally include an insulation material sandwiched between two cladding layers. To construct a firewall, steelwork, e.g. steel joists, are required to support the firewall. In the example of a composite firewall, the cladding is nailed to the steelwork. The fire standard required depends on the environment in which the firewall is used, but for example, in a nuclear power station it is likely that the firewall will need to resist heat transfer through the wall (up to a maximum of 181°C) for 3 hours.

Currently firewalls and/or fire resistant ceilings are built as permanent structures and as such are not designed to be adaptable. However, on occasions it may be desirable to modify a firewall, for example to pass a conduit for wiring or pipes through the wall, or to create a space to hang a fire door. Conventional firewalls are difficult to modify, either because modification requires removal of concrete from the wall or cutting through cladding, clearing insulation, and ensuring that the modifications do not cause any heat leakages, which can be difficult. Moreover, the requirement of specific steelwork means that it can be difficult to erect a firewall in an already erected building, without substantial building work being undertaken. SUMMARY OF THE INVENTION

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

A first aspect of the invention provides a fire resistant structure for use as a firewall or fire resistant ceiling, 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 fire resistant panels arranged to clad the substructure so as to cover a fire-facing face of the substructure.

Using a modular system (i.e. a plurality of frame units attached together) to form a frame structure for the firewall or fire resistant ceiling provides increased flexibility compared to firewalls of the prior art. For example, the modular system permits a user to remove one or more of the frame units and associated fire resistant panels to add a door way to a firewall or provide a conduit for cables, wires or pipes through the firewall or fire resistant ceiling. The term "fire-facing" should be interpreted as meaning on the 'threat' side of the fire resistant structure, or in front of the area to be protected from the effects of fire. It will be understood that, for some embodiments and applications, the fire resistant structure may be positioned between two potential 'threat' zones, and therefore may require two fire-facing faces, e.g. with the front and rear of the substructure fitted with one or more of said fire resistant panels.

By using fire resistant panels to clad and thereby cover the fire-facing face(s) of the substructure, the frame units are in effect protected from the direct effects of a fire, meaning that the risk of overheating of the frame units is reduced (compared to the prior art in which it is common to provide fire resistant panels or material on the inside of a fire-resistant structure). The risk of bowing of the fire resistant structure is therefore also redued, whicih helps to avoid or mitigate loadings at the perimeter of the fire resistant structure.

The fire resistant structure may form a partitioning wall in a building, for example, e.g. extending between the floor and ceiling of the building. In exemplary embodiments, a front face of each frame unit is covered by a respective fire resistant panel, e.g. a first fire resistant panel is configured to cover the front face of a first frame unit, and a second fire resistant panel is configured to cover the front face of a second frame unit. In exemplary embodiments, each frame unit defines a void behind the fire-resistant panel(s). Hence, if the frame units are clad on the front and rear, a hollow region is formed between the front and rear faces of each frame unit. Unlike firewalls of the prior art, no insulation material is provided in the hollow region in the exemplary embodiments. This has several advantages, such as easing the assembly process and making it easy to modify the fire resistant structure. Furthermore, in cases where electrical wiring or cables are intended to be run within the fire resistant structure, the absence of insulation material avoids or mitigates adverse effects on the current flow in the electrical wires or cables.

The or each fire resistant panel may be an insulation board. The fire resistant panel may comprise an endothermic -reactive insulating fibrous material. These types of materials have been found to have improved insulating properties than materials used to form heat resistant panels of the prior art. In exemplary embodiments, the insulating fibrous material includes: (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. Such a material is breathable under normal (non-fire) conditions, which means that when the wall includes a hollow region, electrical cable can be run inside the firewall or ceiling without affecting or with limited effect on electrical current.

The inorganic endothermic filler may be an hydrated compound and at least one of endothermic reactions 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:

MC0 ₃ .nH ₂ 0 ^Heat ) MC0 ₃ + nH ₂ 0 MC0 ₃ ^Heat ) MO + C0 ₂

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. The fire resistant structure may comprise a gasket (e.g. an expandable gasket) for resisting heat conduction through the structure, e.g. to reduces or prevent hot gas flow through the firewall or ceiling. The gasket may be positioned between adjacent frame units of the substructure, for reducing heat transfer between said frame units. The gasket may be positioned to extend along one or more perimeter side faces of each frame unit, for restricting heat flow to neighbouring frame units. Such an arrangement helps to limit hot air movement to within the extremities of each frame unit.

