GlassGlass

Flat Glass Products andFlat Glass Products and

Float Glass Manufacture Float Glass Manufacture

Sept 2007Sept 2007

Rick MitsonRick Mitson

Advanced Programme Manager –Pilkington Advanced Programme Manager –Pilkington

Melting furnace

Float bath

Cooling lehr

Continuous ribbon of glass Cross

cutters

Large plate lift-off devices

Small plate lift-off devices

Raw material feed

Float Glass Process

What is a ‘glass’ ?• ‘A supercooled liquid’ - network of silica

molecules is modified by the introduction of larger metal atoms

• (eg. Sodium, calcium, boron, lead...).• Most common form - • Soda Lime Silica • addition of other metals change the

properties

Soda Lime Silica• Raw materials :• Silica sand - SiO2 - low impurities, small particle size• Soda Ash - Na2 CO3 - natural and synthetic grades• Dolomite - Ca Mg CO3 - mined & crushed • Limestone - Ca CO3 - mined & crushed• Minor ingredients - Salt cake Na2 SO4, Aluminium, Carbon, Iron,

Cobalt, …..

SiO2 + Na2CO3 +Ca CO3 ----> 1500 deg C

(Na20)(SiO2)(CaO) + 3 CO 2

Flat Glass Products

• 1. Basic - Sheet glass , Float glass, Rolled glass• Visual appearance - colour, reflection, pattern.• 2.Safety glass - Laminated - plastic interlayer

- Toughened - pre-stressed surfaces

• 3. Fire-resistant glass - eg. wired, special laminates. • 4. Energy control - eg. low emissivity glass coatings,

tinted glass.

Basic glass - Clear Float

• Thickness• 4mm 6mm 10mm• Light Transmittance 90 % 88 % 87% • Solar Energy Transmittance 85 % 82 % 78%• Light Reflectance 8 % 8 % 8 %• Heat - ‘U’ value W/m2 5.8 5.7 5.6

Basic Glass - Tinted Float

• 4mm thickness Light Arctic• Clear Green Blue• Light Transmittance 90 % 80% 64%• Solar Energy Transmittance 85 % 66% 60%• Light Reflectance 8 % 7% 6%• Heat - ‘U’ value W/m2 5.8 5.8 5.8

• Dark Green, Grey and Bronze similar light transmittance to Arctic Blue.

• Wired glass• On exposure to fire: glass breaks, but held in place by integral wire

mesh

• Example: Pilkington Pyroshield Safety•• EN references: EN 572-1 (Definitions etc.), -3 (Polished wired), -6

(Wired patterned), -8 (Supplied and final cut sizes), -9 (Evaluation of conformity)

Fire resistant glassFire resistant glass

• Special intumescent laminated glass• On exposure to fire: layers crack but are held together by the

inorganic intumescent interlayer, which is chemically compatible with glass and bonds glass layers together

• Examples: Pilkington Pyrostop, Glaverbel Pyrobel•• EN references: EN ISO 12543 series (Laminated glass), prEN 14449

(Evaluation of conformity)

Fire resistant glassFire resistant glass

Low Emissivity Coated GlassPilkington Optitherm™ SN is an off-line coated glass for use in insulating glass units and can be combined with other types of Pilkington glass.

Pilkington Optitherm™ SN consists of Pilkington Optifloat™ which is provided with a coating on one side. Moreover it is available as laminated Pilkington Optilam Therm™ and toughened.

Emissivity of double glazing with low emissivity glass is now below 1.8 W/ sq.m

Self Cleaning GlassPilkington Activ™ - same as conventional glass but with a specially developed coating on the outside. Once exposed to daylight, the coating chemically reacts in two ways.

Breaking down organic dirtUsing a "photocatalytic" process, the coating reacts with ultra-violet rays present in natural daylight to break down and disintegrate organic dirt.

Washing dirt awayThe second part of the process happens when rainwater hits the glass. The coating is "hydrophilic" which means that instead of forming droplets, the water spreads evenly over the surface and as it runs off takes the dirt with it. Compared with conventional glass, the water also dries off very quickly without leaving unsightly "drying spots".

How is it made ?• Basic , Clear & Tinted - Float glass process.

• Coated - On-line in float bath or off-line.

