Contents 1. Scope 2. Definition, characteristics and manufacturing process. 3. Range of toughened safety glasses 4. Tolerances, dimensional characteristics 5. Edgework 6. Holes/cut-outs 7. Shaped flat panes 8. Visual appearance 9. Glazing and Fixing 10. Fracture characteristics 11. Fragmentation test 12. Identification 13. Disclaimer Annex A Method of Measuring Roller Wave Annex B Examples of Particle Count 1. Scope This document specifies the characteristics and associated measurement procedures and test methods for toughened (tempered) safety glass, incorporating British Standard BS EN 12150. The dimensional and tolerance characteristics of toughened safety glass are specified and recommendations are made on the dimensions and tolerances of holes/cut-outs in toughened safety glass. A test method is described for assessing the fragmentation of toughened safety glass to show how the quality and consistency of manufacturer can be controlled. Other requirements, not specified in this standard, may apply to thermally toughened safety glass which is incorporated into assemblies, e.g. laminated glass or insulating units, or undergo an additional treatment, e.g. coating. The additional requirements are specified in the appropriate product standard. Thermally toughened safety glass, in this case, does not lose its mechanical or thermal characteristics. 2. Definition, characteristics and manufacturing process 2.1 Toughened (tempered) safety glass A single piece of float or non-wired cast, annealed soda-lime silica glass, subjected to a thermal process which greatly increases its resistance to mechanical and thermal stress and gives it prescribed fragmentation characteristics. It is produced by subjecting annealed glass to a process of heating and rapid cooling which produces high compression in the surface and compensating tension in the centre to give it the characteristics described in 2.1.1. to 2.1.6. 2.1.1. Strength In general the strength can be increased to as much as four to five times that of the equivalent thickness of annealed glass. The process does not increase the resistance of the surface to scratching or abrasion. The edges have similar vulnerability characteristics to those of all glasses. 2.1.2.Thermal Strength It offers greatly increased resistance to both sudden temperature changes and temperature differentials up to 200ºC compared with annealed glass (up to 40ºC). The stress characteristics of toughened safety glass, of normal soda-lime silica composition, are unchanged for continuing service up to 250ºC. 2.1.3 Fracture characteristics In the event of breakage thermally toughened safety glass fractures into numerous small pieces, the edges of which are generally blunt. Note: Fragmentation in service does not always correspond to that described in Section 11, due to restraint from fixing or reprocessing (e.g. laminating,), or due to the cause of fracture. 2.1.4. Loading:Wind, Snow Although toughened safety glass is much stronger than annealed glass, because the Young’s Modulus of elasticity of both glass types is the same, the deflection characteristics, thickness for thickness are identical. As a consequence, it is necessary to restrict deflection to an acceptable visual degree, rather than design purely according to strength. 2.1.5 Work on toughened safety glass Toughened safety glass cannot be cut or drilled, and should not be surface or edge worked. All edgework, drilling and surface treatment, e.g.: sandblasting, acid embossing and brilliant cutting, should be carried out prior to toughening. Toughened safety glass as manufactured is a finished product. However coatings can be applied (see 3.5). 2.1.6 Light and heat transmission The toughened process does not alter the light transmission and solar radiant heat properties of the glass. These properties of the toughened product are identical to those of the annealed glass used. 2.2 Manufacturing process There are two available methods of producing toughened safety glass. 2.2.1. Horizontally toughened safety glass The glass is processed horizontally, supported on rollers also known as roller hearth toughened. 2.2.2.Vertically toughened safety glass The glass is processed vertically, suspended by tongs. SECTION 4 GGF Standard for the Quality of Thermally Toughened Soda Lime Silicate Safety Glass for Building • Products, Glazing Techniques and Maintenance 4.4 OCTOBER 2004 44-48 Borough High Street London SE1 1XB Tel 0870 042 4255 Fax 0870 042 4266 www.ggf.org.uk Glass and Glazing Federation While every attempt is made to present up to date information, this data sheet, produced by the Glass and Glazing Federation, is issued for guidance but without responsibility for any advice given therein or omission therefrom or for the consequences of acting in reliance thereon and all liability on the part of the Glass and Glazing Federation however arising in connection therewith is expressly disclaimed.