In an exemplary embodiment, the fire resistant structure is a firewall and the gasket is positioned to extend along and substantially cover an end face of at least one of said frame units. In exemplary embodiments, the substructure has first and second frame units, one above the other, and the gasket is, in effect, sandwiched between the upper and lower units. This has been found to greatly reduce heat accumulation in an upper region of the firewall. If the firewall includes multiple frame units, one on top of another, the use of a gasket positioned between each pair of units prevents or mitigates internal convection taking place over the full or near full height of the firewall (which in some embodiments may be 10m or more high). This reduces heat accumulation in an upper region of the firewall and significantly reduces or removes the risk of formation of hot spots in the firewall or ceiling. In exemplary embodiments, the frame units comprise a plurality of holes along a perimeter 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 holes may be used in attachment or the holes may, in use, be free from fasteners, in such cases the holes reduce heat transfer through the frame structure. When holes are free from fasteners, said holes can be used to route cables and pipes across and through the fire resistant structure, which enables the cables and pipes to be protected from damage due to the fire for a longer period of time than achieved with conventional firewalls.

The fire resistant structure may be configured for attachment via fasteners to one or more external structures, e.g. a concrete structure. Such a configuration provides more flexibility than the prior art because the positioning of the firewall or ceiling is not dependent upon the required steelwork being in place from which the firewalls of the prior art are suspended.

The frame units may comprise a series of larger diameter holes and a series of smaller diameter holes along a side face. 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. In tests, some embodiments of the invention using such a connection to an external structure, have been found to have improved performance in seismic tests compared to firewalls of the prior art. 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.

Each frame unit may comprise a series of holes at the perimeter of a front and/or rear face of the frame unit (i.e. distinct from the holes provided around the perimeter side faces or end faces of the units). One or more of said holes may receive a fastener to attach one of the fire resistant panels to said frame unit. The fastener may be a threaded fastener. A threaded fastener is generally easier to remove and replace than other types of fasteners, e.g. the nails used in firewalls of the prior art, which contributes to the ease of modification of the fire resistant structure. The one or more fasteners may extend through one of the fire resistant panels to suspend the fire resistant panel to the frame unit. 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 use of a ferrule eases placement and removal of the fastener and protects the fire resistant panel from damage. The frame units may be made from metal, for example steel.

The heat resistant structure may comprise a heat resistant seal positioned between the frame units and fire resistant panels. The heat resistant seal may be positioned around a perimeter of each frame unit. The heat resistant seal may be dimensioned to overlap an adjacent frame unit so as to prevent heat leakage between fire resistant panels. Such arrangement of the heat resistant seal removes the need to overlap the fire resistant panels so as to avoid or reduce heat leakage at the joints of the fire resistant panels.

The fire resistant structure may require two opposing faces, both capable of being fire- facing. Hence, the fire resistant structure may comprise at least one fire resistant panel on the front and rear of the substructure. In alternative embodiments, fire resistant panels are clad to one side of the substructure, and non-fire resistant panels are clad to the opposite side of the substructure, such that only one side of the fire resistant structure is intended to be fire-facing.

In exemplary embodiments, each frame unit may be formed from two or more frame members folded from a flat-pack configuration. Using a flat-pack configuration eases transportation of the components for construction of the fire resistant structure.

Each frame member may be folded to form two perimeter sides of a frame unit, such that two frame members when fastened together (e.g. by screws or bolts) form a frame unit of continuous perimeter. Alternatively, each frame member may form one, three or four perimeter sides of a frame unit. The frame member may be an elongate member that can be folded to an L-shape. The frame member may comprise two portions that can be folded to form part of the front or rear of the frame unit.

In exemplary embodiments, each frame unit may be square or rectangular 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 fire resistant structure may comprise one or more cover panels positioned over the fire resistant panels to cover a fire-facing face of the fire resistant structure. The cover panels provide protection for the heat resistant panel and can provide a surface that has better characteristics for use e.g. improved appearance, improved feel and/or waterproof. The fire resistant structure may comprise two or more layers of heat resistant panels clad to a single fire facing face of the fire resistant structure. Additional layers of heat resistant panels enable the firewall to be used with different types of fire (e.g. cellulose in building and power stations, and hydrocarbon in petrochemical/oil and gas environments) and for different required durations (e.g. 30 minutes, 1 hour, 90 minutes, 2 hours, etc).

