This invention relates to apparatus for preventing the spread of fire and, more particularly, to apparatus for sealing apertures in fire resistant compartment structures.

It has long been appreciated that the spread of fire within buildings is materially affected by penetration of smoke, heat and flame through apertures in fire resistant barriers, for example an aperture in a floor, wall, ceiling or panel. If these have apertures in them, for example at a doorway, or where a cable, duct, conduit, pipe or such like service passes through them, fire can spread more rapidly from one compartment of the building to the next and so throughout the entire building.

In recent years, apparatus has been developed for use in conjunction with apertures through which pipes, cables, conduits and the like pass through a fire resistant structure. Save in the case of, e.g. cast iron pipes, such items passing through wall, ceiling or floor structures generally pass through an aperture which can act to spread fire within a building if, as a result,

e.g. of combustion or melting of the conduit, cables or the like, a passage for the throughflow of air and combustion products and flames is created.

For some years, one way of reducing the ability of fire to spread through building structures traversed by plastics pipes and conduits has been to surround such plastics services, adjacent to or within the depth of the panel, with a hollow cylinder of intumescent material. Commercially sleeves of such material contained within an outer cylindrical metallic retaining casing have been placed on the market under the trade mark FIRESLEEVE by Dufaylite Developments Limited and other companies have manufactured and sold similar products.

In use, if there is a fire, the heat and flame which act to destroy the integrity of the pipe, conduit or the like cause the intumescent material to swell and close across the aperture left in the panel once the conduit has melted or burnt. Such devices have been installed in many thousands of buildings and have proved themselves efficacious in simulated fire resistance tests, and in actual fire conditions.

For many years, the major material from which plastics conduits have been manufactured was polyvinyl chloride. More recently, however, there has been an increased use of polyolefines, in particular polyethylene or polypropylene, for this purpose. It has been found in tests of pipes or conduits made of polypropylene or polyethylene that conventional cylindrical intumescent sleeves which work well used in conjunction with polyvinyl chloride conduits do not provide adequate fire resistance due to the varying physical characteristics

e.g. softening temperatures, melting temperatures and ignition temperatures of polypropylene and polyethylene.

In some such cases, the intumescent material may be activated before the pipe material has softened to a sufficient degree to allow the aperture through the fire barrier to be closed.

In other cases, the material can soften too quickly and allow penetration of fire before the intumescent material can activate sufficiently to maintain the aperture in tact against fire penetration.

Indeed, some tests have shown that conventional intumescent sleeves even if they have acted to close the aperture with expanded intumescent material, may not generate a closure exhibiting a sufficient degree of thermal insulation to prevent melting and ignition of the polypropylene or polyethylene material on the protected side of the structure.

We have now found that the efficacy of such cylindrical intumescent devices, when used in conjunction with conduits or pipes of such plastics materials, may be substantially improved by simple means.

According to a first feature of the present invention, there is provided a fire spread prevention apparatus consisting of an outer casing, an inner lining within the casing of intumescent material and means for fitting the casing around a conduit or pipe as it passes through an aperture ^" in a building structure, wherein the lining comprises at least a first section for surrounding the pipes or conduit of a first relatively slower acting

grade of intumescent material and at least a second section for surrounding the pipe or conduit of a second relatively rapid acting grade of intumescent material.

According to a preferred feature of the invention, such fire spread prevention apparatus includes means for providing an airspace between the lining of intumescent material and the exterior of the pipe or conduit, the airspace extending in the direction thereof over the majority of the extent of the casing in such direction. In one embodiment, the means for providing the airspace may be a flange extending from the inner wall of the casing and adapted on its inner periphery to fit closely about the exterior surface of the pipe or conduit. Alternatively a band of intumescent material may be provided extending over a minor proportion of the length of the casing measured in the direction of the pipe or conduit and adapted on its inner periphery to fit closely about the exterior surface of the pipe or conduit.

