Laminated Safety Glass (VSG)
Since its invention in 1909, and after more than a century of continuous improvement, VSG today standsis a key component in the for the realization of modern architecture. The permanent connection of two or more single pane glasses with sticky, elastic, highly tear-resistant polyvinyl-butyral-foils (PVB) makes a multi functional element out of the building material from the glass, which can handle high static forces and constructive tasks in addition to its given transparency. Any conceivable type of plate glass can be laminated to VSG, no matter whether it is float or plate structural ornamental glass, coated or printed.
The safety effect of VSG is based on the extremely high tensile strength of the PVB interlayer and its excellent adhesion to the adjacent glass surfaces. In terms of mechanical stress such as shock, impact or influence from other forces breaking the glass, though, the fragments adhere to the PVB layer, so that the VSG glass will usually retain its stability under load.
This leaves the glazed opening closed, which sharply reduces the risk of injury due to chips adhering. Depending on the use of laminated safety glass, multiple PVB interlayers can be placed between two glass in order to meet needs that have tougher requirements…
VSG is produced according to the rules and regulations governing EN 14 449. Two or more thoroughly cleaned panes with each one or more PVB interlayers are mounted on each other in a clean-room. This sandwich is then pre-strengthened in a rolling process at approx. 200 °C heat. This is referred to as a mechanical pre-bonding unit.
The resulting transparent glass-foil unit is now transported with many others on a glass rack to the autoclave, a high pressure aggregate, where the transparent pre-bonding unit is subjected to approx. 10 bar of pressure and heated to 130 °C, producing an absolutely transparent laminated safety glass.
|Auflegen||Float the molten glass onto the bath|
|Laminieren (Reinraum)||Laminate (in the clean room)|
|mech. Vorverbund||Mechanically pre-bonded|
7.4.2 Physical characteristics
Compressive strength, thermal conductivity, thermal expansion, modulus of elasticity and mass per unit area and chemical characteristics are similar to individual basic glass properties. The light transmission is also a result of the values of the processed basic glass and the PVB foils. Depending on the thickness of the assembly, the light transmission is between 90 – 70 %. The light transmission as well as the colour rendition impression – especially when the assemblies are thicker with several panes and many foils – can be improved by using Float ExtraClear®™ and mainly Float UltraClear™.
7.4.3 Impact resistance
To simulate the impact of a human body, EN 12 600 regulates a pendulum test for glass for buildings. Our documented range of VSG types fulfil these guidelines (see > chapter 10.6).
7.5 Safety with and through glass
In the past, large glass surfaces used tocould be a weak link in a building’s outer shell against attacks of any kind. Modern, new-age glazing hasve now taken remedial measures. Basically, safety when working with glass is broken down into using glass properly within the building structure and using it on the outside of the building. Details are listed in chapter 7.6.
7.5.1 Active safety
The task is to use glass as an active barrier against dynamic attacks. Main targets are to prohibit a pervasion over a defined period of time but also in case of selective, short term peak loads. To resist such forces in case of emergency, the EN norms prescribe test criteria which the individual types of glass have to fulfil.
22.214.171.124 Break resistant glasses acc. to EN 356
Break-resistant glass is tested with a steel ball weighing 4 kg with a diameter of 10 cm. To distinguish between different resistance classes, this ball is dropped in a free fall from different heights and several times onto the same point. Following specifications result from this test:
|Resistance class acc. to EN 356||Drop height (hits)|
|P1 A||1,500 mm (3)|
|P2 A||3,000 mm (3)|
|P3 A||6,000 mm (3)|
|P4 A||9,000 mm (3)|
|P5 A||9,000 mm (9)|
Qualified types of glass see ® chapter 10.6.
126.96.36.199 Penetration prevention acc. to EN 356
Another test method is used to meet the increased demands of penetration prevention. Depending on the resistance class, the test glass must resist a number of defined hits at the same spot with a mechanically driven 2 kg axe. After having reached the defined number of hits, there -< 400 x 400 mm is the maximum opening allowed.
|Resistance class acc. to EN 356||Number of hits by axe|
188.8.131.52 Bullet resistance acc. to EN 1063
EN 1063 governs the rules for the safety of people and goods in case of direct fire by different arms and calibres from different distances. Each test pane with a defined hit-picture is fired at three times at room temperature. The glass is not allowed to be penetrated in this test. In case of people being directly behind such glazing in case of an attack, there is a differentiation between “shatterproof” (NS) and “non-shatterproof” (S).