The fire resistant structure may be a firewall configured to extend around a corner. In such an embodiment, a corner member of hollow cross section may connect two or more of the frame units to create the required angle in the firewall. The corner member may have a square cross section. The corner member may comprise a series of holes formed through the sides thereof.

The fire resistant structure may be a firewall and the firewall may comprise door frame members provided to support a fire door in the firewall. The door frame members may have a hollow cross section. The door frame members may comprise holes along the length thereof.

A second aspect of the invention provides a fire resistant structure comprising: a frame structure having a front and rear face, at least one of which intended to be fire- facing; and a plurality of fire resistant panels clad to the front and/or rear face of the frame structure, so as to form a barrier to heat; wherein the fire resistant panels comprises an endothermic-reactive insulating fibrous material.

Endothermic -reactive insulating fibrous material have been found to have improved insulating properties than standard materials used to form heat resistant panels. Accordingly, adapting the use of the material (it is not known to use such materials for firewalls) to form a panel that is suitable for use in a firewall can improve the performance of a firewall compared to firewalls of the prior art.

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. Such a material is breathable under normal (non-fire) conditions, which means that when the wall includes hollow portions, electrical cable can be run inside the firewall or ceiling without affecting or with limited effect on electrical current.

The frame structure may comprise a plurality of frame units, e.g. first and second frame units attached to one another. Each panel may be configured to cover the front and or rear face of a respective frame unit.

Each frame unit may comprise a void intended to define a hollow region behind the front and rear faces of the frame structure.

The fire resistant structure of the second aspect may have any one of, or any combination of, the optional features of the fire resistant structure of the first aspect. A third aspect of the invention provides a fire resistant assembly comprising: a fire resistant structure according to the first or second aspect; the assembly further including one or more frame members positioned to form a door frame, and a fire door supported in the door frame. The fire door may comprise a substructure. The fire door substructure may comprise a plurality of frame units attached together. A fire resistant panel may be clad to a fire-facing face of the fire door substructure so as to form a barrier to heat. A plurality of fire resistant panels may be arranged to clad the fire door substructure so as to cover a fire-facing face of the fire door substructure for reducing heat transfer through the fire door. The fire resistant panel may comprise an endothermic -reactive insulating fibrous material.

The fire door may be of a similar construction to the fire resistant structure of the first and/or second aspect. Accordingly, the fire door may have, where appropriate, one or more optional features of the fire resistant structure of the first or second aspects. A fourth aspect of the invention provides a kit of parts for forming a firewall or ceiling, the kit of parts comprising: a plurality of frame units attachable together to form a substructure of a firewall or ceiling; a plurality of fire resistant panels for cladding the substructure formed by the frame units so as to resist heat transfer through the firewall or ceiling; a plurality of frame unit fasteners for attaching the frame units together to form the substructure; and a plurality of panel fasteners for cladding the fire resistant panels to the substructure.

The kit of parts may comprise a gasket positionable between the frame units for reducing heat transfer in the fire resistant structure.

The kit of parts may comprise a heat resistant seal positionable around a perimeter of each of the frame units, so as to be positioned between the frame units and fire resistant panels. The heat resistant seal may be dimensioned to, when assembled, overlap an adjacent frame unit. For example, the heat resistant seal may be dimensioned to have a height and width greater than a height and width of the respective frame unit. Such a heat resistant seal can, when assembled, reduce heat leakage between adjacent heat resistant panels. The kit of parts of the fourth aspect may form the fire resistant structure of the first aspect.

A fifth aspect of the invention provides a method of forming a firewall or ceiling comprising: attaching a plurality of frame units together to form a substructure; securing said substructure to an existing structure; and cladding a plurality of fire resistant panels to a fire-facing face of the substructure.

Forming a firewall or ceiling by attaching a plurality of frame members, i.e. using a firewall of modular construction, improves flexibility of the wall size and configuration. Attaching the frame units to an existing structure removes the need, as would otherwise be the case with firewalls of the prior art, to have the correct steelwork in place from which to suspend the firewall.

