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66-398: Glass production involves two main methods – the float glass process that produces sheet glass, and glassblowing that produces bottles and other containers. It has been done in a variety of ways during the history of glass . Broadly, modern glass container factories are three-part operations: the "batch house", the "hot end", and the "cold end". The batch house handles the raw materials;

132-403: A treatment to improve the chemical resistance of the inside, called "internal treatment" or dealkalization . This is usually accomplished through the injection of a sulfur- or fluorine-containing gas mixture into bottles at high temperatures. The gas is typically delivered to the container either in the air used in the forming process (that is, during the final blow of the container), or through

198-462: A 600 kPa (87 psi) compressed air plant provided power to pneumatic drills , increasing productivity greatly over previous manual drilling methods. Compressed-air drills were applied at mines in the United States in the 1870s. George Westinghouse invented air brakes for trains starting in 1869; these brakes considerably improved the safety of rail operations. In the 19th century, Paris had

264-439: A bottle and generally powered by compressed air (high pressure – 3.2 bar and low pressure – 2.8 bar), the mechanisms are electronically timed to coordinate all movements of the mechanisms. The most widely used forming machine arrangement is the individual section machine (or IS machine). This machine has a bank of 5–20 identical sections, each of which contains one complete set of mechanisms to make containers. The sections are in

330-421: A continuous ribbon of flat glass by forming the ribbon between rollers. This was an expensive process, as the surfaces of the glass needed polishing. If the glass could be set on a perfectly smooth, flat body, like the surface of an open pan of calm liquid, this would reduce costs considerably. Attempts were made to form flat glass on a bath of molten tin—one of the few liquids denser than glass that would be calm at

396-403: A day 7 days a week. This means that there is little opportunity to either increase or decrease production rates by more than a few percent. New furnaces and forming machines cost tens of millions of dollars and require at least 18 months of planning. Given this fact, and the fact that there are usually more products than machine lines, products are sold from stock. The marketing/production challenge

462-438: A geographical business; the product is heavy and large in volume, and the major raw materials (sand, soda ash and limestone) are generally readily available. Therefore production facilities need to be located close to their markets. A typical glass furnace holds hundreds of tonnes of molten glass, and so it is simply not practical to shut it down every night, or in fact in any period short of a month. Factories therefore run 24 hours

528-430: A lengthy series of inline grinders and polishers, reducing glass losses and cost. Glass of lower quality, drawn glass, was made by drawing upwards from a pool of molten glass a thin sheet, held at the edges by rollers. As it cooled the rising sheet stiffened and could then be cut. The two surfaces were of lower quality i.e. not as smooth or uniform as those of float glass. This process continued in use for many years after

594-401: A nozzle directing a stream of the gas into the mouth of the bottle after forming. The treatment renders the container more resistant to alkali extraction, which can cause increases in product pH, and in some cases container degradation. As glass cools, it shrinks and solidifies. Uneven cooling may make glass more susceptible to fracture due to internal stresses: the surface cools first, then as

660-455: A per unit energy delivered basis. Compressed air is used for many purposes, including: Compressor rooms must be designed with ventilation systems to remove waste heat produced by the compressors. When air at atmospheric pressure is compressed, it contains much more water vapor than the high-pressure air can hold. Relative humidity is governed by the properties of water and is not affected by air pressure. After compressed air cools, then

726-401: A polyethylene coating for abrasion resistance and increased lubricity, inspect the containers for defects, label the containers, and package the containers for shipment. Glass containers typically receive two surface coatings, one at the hot end , just before annealing and one at the cold end just after annealing. At the hot end a very thin layer of tin(IV) oxide is applied either using

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792-487: A powder or as a fine-grained material. Systems for controlling dusty materials tend to be difficult to maintain, and given the large amounts of material moved each day, only a small amount has to escape for there to be a dust problem. Cullet (broken or waste glass) is also moved about in a glass factory and tends to produce fine glass particles when shovelled or broken. Float glass Modern windows are usually made from float glass, though Corning Incorporated uses

858-409: A row, and the gobs feed into each section via a moving chute, called the gob distributor . Sections make either one, two, three or four containers simultaneously (referred to as "single", "double", "triple" and "quad" gob). In the case of multiple gobs, the "shears" cut the gobs simultaneously, and they fall into the blank moulds in parallel. Forming machines are largely powered by compressed air and

924-401: A safe organic compound or inorganic stannic chloride . Tin based systems are not the only ones used, although the most popular. Titanium tetrachloride or organo titanates can also be used. In all cases the coating renders the surface of the glass more adhesive to the cold end coating. At the cold end a layer of typically, polyethylene wax , is applied via a water based emulsion . This makes

