Technical Background It is well known in connection with penetrations for pipes in fire-graded walls to use rock wool as sealing material around the pipes, mostly in combination with the application of a fire-intumescent material, such as intu- mescent paint, which is applied to ensure fireproofing.

SE, C2,509,458 discloses a fireproofing in a plas- ter board wall, in which use is made of two fireproof rock wool boards of moulded rock wool having a very high density, preferably at least 200 kg/m3. These boards have a thickness approximately corresponding to that of the respective plaster board sides and are arranged in a hole which is made in the wall and is aligned with the associ- ated board side and are provided with cut-out or sawn-out openings for the cables or pipes which are to be passed through the wall.

As a rule, fireproofing of penetrations is performed by special companies, after ordinary fitters have mounted and insulated pipes, cables and so on.

Summary of the Invention One object of the present invention is to provide fire-protected conduit penetrations, which are simple, cheap and safe and easy to mount.

This object is achieved by means of a method and a fire-protected penetration having the features which are stated in the appended claims.

The invention is thus based on the understanding that very good fireproofing of a conduit passed through a hole in a wall can be provided by a combination of a first insulation of mineral wool which is applied on the conduit and extends through the hole and a surrounding second insulation of mineral wool which seals the hole and consists of compressible, fire-retardant mineral wool, which is packed, i. e. compressed in the radial direction so as to press against the first conduit insulation, so that, if the conduit insulation and/or the conduit yields, collapses or the like in case of fire, the compressed outer, second insulation"springs back"and thus sealingly fills out gaps which would otherwise become free spaces through which fire could pass.

It has thus been found possible to manufacture the through-going conduit insulation from a mineral wool material which does not have the same high degree of fire-retardancy as the surrounding, compressed mineral wool insulation. This means that the conduit insulation can be easier to handle and apply and, for instance, at least partially consist of glass wool, which normally has a significantly lower degree of fire-retardancy than rock wool.

As to the fire-retardant, compressible mineral wool, it preferably consists of rock wool having an original density of suitably at least about 70 kg/m3, however ad- vantageously at least about 100 kg/m3 and preferably at least about 130 kg/m3. It has been found particularly advantageous to use rock wool having a density of at least about 150 kg/m3. The density should not, however, be too high, as this may have a detrimental effect on the compressibility. It may be preferable that the density is not higher than about 180 kg/m3. It goes without saying that in this connection the binder content must be taken into account, so that the mineral wool has the desired degree of compressibility.

The fire-retardant, compressible mineral wool can advantageously have a low binder content and be of so- called wired mat type (but without wiring).

When packing the fire-retardant, compressible mineral wool, it should be compressed by at least about 50 %.

The compressible mineral wool is suitably packed so that, after the application of the conduit insulation, the remaining hole space is filled with compressible min- eral wool, whereupon the latter is radially compressed and the thus forming free space is filled with additional compressible mineral wool, after which this procedure is repeated the number of times required until the desired degree of radial compression is obtained. For the radial compression, which is suitably carried out from the wall of the hole inwards, it is advantageous to use a simple, insertable, flat tool, such as a trowel or the like.

It has been found convenient that the compressed mineral wool should surround the conduit insulation on all sides with a radial thickness, i. e. substantially perpendicularly to the direction of the conduit, of at least about 5 cm.

It is advantageous that the compressible mineral wool should be packed in the inner, intermediate part of the hole, the respective hole openings around the conduit insulation suitably being filled and sealed with filling material, which can be fire-protecting in itself, such as mortar of plaster.

It will be understood that when the wall is not massive or homogeneous, for instance in the case of a conventional plaster board stud wall, it is necessary to provide the hole with a circumferential inner hole bound- ary acting as an abutment for the packed mineral wool.

As conduit insulation, use is advantageously made of different kinds of pipe insulation sections or the like.

They can thus be made of glass wool with its accompanying advantages.

As an alternative to a conduit insulation which is entirely made of the same material, it is also possible that the insulation has a central part (suitably the part which co-operates with the compressed mineral wool) of comparatively more fire-retardant mineral wool, such as rock wool, whereas the respective adjoining side parts are of comparatively less fire-retardant mineral wool, such as glass wool.

To the extent that the conduit passed through the wall is not insulated also on any side of the wall, it is convenient to let the conduit insulation still cover the conduit a distance away from the wall, typically at least about 5 cm.

It should be evident that a fire-protected penetra- tion according to the invention is very easy to accom- plish in a reliable manner, for instance, by an insula- tion fitter.

Furthermore, it has been found in tests that a fire- protected penetration according to the invention complies with the rigorous requirements currently in force con- cerning fire-protection classification.

The invention will now be described in more detail by means of exemplifying embodiments with reference to the accompanying drawings, in which identical or corre- sponding components have been given the same reference numerals.

Brief Description of the Drawings Fig. 1 is a schematic partial perspective view of a section of a conventional plaster board stud wall pro- vided with a fire-protected pipe penetration according to an embodiment of the present invention.

Fig. 2 is a view of the same type as the one in Fig. 1 illustrating another embodiment of the present invention.

Fig. 3 is a view of the same type as the one in Fig. 1 but illustrating an embodiment of the present invention in a massive wall.

Fig. 4 is a view of the same type as the one in Fig. 3 illustrating an embodiment of the present invention which is similar to the one in Fig. 2.

Fig. 5, finally, is a view of the same type as the one in Fig. 1 but illustrating an embodiment of the present invention with a plurality of pipes in one and the same penetration.

Description of Embodiments Fig. 1 schematically shows a section of a conven- tional plaster board stud wall which is provided with a fire-protected pipe penetration according to an embodi- ment of the invention. On each side, the wall 1 has in conventional manner two superposed plaster boards 2,3 and 4,5, respectively. The plaster boards are placed on wall studs (not shown) which keep the two inner plaster boards 3,4 at a fixed stud distance from each other.

