The batch plant - the process begins
The entire float glass manufacturing process, from the batch plant to final stacked glass, is a complex series of interconnected processes that must all work together over the floatline's 420m length to produce the final high quality flat glass.
The mix of raw materials used in the production of flat glass is known as the batch - which is composed of three main components: silica sand, soda ash and dolomite/limestone. All materials are rigorously checked and analysed for quality to ensure the purity of the batch.
- Raw materials are delivered to the batch plant via trucks.
- Batch is weighed and mixed to very tight tolerances using a specific formula for the types of glass being produced.
- The mixed batch is then transported to the furnace via a series of conveyors.
- The batch plant ensures the highest quality in raw materials preparation and precise control over the production formula.
Melting and refining
The batch of raw material is automatically added at the filling end of the gas fired regenerative furnace flowing as a blanket to form molten glass at 1550°C in the melter.
- The gas firing occurs from alternate sides of the furnace in 20 minutes cycles, this assists fuel efficiency by ensuring combustion occurs in the presence of pre-heated air.
- Melting, refining and homogenising takes place simultaneously in the 2000 tonne furnace. The continuous melting process lasts as long as 50 hours delivering glass to the float bath at 1100°C, smoothly and continuously, free from inclusions and bubbles.
- The melting process is key to glass quality. Compositions can be modified to change the properties of the finished product.
- The furnace combustion is carefully controlled to ensure optimum conditions, maximum energy efficiency and compliance with strict environmental requirements.
Making optically flat glass
Molten glass enters the float bath at 1100°C flowing gently over a narrow refractory spout on to the mirror-like surface of molten tin.
- The glass spreads out on the perfect flatness of the tin so the upper and lower surfaces of the glass remain absolutely flat and parallel.
- The glass can be made thinner by speeding up to the top rollers which control the width of the glass, to create a gentle stretching action.
- The maximum width of the ribbon is 3680mm.
- A controlled atmosphere of nitrogen and hydrogen in the float bath prevents oxidation of the tin.
Making high performance coated glass
World leading technology is used to apply coatings that make profound changes in the optical properties of the glass, including energy efficient Low E glass to improve comfort and reduce year-round energy requirements of your home. A 'Chemical Vapour' coater applies thin metal oxide layers to molten glass in a pyrolytic reaction to produce high performance hard coated glass.
- A gaseous chemical mixture is brought in contact with the hot glass substrate while it is still in a semi-molten state (approximate temperature 730°C).
- Within seconds of the gas being turned on, a pyrolytic reaction occurs on the surface of the substrate leading to the deposition of a coating which bonds glass.
- Often referred to as a 'hard coat', the chemical layers bond at the molecular level and become an integral and highly durable part of the surface of glass.
- The pyrolytic coated surface can be extremely thin and transparent. The coated surface has a thickness similar to laying a 50 cent coin on top of Melbourne's 63 storey Rialto tower.
- The chemical composition of the coating can be changed to achieve different properties and characteristics including a range of energy efficient Low E glass.
Controlled cooling glass
The annealing lehr removes stresses in the glass by carefully cooling down the ribbon from 600°C to room temperature.
- Considerable stresses are developed in the glass ribbon as it cools.
- Too much stress and the glass will break inside the lehr or will not cut into the sheets.
- Careful control of the ribbon cooling inside the lehr allows the glass to be cut at the cold end. This ensures that the customer is presented with a final sheet of glass that conforms to very high standards of edge quality, flatness and low residual stress.
- Scanning technology is used to automatically detect stress levels in the glass and control the temperatures within the lehr over its 134 length.
Quality Control - Inspection
Coating inspection - the 'catwalk'
A rigorous inspection and testing regime is used to ensure the precisely controlled coating meets quality performance and standards.
- Sophisiticated online quality measurement systems give real time feedback on coating properties.
- Continuous visual inspection of the glass is undertaken by operators.
- A specifically designed lighting system highlights even the slightest coating defect on the glass.