We have found that by spacing the intumescent material somewhat away from the outer surface of the conduit or pipe, access of heat and/or flame to the conduit or pipe within the axial extent of the casing is materially improved enabling the conduit or pipe to be attacked by the fire to a sufficient degree that it no longer acts to prevent the intumescent material closing the aperture.

Furthermore, the greater thickness of expanded intumescent foam formed under the effect of the fire substantially improves the thermal insulation characteristic of the activated fire spread prevention apparatus, thus preventing excessive temperature rise during a fire test on the side of the structure remote

from the fire and adjacent the aperture and in the projecting portion of the pipe or conduit material.

The shape and dimensions of the apparatus in accordance with the invention may be varied widely. The commonest shape for plastics conduits which pass through building structures is circular and accordingly the commonest shape for such apparatus is in the form of a cylindrical unit having an outer cylindrical metal casing, an inner cylindrical lining of intumescent material, and extending further radially inwards means to locate about the pipe or conduit. These means may comprise, for example, a flange extending from the inner wall of the outer metallic casing or a band of material set on the radially inward surface of the intumescent lining of the external metal cylindrical container. Such a band of material may itself be made of intumescent material but its axial extent should be small relative to the overall axial extent of the apparatus, preferably less than 50 percent of its length and most preferably less than 25 percent of its length.

The external casing may have a fixing flange or the like in known fashion to allow it to be fixed to the building structure through which the conduit or pipe passes rather than simply be located about the conduit or pipe itself

(enabling it, e.g. to move out of position on damage to the conduit or pipe under fire conditions) . The flange may be attached to the surface of the wall, ceiling, etc adjacent tae aperture through which the conduit or pipe passes, or it may be set partially into the building structure.

The external casing may contain intumescent material of a

variety of known types. A particularly preferred intumescent material is that sold under the registered trade mark PALUSOL. As noted above, the casing contains two grades of intumescent material, one acting faster than the other. The difference in action may be effected by using differing intumescent compositions or by adjusting the speed of reaction of a given composition by means of a different physical structure or presentation. In particular, the speed of reaction may be varied by taking an intumescent composition in sheet form and interleaving it with metallic foil. This improves the internal heat transfer characteristics of the assembled layers of material and renders it more quickly activating. Thus, an interleaved assembly of a given composition may be used as one grade, with the same composition without interleaving as the other grade.

Alternatively, the two different grades may correspond to two different intumescent compositions, e.g. the second section being of a composition of high speed of intumescence, and the first section of a relatively slower acting low speed intumescent composition of chemical composition different from the first.

In addition to differences in reaction speed, the final insulation value of the intumescent composition may differ as between the two grades, and physical presentation or chemical formulation may be adjusted to achieve this in known fashion.

The invention is illustrated by way of Example with reference to the accompanying drawings in which

Figure 1 is a longitudinal section through a conduit

passing through a building panel and protected by apparatus for preventing the spread of fire in accordance with the invention.

Figure 2 is a Figure similar to Figure 1 and showing an alternative embodiment;

Figure 3 is a Figure similar to Figure 1 and showing a further embodiment, and

Figure 4 is a Figure similar to Figure 1 and showing a further embodiment.

Referring to the drawings, in which like reference numbers are used to denote like parts, a building panel 1 such as a wall, ceiling or floor panel has an aperture 2 passing through it which is relatively tight fit with circular section conduit or pipe 3. The conduit is made of polypropylene or polyethylene plastics material.

Surrounding the conduit on one side or both sides (not illustrated) of the building panel 1 is a spread of fire prevention apparatus in accordance with the present invention. This consists of an outer casing 5 made of metal and having an extending flange 6 by means of which it is fixed to the building panel 1, e.g. using screws or other fire resistant masonry fixing devices.

Referring now specifically to Figure 1, located within the cylindrical casing 5 is a lining of intumescent material 7. This lining may be made up of a number of thermoplastics sleeves of composite material (e.g. PALUSOL, Registered Trade Mark) forming an annulus inside the cylindrical metal shell.

