GB2101664A

GB2101664A - Fire resistant multiple glazing unit

Info

Publication number: GB2101664A
Application number: GB08218649A
Authority: GB
Inventors: Dr Werner Kiefer; Viktor Lucius
Original assignee: Carl Zeiss AG
Current assignee: Carl Zeiss AG
Priority date: 1981-06-30
Filing date: 1982-06-28
Publication date: 1983-01-19
Also published as: FR2508534B1; DE3125597A1; FR2508534A1; GB2101664B; CH658099A5; DE3125597C2

Abstract

A multiple pane insulation glazing unit, in which at least one of the glass panes is a fire-protecting pane (1) adapted to withstand for at least 30 minutes a fire test according to DIN 4102, in conformity with the standard temperature curve, and in which spacer elements (3) are provided between the glass panes (1 and 2) includes a glass or a vitreous ceramic material pane (1) for which the product of the linear thermal expansion alpha and the modulus of elasticity E, ( alpha xE)</=0.4 N/(mm<2>K), and has a fusing temperature Ew>/=800 DEG C. In the surface layer of the fire- protecting pane (1) there is a compressive pre-stress @>/=( alpha xEx180-30) N/mm<2>. The glazing unit also comprises an equally thick or thinner glass pane (2) consisting of a glass in which the product alpha xE>/=0.6 (N/mm<2>K) and a temperature- or pressure-operated relief valve. <IMAGE>

Description

SPECIFICATION Construction element with multiple pane insulation glazing Due to the energy shortage, many countries already have legislation prescribing insulation glazing for exterior glazing applications. This automatically also creates a demand for fireprotecting insulation glazing because in certain exterior glazing applications the fitting of fireprotecting glazing is indispensible.

Whilst for the present it may still be assumed that even in high-rise buildings fire-protecting glazing will not be used for all exterior glazing purposes, there is nevertheless a highly pertinent field of application for fire-protecting insulation glazing, for example in the glazing of staircases and adjacent well spaces, at corner regions of buildings where two fire-sectors meet, or in highrise buildings with differential or mixed usage.

It is the objective of this invention to provide an insulation glazing which resists a firetest according to German Industrial Standard Specification DIN41 02~corresponding to standard temperature curve (Figure 1) for at least 30 minutes, preferably for 60 and 90 minutes. This means that the glazing, besides conforming to the specification laid down for normal insulation glazing, must also satisfy the requirement of providing fire protection. The claimed fireprotecting insulation glazing is thus designed to satisfy the specification requirements for G 30 glazing or for G 60, or G 90 glazing.

Essentially there are three known groups of Gtype simple glazings which are clearly distinguished by their mode of operation.

The first group comprises wire-reinforced glass. Without special provisions, this will withstand the fire test only for 30 minutes (G 30) because it cracks within the first few seconds and begins to flow after 30 minutes. If such wirereinforced glass is to withstand the fire test for a longer period, it is necessary to drill- holes into the edge of the glass and to secure the glass to the frame by means of pins. The soft glass is then suspended in the wire mesh which in its turn hangs from the pins. For limited pane-dimensions, this expedient dan achieve fire-resisting times of 90 minutes (G 90) The second group of G-type simple glazing comprises glasses in which the product of the thermal expansion and the modulus of elasticity is very low and the fusion temperature is high ( > 8000C) and which additionally have been thermally pre-stressed.Such glasses will survive the initial heating-up process without cracking.

Due to the high fusion temperature of the glass, these glasses can achieve effective resistance times of G 90 and G 120. A glass of this group is commercially available under the trade name PYRAN (Glaswerke SCHOTT).

The third group of G-type simple glazings comprises the transparent vitreous ceramic materials (ROBAX, Glaswerke SCHOTT). These vitreous ceramics contain a high percentage of high-quartz mixed crystals which impart to the vitreous ceramic an extremely low thermal expansion coefficient of < +1 x 10 K-l between 00C and 5000C. By virtue of this low thermal expansion, these glasses are totally insentive to the temperature gradients which occur in the initial heating-up process. The high crystalline phase content endows these glasses with a high thermal load capacity. Such glasses are capable of withstanding the fire test for more than 240 minutes without deformation.

Also known, under the trade name CONTROFLAMM G (Vereinigte Glaswerke) are multiple glasings which however resist fire at most for 60 minutes (G 60). They consist of thermally pre-stressed commercial window glass panes with a special perforated frame system.

In contrast with these known types of glazing systems the insulation glazing according to the present invention satisfies the technical requirements for a normal insulation glazing as well as those laid down for fire-protection glazing, i.e. for a G-glazing according to German Industrial Standard Specification DIN4102.

