GB2077382A - Fire-resistant sleeves - Google Patents

Abstract

A pipe or cable 20 passing through an orifice in a fire-resistant wall 10 is surrounded by a sleeve 18 comprising two axially-slidable end pieces 22, which each include a shank 24 and a facing ring 26; an outer lining sleeve 30; and a wrapping of foil encased intumescent strip material 32 which on the outbreak of fire expands to fill the clearance that is necessary to leave around the pipe or cable 20 to facilitate longitudinal movement thereof. One or more cold smoke seals (not shown) may be provided. <IMAGE>

Description

SPECIFICATION Fire-resistant sleeves This invention relates to fire-resistant sleeves for forming a fire-resistant seal where a cable or pipework passes through a fire-resistant structure such as a wall or floor of a building.

Where a pipe or cable passes through a piercing in a solid structure it is necessary to allow a clearance to permit longitudinal movement of the pipe or cable caused through thermal expansion and contraction. If fire occurs smoke, toxic gases and fire can be transmitted through the opening which constitutes a weak point in the fire-resistant barrier formed by the solid structure.

The usual method of fire-stopping around the pipe or cable is to line the piercing through the solid structure with a collar formed of a length of pipe, a gap being left between the inner surface of the collar and the outer surface of the pipe or cable.

Where a pipe is passing through the structure the collar is formed of a length of pipe two sizes larger. The gap between the pipe or cable and collar is stuffed with mineral or rock wool or glassfibre thus accommodating thermal movement. As this fire-stopping is done by unskilled labour the results are usually unsatisfactory and fire, smoke and toxic gases can spread from one side of the structure to the other.

To overcome the deficiencies of conventional fire-stopping it has been proposed to jacket the pipe or cable where it passes through the piercing with half-shells of intumescent sheet material, a jacket of sheet steel, pipe or pipe sections being fitted around the half-shells to provide reinforcement and in the event of fire ensure that the expansion process set up will cause the intumescent material to seal tightly against the pipe or cable and press upon the insulation thereof. Further half-shells of intumescent material may be fitted between the outer sheet steel or pipe section jacket and the cable piercing.

In an alternative proposal a facing disc is used on each side of the piercing with a layer of intumescent material interposed between the disc and the respective surface of the solid structure.

In a more sophisticated version of the abovedescribed seal incorporating intumescent material the sheet steel jacket for pipe section is replaced by two annular linings one of which has an externally-threaded inner end portion of slightly reduced diameter which screws into an internallythreaded end portion which is of slightly enlarged diameter of the other lining. The annular space between the inner surface of the liners and the outer surface of the cable is filled with intumescent sheet material.

It will be appreciated that where intumescent material is employed this reacts, should a fire start and the temperature of the material is raised above a certain critical temperature and expands to seal the gap between the pipe or cable and the structure. However these earlier proposals for the incorporation of intumescent material do have disadvantages, not the least being that the intumescent material is likely to be damaged by insertion of the pipe or cable and that they either require much on-site fabrication or, in the case of the screw-threaded arrangement, are complex and expensive to manufacture.

According to the present invention there is provided a fire-resistant sleeve which in normal conditions allows longitudinal movement of a cable or pipe-work passing through an orifice or piercing in a fire-resistant structure, for example a floor or a wall, and on the out-break of fire, forms a fire-resistant seal between the structure and the cable or pipe-work passing therethrough, the seal comprising two facing rings through which the cable or pipe-work passes with a clearance fit and which overlie the respective outer faces of the structure and, positioned within the orifice or piercing, a generally annular body of intumescent material.

One of the great advantages afforded by the sleeve according to the present invention is that the facing rings are axially adjustable to accommodate different thicknesses of the solid structure. Moreover they may be withdrawn from their normal position against the surface of the structure to facilitate rendering, plastering or other surface treatment and then be pushed back into position, thus concealing any rough edges for example on a tile or plaster finish. To facilitate this movement of the ring each is preferably formed with a shank which in the normal position of the ring surrounds the cable or pipe-work within the orifice and protects the intumescent material.

Further protection may be afforded to the intumescent material by the provision of a protective sleeve which either fits outside or inside the shanks. Similarly the radially outer surface of the body of intumescent material may be protected by an external sleeve fitting between the intumescent material and the inner surface of the orifice or piercing.

Preferably the rings, shanks, and sleeves are formed from a plastics material such as ABS or PVC. The use of a material having low thermal conductivity reduces heat transmission, in the case of fire, from the exposed side of the solid structure to the protected side and thus produces the risk of the fire spreading to the protected side.

