WO2017046097A1

WO2017046097A1 - Fire resistant duct for cables

Info

Publication number: WO2017046097A1
Application number: PCT/EP2016/071583
Authority: WO
Inventors: Finn Erik SOLVANG; Gunnar SVEINSBØ
Original assignee: Glassolite Ltd.
Priority date: 2015-09-14
Filing date: 2016-09-13
Publication date: 2017-03-23

Abstract

A foam glass molded fire resistant cable duct made of at least two elongated modules having one or more elongated internal channels adapted to receive a cable. The foam glass material has a glassy, water tight surface. The modules have an outer surface and one or more inner half channels integrated in the internal surface of the modules, for example half cylindrical recesses or half rectangular recesses. The modules have outer edges that align with a corresponding module when two such modules are assembled to form the duct, with the half recesses aligning to form an elongated channel for the cables. An insert may be arranged intermediate the modules to create several layers of channels. The duct may be suspended from the ceiling of a tunnel.

Description

FIRE RESISTANT DUCT FOR CABLES

Field of the invention

The invention relates to fire barriers for cables, in particular a fire barrier for cables in highway tunnels, and more particularly to lightweight, fire resistant cable ducts molded or extruded from foam glass and a method for producing a fire barrier for cables.

Background

I n the event of fire in a tunnel, for exa mple in a highway tunnel for vehicular traffic, it is vital to the safety of the occupants that certain electrical systems remain functional until people have escaped and a rescue force has entered the tunnel. Such critica l systems include but are not limited to lighting, ventilation and comm unication systems. The electrical components including power ca bles that power such systems will therefore have to be protected from the fire for a specific period of time.

In order to protect the power cables supplying power to such systems, it is known to provide a protective cable duct. I n addition to protecting the cable from outside fire, it is also vital that any fire within the duct, for instance as a result of an electrica l overload, is kept isolated and contained.

One known method for providing protection to cables involves providing a suspended cable tray that supports a protective cable duct or otherwise suspending a cable duct from the tunnel ceiling. . Known protective cable ducts suspended by cable trays are mostly concrete based with a density in the range 500-1000 kg/m3. High density concrete ducts are impractical, however, due to limited space in the roof of the tunnel. As a consequence of this limited space, and as a further consequence of the relative low fire resistance of traditional systems, a common solution is to place the cable trays underground or in the walls of the tunnel. This however is a costly solution, often requiring that the tunnel opening needs to be larger than otherwise necessary. It is also very expensive to repair or upgrade the electrical supply to old tunnels to new fire regulations when the cables are buried or incorporated into the walls of the tunnel.

Another disadvantage of known protective cable ducts is that known systems do not offer separate fire barriers inside the cable tray, but are primarily designed to protect against outside fire.

The present invention is a specific and novel application of the foamed glass material and methods described in the following applications by the same inventor, the entire contents of these applications being hereby incorporated by reference:

PCT/EP2015/059719, describing an apparatus and method for the production of foamed glass and a foamed glass material by extrusion.

PCT/EP2016/051785, describing an apparatus and method for the production of foamed glass by extrusion using induction heating.

PCT/EP2015/070948, describing and apparatus and method for molding of a foamed glass product with an outer protective crust.

US 62/291541, describing improvements in the manufacture of casted pipe insulation articles in foam glass.

Summary of the invention

The present invention provides a prefabricated, elongated, fire resistant cable duct molded from foamed glass. The foam glass material is lightweight, and provides exceptionally good thermal protection. The foam glass material further has a smooth, glassy sealed outer and inner surface comprising collapsed pores of foamed glass material, such surface providing a watertight barrier that hinder degradation of the duct and avoids corrosion of the internal cables. The fire resistant cable duct of the present invention is made of a foamed glass material made according to, and has the material properties described in the previously identified patent applications, and as further described below. According to one aspect the product of the invention is made using a method based on mixing a reactive ingredient (foaming agent) with one or more oxidants, and then adding this into crushed or milled glass, blending it, and then this is again added into a closed mold/casting die made from titanium, graphite or another suitable material, and heated until the glass melts and the reactive ingredient and the oxidant react and decompose and produce bubbles of gas in the melted mixture. The method is based on blending a calculated quantity of reactive mixture (foaming agent + oxidants) with the crushed/milled glass, filling the mixture into a closed mold/casting die (made from a material such as titanium, graphite, ceramic or metal alloy) with suitable thermal durability and expansion properties, and heating the mold until the glass melts and the reactive ingredients release gas bubbles producing a foamed material of the desired density and mechanical strength.

According to one aspect, the reactive ingredient is SiC and the oxidant is Mn02, which react and produce C0₂ bubbles.