Transcript
Contents
1. Scope 2. Definition, characteristics andmanufacturing process.3. Range of toughened safety glasses4. Tolerances, dimensional characteristics5. Edgework 6. Holes/cut-outs7. Shaped flat panes8. Visual appearance9. Glazing and Fixing10. Fracture characteristics11. Fragmentation test12. Identification13. DisclaimerAnnex A Method of Measuring RollerWaveAnnex B Examples of Particle Count
1. ScopeThis document specifies the characteristicsand associated measurement proceduresand test methods for toughened (tempered) safety glass, incorporatingBritish Standard BS EN 12150.
The dimensional and tolerance characteristics of toughened safety glassare specified and recommendations aremade on the dimensions and tolerancesof holes/cut-outs in toughened safety glass.
A test method is described for assessingthe fragmentation of toughened safetyglass to show how the quality and consistency of manufacturer can be controlled.
Other requirements, not specified in thisstandard, may apply to thermally toughenedsafety glass which is incorporated intoassemblies, e.g. laminated glass or insulatingunits, or undergo an additional treatment,e.g. coating. The additional requirementsare specified in the appropriate productstandard.Thermally toughened safety glass, in thiscase, does not lose its mechanical orthermal characteristics.
2. Definition, characteristics andmanufacturing process
2.1 Toughened (tempered) safety glass A single piece of float or non-wired cast,annealed soda-lime silica glass, subjectedto a thermal process which greatlyincreases its resistance to mechanical andthermal stress and gives it prescribedfragmentation characteristics.
It is produced by subjecting annealed glassto a process of heating and rapid coolingwhich produces high compression in thesurface and compensating tension in thecentre to give it the characteristicsdescribed in 2.1.1. to 2.1.6.
2.1.1. StrengthIn general the strength can be increasedto as much as four to five times that ofthe equivalent thickness of annealed glass.The process does not increase the resistance of the surface to scratching or abrasion. The edges have similar vulnerability characteristics to those of all glasses.
2.1.2.Thermal StrengthIt offers greatly increased resistance toboth sudden temperature changes andtemperature differentials up to 200ºCcompared with annealed glass (up to40ºC). The stress characteristics oftoughened safety glass, of normal soda-limesilica composition, are unchanged for continuing service up to 250ºC.
2.1.3 Fracture characteristicsIn the event of breakage thermally toughened safety glass fractures intonumerous small pieces, the edges ofwhich are generally blunt.
Note: Fragmentation in service does notalways correspond to that described inSection 11, due to restraint from fixing or
reprocessing (e.g. laminating,), or due tothe cause of fracture.
2.1.4. Loading:Wind, SnowAlthough toughened safety glass is muchstronger than annealed glass, because the Young’s Modulus of elasticity of bothglass types is the same, the deflectioncharacteristics, thickness for thickness areidentical. As a consequence, it is necessaryto restrict deflection to an acceptablevisual degree, rather than design purelyaccording to strength.
2.1.5 Work on toughened safety glassToughened safety glass cannot be cut ordrilled, and should not be surface or edgeworked. All edgework, drilling and surfacetreatment, e.g.: sandblasting, acid embossingand brilliant cutting, should be carried outprior to toughening.
Toughened safety glass as manufactured isa finished product. However coatings canbe applied (see 3.5).
2.1.6 Light and heat transmissionThe toughened process does not alterthe light transmission and solar radiantheat properties of the glass. These properties of the toughened product are identical to those of the annealedglass used.
2.2 Manufacturing process There are two available methods of producing toughened safety glass.
2.2.1. Horizontally toughened safety glass
The glass is processed horizontally,supported on rollers also known as rollerhearth toughened.
2.2.2.Vertically toughened safety glassThe glass is processed vertically,suspended by tongs.
SECTION4GGF Standard for the Quality of Thermally Toughened Soda Lime Silicate Safety Glass for Building
•Products, Glazing Techniques and Maintenance
4 . 4 O C TO B E R 2 0 0 4
44-48 Borough High StreetLondon SE1 1XBTel 0870 042 4255Fax 0870 042 4266www.ggf.org.ukGlass and Glazing Federation
While every attempt is made to present up to dateinformation, this data sheet, produced by the Glassand Glazing Federation, is issued for guidance butwithout responsibility for any advice given therein oromission therefrom or for the consequences of actingin reliance thereon and all liability on the part of theGlass and Glazing Federation however arising inconnection therewith is expressly disclaimed.