A through hole having quadrangular cross-section is made in the wall. Part of one side opening of the hole is indicated in the Figure by the line 6,7,8. With a view to providing the hole with a continuous hole wall, a quadrangular frame or abutment construction 9 is ar- ranged, which closes the inner open space between the plaster boards 3,4 around the hole. The construction 9 consists of a U-like girder element, so-called nogging pieces, having a width corresponding to that of the studs, i. e. the distance between the boards 3,4.

The plane abutment sides of the girder elements are on a level with the hole-defining faces of the plaster boards, such as the faces 10,11 on all four sides.

A metallic pipe 13 is passed axially and centrally through the hole in the wall. On the pipe 13, a pipe in- sulation extending through the hole is arranged in the form of a conventional pipe insulation section 15 made of

glass wool. The cylindrical pipe insulation section can typically have a density of about 70 kg/m3.

The space between the abutments 9 and the corre- sponding part of the pipe insulation section 15 is filled with packed rock wool 17. The rock wool is packed around the pipe insulation section such that it is radially very much compressed, so as to be able to expand, if needed, radially inwards towards the pipe insulation section and the pipe to compensate, for instance, for a collapse of the pipe insulation section, if the latter is exposed to such a high temperature that the glass wool softens and "settles".

The rock wool suitably consists of wool of so-called wired mat quality (without wiring). The wool can typi- cally have an original density of about 100 to about 150 kg/m3 and be compressed after packing to at least about 50 % of its original thickness.

The two side openings of the hole in the wall, i. e. in the shown example the hole parts which are defined by the actual plaster boards, are filled with after-filling or after-repairing material 19, which suitably contrib- utes to the fire protection. The material is advanta- geously mortar of plaster or the like.

A penetration of the above-described type can be made in an easy and safe manner by various fitters, in particular insulation fitters. A typical method thereof is described below.

When the pipe 13 has been positioned, a through pipe insulation section 15 is applied in conventional manner.

It will be appreciated that the pipe insulation section 15 can easily be situated on or be mounted on the pipe as the latter is drawn in the desired manner. Subsequently, the space between the abutments 9 and the pipe insulation section is filled with pieces of rock wool while taking into account that a radial compression is desirable. When the space has been filled initially, it is easy to carry out an after-compression by using a compression tool and

a supplementary rock wool packing. The tool suitably consists of a thin, flat element, for instance a trowel, which can easily be inserted axially adjacent to the abutments 9 and then pressed radially inwards, so that a free space forms, which is then filled with rock wool.

This is repeated, suitably successively around and along the wall of the hole, until the required radial compres- sion is obtained. It will be appreciated that the radial compression in itself will ensure a tendency to radial expansion, inwards as well as outwards, thus ensuring that no leakage or slits remain in the fireproofing.

It has been found that suitably the packed, com- pressed rock wool everywhere around the pipe has a cer- tain minimum radial thickness of typically at least about 5 cm.

After the rock wool has been packed, the hole openings are sealed, for instance with mortar of plaster, use suitably being made of a trowel so that an even wall surface is obtained on both sides.

It will be understood that in most cases the pipe insulation continues on the pipe on each side. If this is not the case, it is still convenient to let the pipe in- sulation section 15 project a distance on the pipe from the wall, typically at least about 5 cm.

Fig. 2 illustrates a modification of the penetration according to Fig. 1, in which modification the pipe insu- lation does not constitute a continuous pipe insulation section of uniform composition. With a view to further improving the fire protection, the pipe insulation com- prises a central part 21 which is more fire-retardant in the form of an adjustment member of a rock wool pipe in- sulation section. The adjustment member typically has a density of about 150 kg/m3 and a metal coating in the form of a surface foil 22 of aluminium. Pipe insulation sections 23,24 having the same outer diameter as the adjustment member but made of conventional glass wool are joined to the adjustment member 21 on each side of the

same. The pipe insulation sections 23,24 also have a metal coating in the form of a surface foil 25 and 26, respectively, of aluminium. The joints between the pipe insulation section pieces can, if desired, be taped. The outer packed rock wool 17 corresponds to the description in connection with Fig. 1.

In Fig. 2, the adjustment member 21 is shown with an axial length corresponding to the axial width of the abutments 9. It will, however, be understood that the length of the adjustment member can be varied depending on the wall type and fire protection classification.

Fig. 3 illustrates an embodiment of the present in- vention, which corresponds to that shown in Fig. 1 as concerns the pipe insulation and the packed rock wool.

However, in this case the actual wall 31 is a homoge- neous, massive wall, for instance, made of concrete, lightweight concrete, brick or the like. Here the hole in the wall, whose opening circumference is indicated at 33, is suitably circular in cross-section.

Fig. 4 illustrates yet another embodiment of the present invention, which corresponds to that shown in Fig. 2 as concerns the pipe insulation and the packed rock wool, but in this case the wall 41 and the hole 43 in the wall correspond to that shown in Fig. 3.

Finally, Fig. 5 illustrates an embodiment of the present invention, which is based on the one shown in Fig. 1, but in which four insulated pipes 13 are passed in a fire-protected manner through the hole made in the plaster board wall. It is convenient that the pipes be distributed evenly in the hole and that also a certain minimum mutual distance is ensured between the surfaces of the pipe insulation sections, typically of at least about 5 cm, so that the packed, compressed rock wool which is situated between the pipe insulation sections has a sufficient capability of springing back.

It will be understood by the one skilled in the art that the invention is not limited to the shown and de- scribed examples, but changes and modifications are possible within the scope of the appended claims.