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Flat glass products & float manufacture2007
- 1. Glass Flat Glass Products and Float Glass Manufacture Sept 2007 Rick Mitson Advanced Programme Manager –Pilkington
- 2. Float Glass Process Continuous ribbon of Cooling glass Cross lehr Float cutters bath Melting furnace Large plate lift- Small plate lift- off devices off devices Raw material feed
- 3. 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
- 4. 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
- 5. 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.
- 6. 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
- 7. 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.
- 8. Fire resistant glass •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)
- 9. Fire 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)
- 10. Low Emissivity CoatedGlass Pilkington 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
- 11. Self Cleaning Glass PilkingtonActiv™ - 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 dirt Using a "photocatalytic" process, the coating reacts with ultra-violet rays present in natural daylight to break down and disintegrate organic dirt. Washing dirt away The 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".
- 12. How is itmade ? • 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
- 13. 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
- 14. Float Glass Process Continuous ribbon of Cooling glass Cross lehr Float cutters bath Melting furnace Large plate lift- Small plate lift- off devices off devices Raw material feed
- 15. Spain - Saguntostarted up Feb. 2000
- 16. France Float GlassPlant started-up November 2001 Batch Plant, Feed conveyor, Furnace building and chimney
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- 18. Raw Material Feedto Furnace Mixed raw material is continuously pushed under the front wall of the furnace
- 19. Gas firing intofurnace
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- 21. Float Glass Process Continuous ribbon of Cooling glass Cross lehr Float cutters bath Melting furnace Large plate lift- Small plate lift- off devices off devices Raw material feed
- 22. The Float Bath Glass Ribbon Tin • 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
- 23. 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
- 24. Glass Equilibrium Thickness Forces: Surface Tension Hydrostatic (Gravitational) At equilibrium all the forces balance F = nett surface tension ρg = glass density ρt = tin density h = 6.7mm
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- 26. Thin Glass Manufacture Top Rolls Top 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
- 27. Thick Glass Manufacture Top Rolls Fenders Fenders: •Restrict the spread of the ribbon •Are used to make glass in thicknesses from 8mm to 25mm
- 28. On-line coating infloat bath Multi-layer coatings - including Silicon, Tin, Titanium, Optical systems to control colour in reflection
- 29. Float Glass Process Continuous ribbon of Cooling glass Cross lehr Float cutters bath Melting furnace Large plate lift- Small plate lift- off devices off devices Raw material feed
- 30. 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
- 31. Glass cutting formarket • 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.
- 32. Glass stacking ontopallets Large plate stacker Pallet loaded with special grab
- 33. Storage Single ‘Standard endcap’ Endcaps should be to an agreed design and have been tested and 10 approved by Group This is unstable MI Single ‘standard endcaps’ are unstable unless the height 1 is less than 1.5 times the depth Ground should be clean and level
- 34. Manning Safety Zones Keep clear of the danger zone!
- 35. Manning Keep clear of the danger zone Remember as you lift the zone gets bigger
- 36. Glass Transport • WesternEurope - 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.
- 37. Global* Flat GlassCapacity and Utilisation Available Capacity Demand Capacity Utilisation 50 105% 100% 40 95% Mn Tonnes 30 90% 85% 20 80% 10 75% 0 70% 1999 2000 2001 2002 2003 2004 2005 2006 Estimate Estimate Calendar Year Global utilisation continues to tighten * Worldwide including China
- 38. Float Glass Process Continuous ribbon of Cooling glass Cross lehr Float cutters bath Melting furnace Large plate lift- Small plate lift- off devices off devices Raw material feed
- 39. Glass References www.pilkington.com Pilkington Technical Advisory Service Groupement Europeen des Producteurs de Verre Plat - info@gepvp.be
Editor's Notes
- #38 Notes