- The catwalk has the same control capability as the main control room enabling the operator to see all of the online quality measures as well as the ability to make process changes. When a defect is observed, the operator has the ability to reject the glass and will make any necessary adjustments to the process conditions.
Cutting and stacking of quality controlled glass ready for customer delivery.
Cold end manual inspection quality control booth
To ensure the glass ribbon continues to flow, the ribbon is visually inspected for quality control, with faults cut out, or the mainline breaker engaged. Removed glass 'cullet' is retired by conveyors to the furnace to be recycled.
Washing machine - cleaning, cooling and modifying glass
Glass enters the washing machine at 70°C for three key purposes
- Clean the glass to remove layer of sulphate applied to protect glass from roller marks.
- Cool the glass to less than 50°C making it suitable for final packing of cut sheets.
- Modify the strain in the glass to make it easier to cut.
Online scanning and strain viewer
Checks to ensure the lehr and washing machine have successfully cooled the glass for easy cutting and inspection of the ribbon for any faults.
Longitudinal and cross cutters
The ribbon is now ready to cut. It passes under the longitudinal and cross cutters splitting the ribbon into various sheet widths.
Rough edge removal
The 'selvedge removal booth' is where pneumatic wheels are guided onto the ribbon applying downward pressure to snap off the rough edges created by rollers in the tin bath.
Glass enters the centre splitter which separates the ribbon into various sizes. The vision system is an additional quality control step checking for faults in the cut sheets.
The 'chip blower' removes any glass cullet fragments that have remained during the cutting process. Lucite coating is added to ensure stacked glass does not get marked.
Post processing and floatliner customer deliveries
Finished sheets are sent in various directions to be loaded onto storage devices ready for further processing or by 'Jumbo Stackers' onto specialised 'Floatliner' glass transport vehicles ready for deliveries direct to customers.
Quality Control - Testing
Quality testing booth in the cold end
Float and coated glass samples are cut and submitted for rigorous quality control testing.
Quality testing of the coated glass is conducted by taking samples from the line every 30 minutes for examination using a range of instrumental methods.
Each of the samples taken from across the ribbon are tested for:
- Reflective colour
- Electrical conductivity is used to measure the performance of the coating
- In addition all float glass is tested to ensure excellent optical, physical and performance characteristics
All results are fed back online to the glassmaking and coating operators so any adjustments to the process can be made to ensure the strictest quality control targets are met.
Oceania Glass floatliner - a new perspective in glass transport
Floatliners are a rapid glass transport system which significantly improves the safety and efficiency of glass delivery for our customers. They form a critical part of Oceania Glass' capabilities for 'whole of supply chain solutions', from manufacturing to customer delivery. Our floatliners have been awarded the prestigious 2007 Australian Freight Industry Awards for Innovation and Technology.
Benefits to customers
Greater efficiency - rapid loading/unloading
- Significantly reduces unloading times from typically 2.5 hours to 30 minutes
- Glass presented on frames ready for off-loading
- Rigorous OH&S procedures developed in conjunction with 'WorkSafe'
- Less handling and direct interaction with glass required by customer and Oceania Glass warehouse staff
- Ability to load and unload at floor level for reduced risk
- Easier inspection of unloaded glass on frame to ensure product integrity.
Reduced accidental damage of glass
- Load restraint is integrated into the design of the floatliner
- Less handling reduces chance of accidental damage
- Greater weather protection from dust and moisture
No packaging waste materials
Integrates into customer's manufacturing process
- Frames can be integrated into the customer's manufacturing process to create a circuit system to achieve greater efficiency.
How does it work?
Load pick up
- Floatliner is hydraulically lowered
- Driver opens rear doors and removes spreader bars
- Driver reverses floatliner into position over pre-loaded frame
- Driver hydraulically raises the floatliner to road travel height
- Activates the padded arms to apply controlled pressure onto the glass to provide substantial load restraint
- Inspects load integrity and condition through visual and onboard camera inspection
Unloading at customer premises
- Floatliner arrives at customer premises, reverses into delivery bay and lowered
- Restraint system is disengaged and the door is opened
- Floatliner is driven away, with frame left in position ready for customer unloading