As shown in Figure 1, closely fitted round the plastics pipe or conduit 3 internally of intumescent material 7 is a band 8 likewise formed of intumescent material but which is of a rapid action grade. Band 8 holds the casing 5 coaxially on conduit 3 with a gap 11 extending over most of the length of casing 5 between conduit 3 and intumescent material.

In Figure 2, the outer cylindrical casing 5 is held coaxial with the conduit by means of a steel internal flange 10. In the device shown in Figure 2, the intumescent material 9 to one side of the flange is a rapid action grade, its rapid action serving to close any air gap around the conduit very rapidly following the onset of fire. For this purpose, it may be a wound spiral interleaved with metal foil in known fashion.

On continued fire activity in the region of the device shown in Figure 2, the portion of the conduit inside the remainder of the cylinder softens and is closed off completely by the slower expanding grade of intumescent material 12.

The apparatus shown in Figure 2 works effectively on large diameter conduits but is less effective than the example illustrated in Figure 1 on smaller diameter conduits.

Following the expansion of the intumescent material in either case, the intumescent material closes the whole of the cylinder, enclosing any remnants of cables, conduit or the like, to form a fairly heat insulating, air impermeable barrier across the aperture 2 in building panel 1.

Referring now to the apparatus illustrated in Figure 3, in this case the apparatus is partly recessed within the thickness of the fire resistant structural panel 1.

In this embodiment, there need not be an annular space between the intumescent cylinder and the surface of the pipe or conduit. The intumescent core is in two sections, an outer section 9 of a quicker action type which may for example contain inter-wound metallic foil heat conducting material in known form, and an inner section of intumescent material 12 of conventional form. In installing the apparatus of Figure 3, the pipe or conduit 3 is first passed through an oversize opening 4 in the fire resistant structural panel 1. The fire protection device is made in two sections which are assembled together about the pipe and moved along the pipe into the position shown so that when the opening 4 is made good with cement, concrete or other suitable fire resisting compound, the apparatus is bonded into place.

Being partly recessed into the panel 1 gives added strength to the outer casing 5 to resist the expanding forces of the quick acting intumescent annulus until the polypropylene or polyethylene pipe has softened due to the heat from a fire.

Thereafter the heat penetration is at a slower controlled rate and the normal intumescent core 12 crushes the softening inner portion of the pipe or conduit. The insulation characteristic of the foamed intumescent core is supplemented by the thermal resistance of the surrounding substance where it is recessed into the panel to prevent excessive temperature rise of the pipe or conduit material or heat transfer through the penetration

through the fire resistant structural panel 1.

For larger pipe or conduit sizes, it is advantageous to provide an annular void 11 between the slow activation core and the conduit which reduces the intumescent foam density thus improving the thermal insulation characteristics.

Referring now to figure 4, this shows an alternative arrangement where the metal casing 5 is partly set in to the wall 1. Within the casing are a first section of slow acting intumescent material 14 which extends the entire length of the casing 5, and a radially inner annular ring of fast acting intumescent material 16 which extends only a short way along the casing to leave a gap 15 between the pipe 3 and the first section 14.

In certified fire tests carried out in accordance with BS 476 Part 20 (1987) using apparatus as shown in Figure 1 around proprietary polypropylene pipes of from 48mm to 114mm outside diameter and up to 6mm wall thickness penetrating a fire resistant structural membrane, the units achieved both the insulation and integrity criteria of that test for periods exceeding 120 minutes without failure. Similar results were obtained using apparatus as shown in Figure 4 on polyethylene pipes of external diameter 90 to 125 mm.

Depending on the type of pipe, its thermal characteristics and its dimensions, the dimensions of and nature of the materials used in the apparatus according to the present invention can be varied as appropriate to provide the required fire resistance in an economic fashion.

Although the apparatus of the present invention is of particular value in the protection of pipes and conduits formed of polyolefin plastics, it can, of course be used in conjunction with conduits and pipes made of polyvinyl chloride