990-952: A system of pipes installed for municipal distribution of compressed air to power machines and to operate generators for lighting. Early air compressors were steam-driven, but in certain locations a trompe could directly obtain compressed air from the force of falling water. Air for breathing may be stored at high pressure and gradually released when needed, as in scuba diving , or produced continuously to meet requirements, as in surface-supplied diving . Air for breathing must be free of oil and other contaminants; carbon monoxide, for example, in trace volumetric fractions that might not be dangerous at normal atmospheric pressure may have deadly effects when breathing pressurized air due to proportionally higher partial pressure . Air compressors, filters, and supply systems intended for breathing air are not generally also used for pneumatic tools or other purposes, as air quality requirements differ. Workers constructing

1056-462: A typical glass works will have several large compressors (totaling 30k–60k cfm) to provide the necessary compressed air. However in recent times servo drives have been implemented in the machines which achieve a better digital control of the forming process. It is one step to initialize industries 2.0 in this branch. Furnaces, compressors, and forming machines generate large quantities of waste heat which are generally cooled by water. Hot glass which

1122-591: A variety of applications such as Most forms of specialized glass such as toughened glass , frosted glass , laminated safety glass and soundproof glass consist of standard float glass that has been further processed. As of 2009, the world float glass market, not including China and Russia, is dominated by four companies: Asahi Glass , NSG / Pilkington , Saint-Gobain , and Guardian Industries . Other companies include Sise Cam AS, Vitro, formerly PPG , Central Glass, Hankuk (HanGlas), Carlex Glass, and Cardinal Glass Industries. Compressed air Compressed air

1188-438: A variety of faults. Typical faults include small cracks in the glass called "checks" and foreign inclusions called "stones" which are pieces of the refractory brick lining of the melting furnace that break off and fall into the pool of molten glass, or more commonly oversized silica granules (sand) that have failed to melt and which subsequently are included in the final product. These are especially important to select out due to

1254-658: Is air kept under a pressure that is greater than atmospheric pressure . Compressed air in vehicle tyres and shock absorbers is commonly used for improved traction and reduced vibration. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers , drills , wrenches , and others, as well as to atomize paint, to operate air cylinders for automation, and can also be used to propel vehicles. Brakes applied by compressed air made large railway trains safer and more efficient to operate. Compressed air brakes are also found on large highway vehicles. Compressed air

1320-400: Is a hazard when diving. For diving much beyond 30 metres (100 ft), it is less safe to use air alone and special breathing mixes containing helium are often used. In industry, compressed air is so widely used that it is often regarded as the fourth utility, after electricity, natural gas and water. However, compressed air is more expensive than the other three utilities when evaluated on

1386-441: Is common, however the environmental impact of washing containers as against remelting them is uncertain. Factors to consider here are the chemicals and fresh water used in the washing, and the fact that a single-use container can be made much lighter, using less than half the glass (and therefore energy content) of a multiuse container. Also, a significant factor in the developed world's consideration of reuse are producer concerns over

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1452-406: Is created by the forming machines. Operated by compressed air, they can produce noise levels of up to 106 dBA . How this noise is carried into the local neighborhood depends heavily on the layout of the factory. Another factor in noise production is truck movements. A typical factory will process 600 T of material a day. This means that some 600 T of raw material has to come onto the site and

1518-676: Is limited only by the quality of the furnace’s superstructure material and by the glass composition. Types of furnaces used in container glass making include "end-port" (end-fired), "side-port", and "oxy-fuel". Typically, furnace size is classified by metric tons per day (MTPD) production capability. Modern furnaces use electric heating methods that improve energy efficiency compared to traditional fossil fuel systems, contributing to reduced pollution and emissions. Electrodes made from molybdenum , graphite , or alloys are used in glass furnaces to conduct electricity and generate energy. There are currently two primary methods of making glass containers:

1584-521: Is manufactured into glass products. The batch enters the furnace, then passes to the forming process, internal treatment, and annealing. The following table lists common viscosity fixpoints, applicable to large-scale glass production and experimental glass melting in the laboratory : The batch is fed into the furnace at a slow, controlled rate by the batch processing system. The furnaces are natural gas - or fuel oil -fired, and operate at temperatures up to 1,575 °C (2,867 °F). The temperature

1650-407: Is not used in the forming machine is diverted and this diverted glass (called "cullet") is generally cooled by water, and sometimes even processed and crushed in a water bath arrangement. Often cooling requirements are shared over banks of cooling towers arranged to allow for backup during maintenance. After the forming process, some containers—particularly those intended for alcoholic spirits—undergo