GGF Standard for the Quality of Thermally Toughened Safety Glass for Building. GGF data Sheet 4.4. October 2004.
2.3 Flat toughened safety glassA product that has not been deliberatelygiven a specific profile in the course ofmanufacture.
2.4 Curved toughened safety glassA product that has been deliberatelygiven a specific profile in the course ofmanufacture.
There is not a standard for this product asthere is insufficient data available.However, the information given onthickness, edgework and fragmentation isalso applicable to curved thermallytoughened safety glass.
3.Range of toughened safety glasses.
3.1 Transparent toughened safety glassClearManufactured from clear float glass
Body tintedManufactured from float glass of uniformcolouration throughout the body of theglass. Colours generally available are blue,bronze, green, grey and pink.
Surface coatedManufactured from float glass, which hasreceived, during manufacture, a surfacetreatment, which modifies the opticalproperties and/or surface emissivity.
3.2 Translucent toughened safety glassClearManufactured from clear, patterned glass.
Body tintedManufactured from patterned glass ofuniform colouration throughout the bodyof the glass.
3.3 Enamelled toughened safety glassThis is also known as opaque toughenedsafety glass.This is manufactured fromannealed glass which has had its surfacecoated with coloured ceramic frit, which isfired in during the toughening process.The enamel becomes an integral part ofthe glass surface. Colours should bespecified in accordance with BS or RAL"specification for external cladding coloursfor building purposes". The manufacturers should be consultedregarding the availability of their standardand non-standard colour ranges.
3.4 Decorative toughened safety glass
This covers surface work on glass, e.g. acidembossing, sandblasting, brilliant cuttingand engraving. This must be carried outprior to toughening. (See BS 952 Part 2"Terminology for work on Glass" fordescriptions of types of surface work).Certain types of screen-printing must bedone prior to toughening where thecolour medium requires firing in duringthe toughening process.
3.5 Others Toughened safety glass as manufactured isa finished product, however, certaincoatings, e.g. for solar control performanceand improvement of surface emissivityand some decorative treatments e.g.certain types of screen printing, silvering,etc. can be applied subsequent totoughening.
4.Tolerances. dimensional characteristics
4.1 GeneralThis section deals with methods ofdetermination of tolerances on thickness,dimensions, squareness and flatness ofpanes; and glass thickness and maximumand minimum sizes normally available
4.2 Nominal thickness and tolerancesThe nominal thickness and tolerances areshown in Table 1.
Table 1: Nominal thickness and thickness tolerances
Dimensions in millimeters
4.2.1 Method of measurementThe thickness of a pane is calculated asthe average of the measurements carriedout to the nearest 0.01 mm taken at thecentres of four edges. For verticallytoughened glass, measurements should bemade centrally between tong marks and aminimum of 50 mm in from the edge.
The minimum and maximum values,rounded to the nearest 0.1 mm, must bewithin tolerances shown in Table 1.Note: For cast/patterned glass themeasurements must be made by meansof an instrument of the callipermicrometer type with plates of adiameter of 55 mm.
4.2.2 Maximum and minimum sizesnormally availableMinimum size of pane is dependant onmethod of toughening. For horizontallytoughened safety glass the minimum sizeof pane should generally not be less than300 mm x 100 mm, but the manufacturershould always be consulted for minimumand maximum sizes normally available.
BFigure 1: Examples of width, B and length, H, relative to the pane shape
B
H
4.3.4. Flatness
4.3.4.1 GeneralBy the very nature of the tougheningprocess, it is not possible to obtain aproduct as flat as annealed glass. Thedifference depends on the nominalthickness, the dimensions and the ratiobetween the dimensions. A distortionknown as bow can occur. There are twokinds of bow (see Figure 4):
Overall or general bow1)
Local bow2)
Note 1): Overall bow can, in general, beaccommodated by the framing system.
Note 2): Local bow needs to be allowedfor in the glazing materials and weatherseals. For special requirements themanufacturers should be consulted.