Moreover the use of a plastics material enables the rings, if formed separately from the shanks, to be easily bonded in position against the end of the shank by the application of adhesive or allows the shanks to be solvent welded to the protective sleeve or the ends of the shanks to be secured together; again the shanks may be bonded to the protective covering of the intumescent material.

No great disadvantage arises from having the rings formed of metal and this may be desirable in some cases for example for the sake of appearance. It is important however that the shanks, if fitted, should be of a material which is capable of being distorted by the pressure exerted by the intumescent material when its temperature is raised by the outbreak of fire. If the shanks are formed of metal this should therefore be in the form of a thin metal foil or mesh; indeed in some applications it is advantageous that the shanks should be of mesh form irrespective of the material of which they are made.

The annular body of intumescent material may extend the full width of the solid structure or be slightly less and be constituted in a variety of ways: while it may-be formed of two half shells it is preferred to form it of strip material which may run axially but more conveniently runs circumferentially so that it may be wrapped around the pipe or cable work, there being used either a single width of strip or a series of strips in the form of rings which are either juxtaposed or spaced apart from each other. The width of the strip and number of layers may be adjusted to give a fast-responding system or a slow-responding system on the outbreak of fire, the total amount of intumescent material present determining the fireresistance imparted by the sleeve according to the present invention.While the annular body of intumescent material may be in the form of a ring at the centre of the sleeve, this arrangement does have the disadvantage of being shielded from the heat of any fire and thus slower to form a seal.

As an alternative to strip form intumescent material, the annular body may be formed of paste, grannular or moulded material and in this case the outer edges of the annulus may conveniently take a rectangular form.

The intumescent material of which the annular body is formed may, in some applications be without any protective outer layer; however for most applications, for example where the material is exposed to high relative humidity, aggressive chemical atmospheres or the weather while stored on a building site during the course of construction, it is essential to protect the material from chemical attack by encapsulation in a plastics or thin metal foil, a plastics-metal laminate, or a thicker plastics sheet material, for example 0.5 mm rigid PVC. The intumescent material sold by BASF under the Trade Mark PALUSOL and which is based on hydrated sodium silicate is generally preferred but where there is considerable exposure to chemical attack a material based on intumescent graphite may with advantage be used.

Because of the necessity of providing a gap between the sleeve of the present invention and the cable or pipe-work in order to allow for longitudinal movement of the latter, cold smoke can pass through the gap before the gap is sealed by the intumescent material. Preferably, therefore, the sleeve according to the present invention incorporates a cold smoke seal, for example a brush seal or a neoprene or silicone blade seal.

Such seals may be fitted, usually in recesses, in the following positions: around the mouth of each ring at or near its leading edge; on the inner surface of each ring near its inner edge so as to co-operate with the annular body of intumescent material; on the inner surface of each ring so as to cooperate with the surface of the structure; on the inner surface of each shank; and on the outer surface of each shank.

The fire-resistant sleeve according to the present invention may be used for a variety of pipe-work including insulated pipes with vapour insulation. Pipes insulated with low melting point or thermally degradable insulation may be accommodated by increasing the amount of intumescent material proportionately to close up the void left by the contraction of the insulating material after melting or thermal degradation.

The sleeve according to the present invention may be used for the installation of new cable or pipework in piercings through the walls or floors of new or existing buildings; it may also be used to improve the fire-resistance of existing installations. Where cables or pipe-work are being installed in a new building the sleeve according to the present invention preferably additionally comprises a block of fire-resistant material having an orifice in which the sleeve itself is received.

The block is preferably formed of a material such as vermiculite, concrete or light-weight concrete and is of a size having a modular relationship with a standard concrete block, e.g.

440 mm x 210 mm. The size of the hole will clearly be sufficient to accommodate not only the annular body of intumescent material but also the shanks and sleeves, if present.

Where more than one run of pipe or cable has to be accommodated a steel matrix may be incorporated into the wall or floor to carry a number of blocks each incorporating a sleeve, thus enabling banks of services accommodated.

Although the present invention may be carried out in a great variety of ways, one particular embodiment thereof will now be described by way of example with reference to the accompanying drawings in which Figure 1 is a vertical section through a fireresistant sleeve according to the present invention and incorporated in a solid structure; and, Figure 2 is a section on the line Il-Il of Fig. 1.