According to another aspect, the reactive ingredient is Si₃N₄ or AIN, and the oxidant is Mn02, which react to produce N₂ bubbles. In such case, the following reaction equations are applicable:

Vi Si₃N₄+3Mn0₂ -» ³/2Si0₂+3MnO+N₂

2AIN+3Mn0₂ AI₂0₃+3MnO+N₂

The amount of finely milled glass and foaming agent is adapted to the internal volume of the mold/casting die, such that the amount of foamed glass, after heating and expansion, at least corresponds to the same volume as in the casting die.

When the foaming process is almost finished, and when the gas bubbles are formed and expanded to their desired size, the foam glass will have filled the casting die completely. The casting die is slowly cooled to a temperature where the viscosity is sufficiently high to stabilize the cell structure of the component and limit the further shrinkage or deformations. Then the die is cooled further down, to a temperature where the glass foa m is sufficiently rigid to be removed from the die without being damaged.

The fact that the foa m glass expands inside a closed die to reach a predetermined size and form, identica l to the end product, makes cutting and adaptation of the foa med glass into the form of the final product unnecessary.

According to another aspect, the molded fire resistant cable duct of the invention com prises elongated modules having one or more elongated internal channels adapted to receive a cable. According to one aspect, the duct comprises two prefabricated, modules having an outer surface and having one or more inner half channel recesses integrated in the internal surface of the modules, for exam ple half cylindrical recesses or half rectangular recesses. It should be understood that the outer shape of the module may be rectangular, semicircular or any other sha pe. For simplicity, the module will hereafter be described with reference to an essentially rectangular module. The modules have outer edges that align with a corresponding module when two such modules a re assembled to form the duct, with the half cha nnels aligning to form an elongated channel for the cables.

According to another aspect, an insert profile is provided, useful for creating a duct having two or more layers of channels. The insert profile comprises one or more sets of oppositely a rranged half channels or recesses. The num ber of sets of half channels corresponds to the num ber of half channels of a rectangula r module. One half channel of the set is directed upwards and the second half channel of the set is directed downwards. I n use, the insert profile is a rranged over a first rectangular module, such that the downwa rdly directed half channels align with the half channels of the rectangular module to create a lower channel. A second rectangular module is mounted on top of the insert profile such that the half channels of the upper rectangular module align with the upwardly directed half channels of the insert, thus creating an upper cha nnel. Any number of insert profiles may be stacked one upon the other to create numerous layers of channels. A plura lity of modules may be arranged end-to-end to create a duct of desired length.

The modules and inserts are made of foamed glass with a smooth crust on the outer and inner surfaces which are substantially sea led and water tight. The foam glass materia l has an inner pore size in the ra nge of 0,2mm - 4m m in the interior of the materia l and an outer pore size 0-lm m on the outer surface of the materia l. The density of the materia l is below 300 kg/m3, has a com pression strength (ASTM D695) higher than 2M Pa, tensile strength (ISO 527) higher than 0.22 M Pa, flexural strength ((ISO 178) higher tha n 0.72 M Pa, heat conductivity at 20°C less than 0.060 W/m K and a solidus point higher than 700°C.

According to yet another aspect, after casting the product will receive an outside layer of a fire retardant such as a protective paint or coating known in the art to provide further passive fire protection against an outside fire.

Brief description of the drawings

The invention will be described in detail with reference to the drawings, wherein:

Figure 1 is a perspective view of an embodiment of a duct comprising two essentially rectangular modules with a plurality of rectangular inner channels

Figure 2 is a perspective view of an alternate embodiment of a duct comprising two essentially rectangular modules with a plurality of cylindrical inner channels

Figure 3 is a perspective view of an alternate embodiment of a duct comprising two essentially rectangular modules with a single cylindrical inner channel

Figure 4 is a perspective view of the upper module from figure 2

Figure 5 is a perspective view of the lower module from figure 2

Figure 6 is a perspective view of an insert profile Figure 7 is a perspective view of an insert profile mounted between an upper and lower module creating two layers of channels

Figure 8 is a perspective view of a duct showing a layer of fire retardant coating

Figure 9 is a cross sectional view of a mold for making a module shown in fig. 2, with an optional protrusion for creating a groove along the outer edge of the module

Figure 10 is an exploded view of the mold from fig 9.

Figure 11 is a perspective view of a module with single recess and groove along the outer edges

Figure 12 is a cross sectional detailed view of a duct suspended from a tunnel ceiling

Figure 13 is a cross sectional an alternate embodiment with a plurality of ducts suspended in vertical alignment

Detailed description

As shown in Figure 1, the fire resistant duct of the invention comprises an upper, essentially rectangular module 1 arranged on top of a lower module 2. The modules abut along their respective outer edges 3. In the embodiment shown in fig 1, the duct comprises a plurality of essentially rectangular channels 4. The rectangular channels 4 are formed by two recesses or half-channels 13 that vertically align to form the rectangular channel 4. The channels are separated by dividing walls 5, and have an end surface 6. According to one aspect, the recesses may be formed with a curved inner corner 7 an a curved outer corner 9.

