GB2591226A

GB2591226A - Improvements in and relating to open state cavity barriers

Info

Publication number: GB2591226A
Application number: GB1918714.5A
Authority: GB
Inventors: Hainsworth Ian; reid Daniel
Original assignee: Tenmat Ltd
Current assignee: Tenmat Ltd
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2021-07-28
Anticipated expiration: 2039-12-18
Also published as: GB201918714D0; GB2591226B

Abstract

An open state cavity barrier 200 is disclosed for sealing a cavity 14 when exposed to fire. The barrier comprises a porous carrier body 202, an intumescent material layer 204 provided on a surface of the porous carrier body, and a wrapper 206 arranged to at least partly enclose the carrier body and intumescent material layer. The carrier body preferably comprises 0.2-1% moisture by weight and when exposed to fire, hot vapour released from the carrier body and trapped by the wrapper pre-heats the intumescent material, thereby causing the intumescent layer to reach reactant temperature quickly. The wrapper may be aluminium foil. Also disclosed is a method of installing an open state cavity barrier.

Description

IMPROVEMENTS IN AND RELATING TO OPEN STATE CAVITY BARRIERS Field of the Invention [1] The present invention relates to open state cavity barriers, such as those used in high rise buildings to prevent fire spreading through a cavity formed by external building cladding.

Background

[2] When external cladding is fitted to the outside of a building it usually leaves a hollow cavity between the cladding and external wall of the structure. This cavity is important, particularly for tall buildings, as it is vital for the movement of air around the building during normal use and so provides ventilation of the building during habitation. Whilst such a cavity is therefore necessary, a disadvantage is that the cavity creates a vertical 'chimney' which can allow fire and smoke to spread rapidly up the building in the event of a fire. Thus, the cavity formed between the cladding and the building has the problematic requirement of allowing free air flow during normal use but preventing air flow during a fire.

[3] A known solution to preventing the spread of fire through a cladding cavity, particularly in high rise buildings, is through the use of an open state cavity barrier, hereafter an 'OSCB'. Figure 1A shows an example of a typical prior art OSCB 100 mounted in a cavity 14 of usually 100-400 mm width formed between a building wall 10 and external cladding 12. Here, an intumescent material layer 104 is mounted on a leading edge of a slab of non-combustible material 102 facing an open gap 16 of usually 25-50 mm to the external cladding 12.

[4] During a fire, hot air flows through the gap 16 between the OSCB 100 and cladding 12 and therefore past the intumescent material 104. This hot air heats the intumescent material layer 104 which typically begins to expand once the internal temperature of the intumescent material exceeds around 200 degrees Celsius. The expanded intumescent layer seals the cavity 14 to provide a fire and smoke resistant barrier, as shown by Figure 1B.

[5] When determining the effectiveness of an OSCB, key performance criteria include the speed of closure and the ability after closure to maintain the insulation and integrity for as long as possible during a fire. For example, OSCBs which meet the ASFP TGD 019 (2017) fire resistance test typically span an air gap of 25-50mm in around 5 minutes from the start of a fire.

[6] One problem faced by OSCBs is that during a fire situation, air pressure in the wall cavity 14 increases dramatically as the air is heated and expands. The increase in air pressure causes a significant air flow through the open cavity which can degrade the intumescent material 104 as it expands; in essence the intumescent material 104 is 'blown away' by the hot air flow.

[7] Another problem is that as the intumescent material begins to expand it creates an insulating char around itself. This char slows the rate of expansion as the inner parts of the intumescent material are insulated from the heat of the fire 18. The result is that the intumescent does not expand as a whole but in layers as the heat eventually penetrates the material.

[8] Thus, there is difficulty in maintaining the optimum integrity of the intumescent material and the insulation it provides in existing OSCBs.

Summary

[9] It is an aim of the present invention to overcome one or more of the aforementioned problems. In particular, it is an aim of the example embodiments of the present invention to provide an OSCB which reacts quicker to a fire 18, thereby preventing the spread of fire at an earlier stage during evolution of the fire and reducing possible degradation of the intumescent seal.

[10] As such there is defined an improved open state cavity barrier according to the independent claim(s). Additional features will be appreciated from the dependent claims and the description herein. Any embodiments which are described but which do not fall within the scope of the claims are to be interpreted merely as examples useful for a better understanding of the invention.