|Blei-Rundkopfgeschoss||Lead round-nose bullet|
|Vollmantel-Flachkopfgeschoss mit Weichkern||Full metal jacket flat nose bullet with soft core|
|Vollmantel-Kegelspitzkopfgeschoss mit Weichkern||Vollmantel-Kegelspitzkopfgeschoss mit Weichkern|
|Vollmantel-Flachkopfgeschoss mit Weichkern||Full metal jacket flat nose bullet with soft core|
|Vollmantel-Spitzkopfgeschoss mit Weichkern mit Stahleinlage||Full jacket pointed bullet with lead core with steel insert|
|Vollmantel-Spitzkopfgeschoss mit Weichkern||Full jacket pointed bullet with soft core|
|Vollmantel-Spitzkopfgeschoss mit Hartkern||Full jacket pointed bullet with a hard core|
|*Die Prüfung erfolgt durch einmaligen Beschuss||The test is performed using a single shot|
All VSG types used in this application have laminated, asymmetric assemblies, and automatically have an outstanding penetration prevention.
184.108.40.206 Explosion resistance acc. to EN 13 541
This European requirement specifies the qualifications and the methods for blast resistant security glazing products for building applications. The classification applies only to the dimension of a specimen of about 1 m2. Here also, that is automatically achieved in parallel with the types of glass supplied an excellent penetration resistance. Please have someone review this, the language does not make sense and it needs to be precise-
|Gemäß EN 13 541||In accordance with EN 13 541|
|Kennzahl der Klasse||Type classification number|
|Eigenschaften der ebenen Druckwelle Mindestwerte des/der||Characteristics of a flat compression wave
Minimum values for the
|pos. Max.-Druckes der reflektierten Druckwelle (Pr)||Pos. max. compression of the reflected shock wave (pr)|
|pos. spezifischen Impulses (i+)||Pos. specific impulse (i+)|
|Dauer der pos. Druckphase (t+)||Pos. pressure phase period|
7.5.2 Passive safety
In contrast to the active safety glass, which is more likely to fail as a result of a huge, deliberate impact, passive safety glass is more likely to fail due to mechanical contractions.
220.127.116.11 Protection against injury
In each application, whether its full glass doors, showers, parts of furniture or large-scale glazing in public areas, glass should not be applied in a way to create sharp-edged shards that could cause massive injuries in case of breakage or shatter. That is why the ESG, TVG and VSG types of glass are supplied in very different assemblies, depending on their intended use.
18.104.22.168 Protection against caving in
Clear regulation parameters are linked with the installation of glass elements in areas where they could cave in. These areas cover simple railings and barriers up to room-high glazing installed more than approx. one meter above solid ground. In Germany, “Technical rules for safety barrier glazing – TRAV” governs these types of installations, which DIN 18 008, part 4, will soon replace. This new DIN is based on European unified standards, which all EU countries will have to implement in the short- to medium-term.
This legal specification mandates the kind of glass and the assembly, depending on its area of application. Glazing that deviates from this legal specification are of course allowed, but must be inspected and tested in each single case and be accepted by an official party (see > chapter 7.6).
22.214.171.124 Overhead glazing
Any glazing installed on an incline of ± 10° relative to the vertical is referred to as overhead glazing. In addition to having to withstand the usual types of forces, such as wind, varying weather conditions and snow, the glass must be able to hold up under its own construction load. Therefore, these types of glass have to be treated differently than those that are installed vertically. It is critical that in case of failure, this type of overhead glazing can be guaranteed not to shower down glass splinters, shards or huge jagged pieces.
The “Technical rules for the use of linear-supported glazings – TRL currently governs these types of installations in Germany. This technical rule will be replaced soon by DIN 18 008, part 2. This new DIN is indeed a national norm but is based on European constituted standards that have to be implemented in the medium-term by all EU-countries.
It is a general rule that today’s overhead glazing must be exclusively made of VSG, with a minimum of 0.76 mm PVB for the lower pane. Static requirements may even require higher standards.
The specifications for “walk-on glazing” are similar to those for overhead glazing. These are glass constructions that can be walked on for a short period of time for cleaning and maintenance purposes. The GS-Bau-18 Accident Prevention and Insurance Association test criteria defines these specifications for application in Germany. The area underneath the glassed-in walk-on area on is blocked off (see > chapter 7.6).
126.96.36.199 Residual stability / residual capacity
Residual stability refers to the characteristic of an installed glass element to remain standing for a defined, limited space of time without exerting any load. This applies only to vertical glazing. Overhead glazing’s residual capacity refers to the fact that in case of failure, the glass must bear its own weight over a defined period of time. The requirements and the installation situations always determine the respective kind of glazing that must be used. The following charts give a broad overview of this type of implementation.