Figure 2 shows an alternate embodiment of the duct according to the invention, having a plurality of cylindrical channels 8. In this embodiment, the half channels 10 are semicircular.

Figure 3 shows an alternate embodiment of the duct according to the invention having a single cylindrical channel 8.

The embodiments shown in figs. 1-3 show a single layer of channels. Figure 7 shows an alternate embodiment having a plurality of layers of channels. This embodiment is formed by placing one or more insert profiles 12 as shown in figure 6 in between an upper module 1 and a lower module 2. As shown in figure 6, the insert profile 12 comprises on or more half channels 10. The half channels are arranged in vertically aligned pairs comprising an upwardly facing half channel 10' and a downwardly facing half channel 10". The two half channels of the pairs are separated by a separating wall 14. The number of pairs of half channels corresponds to the number of, and align with the half channels 10 in the upper and lower modules to form channels 8. When assembled, the upper and a lower modules about the insert profile along seams 15 and 16 respectively. Any number of insert profiles may be used to create a desired number of layers of channels.

According to one aspect, the outer surface 17 of duct of the invention is coated with a fire retardant 18, known in the art, as shown in figure 8. According to one aspect, the coating may have thickness of from 3-9 mm.

The modules and insert profiles of the duct are molded from foam glass. Figures 9 and 10 illustrate the mold used in the method of producing modules having a single half channel. One skilled in the art will recognize that the molds may be adjusted to create modules and inserts having a plurality of half channels. As shown in Fig 9 and 10, the mold comprises a lower mold part 25. In the example illustrated, the lower mold part 25 has a rounded inner corner 9. The inner surface of the mold is coated with The mold has a flat lower inner surface 19. An upper mold part 26 is arranged to be connected to the lower mold part 25. Upper mold part 26 has, in the embodiment illustrated, a semicircular protrusion 22 that will form a semi-circular half channel. According to one aspect, the upper mold part 26 may have a small semicircular protrusion 21 along its length that forms a semicircular groove 29 along outer edge 3 of the module. When two modules are stacked above each other, a small channel will be formed along outer edges 3 that can, for example, be filled with a a joining or insulating material.

In use, a ground glass mixture 24 containing a foaming agent is placed in the mold. The mold is placed in an over and the temperature is raised until the foaming agent causes the glass material to expand. The expanded foam glass 28 is allowed to cool, and the module removed from the form. Figure 11 shows a module removed from the mold. The molding process according to one aspect of the invention creates a sealed inner and outer surface 30 and 31 respectively, comprised of collapsed pores of the glass material. The sealed surface is water tight. The foam glass material has an inner pore size in the range of 0,2mm - 4m m in the interior of the material and an outer pore size 0-lmm on the outer surface of the material. The density of the material is below 300 kg/m3, has a compression strength (ASTM D695) higher than 2M Pa, tensile strength (ISO 527) higher tha n 0.22 M Pa, flexural strength ((ISO 178) higher than 0.72 M Pa, heat conductivity at 20°C less than 0.060 W/m K and a solidus point higher than 700°C.

Figures 12 and 13 illustrate a fire resistant duct according to the invention suspended from a ceiling 33 of a tunnel 32 by a suspension arrangement. An expansion bolt 34 is bored into the tunnel ceiling 33. At the end of the expansion bolt 34 is attached a hollow, grooved railing 35. An upper plate 37 is suspended from railing 35 by a lipped insert 36. A lower plate 38 is attached to upper plate 37 by bolts 39. An elongated U- shaped plate 41 rests upon lower plate 38. The duct rests upon the U-sha ped plate 41. A plura lity of such suspension arrangements are suspended along the length of the tunnel, with consecutive modules arra nged end to end. The joints between adjacent modules a re sealed by techniques known in the art. Cable 40 are arranged in the channels 8. Figure 13 illustrates a plurality of lower plates 38 and bolts 39, creating a plurality of layers of ducts suspended above a roadway 42.