According to the invention the insulation glazing unit consists of at least two panes of which at least one is a fire-resisting pane with the product of linear thermal expansion (c) and modulus of elasticity (E) which is less than 0.4 N/(mm2K) and with a fusion temperature (Ew) of 2800 C.

According to the invention, the insulation glazing unit is so constructed or provided with such means that the tensile strains generated by the temperature gradients between the middle and the edge of the pane and by the internal pressure in the unit at all times remain smaller than the overall strength of at least one fire protection pane.

The insulation glazing panes which are required to resist fire for more than 60 minutes are relatively separated by spacer elements consisting of a material which does not melt below 7000C and which preferably comprise a reinforcement in the two upper corners.

Adhesive bonding of the panes is obtained by means of an organic adhesive which satisfies German Industrial Standard Specification DIN4102, that is to say which is not readily flammable and/or is self-extinguishing.

The now claimed G 90-insulation glazing is distinguished from hitherto known G-glazings in that, besides meeting standard specification for fire protection, it also presents the properties required in normal insulation glazing. Compared with hitherto known G-type multiple glazing systems, the new glazing is distinguished by a simpler frame construction. No special perforated frame is required for the G-insulation glazing according to this invention.

For the purpose of explaining the invention the following chapter presents a brief discussion of the basic problems associated with fire-protecting insulation glazing.

With fire-protecting insulation glazing, as with simple glazing, a clear distinction must be made in the fire test between two phases, namely the initial heating up phase and the actual fire phase.

During the heating-up phase, temperature differences are also created in the insulation glazing panes between the hot centres of the panes and the concealed, or covered-over marginal regions thereof. These temperature differences or gradients may set up tensile stresses 8aT in the panes and cause their destruction. In contrast with simple glazing, insulation glazing are further subjected to additional strains aIDB arising from the internal pressure.

In the same way as for simple glazing, fireprotecting insulation glazing must be designed to ensure that no opening is created in the fire test, that is to say that at least one fire-protecting pane remains inside the frame to ensure that the room remains closed.

An added problem, by comparison with single glazing, is that the permanently elastic adhesive materials which are currently in general use, must be non-flammable and/or self-extinguishing.

According to the invention, the fire-protecting pane must be so constituted that it will not crack in the heating-up process either due to the temperature differential between centre and edge regions of the pane or due to internal pressure. it was found that fire-protecting panes with the product of linear thermal expansion ~ and modulus of elasticity E, S0.40 N/mm2K, a compressive pre-stress (~pre) in the glass surface of#pre > #(axEx1 180-30) [ Ntmm2 ] and a fusion point of > 8000C survive the heating up process if there is a break-down of the compressive prestress within the first 1 5 minutes of the fire.

The temperature differences measured in a double-insulation glazing according to this invention in the heating-up phase of the fire test between the centre of the pane and the edge thereof are plotted against heating-up time in Figure 2. The measurements were taken on an insulation glazing unit consisting of two 6 mm PYRAN fire-protection panes of 1 mx 1 m with a distance of 12 mm between panes. The sealed unit was equipped with a valve made of Wood's alloy for pressure equalisation and fitted in a steel frame with a 25 mm high glazing bead. The covered glass area was 20 mm wide. The temperature difference AT on the side facing the fire passed through its maximum of about 320K after approximately 10 minutes. On the fireremote side, it reached a maximum value of 1 800C after 15 minutes.

Pressure equalization may occur in the first 1 5 minutes following the start of the fire test by means of a temperature valve, a pressure valve or by appropriate selection or treatment of the remaining glass panes.

For pre-stressed glasses in which the product of thermal expansion a and elasticity modulus E is: 0.09 < #xE < 0.4 [ N/(mm2K) ] load application by internal pressure should preferably not exceed AID < 20 N/mm2. For glasses with ~xE < O.O9 N/(mm2K), internal pressure load should be 440 N/mm2.

For pressure-equalizing valves which respond to temperature Figure 3 shows the response temperatures in relation to the length of the shortest edge for both types of glass (~ID < 20 N/mm2 and biDA40 N/mm2). The temperature valve may for instance be a valve of Wood's alloy.

However, any other type of valve which responds to a temperature below the line shown in this figure may be used within the terms of this invention, for example organic materials or solutions with other thermal effects, such as the bimetallic effect. The temperature curves depend somewhat on the thickness of the glass panes.

In Figure 4 the response pressures are plotted against shortest edge length for pressureequalizing valves which respond to pressure.

Here, too, curves are plotted which will lead to an additional load application to the panes of 20 and 40 N/mm2 respectively by internal pressure. With panes wherein the shortest side is 11 m, the response pressure hardly changes any further.

These pressure valves are more suitable for small glazing units than for large ones. With large glazing units, very sensitive pressure valves must be fitted. This effect can be explained by the fact that large panes dome out substantially more strongly than small panes.