[11] In one aspect of the invention there is described an open state cavity barrier comprising a porous carrier body, an intumescent material layer provided on a surface of the porous carrier body, and a wrapper arranged to at least partly enclose the porous carrier body and intumescent material layer. When the OSCB is exposed to a fire, hot vapour released from the carrier body and trapped by the wrapper pre-heats the intumescent material, thereby causing the intumescent layer to reach reactant temperature quickly.

[12] In one example, the wrapper comprises a join proximate to a leading surface of the intumescent material layer. The join opens when the intumescent material expands, providing an outlet for the hot vapour near to the intumescent material, and thereby drawing the hot vapour across the intumescent material to further pre-heat the intumescent material.

[13] In one example, the join is formed by one or more folds in the wrapper. In another example the join is formed by a weakened line through the wrapper. In a further example the join is formed by a temperature susceptible glue. Suitably the wrapper may be readily manufactured to comprise the join and the join readily facilitates opening of the wrapper to draw hot air across the intumescent.

[14] In one example the wrapper is heat conducting, so as to provide efficient heat transfer from a fire to the OSCB, thereby vaporising moisture within the carrier body quicker.

[15] In one example the wrapper is non-combustible, so as to withstand a fire until after the pre-heating effect on the intumescent material has been achieved -that is, the intumescent has reached reactant temperature.

[16] In one example the wrapper is formed from a non-porous material so as to better contain hot vapour inside the wrapper without leakage.

[17] In one example the wrapper is formed from metallic foil, and may suitably comprise aluminium. Foil is a readily available material provides the advantageous effects of heat conduction and sufficient non-combustibility.

[18] In one example the intumescent material layer is porous, thereby allowing hot vapour to flow through the inside of the intumescent material layer and further improving the pre-heating process.

[19] In one example the intumescent material layer is provided on a leading edge of the carrier body, so as to directly span a gap in a cavity in which the OSCB is placed once the intumescent begins to react.

[20] In one example the porous cavity body comprises at least 0.2-1% moisture by weight, thereby providing sufficient vapour (once the moisture has evaporated) to circulate within the OSCB to pre-heat the intumescent material.

[21] In another aspect of the invention there is described a cavity comprising a first wall, a second wall, and an example open state cavity barrier mounted therebetween.

[22] In another aspect of the invention there is described a method of installing an example open state cavity barrier into an example cavity, the method comprising mounting the carrier body and the intumescent layer to the first wall of the cavity, and enclosing the wrapper around the carrier body and intumescent layer and sealing the wrapper to the first wall.

Brief Description of Figures

[23] The invention will now be described by way of example only by reference to the accompanying drawings, in which: [24] Fig 1A shows an example open state cavity barrier 'OSCB' known from the prior art; [25] Fig 1B shows the OSCB of Fig. 1A during a fire; [26] Fig 2A shows an example improved OSCB during an early stage of a fire; [27] Fig 2B shows the example improved OSCB of Fig. 2A during a later stage of a fire.

Detailed Description

An improved open state cavity barrier [28] Figures 2A and 2B show an example improved OSCB 200. Figure 2A shows the example OSCB 200 at an early stage of a fire, while Figure 2B shows the OSCB 200 at a later stage of the fire. Like Figure 1, the OSCB 200 is mounted on a building wall 10 which defines one side of a cavity 14 extending between the wall 10 and external cladding 12.

[29] The OSCB 200 comprises a carrier body 202, an intumescent layer 204, and a wrapper 206.

[30] The carrier body 202 is porous, and therefore able to retain moisture as well as allow for fluid to flow through the carrier body 202. The carrier body 202 retains some degree of liquid -e.g. water -within it such that the carrier body 202 is considered moist. Suitably the carrier body 202 may be mineral fibre based. A preferred example material is Tenmat mineral fibre slab material with typical density of 90-140Kg/cubic Metre, which comprises typically 0.2-1% liquid by weight. Other suitable materials can of course be used instead.

[31] The intumescent layer 204 is provided on a leading edge 208 of the carrier body 202. Here the term leading edge is used to mean generally an edge positioned toward the direction in which the intumescent layer 204 will expand in response to heat; i.e. in this example, the leading edge 208 defines an X-Z plane orthogonal to a Y axis directed toward the other side of the cavity 14 such that the intumescent positioned on that edge 208 expands across the gap 16. The intumescent material used in the layer 204 can be any suitable material known to those in the art.