4.3.4.2 Measurement of overall bowThe pane of glass shall be placed in avertical position and supported on itslonger side by two load bearing blocks atthe quarter points (see Figure 5).The deformation shall be measured alongthe edges of the glass and along the
diagonals, as the maximum distancebetween a straight metal ruler, or astretched wire, and the concave surface ofthe glass (see Figure 4).The value for the bow is then expressed asthe deformation, in millimetres, divided bythe measured length of the edge of theglass, or diagonal, in mm, as appropriate.The measurement shall be carried out atroom temperature.
4.3.4.3 Measurement of local bow Local bow can occur over relatively shortdistances on the edges of the glass. Localbow shall be measured over a limitedlength of 300 mm by using a straight metalruler, or a stretched wire, parallel to theedge at a distance of 25 mm from the edgeof the of the glass (see Figure 4).Local bow is expressed as millimetres/300mm length.For patterned glass, local bow shall bedetermined by using a straight metal rulerresting on the high points of the pattern andmeasuring to a high point of the pattern.
H - t
B - t
B + t
H + t
Figure 2:Tolerance limits for dimensions of rectangular panes
dimensions are quoted for rectangularpanes, the first dimension shall be thewidth, B, and the second dimension thelength, H, as shown in Fig.1. It shall bemade clear which dimension is the width,B, and which is the length, H, whenrelated to its installed position.
4.3.2.Tolerances and squarenessThe nominal dimensions for width andlength being given, the finished pane shallnot be larger than a prescribed rectangleresulting from the nominal dimensionsincreased by the tolerance, t, or smallerthan a prescribed rectangle reduced bythe tolerance, t. The sides of theprescribed rectangles are parallel to oneanother and these rectangles shall have acommon centre (see Figure 2). The limitsor squareness are also the prescribedrectangles. Tolerances are given in Table 2.
4.3.3. Edge deformation produced byvertical tougheningThe tongs used to suspend the glassduring toughening result in surfacedepressions, known as tong marks (seeFigure 3). The centres of the tong marksare situated up to a maximum of 20 mmin from the edge. A deformation of theedge less than 2 mm can be produced inthe region of the tong mark and theremay also be an area of optical distortion.These deformations are included in thetolerances in Table 3
GGF Standard for the Quality of Thermally Toughened Safety Glass for Building. GGF data Sheet 4.4. October 2004.
GGF Standard for the Quality of Thermally Toughened Safety Glass for Building. GGF data Sheet 4.4. October 2004.
Table 3: Maximum values for overall andlocal bow
4.3.4.4 Limitation on overall and local bowThe maximum allowable values for theoverall bow, when measured according to4.3.4.2, and local bow, when measuredaccording to 4.3.4.3, for glass withoutholes and/or notches and/or cutouts aregiven in Table 3.
Figure 4: Representation of local oroverall bow
Figure 5: support conditions for themeasurement of overall bow
5. Edgework
5.1 General Any edge working must be in accordancewith BSEN 12150 Part 1 It is importantthat the edge remaining after mitrebevelling is not less than 2mm or 1/3rd ofthe thickness, whichever is the larger.Normally every glass, which is to bethermally toughened, has to be edgeworked prior to toughening.The simplest type of edge working is thearrissed or linished edge (see Figure 6a).Other common types are shown inFigures 6 b) to 6 d). For specialist edgework, such as water jet cutting, or" as cut"edges the manufacturers should beconsulted.
5.2 Profiled edgesVarious other edge profiles can bemanufactured with different types ofedgework. The manufacturer should beconsulted
6. Holes/Cut-Outs
6.1 WarningThermally Toughened Safety glass shouldnot be cut, sawed, drilled or edgeworkedafter toughening.
6.2 GeneralThis section deals with the types, sizes andposition of holes/cut outs that can beincorporated within toughened safetyglass of thickness of 4 mm and greater.Tolerances are given on hole/cut- out sizeand position. Comments are made on thequality of edgework-associated holes/cut-outs.Where there are more than four holes ina pane or the total area of all holesexceeds one sixth of the plate area, themanufacturer should be consulted.
6.3 Round Holes
6.3.1 GeneralThis standard considers only round holesin glass that is not less than 4mm nominalthickness. The manufacturers should beconsulted about edge working of holes.
6.3.2 Diameter of holesThe diameter of holes (ø), shall not, ingeneral, be less than the nominal thicknessof the glass. For smaller holes, themanufacturers should be consulted.