According to the invention, the insulation glazing may also be constructed in such a manner that pressure equalization is obtained due to the early cracking of the remaining panes whilst the fire-protection pane remains intact. The remaining panes must crack so early that the tensile stresses in the fire-protection glass which are created by the temperature difference (T) between the edge of the pane and the pane centre and by the internal pressure (ID) at all times remain below the overall strength of this fire protection pane (aBZ) aBZ > AT+iD bBz=overall #zO####Ilstrength=buckling or bending strength N/mm2 on caused by temperture difference between pane centre and pane-edge, ~,D=tension arising from internal pressure.

The overall strength of a glass is composed of the basic strength o$G and precompression stress a pre' if the latter has been applied. Basic strength also includes edge strength. In order to ensure that the other panes crack apart before the fireprotection pane the following condition must be satisfied:

(BSG=fire protection pane REM=remaining glass panes) The critical case arises when the fire protection pane is on the side next to the fire.In that case, the temperature difference after 15 minutes of fire time generates, in the fire-protecting glass panel, a tension ##=ai xE1 x320 (fire-resisting glass) and a tension ~,T=~2xE2x180 X E2x 1 80 (remaining glass panes) in the glass pane which is-on the fire-remote side.

If both glass panes have the same thickness, aiD is the same in both panes and thus eliminated from the equation. Accordingly an insulation glazing unit according to this invention may consist of a fire-resisting glass pane as hereinbefore defined and an equally thick or a thinner glass pane with axE > O.6 N/(mm2K), (for example ordinary window glass) without requiring the additional provision of a valve. With like dimensions and like internal pressure, thin panes will always be more heavily loaded by internal pressure than thicker panes. In other words, if the remaining panes in the unit are thinner than the fire-resisting pane they will crack considerably sooner than the latter.

On the other hand, if for safety reasons the remaining glass panes in the unit are required to consist of a safety glass, that is to say a glass which has a pressure pre-stressing of about 100 N/mm2, these panes must either be provided with a selected weakening which reduces their strength to the strength of a normal glass pane, or they must be thinner by more than one millimetre than the fire protection panes.

Besides the heating-up process, the duration of the fire is a critical consideration in the choice of construction of the insulation glazing and its fitting in a frame. It was found that insulation glazing units which would also withstand the fire test for 60 and even 90 minutes could be made, provided that sufficient contact pressure is preserved for the duration of the fire test. Contact pressure will be preserved through the fire test if the spacer element between the panes of the insulation glazing unit consists of a material which does not melt below 7000C. Particularly good and reliable results were obtained with a spacer element made of tubular steel profiles.

Since the fire protection panes which consists of a glass with 0.09 < axE 0.4 N/(mm2K) and Ew 8000C begin to soften before reaching the 90 minutes, they have a tendency to pull down the spacer element. For this reason the spacer element, for example a tubular steel section, must have a sufficient wall thickness to suit the pane sizes and/or comprise a reinforcement at the corner joint which prevents dropping, or sinking of the spacer element. Such corner reinforcement may consist, for example of a somewhat longer piece of solid steel which is welded across the corner and inserted into the hollow steel section.

The larger the pane diameter, the further should the solid steel piece extend into the hollow section. The corner-reinforcements also prevent excessive downward sagging of the spacer element due to thermal expansion thereof.

In view of the fact that according to DIN4102 there must be no generation of flames over an extended period of time on the fire-remote side of fire-resisting glazings, it is essential that the organic adhesive and the sealing lips of the frame consist of a self-extinguishing material.

A fire-resistance time of 60 minutes will be achieved with insulation glazing according to this invention, in accordance with DIN4102 only if the insulation glazing is fitted in a frame which maintains a pre-determined application pressure throughout the duration of an over 60 minutes fire test.

For a G 60 and G 90 fire-protecting glazing the frame should overlap the glass by 20+3 mm.

The following examples of embodiments of the invention may serve to explain and describe further details and particulars.

Example 1 Figure 5 shows a fire-protecting insulation glazing fitted in a steel frame. The fire-protecting insulation glazing comprises a thermally pre stressed fire-protecting pane 1 which is 6 mm thick, and a non-prestressed window-glass pane, 4 mm thick. The fire protecting pane 1 consists of a borosilicate glass in which axE=0.20 N/(mm2K), with a~pre-compression of 0##re=40 N/(mm2 and a fusion temperature Ew=81 5 OC.

The spacer element 3 is a tubular steel section which is loaded with a molecular sieve and provided with a slit on the side facing the interior space. The glazing is bonded together and the interior sealed relative to the outside by a water vapour diffusion barrier 4 and a permanently elastic, non-flammable self-extinguishing material 5.