[32] The wrapper 206 is arranged to enclose the carrier body 202 and intumescent material 204. When the OSCB 200 is exposed to heat from a fire 18, moisture within the porous carrier body 202 is evaporated and trapped within the OSCB 200 by the wrapper 206. The trapped hot vapour 216 raises the internal temperature of the OSCB 200, and therefore pre-heats the intumescent layer 204. In other words, the wrapper 206 acts like an oven to heat the OSCB 200 to raise the intumescent material layer 204 to reactant temperature quicker.

[33] By pre-heating the intumescent material layer 204, the example OSCB 200 reduces the time it takes for the intumescent material to reach its reacting temperature -e.g. around 200°C for typical intumescent materials. Furthermore, energy from the fire which would otherwise be wastefully expended on an underside 210 of the OSCB 200, is instead put to good use improving the closure time of the OSCB 200. That is, in contrast to existing systems, the example OSCB 200 does not rely solely on heat flow past an exposed face of intumescent material to heat said intumescent material.

[34] It will be appreciated that although the wrapper 206 here is described as fully enclosing the carrier body 202 and intumescent material 204, other arrangements are possible whereby the wrapper 206 only partly encloses the carrier body 202 and intumescent material 204, while still achieving the preheating effect. For example, the wrapper 206 may not cover a surface of the carrier body which abuts the wall 10 of the building, such that the wall 10 completes the enclosure to retain the hot vapour 216 within the OSCB 200.

[35] Expansion of the intumescent layer 204 will cause the wrapper 206 to open (e.g. break), normally on an area of the wrapper 206 abutting a leading edge 212 of the intumescent layer 204, as this is where direct pressure from the expanding intumescent layer 204 acts against the wrapper 206. Suitably the pressure gradient between the OSCB 200 and cavity 14 will cause the trapped hot vapour 216 to exit the OSCB 200 by flowing past the intumescent layer 204, thus further pre-heating of the intumescent layer 204 is achieved.

[36] To better facilitate opening of the wrapper 206, the wrapper 206 is preferably provided with a join 214 in an area of the wrapper 206 proximate to the leading surface 212 of the intumescent material layer 204. The join 214 provides control over the precise region at which the hot vapour will exit the OSCB 200, and so avoids a potential problem with the wrapper opening elsewhere. That is, the join 200 defines the direction the hot vapour 216 will travel once the intumescent layer 204 expands sufficiently to open the join 214. In this way the join 214 ensures that the hot vapour 216 trapped within the OSCB 200 flows past the intumescent layer 204.

[37] It will be appreciated that there will be a number of ways to provide a join 214 in the wrapper 206 known to those skilled in the art. In one example the join 214 may be formed by an overlap of two ends of the wrapper 206, as exemplified in Figures 2A & 2B. In another example the join 214 may be formed by one or more folds in the wrapper 206, e.g. folding two ends of the wrapper 206 together. In yet another example join 214 may be formed by a weakened area in the wrapper 206; e.g. a perforated line through the wrapper 206. In a further example, the join 214 may be formed by a temperature susceptible glue joining two ends of the wrapper together; that is, a glue which melts when it reaches a certain temperature, such as a pressure sensitive acrylic adhesive.

[38] Suitably the wrapper 206 may be formed from a heat conducting material. In this way more efficient transfer of heat from the cavity 14 to the carrier 202 may be achieved, thereby reducing the time for moisture within the carrier body 202 to evaporate. The wrapper 206 may also suitably be formed from a non-combustible material, such that the fire 18 does not degrade the wrapper 206 before the internal temperature of the OSCB 200 has risen sufficiently to evaporate moisture within the carrier body 202 and pre-heat the intumescent layer 204. Further suitably the wrapper may be formed from a non-porous material, thereby ensuring that the hot vapour 216 cannot escape the wrapper 206 except through the opening 214. An example material which satisfies all these aims is a metallic foil. Preferably such a foil would comprise aluminium.

[39] To further improve pre-heating of the intumescent layer 204 by the hot vapour 216, the intumescent material layer 204 may be suitably formed from porous intumescent material, and preferably a mineral fibre based intumescent comprising graphite as its active component, such as Tenmat FF107 or FF102 materials In this way the hot vapour 216 can penetrate the interior of the intumescent material layer 204 further aiding the pre-heating process. This applies during the early stages, when the hot vapour 216 is contained within the wrapper 206, and also the later stages, whereby the hot vapour 216 can flow through the interior of the intumescent layer 204 on its escape from the OSCB 200.