6.3.3 Limitations on position of holes
In general, the limitations on holepositions relative to the edges of the glasspane, the corners of the glass pane and toeach other depends on:
The nominal glass thickness (d);The dimensions of the pane (B, H);The diameter of hole (ø);The shape of the pane;The number of holes.
2. B, or H, or diagonal length3. Local bow4. 300mm length
3 2 31
4
1. B or H2. B/2 or H/23. B/4 or /44. Maximum 100mm
Figure 6a: Arrissed edge (with blank spots)
Figure 6b: Ground edge (with blank spots)
Figure 6c: Smooth ground edge (no blank spots)
Tough-ening
Process
Type ofglass
Maximum values
Overall bow
mm/mm
Local bow mm/300 mm
Horiz- Float to 0,003 0,5ontal EN 572-
2
Others 0,004 0,5
Vertical All 0,005 1,0
The recommendations given below arethose, which are normally available andare limited to panes with a maximum of 4 holes.
Figure 7: Relationship between hole andedge of pane
1) The distance, a, of the edge of a hole tothe glass edge should be not less than 2d.
Figure 8: Relationship between two holes
2) The distance, b between the edges oftwo holes should be not less than 2d.
Figure 9: Relationship between hole andcorner of pane
3) The distance, c, of the edge of a holeto the corner of the glass should not beless than 6d.
Note: If one of the distances from theedge of the hole to the edge of the glassis less than 35mm, it can be necessary toposition the hole asymmetrically withrespect to the corner. The manufacturersshould be consulted.
6.3.4 Tolerances on hole diametersThe tolerances on hole diameters aregiven in Table 4
Dimensions in millimetres
Table 4:Tolerances on hole diameters
6.3.5.Tolerances on positions of holesThe tolerances on positions of holes arethe same as the tolerances on the width,B, and the length, H, (see Table 3). Thepositions of holes are measured in twodirections at right angles (x- and y-axes)from a datum point to the centre of theholes. The datum point is generallychosen as a real or virtual corner of thepane (see Figure 10 for examples) The position of a hole (X,Y) is x±t, y±t),where x and y are the requireddimensions and t is the tolerance fromTable 3.
NOTE:The manufacturers should beconsulted if tighter tolerances on holepositions are required.
6.4 Notches and cutoutsMany configurations of notches andcutouts can be supplied .Themanufacturers should be consulted aboutedge working of notches and cut-outs.
Note: radius (minimum 10mm) not lessthan glass thickness.
Figure 11: Examples of notches
Figure 11a: Examples of Cut-outs
GGF Standard for the Quality of Thermally Toughened Safety Glass for Building. GGF data Sheet 4.4. October 2004.
Figure 10: Examples of the positioning of holes relative to the datum point
Note: radious not less than 10mmor glass thickness if greater
a
BL
X
X
Z
YD
y
b
Nomainal holediameter
4 ≤ ø ≤ 20
20 < ø ≤ 100
100 < ø
Tolerances
± 1,0
± 2,0
Consult themanufacturer
GGF Standard for the Quality of Thermally Toughened Safety Glass for Building. GGF data Sheet 4.4. October 2004.
B, L and D all less than a/3, or b/3,whichever is the smaller ;X and x not less than the smaller of L/2or B/2;Y and y not less than D/2;Z not less than the larger of B/2, or L/2and D/2Note: the Manufacturer should beconsulted about edge working of notchesand cutouts.
7. Shaped flat panes
7.1 GeneralMany different shapes of pane, other thanrectangular, can be manufactured. Thereare more variations available withhorizontal toughening than with verticalToughening but, because of the number ofvariations, the manufacturers should beconsulted.Shapes can be produced either fromtemplates or from fully dimensioneddrawings. The manufacturer should beconsulted as to which is the moreappropriate, for the shapes required.
7.2 TemplatesAccurate templates must be supplied foreach pane with sufficient information todetermine clearances and allowancesrequired to manufacture. Templates mustbe of sufficient rigidity and of such suitablematerial so as not to distort the desiredfinished size.
8.Visual appearance
8.1 GeneralThis section covers optical quality i.e.distortion of the glass which is visible inreflection, visual quality, i.e. defects on orwithin the glass, which can be seen intransmission, and colour consistency, i.e.changes in hue, which can be seen ineither transmission and/or reflection.