The existing structure may be a concrete structure.

The method may comprise configuring one or more flat-pack frame members to form one of said frame units. Providing the frame members in flat-pack form and then folding the frame members to the required shape enables the components of the firewall or ceiling to be easily stored and transported.

Each frame unit may comprise a series of larger and smaller diameter holes along a side face of the frame unit, and the method comprises using a bolt or screw and a plate to connect one or more of the frame units to an external structure. The plate may be of larger diameter than the larger hole in the frame unit. Using such a plate means that the bolt can be of smaller diameter than the larger hole, which means that the accuracy required for attachment of the frame unit to the external structure is reduced.

The method may comprise removing one or more of the plurality of fire resistant panels from the substructure; removing one or more of the plurality of frame units from the substructure; and positioning a component such as a door, window or conduit in a position corresponding to the removed fire resistant panels and frame units.

The method may comprise leaving a gap between one or more of the plurality of frame units; and leaving the gap uncovered or partially uncovered with fire resistant panels; and positioning a component such as a door, window or conduit in or through said firewall or ceiling.

The method may comprise forming the fire resistant structure of the first aspect and/or the firewall or ceiling formed may have one, or any combination, of the optional features of the first aspect.

A sixth aspect of the invention provides a method of modifying a fire resistant structure, e.g. a firewall or a fire resistant ceiling, 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 fire resistant panels, each panel attached to one of the plurality of frame units for resisting heat transfer through the fire resistant structure, and the method comprising removing one or more frame units and one or more fire resistant panels from the fire resistant structure so as to form a gap in the fire resistant structure to accommodate a desired feature, e.g. a door, or window or a conduit for wires, cables or piping. The fire resistant structure may have any one of, or any combination of, the optional features of the fire resistant structure of the first aspect.

A seventh aspect of the invention provides a fire door comprising: a plurality of frame units attached together to form a substructure of the fire resistant structure; and a plurality of fire resistant panels arranged to clad the substructure so as to cover a fire- facing face of the substructure for reducing heat transfer through the fire resistant structure.

The fire door of the seventh aspect may have, where appropriate, any one, or any combination, of optional features of the first aspect.

An eighth aspect of the invention provides a fire door comprising: a frame substructure; and a fire resistant panel clad to a fire-facing face of the frame substructure (so as to form a barrier to heat); wherein the fire resistant panel comprises an endothermic-reactive insulating fibrous material.

The fire door of the eighth aspect may have, where appropriate, any one, or any combination, of optional features of the fire resistant structure of the second aspect. 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 an assembled firewall connected to an external structure;

Figure 2 shows a perspective exploded view of the firewall of Figure 1;

Figure 2A shows a detail view of the encircled section of Figure 2;

Figure 3 shows a perspective view of an assembled frame structure of the firewall of Figure 1; Figure 4 shows a perspective exploded view of a frame unit forming part of the frame structure of Figure 3;

Figure 5 shows a flat-pack frame member of the frame unit of Figure 4;

Figure 6 shows a perspective partially exploded view of two frame units of Figure 4 and a corner frame member; Figure 7 shows a perspective view of a fire door without the door furniture; and

Figure 8 shows a perspective view of an assembled frame structure of the fire door of Figure 7.

DETAILED DESCRIPTION OF EMBODIMENT(S)