1716-565: Is perceived as a "premium" quality packaging format. Glass containers are wholly recyclable and the glass industries in many countries have a policy, sometimes required by government regulations, of maintaining a high price on cullet to ensure high return rates. Return rates of 95% are not uncommon in the Nordic countries (Sweden, Norway, Denmark and Finland). Return rates of less than 50% are usual in other countries. Of course glass containers can also be reused , and in developing countries this

1782-463: Is pulled off the bath by rollers at a controlled speed. Variation in the flow speed and roller speed enables glass sheets of varying thickness to be formed. Top rollers positioned above the molten tin may be used to control both the thickness and the width of the glass ribbon. Once off the bath, the glass sheet passes through a lehr kiln for approximately 100 m, where it is cooled gradually so that it anneals without strain and does not crack from

1848-418: Is referred to as a "tear". In the "press and blow" forming, if a plunger and mould are out of alignment, or heated to an incorrect temperature, the glass will stick to either item and become torn. In addition to rejecting faulty containers, inspection equipment gathers statistical information and relays it to the forming machine operators in the hot end. Computer systems collect fault information and trace it to

1914-411: Is stabilised to approximately 1,200 °C to ensure a homogeneous density . The molten glass is fed into a "tin bath", a bath of molten tin (about 3–4 m wide, 50 m long, 6 cm deep), from a delivery canal and is poured into the tin bath by a ceramic lip known as the spout lip. The amount of glass allowed to pour onto the molten tin is controlled by a gate called a tweel . Molten tin

1980-417: Is suitable for the float glass process because it has a higher density than glass, so the molten glass floats on it. Its boiling point is higher than the melting point of glass, and its vapour pressure at process temperature is low. However, tin oxidises in a natural atmosphere to form tin dioxide (SnO 2 ). Known in the production process as dross, the tin dioxide adheres to the glass. To prevent oxidation,

2046-675: Is the Applied Ceramic Labelling process (ACL). This is screen-printing of the decoration onto the container with a vitreous enamel paint, which is then baked on. An example of this is the original Coca-Cola bottle. Glass containers are packaged in various ways. Popular in Europe are bulk pallets with between 1000 and 4000 containers each. This is carried out by automatic machines (palletisers) which arrange and stack containers separated by layer sheets. Other possibilities include boxes and even hand-sewn sacks. Once packed,

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2112-477: Is then picked up from the mould by the "take-out" mechanism, and held over the "deadplate", where air cooling helps cool down the still-soft glass. Finally, the bottles are swept onto a conveyor by the "push out paddles" that have air pockets to keep the bottles standing after landing on the "deadplate"; they're now ready for annealing. The forming machines hold and move the parts that form the container. The machine consists of 19 basic mechanisms in operation to form

2178-420: Is therefore to predict demand both in the short 4- to 12-week term and over the 24- to 48-month-long term. Factories are generally sized to service the requirements of a city; in developed countries there is usually a factory per 1–2 million people. A typical factory will produce 1–3 million containers a day. Despite its positioning as a mature market product, glass does enjoy a high level of consumer acceptance and

2244-545: Is to produce compressed air—amounting to 80 terawatt hours consumption per year. Industrial use of piped compressed air for power transmission was developed in the mid-19th century; unlike steam , compressed air could be piped for long distances without losing pressure due to condensation. An early major application of compressed air was in the drilling of the Mont Cenis Tunnel in Italy and France in 1861, where

2310-426: Is used as a breathing gas by underwater divers . It may be carried by the diver in a high-pressure diving cylinder , or supplied from the surface at lower pressure through an air line or diver's umbilical . Similar arrangements are used in breathing apparatus used by firefighters, mine rescue workers and industrial workers in hazardous atmospheres. In Europe, 10 percent of all industrial electricity consumption

2376-493: The gob cutting shear blades . This oil-laden water mixes with the water outflow stream, thus polluting it. Factories usually have some kind of water processing equipment that removes this emulsified oil to various degrees of effectiveness. Nitrogen oxides are a natural product of the burning of gas in air and are produced in large quantities by gas-fired furnaces. Some factories in cities with particular air pollution problems will mitigate this by using liquid oxygen , however

2442-489: The overflow downdraw method . Most float glass is soda–lime glass , although relatively minor quantities of specialty borosilicate and flat panel display glass are also produced using the float glass process. Until the 16th century, window glass or other flat glass was generally cut from large discs (or rondels) of crown glass . Larger sheets of glass were made by blowing large cylinders which were cut open and flattened, then cut into panes. Most window glass in