8.2. Optical distortion
8,2.1GeneralThe toughening process will inevitablyresult in a product whose optical quality islower than that of the glass from which itis produced.Surface distortion is produced by areduction in the surface flatness, whichcan be seen particularly in reflection.This can be exacerbated when the glassused is body tinted, surface coated(including post-toughening coating) orenamelled and/or incorporated intodouble-glazing units.
8.2.2 Thermally toughened safety glassproduced by vertical tougheningThe distortion is generally of a randomnature. However, the tong marks canproduce additional optical distortion, whichis generally in an area of radius 100 mmcentred on the tong mark (see Figure 3)
8.2.3 Thermally toughened safety glassproduced by horizontal tougheningWhile the hot glass is in contact with therollers during the toughening process, asurface distortion is produced by areduction in surface flatness, known asroller wave. Roller wave is generallynoticed in reflection.Glass, which is 8 mm or thicker, mayshown signs of small imprints in thesurface (roller pick-up). As a general rule,the degree of distortion will be less withhorizontally toughened glass than withvertically toughened glass.
On toughened sheet glass, or toughenedpatterned glass, it is not possible tomeasure roller wave, due to the inherentdistortion of the basic glass.The Methodof Measuring Roller Wave will be found inAnnex A
8.3 Anisotropy (iridescence)The toughening process produces areasof different stress in the cross section ofthe glass. These areas of stress produce a bi-refringent effect in the glass, which isvisible in polarised light.When thermally toughened safety glass isviewed in polarized light, the areas ofstress show up as coloured zones,sometimes, known as "leopard spots".Polarised light occurs in normal daylight.The amount of polarized light depends onthe weather and the angle of the sun.The bi-refringent effect is more noticeable
either at a glancing angle or throughpolarized spectacles.
8.4 Visual quality
8.4.1. Body faults, e.g. seeds, bubblesThe number, size and distribution ofseeds, bubbles, etc. are defined for theglasses under consideration in theappropriate parts of BS.EN 572.No change will occur as a result of thetoughening process.Assessment of body faults should beundertaken using the method/criteriagiven, for the basic glasses in theappropriate parts of BS.EN 572.
8.4.2 Surface faults e.g. scars, scratchesToughened safety glass shall be deemedacceptable if the following phenomena areneither obtrusive nor bunched: hairlinesor blobs; fine scratches not more than25mm long; minute imbedded particles.Obtrusiveness of blemishes shall bejudged by looking through the glass, not atit, when standing at right angles to it onthe room side at a distance of not lessthan 3 metres in natural daylight and notin direct sunlight. The area to be viewedis the normal vision area with theexception of a 50mm wide band aroundthe perimeter of the glass.Pattern ghosting can occur on glasses witha textured finish.
8.5 Colour consistency
8.5.1 Body tinted glassToughening will not produce anysignificant variation in colour. However, ifa piece of toughened body tinted glass isplaced next to a piece of annealed bodytinted glass there may be a discernibledifference.A far larger problem will occur if differentthicknesses of body-tinted glass are placedside by side as the colour is throughoutthe glass thickness. This can occur inthose areas where toughened safety glassis required and an attempt is made to usethe increased strength of the toughenedsafety glass by reducing the thickness ofthe glass. Body tinted glass from differentmanufacturers, or from different batchesfrom the same source manufacturer canshow different shades.
8.5.2 Surface coated glassAs a general rule those surface coatedglasses which can be toughened mayexhibit different visual characteristics or aslight colour variation as a result oftoughening. Care should be taken toensure that the coated surface is notcontaminated before toughening by, forexample grease, sweat, etc, as thesematerials may be burnt in during thetoughing process. This could producepatches on the coating where there is asignificant colour variation.Glass, which is coated after toughening,will be within the same manufacturerscolour tolerance as coated annealed glass.
8.5.3 Enamelled toughened safety glassWith this product the ‘colour’ results fromthe firing in of a ceramic frit. No colourvariation will result from the tougheningprocess itself. However, the manufacturershould be consulted as to the likelytolerances on the colour and the possiblevariation between batches of ceramic frit.There is also a possibility that a colourvariation may be noticeable if panes ofdifferent glass thickness or from differentglass suppliers.