Referring to Figures 1 and 2, a firewall is indicated generally 10. A plurality of frame units 12 are attached together to form a substructure of the firewall 10. Two coincident fire resistant panels 14a, 14b are clad to each one of the frame units 12. The fire resistant panels 14a 14b restrict heat flow through the firewall 10. The fire resistant panels 14a, 14b are clad to a fire-facing side of the firewall 10, so as to reduce heat flow to the frame units 12. This reduces bowing of the substructure and therefore loadings at a perimeter of the firewall 10 are reduced. In alternative embodiments, only one fire resistant panel may be used, or in further alternative embodiments three or more fire resistant panel layers may be used. The number of fire resistant panels can be varied depending on the fire protection required, e.g. the fire protection duration and/or the type of fire (e.g. cellulose as in buildings and power stations, and hydrocarbon as in petrochemical/oil and gas). A cover panel 16 is positioned over each of the outer most fire resistant panels 14b. In this embodiment the cover panel 16 is made from a powder coated carbon steel, but in alternative embodiments any suitable material may be used. The cover panel 16 provides a finish to the firewall 10 which is both protective of the fire resistant panel 14b and a more desirable material for an external surface of a wall in a building. An expandable gasket 18 is positioned between each of the attached frame units 12. The expandable gasket 18 is positioned so as to overlay the sides of the frame units 12 that are in contact with other frame units, such that each frame unit 12 is surrounded by gasket 18. The gasket limits heat conduction between frame units 12, which in turn limits any air movement to within the extremities of each frame unit. Limiting air movement to within the extremities of each frame unit can help to reduce hot spots. Particularly, important for contributing to the reduction of hot spots is the gasket 18 arranged between upper and lower frame units, which prevents or mitigates against internal convection taking place over the full height of the firewall, thereby reducing the tendency for hot spots to occur in an upper region of the firewall 10. In some embodiments the firewall may be up to 10 m or more in height, and this arrangement of gaskets (i.e. sandwiched between upper and lower frame units) prevents internal convection taking place over the full height of the firewall.

A heat seal, e.g. refractory paper 15, is positioned around a perimeter of the front face of each frame unit 12 and between the heat resistant panel 14 and the frame unit 12. This heat seal is dimensioned to overlap with the front face of adjacent frame units 12, so as to restrict heat leakage at the point of abutment of the heat resistant panels 14a, 14b.

In this embodiment, the firewall has two fire-facing faces, and so fire resistant boards 14a, 14b and cover boards 16 are clad to both the front and rear (as viewed in Figure 1) of each frame unit 12. However, in alternative embodiments, the firewall may only have one fire-facing face, i.e. fire resistant boards 14a, 14b are only clad to one face of the frame unit 12. In such an embodiment, a non-fire resistant panel, or just a cover panel may be clad to the other face of the firewall. In the present embodiment, the heat resistant panels 14a, 14b and cover panels 16 are coincident with the frame units 12, i.e. so that a first set of panels 14a, 14b, 16 is configured to cover a first frame unit and a second set of panels 14a, 14b, 16 is configured to cover a second frame unit. However, in alternative embodiments the heat resistant panel and cover panels may be clad to the frame units using any appropriate configuration.

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 fire 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. Referring to Figure 4, the frame units 12 are rectangular in shape. 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 5. The frame member 20 includes a side face 22 that connects to another frame unit 12 or to an external structure. 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 14 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 fire-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 a fastener 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 1 to 4, the frame units 12 are connected together using a fastener, e.g. a bolt, received through the smaller holes 30. In this embodiment, the position of the fasteners is alternated to create a zig-zag pattern of bolts, as illustrated by the shaded holes 35a, 35b, 35c and 35d. The holes 30 not used for attachment contribute to reducing heat build-up in the frame unit 12 during a fire situation. Ferrules 36 are positioned through each fire resistant panel 14a, 14b. A fastener 38 extends through the frame unit 12, the ferrule 36, and the cover panel 16. A nut or cap secures the cover panel 16 and the heat resistant panels 14a, 14b with respect to the fastener 38, so as to attach the fire resistant panels 14a, 14b and the cover panel 16 to the frame unit 12.

It can be seen from the exploded view shown in Figure 2, that a central region of the frame unit defines a void. This creates a series of hollow regions 40 between the two fire-facing walls of the firewall. Such a hollow region reduces heat flow through the firewall. It also enables electrical cables and/or wires to be run through the firewall uninhibited, e.g. with limited effect on current flow (during a non-fire situation). Further, the holes 30 and 32 of the frame units 12 can be used to route cables and pipes within and through the firewall. Such arrangement of cables and pipes can protect the cables and pipes usually for up to at least 50% of the duration of protection provided by the firewall 10, without any requirement for additional fire protection of the cables and pipes.

To assemble the firewall 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.

The frame units 12 are then bolted together using the smaller holes 32, as discussed previously. Strips of the expandable gasket 18 are positioned to extend along and cover each of the side faces 22 of each of the frame units 12. Referring to Figure 3, the assembled frame structure is then connected to an external structure 46. In this embodiment the external structure 46 is a concrete support. The frame structure is connected to the external structure 46 using a plurality of two part fasteners, and a plurality of plates 42 dimensioned to be of greater width than the diameter of the larger hole 30 of the frame unit 12. A threaded portion 44 of the two part fastener passes through the plate 42, through one of the larger holes 30, and into the external structure 46. A head 44 of the two part fastener secures the plate against the frame unit 12 so as to attach the frame unit to the external structure 46. In alternative embodiments, any other suitable method of attachment of the firewall 10 to an external structure 46 may be used.