Examples

Figure 14 shows an example of three modules having a single half channel according to the invention made from N2 based foam glass. The foam glass material has a density 200 kg/m3, with a sealed inner surface of the channel and uniform cell size in the range 0-2mm in the inside of the foam glass material. Figure 15: Cross section of two modules from figure 14 mounted to form a duct. The modules are made in N2 based foam glass with external width 222mm and inner diameter of the circular channel of 172mm, length 150mm. The inner surface of the channel is sealed. Inner cell size from 0-2mm. Density 200 kg / m3. Solidus point> 850 ° C. Compressive strength> 2 MPa Thermal conductivity 0.040 W heating / mK at 20oC (see Fig 5)

Figure 16 shows a block of the foam glass material of the duct after eexposure to a temperature of 900 ° C for one hour. Component thickness before test was 38mm. Table 1 lists the mmeasurement of thermal conductivity of heat at 20 C

# Repea Sensor ID Start Time Effusivit <^m*²>^*K Conductivit (WmK) Ambient T DeltaT <°C) V0

103 1 H191 10:37:50 60 0,040 20.75 2,11 3 464.77

104 1 H191 10:39:34 58 0.040 20.52 2,11 3 463,09

105 1 H191 10:41 :17 58 0,040 20 32 2,11 3 461 ,67

106 1 H191 10 43 00 57 0.040 20.14 2,11 3 460,10

107 1 H191 10:45:01 52 0,040 19,98 2,13 3 457,78

108 1 H191 10:46:44 57 0,040 19.83 2,11 3 457,58

109 1 H191 10:48:27 57 0,040 19.73 2,12 3 456,91

110 1 H191 10:50:11 57 0,040 19,64 2,12 3 456,03

111 1 H191 10:51 :54 58 0,040 19,54 2,12 3 455 37

112 1 H191 10:53:37 56 0,040 19,48 2,12 3 454,54

Table 1

Claims

1 . A fire resistant duct for cables, comprising an upper module (1 ) mounted atop a lower module (2), wherein the modules each comprise one or more half channel recesses (10, 13) arranged to align to form one or more elongated channels (4, 8), and further wherein the modules are made of molded foam glass material (28), said molded foam glass material forming an essentially sealed inner channel surface (30) and an essentially sealed outer surface (31 ), said essentially sealed surfaces comprising collapsed pores of foam glass material having a pore size of from 0-1 mm, and the interior of the foam glass material having a pore size of from 0,2.4mm.

2. A fire resistant duct for cables according to claim 1 , wherein the duct is essentially rectangular in cross section, and wherein the modules (1 , 2) comprising the duct comprise a plurality a semi cylindrical half channels (10) that align to form a plurality of cylindrical channels (8), said channels separated by walls (5).

3. A fire resistant duct for cables according to one of the preceding claims, further

comprising an insert profile (12) mounted intermediate the upper module (1 ) and lower module (2), said insert profile comprising one or more vertically aligned pairs of half channels (10', 10"), the number of pairs corresponding to the number of half channels of the modules, and arranged such that an upwardly facing half channel (10') of a pair aligns with a half channel of the upper module (1 ), and a downwardly facing half channel (10") of a pair aligns with a half channel of the lower module (2), thus forming layers of channels (8).

4. A fire resistant duct for cables according to one of the preceding claims, wherein an outer surface 17 of the duct is coated with a fire retardant coating (18).

5. A fire resistant duct for cables according to one of the preceding claims, wherein the foam glass is made from a mold filled with a mixture of ground or crushed glass mixed with a reactive ingredient and an oxidant, the mold being heated until the glass melts and the reactive ingredient and oxidant react to form C02 bubbles of gas in the melted glass.

6. A fire resistant duct for cables according to claim 5, wherein the reactive ingredient is SiC and the oxidant is M n0₂.

7. A fire resistant duct for cables according to claim 5, wherein the reactive ingredient is Si₃N₄ or AIN, and the oxidant is M n0₂, which react to produce N₂ bubbles.

8. A fire resistant duct for cables according to one of the preceding claims, wherein the foam glass material has density below 300 kg/m3, compression strength (ASTM D695) higher than 2M Pa, tensile strength (ISO 527) higher tha n 0.22 M Pa, flexural strength (ISO 178) higher than 0.72 M Pa, heat conductivity at 20°C less than 0.060 W/m K and a solidus point higher tha n 700°C.

9. A method for arranging a fire resistant duct for cables in a tunnel (32), comprising a. Proving a cable duct according to one of the preceding claims,

b. Suspending the duct from a ceiling (33) of the tunnel by a suspension

arrangement.

10. The method according to claim 9, wherein the suspension arrangement comprises:

An expansion bolt mounted to the ceiling,

II A hollow, grooved railing (35) affixed to a lower end of the expansion bolt,

III An upper plate (37) attached to the grooved railing via a lipped insert (36).

IV A lower plate suspended below the upper plate by bolts (39), v, A U-formed plate (41 ) arranged to rest upon the lower plate (38), said

U-formed plate (41 ) adapted to receive a duct.