9. Glazing and fixing
9.1 GeneralGlazing should be in accordance withBS6262, BS 8000 Part 7, Glass and GlazingFederation Glazing Manual or otherappropriate standard.Thermally toughened safety glassconforming to BS 6206 and orBSEN12600 meets the safety glazingrequirements of Building Regulations andBS 6262: Part 4Appropriate edge clearances must alwaysbe allowed taking into account glass type,e.g. clear or solar control and either singleor double-glazed. Suitable insulation orcushioning should be used to preventcontact with hard materials.
9.2 Use of mechanical fixingsGlass to metal contact must be eliminatedat all times by the use of gaskets, bushes,linings and setting blocks.These should be of appropriate material,which has been approved by thetoughened safety glass manufacturer. Allfittings to which the glass is to be clampedmust be free from high spots and/orburrs. Care should be taken to ensurethat when the glass is being clamped theclamping pressure is evenly distributed.
10. Fracture characteristicsThe actual size/shape of fragments willdepend on the type of loading, e.g. hardbody impact, soft body impact oruniformly distributed, causing thebreakage.
In the majority of applications toughenedglass is regarded as a safety materialtherefore it should comply with therequirements of BS EN 12,600 which is asemi-hard body.
When toughened glass is tested inaccordance with BS EN 12,600 , it shalleither not break or if it breaks the tenlargest crack free particles remaining 3minutes after impact shall weigh no morethan the equivalent weight of 6500mm2 ofthe original material.
11.Fragmentation test
11.1 GeneralThe fragmentation test determineswhether the glass breaks in the mannerprescribed for a thermally toughenedsafety glass
11.2 Dimensions and number of testspecimensThe dimensions of the test specimensshall be 360 mm x 1100 mm, withoutholes, notches or cutouts.Five specimens shall be tested.
11.3 Test procedureEach test specimen shall be impacted, usinga pointed steel tool, at a position 13 mm infrom the longest edge of the test specimenat the mid-point of that edge, untilbreakage occurs (see Figure 12).Note:The fragmentation characteristics ofglass are unaffected by temperaturesbetween –500ºC and +1000ºC.Examples of steel tools are a hammer ofabout 75g mass, a spring loaded centrepunch, or other similar appliance with ahardened point. The radius of curvature ofthe point should be approximately 0.2 mm.The test specimen shall be laid flat on atable without any mechanical constraint.In order to prevent scattering of thefragments, the specimen shall be simplyheld at the edges, e.g. by a small frame,adhesive tape etc., so that the fragmentsremain interlocked after breakage yetextension of the specimen is not hindered
Figure 12: Position of impact point
1 Impact PointNote: for thermally toughened safety glassmanufactured by vertical toughening, theimpact point shall not be on the tongmark edge.
11.4 Assessment of fragmentationThe particle count and measuring of thedimensions of the largest particle shall bemade between 4 to 5 minutes afterfracture. An area of radius 100 mm,centred on the impact point, and aborder of 25 mm, round the edge of thetest specimen (see figure 13), shall beexcluded from the assessment.The particle count shall be made in theregion of coarsest fracture (the aim beingto obtain minimum value).The particlecount shall be made by placing a mask of(50±- 1) mm x (50±- 1) mm on the testpiece (see Annex B). The number ofcrack-free particles within the mask shallbe counted. (See Table 6). A particle iscrack-free if it does not contain anycracks, which run from one edge toanother (see figure 14).In the particle count, all particles whollycontained within the area of the maskshall be counted as one particle each andall the particles, which are partially withinthe mask, shall be counted as 1/2 particleeach (see Annex B).
Area to be excluded
Figure 13: Area to be excluded from theparticle count determination and largestparticle measurement.
GGF Standard for the Quality of Thermally Toughened Safety Glass for Building. GGF data Sheet 4.4. October 2004.
GGF Standard for the Quality of Thermally Toughened Safety Glass for Building. GGF data Sheet 4.4. October 2004.
11.5 Minimum values from the particlecountIn order to classify a glass as a thermallytoughened safety glass, the particle countof each test specimen shall not be lessthan the values given in Table 6.
11.6 Selection of the longest particleThe longest particle shall be chosen fromthe body of the test specimen. It shall notbe in the excluded area (see 11.4)
11.7 Maximum length of longest particleIn order to classify the glass as thermallytoughened safety glass, the length of thelongest particle shall not exceed 100 mm.