The refractory paper 15 is positioned on each of the perimeters of the frame units 12 formed by sides 24 of the frame members. The refractory paper 15 being positioned so as to be substantially coincident with the frame unit 12, and overlapping any adjacent frame units. The fire resistant panels 14a, 14b and cover panels 16 are attached to the frame units using fasteners 38.

In the presently described embodiment, the firewall has the overall thickness of 200 mm to 210 mm. Each fire resistant panel 14a, 14b is 20 to 30 mm thick. The frame unit 12 is 100 to 110 mm thick, and formed from a sheet metal of 2 mm thickness. Each frame unit and panel has an area of wall coverage of 1520 to 1540 mm by 770 to 790 mm, but in alternative embodiments, any suitable dimensions may be used.

The firewall 10 of the described embodiment was tested using standard 3 hour fire testing. To pass the test no part of the firewall on the opposite side to the fire should reach 181°C in a period of 3 hours. When tested, the described firewall reached a maximum temperature of approximately 70°C in a period of 4 hours. It was also found that there was no significant bowing of the firewall, indeed the bowing was substantially reduced compared to a firewall of the prior art. The firewall 10 was further subjected to seismic tests and found to out perform the firewalls of the prior art.

As well as providing improved performance in fire tests, the modular nature of firewall 10 also provides improved ease of assembly and flexibility of assembly. This is because the frame units can be assembled as required to form a firewall of the desired dimensions and including any desired features, such as a door frame. The removable nature of the fire resistant panels 14a, 14b and the frame units 12 from the firewall 10 also means that the firewall can be easily modified to accommodate, e.g. a door or pipe conduit, as required. The ability to connect the firewall 10 to an external structure 46 using the fasteners and plates provides increased flexibility of where to position the firewall because it is not dependent upon the provision of the steelwork necessary to erect firewalls of the prior art. In alternative embodiments, the firewall may be arranged to extend around a corner, an example of such a configuration is indicated generally at 50 in Figure 6. To extend around a corner a corner frame member 52 is used. The corner frame member 52 comprises two frame members 54, each bent so as to form a substantially L-shaped member and then connected together using fasteners. The corner member 52 includes larger diameter holes 56 and smaller diameter holes 58 of similar configuration as the holes in the frame unit 12.

In a further alternative embodiment, the firewall may be constructed so as to accommodate a fire door. In this embodiment, the frame units 12 are connected together as previously described, but are arranged to leave a space in the firewall for accommodating a fire door. In exemplary embodiments, door frame members may then be positioned around the edge of the space, ready for supporting the fire door. The door frame members may be of any suitable form.

The fire door may be of standard construction. Alternatively, the fire door may be of a similar construction to the firewall 10. An example is shown in 8, indicated generally at 170. The fire door 170 includes a substructure formed from a plurality of frame units 112 (shown clearly in Figure 7). One or more fire resistant panels 114 are then clad to the substructure (see Figure 8), and one or more cover panels 116 may be clad to the fire resistant panels 114. An expanding gasket 118 may be positioned between the frame units 112. A heat seal may also be also positioned in a similar manner between the heat resistant panels 114 and the frame units 112, and dimensioned so as to overlap between adjacent heat resistant panels, in a similar manner to that described for the firewall 10. Appropriate door furniture can then be used to complete the door construction. An example of appropriate door furniture is the Sure McGill 3 point latch and hinges, available from Sure McGill Ltd, 26 The Business Centre, Molly Millars Lane, Wokingham, Berkshire RG41 2QY. 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, in alternative embodiments the described construction or similar, may be used to form other types of fire resistant structures, for example fire resistant ceilings, or barriers between fire prone structures such as transformers.

In an alternative embodiment, the fire resistant structure may not be of modular construction. In such embodiments the frame substructure may be formed using any appropriate configuration of panel supports, e.g. steel supports. A plurality of fire resistant panels may then be attached to the panel supports to form the fire resistant structure.