[40] It will be readily appreciated that the example OSCB 200 may be provided as a single item ready for installation in a cavity, or as separate components ready for construction on site. In the former case, care must be taken to ensure that any damage to the wrapper 206 caused during mounting of the OSCB 200 is sealed using appropriate means; if the hot vapour 216 is allowed to escape the OSCB 200 may not perform as expected. In the latter case it is particularly envisaged that an outer wrapper 206 may be applied on site around an existing suitable OSCB; i.e. around a premade OSCB with suitable carrier body and intumescent material, such that the wrapper 206 covers all sides of the OSCB except that which is mounted to the wall 10 of the cavity, the wrapper 206 then being sealed to the cavity wall 10.

Test results [41] Testing performed on the example OSCB 200 described herein has shown a marked improvement of OSCB performance compared to prior art systems.

[42] Compared to an identical OSCB without the wrapper 206, the improved OSCB 200 reduces the time taken to close the cavity gap 16 by half. For example, as shown by Table 1, it takes 5 minutes for an identical OSCB to close and seal a gap of 50 mm (the largest gap size typically left after an OSCB is installed), whereas the improved OSCB closes and seals a gap of 50 mm in just 2.5 minutes.

Gap spanned Time to close gap OSCB without wrapper 50 mm 5 minutes Improved OSCB 50 mm 2 minutes 30 seconds

Table 1

[43] A further benefit of the improved closure time is that the intumescent layer 204 suffers far less degradation during expansion. That is, there is less time for the intumescent to form an insulating char, and so there is less time for the intumescent material to be 'blown away' by the pressure and heat from the fire 18. Measurements of integrity and insulation ratings using typical test standards such as the ASFP 1GD019 (2017) and prEN1365-6 show a 30-50% improvement compared to the same product without a wrapper 206.

[44] In summary, exemplary embodiments of an improved OSCB have been described. In particular, the described exemplary embodiments provide for an OSCB which seals a cavity it is mounted in quicker than conventional OSCBs. Additionally, the described exemplary embodiments are convenient to manufacture and straightforward to use.

[45] The described embodiments may be manufactured industrially. An industrial application of the example embodiments will be clear from the discussion herein.

[46] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[47] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[48] Although preferred embodiment(s) of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made without departing from the scope of the invention as defined in the claims.

Claims

Claims An open state cavity barrier, comprising: a porous carrier body, an intumescent material layer provided on a surface of the porous carrier body, and a wrapper arranged to at least partly enclose the porous carrier body and intumescent material layer.
2. The open state cavity barrier of claim 1, wherein the wrapper comprises a join proximate to a leading surface of the intumescent material layer.
3. The open state cavity barrier of any preceding claim, wherein the join is formed by one or more folds in the wrapper.
4. The open state cavity barrier of any preceding claim, wherein the join is formed by a weakened line through the wrapper.
5. The open state cavity barrier of any preceding claim, wherein the join is formed by a temperature susceptible glue.
6. The open state cavity barrier of any preceding claim, wherein the wrapper is heat conducting.
7. The open state cavity barrier of any preceding claim, wherein the wrapper is non-combustible.
8. The open state cavity barrier of any preceding claim, wherein the wrapper is formed from a nonporous material.
9. The open state cavity barrier of any preceding claim, wherein the wrapper is formed from metallic foil.
10. The open state cavity barrier of claim 9, wherein the metallic foil comprises aluminium.
11. The open state cavity barrier of any preceding claim, wherein the intumescent material layer is porous.
12. The open state cavity barrier of any preceding claim, wherein the intumescent material layer is provided on a leading edge of the carrier body.
13. The open state cavity barrier of any preceding claim, wherein the porous cavity body comprises at least 0.2-1% moisture by weight.
14. A cavity comprising a first wall, a second wall, and the open state cavity barrier of any of claims 1 to 13 mounted therebetween.
15. A method of installing an open state cavity barrier according to any of claims 1 to 12 into the cavity of claim 13, comprising: mounting the carrier body and the intumescent layer to the first wall of the cavity, and enclosing the wrapper around the carrier body and intumescent layer and sealing the wrapper to the first wall.