12 Identification
12.1 BS EN 12150 - ThermallyToughened Soda Lime Silicate SafetyGlass - Part 2 - Evaluation of ConformityToughened Soda Lime Silicate safety glassshall be marked and/or labelled inaccordance with the above standard.
12.2 MarkingThermally toughened safety glassconforming to BS 6206 and/or BS EN12150 shall be permanentlymarked before installation in a position toremain visible after installation. Themarking shall give the followinginformation:• name or trademark• number of the standard• classification level• the word "toughened" or the letter "T"
13.DisclaimerIt is the responsibility of the user toensure that the products and materialsare appropriate for the particularapplication and that such applicationcomplies with all relevant local andnational legislation, standards, codes ofpractice and other requirements.
The Glass and Glazing Federation herebydisclaim all liability whatsoever arising fromany error or omission in this publicationand for all consequences of relying on it.
Figure 14: Examples of crack-free particles and the assessment regardingthe number
Glasstype
Nominalthickness(d) in mm
Minimumparticlecount
Float anddrawsheet
Patterned
3
4 to 12
15 to 19
4 to 10
15
40
30
30
Table 6: Minimum particle count values
Annex A: Method of Measuring Limits for Roller Wave
A1.ApparatusThe apparatus consists of an aluminium channel, 350 mm long,with a centrally mounted dial gauge.A2. MethodThe apparatus is placed on the glass at right angles to the rollerwave, so that it can bridge from peak to peak of the wave(figure A1).Figure A1: Place the apparatus across the roller wave
The apparatus is then moved along its axis until the dial gaugereads the highest
Figure A2: Set the zero of the gauge on a peak of the rollerwave.
Value (Figure A 2).At this point, the dial gauge is resting on a peak of the roller wave.The scale of the gauge is positioned (rotated) so that the needlepoints to 0 (zero) on the scale.The apparatus is then moved again along its axis until the gaugereads the lowest value (Figure A3). At this point, the dial gauge isresting in the lowest point of the trough.
The reading is then taken, and the depth of the roller wave isthe difference between the zero point and the readingFigure A3: move the apparatus to take the lowest reading.
NOTE:The dial gauge scale is usually arranged so that a positivevalue is obtained by raising the post. Care should be taken to notmisread the depth of the roller wave.
The roller wave depth is recorded to the nearest 0.05 mm.The above procedure can be performed several times on thesame pane, giving a variety of answers, since the roller wavesare unlikely to be consistent. The worst roller wave of thoserecorded is the value of the pane.
A3. Limitations
A3.1 Pane SizeThe apparatus should only be used on panes with a dimensionlarger than 600 mm at right angles to the roller wave.There is an exclusion area, 200 mm from the edge of the pane.
A3.2 BowA true measurement of roller wave can only be obtained onan otherwise flat pane of glass. If the pane has an overall bow,this will contribute to the value measured by the roller waveand must be taken into account. In the factory, this can bereduced by laying the pane of glass flat on a table, which willreduce the overall bow in the pane due to the self weight ofthe pane, particularly with larger panes.The apparatus is accurate only when used in a factory tomeasure roller wave in panes laid flat on a table.
A3.3. Measurement on siteThere will always be requests for site measurement of rollerwave.Measurements taken on site will be incorrect if the pane hasany bow in it. This will be particularly the case if the pane isone side of an insulating glass unit, since insulating glass unitsare nearly always bowed in or out, from variations in airpressure. However, even single panes may be bowed in situ,either by innate overall bow (allowed up to 2 mm/m) or dueto distortion induced by the fixing or framing system.Site measurement of roller wave should take into account theoverall bow of the pane, especially if the pane is part of aninsulating glass unit.
GGF Standard for the Quality of Thermally Toughened Safety Glass for Building. GGF data Sheet 4.4. October 2004.
GGF Standard for the Quality of Thermally Toughened Safety Glass for Building. GGF data Sheet 4.4. October 2004.
Annex B Examples of particle countFigure B1 (see below) Select the area of coarsest fracture, placethe template on the test specimen and draw round the template.
Figure B2 (see below) Mark and count the perimeter fragmentsas half particle each.Number of perimeter particles = 32/2 = 16
Figure B3 (see below) Mark and count the central fragmentsand add these to the perimeter count to obtain the particlecount for the specimen.
Number of central particles = 53Total number of particles = 16 + 53 = 69