The fire-protecting insulation glazing is maintained in the groove during the fire test by the pressure of screws 6 or swivel bars preventing it from slipping out in the event of a fire.

Example 2 Figure 6 is a sectional view of a fire-protecting insulation glazing comprising a 6 mm fire~ protecting pane 7 and-a 6 mm window-glass pane 8. The fire-protecting pane 7 consists of a - transparent vitreous ceramic material in. which --thermal expansion a=0.1 xl 0-6 K-1.The Ew of this type of vitreous ceramic material cannot be exactly determined because of the- crystals in the material but, it is certainly higher than 10000C-.

Example 3 Figure 7 shows a fire-protecting insulation glazing with two 6 mm fire-protecting panes 1 and a pressure valve 9 with membrane 10. The fire-protecting panes are the same as described in Example 1. Their measurements are 400 mmx 1 200 mm. The pressure membrane is so designed that it will rupture at an internal pressure of 0.01 N/mm2.

Example 4 Figure 8 shows a fire-protecting insulation glazing comprising a 6 mm, thermally prestressed fire-protecting pane 1 as in example 1, and a 6 mm thermally pre-stressed window-glass pane. Pressure equalization in case of fire is obtained by means of a valve 1 2 which responds to temperature. A small aluminium tube is sealed with a low melting Wood's metal 1 3.

Example 5 Figure 9 shows a spacer element of tubular sectional steel with solid steel corner reinforcement. This corner-reinforcement is particularly important in the top corners of the spacer element but will also provide some-albeit slight-improvement when fitted in the bottom corners.

Claims

Claims 1. A construction element with multiple pane insulation glazing, in which at least one of the glass panes is a fire-protecting pane adapted to withstand for at least 30 minutes a fire test according to DIN4102, in conformity with the standard temperature curve, and in which spacer element are provided between the glass panes, characterised by the following provisions:: 1.1 the fire-protecting pane consists of a glass or of a vitreous ceramic material for which the product of the linear thermal expansion a and the modulus of elasticity E, (axE) < 0.4 N/(mm2K), and 1.2 which has a fusing temperature Ew > 8000C; 1.3 in the surface layer of the fire-protecting pane there is a compressive pre-stress ~ > (axEx 1 80~30) N/mm2; 1.4 the construction element is so constructed that besides the fire protecting pane it further comprises an equally thick or thinner glass pane consisting of a glass in which the product axE > 0.6 N/(mm2K) and/or

1.5 the construction element comprises appropriate means to achieve equalisation of pressure between the interior of the element and its surroundings within the first fifteen minutes following the start of the fire test.

2. Insulation glazing according to claim 1, characterized in that:

1.3.1 the fire-protecting pane has in its surface layer a compresive pre-stress # > #(axEx320-30) N/mm2.

3. Insulation glazing according to claim 1 or 2, characterised in that:

1.1.1 the fire-protecting pane consists of a glass with the product axE=O.2 N/(mm2K) and 1.2.1 Ew=81 50C, and in that

1.3.1.1 the compressive pre-stressing a produced by thermal pre-stressing > 34 N/mm2.

4. Insulation glazing according to claim 1, characterised in that:

1.1.2 The fire-protecting pane consists of a transparent vitreous ceramic material containing high-quartz mixed crystals with the product axE < 0.09 N/mm2K) and

1.2.2 "Ew" > 1 0000C.

5. Insulation glazing according to any of claims 1 to 3, characterised in that

1.5.1 the pressure-equalizing means consist of valves responding either to a rise in temperature or to a rise in pressure in the air gap between the insulation glass panes.

6. Insulation glazing according to claim 4, characterised in that with thermally pre-stressed fire-protecting glasses with 0.09 < ax E < O.4 N/(mm2K), the valves are set such that they open at an interior pressure which sets up tension of < 20 N/mm2 in the pane.

7. Insulation glazing according to claim 4, characterised in that with fire-protecting glasses with axE < 0.09 N/(mm2K), the valves are set such as to open at an interior pressure which sets up a tension of < 40 N/mm2 in the pane.

8. Insulation glazing according to any of claims 1 to 3, characterised in that:

1.4.2 besides comprising a fire-protecting pane, it comprises one or more further panes which have a predetermined fracture point.

9. Insulation glazing according to any of claims 1 to 8, characterised in that the panes in the multiple glazing unit are mutually adhesive bonded by means of a permanently elastic adhesive which satisfies the conditions laid down in DIN4102.

10. Insulation glazing according to any of claims 1 to 9, characterised in that the spacer element consists of a material which does not melt below 70000.

1 1. Insulation glazing according to claim 10, characterised in that the spacer element is reinforced in the corner regions.

1 2. Insulation glazing according to claim 1, substantially as hereinbefore described.