• Laminated - High pressure & temp. in autoclave

• Toughened - Heated with blasts of air in an oven

• Wired & Patterned - Glass formed between rollers

Basic Float Costs - 2003 UK delivered• Raw materials 25 %• Processing materials 4 %• Process labour 13 %• Energy 13 %• Packaging etc. 6 %• Overheads & admin 9 %• Depreciation 13 %• Marketing, R&D etc. 7 %• Transport 10 %

• Costs £ 300 to 500 per tonne - depending on product

Melting furnace

Float bath

Cooling lehr

Continuous ribbon of glass Cross

cutters

Large plate lift-off devices

Small plate lift-off devices

Raw material feed

Float Glass Process

Spain - Sagunto started up Feb. 2000

France Float Glass Plant France Float Glass Plant started-up November 2001started-up November 2001

Batch Plant, Feed conveyor,

Furnace building and chimney

Furnace cross-section

Raw Material Feed to Furnace

Mixed raw material is continuously pushed under the front wall of the furnace

Gas firing into furnace

Furnace cross-section

Melting furnace

Float bath

Cooling lehr

Continuous ribbon of glass Cross

cutters

Large plate lift-off devices

Small plate lift-off devices

Raw material feed

Float Glass Process

The Float Bath

• A bath is typically 60m long and 7m wide • The tin is about 60mm deep• Glass enters bath at ~ 1100°C• Glass leaves bath as a continuous ribbon at ~600°C• Controlled atmosphere above the glass / tin

Tin

Glass Ribbon

Flow Over Spout

• Glass flow into bath controlled by tweel height

• Most of glass flow off spout goes downstream, a few percent flows upstream into ‘wetback’

• Glass in the wetback then flows out to the edges of the ribbon

Glass Equilibrium Thickness

At equilibrium all the forces balance

Forces : Surface TensionHydrostatic (Gravitational)

F = nett surface tension

g = glass density

t = tin density

h = 6.7mm

Glass thickness control

Thin Glass Manufacture

Top RollsTop Rolls:

•Control the speed of the ribbon

•Provide a transverse stretch to the ribbon

•Are used to make glass in thicknesses from 1mm to 8mm

Thick Glass ManufactureTop Rolls

Fenders:

•Restrict the spread of the ribbon

•Are used to make glass in thicknesses from 8mm to 25mm

Fenders

On-line coating in float bath

Multi-layer coatings - including Silicon, Tin, Titanium,

Optical systems to control colour in reflection

Melting furnace

Float bath

Cooling lehr

Continuous ribbon of glass Cross

cutters

Large plate lift-off devices

Small plate lift-off devices

Raw material feed

Float Glass Process

Cooling Lehr - Annealing Furnace

• Controlled cooling to avoid internal stress.

• Radiant and convective cooling by air

• Edges stress control by additional heating

• Distortion of polarised light shows stress levels in glass

Glass cutting for market• Standard glass ribbon width in Europe - 3210 mm • Largest standard plate size 6000 x 3210 mm - Jumbo plate

• Other standard plates 2800 mm to 3200 mm - Lehr End Sizes

• Some float lines cut small sizes less than 3210 mm wide and less than 2800 mm long.

Glass stacking onto pallets

Large plate stacker Pallet loaded with special grab

Single ‘Standard endcap’

Endcaps should be to an agreed design and have been tested and approved by Group MI

Single ‘standard endcaps’ are unstable unless the height is less than 1.5 times the depth

1

10

Ground should be clean and level

This is unstable

Storage

Safety Zones

Manning

Keep clear of the danger zone!

Keep clear of thedanger zone

Rememberas you lift thezone gets bigger

Manning

Glass Transport• Western Europe - Float lines product mainly

Jumbos and LES sizes. • Economic transport distance 200km to 600km. • Processing plants located closer to final customers.

• UK Float lines: 3 Pilkington, St.Helens, Lancashire

• 1 St.Gobain, Eggborough, Yorks.• 1 Guardian, Hull, Yorks.

0

10

20

30

40

50

1999 2000 2001 2002 2003 2004 2005Estimate

2006Estimate

Calendar Year

Mn

Ton

nes

70%

75%

80%

85%

90%

95%

100%

105%

Available Capacity Demand Capacity Utilisation

Global* Flat Glass Capacity and UtilisationGlobal* Flat Glass Capacity and Utilisation

* Worldwide including China

Global utilisation continues to tighten

Melting furnace

Float bath

Cooling lehr

Continuous ribbon of glass Cross

cutters

Large plate lift-off devices

Small plate lift-off devices

Raw material feed

Float Glass Process

Glass ReferencesGlass References

www.pilkington.comwww.pilkington.com

Pilkington Technical Advisory Service

Groupement Europeen des Producteurs de Verre Plat - Groupement Europeen des Producteurs de Verre Plat - info@gepvp.beinfo@gepvp.be