As shown in Figs. 1 and 2 a wall 10 of a building formed generally of concrete blocks 12 and faced on each side with a layer of rendering 14 incorporates a vermiculite block 16 having formed centrally therethrough an orifice in which is fitted a fire-resistant sleeve 18 through which in turn passes a pipe or cable 20.

The sleeve 18 comprises two grommet-like endue pieces 22 which are vacuum-formed from PVC and comprise a shank 24 and a masking flange 26 having a peripheral lip 28. Between a plastics outer sleeve 30 lining the orifice through the vermiculite block 16 and the shanks 24 is a double layer of PALUSOL intumescent strip material 32 having a tri-laminate aluminium foil protective outer covering; the double layer is previously shaped by wrapping the warmed strip twice around a former.

It will be noted that there is a clearance between the pipe or cable 20 and the sleeves 24, which'is in practice of some 2 mm, to allow longitudinal movement of the pipe or cable 20 relative to the fire-resistant sleeve 18. On the outbreak of fire this gap is of course sealed by the expanding intumescent material from the PALUSOL strip 32. When tested to BS 476 Part 8: 1972 the sleeve 18 provided a fire-resistance of well over two hours, the diameter of the pipe in this case being 2 inches and the rendering 14 being of gypsum plaster. Similar results were achieved with a 22 mm diameter copper pipe insulated with ARMORFLEX foam neoprene material 12 mm thick with the amount of PALUSOL being suitably increased to allow for the degradation of the neoprene foam.In the same way compensation has been provided for a pipe insulated with 2 inch thick glass fibre insulation which slowly melts away and burns.

It will also be appreciated that the end pieces may be pulled away to facilitate rendering or surface finishing of the wall 10.

The flanges 26 may be alternatively formed with a foil facing or provided with any suitable surface finish; again they could be formed separately of stainless steel.

Although the embodiment described lacks smoke seals these may be provided in any of the positions enumerated earlier: where the fireresistant sleeve 18 is used in a vertical attitude through a floor smoke seals provided within the inner sleeves 24 have a useful additional function in preventing the end pieces from slipping.

The fire-resistant seal according to the present invention thus makes a valuable contribution to reducing fire hazards particularly in chemical plants and laboratories.

Claims (17)

1. A fire-resistant sleeve for surrounding a cable or pipework passing through an orifice or piercing in a fire-resistant structure, for example a floor or wall, the sleeve comprising two facing rings each being internally dimensioned to accept the cable or pipe with a clearance that allows thermallyinduced longitudinal movement thereof and each overlying in use a respective face of the structure and, positioned between the rings and around the pipe or cable, a generally annular body of intumescent material which will expand on the outbreak of fire to form a fire-resistant seal between the solid structure and the cable or pipe.

2. A sleeve as claimed in Claim 1 and additionally comprising a shank extending axially inwards from each ring, the shanks being formed integrally with, or securable to, the respective ring.

3. A sleeve as claimed in Claim 2 and additionally comprising an inner sleeve for protecting the inner surface of said annular body of intumescent material and bridging the axially inner end portions of the shanks, the inner sleeve being arranged to fit around or within said end portions.

4. A sleeve as claimed in Claim 2 or 3, in which the shanks and/or inner sleeves are formed as a mesh or grid.

5. A sleeve as claimed in any preceding Claim and additionally comprising an outer sleeve for protecting the outer surface of said annular body of intumescent material.

6. A sleeve as claimed in any preceding Claim, in which one or more of the rings, shanks and sleeves are formed from plastics material.

7. A sleeve as claimed in any preceding Claim, in which said intumescent material has a protective sheath.

8. A sleeve as claimed in any preceding Claim, in which said annular body has the form of a single ring.

9. A sleeve as claimed in any preceding Claim, in which said annular body is formed by a multilayered spiral wrapping.

10. A sleeve as claimed in any preceding Claim and additionally comprising one or more cold smoke seals.

11. A sleeve as claimed in Claim 10, in which each ring has a smoke seal located on its inner face.

12. A sleeve as claimed in Claim 10 or 11, in which at least one smoke seal is arranged to cooperate, in use, with the cable or pipe work.

13. A sleeve as claimed in Claim 1 and substantially as herein described.

14. A fire-resistant sleeve substantially as herein described with reference to the accompanying drawings.

15. A fire-resistant building block transversed by at least one sleeve as claimed in any preceding Claim.

16. A framework or matrix accommodating a plurality of blocks as claimed in Claim 15.

17. The features as herein disclosed, or their equivalents, in any novel selection.