2508-431: The "blow and blow" method for narrow-neck containers only, and the "press and blow" method used for jars and tapered narrow-neck containers. In both methods, a stream of molten glass at its plastic temperature (1,050–1,200 °C [1,920–2,190 °F]) is cut with a shearing blade to form a solid cylinder of glass, called a "gob". The gob is of predetermined weight just sufficient to make a bottle. Both processes start with

2574-425: The "blowhead", blows the glass out, expanding into the mould, to make the final container shape. In the press and blow process, the parison is formed by a long metal plunger which rises up and presses the glass out, in order to fill the ring and blank moulds. The process then continues as before, with the parison being transferred to the final-shape mould, and the glass being blown out into the mould. The container

2640-414: The batch house measures, assembles, mixes, and delivers the glass raw material recipe (batch) via an array of chutes, conveyors, and scales to the furnace. The batch enters the furnace at the "dog house" or "batch charger". Different glass types, colours, desired quality, raw material purity/availability, and furnace design will affect the batch recipe. The hot end of a glassworks is where the molten glass

2706-536: The careful balance of the volume of glass fed onto the bath, where it was flattened by its own weight. Full scale profitable sales of float glass were first achieved in 1960, and in the 1960s the process was licensed throughout the world, replacing previous production methods. Float glass uses common glass-making raw materials , typically consisting of sand , soda ash ( sodium carbonate ), dolomite , limestone , and salt cake ( sodium sulfate ) etc. Other materials may be used as colourants, refining agents or to adjust

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2772-413: The details (such as cap sealing surface, screw threads, retaining rib for a tamper-proof cap, etc.) at the open end of the container. Then compressed air is blown through the glass, which results in a hollow and partly formed container. Compressed air is then blown again at the second stage to give final shape. Containers are made in two major stages. The first stage moulds all the details ("finish") around

2838-547: The development of float glass. Between 1953 and 1957, at the Cowley Hill Works St Helens, Lancashire, Sir Alastair Pilkington and Kenneth Bickerstaff of the UK's Pilkington Brothers developed the first successful commercial application for forming a continuous ribbon of glass using a molten tin bath on which the molten glass flows unhindered under the influence of gravity. The success of this process lay in

2904-530: The disease on projects such as the Brooklyn Bridge and the Eads Bridge and it was not until the 1890s that it was understood that workers had to decompress slowly, to prevent the formation of dangerous bubbles in tissues. Air under moderately high pressure, such as is used when diving below about 20 metres (70 ft), has an increasing narcotic effect on the nervous system. Nitrogen narcosis

2970-413: The early 19th century was made using the cylinder method . The 'cylinders' were 6 to 8 feet (180 to 240 cm) long and 10 to 14 inches (25 to 36 cm) in diameter, limiting the width that panes of glass could be cut, and resulting in windows divided by transoms into rectangular panels. The first advances in automating glass manufacturing were patented in 1848 by Henry Bessemer . His system produced

3036-402: The fact that they can impart a destructive element to the final glass product. For example, since these materials can withstand large amounts of thermal energy, they can cause the glass product to sustain thermal shock resulting in explosive destruction when heated. Other defects include bubbles in the glass called "blisters" and excessively thin walls. Another defect common in glass manufacturing

3102-469: The foundations of bridges or other structures may be working in a pressurized enclosure called a caisson , where water is prevented from entering the open bottom of the enclosure by filling it with air under pressure. It was known as early as the 17th century that workers in diving bells experienced shortness of breath and risked asphyxia, relieved by the release of fresh air into the bell. Such workers also experienced pain and other symptoms when returning to

3168-507: The glass slippery, protecting it from scratching and stopping containers from sticking together when they are moved on a conveyor . The resultant invisible combined coating gives a virtually unscratchable surface to the glass. Due to reduction of in-service surface damage, the coatings often are described as strengtheners, however a more correct definition might be strength-retaining coatings. Glass containers are 100% inspected; automatic machines, or sometimes persons, inspect every container for

3234-416: The gob falling, by gravity, and guided, through troughs and chutes, into the blank moulds, two halves of which are clamped shut and then sealed by the "baffle" from above. In the "blow and blow" process, the glass is first blown through a valve in the baffle, forcing it down into the three-piece "ring mould" which is held in the "neckring arm" below the blanks, to form the "finish". The term "finish" describes

3300-453: The high temperatures needed to make glass—most notably in the US. Several patents were granted, but this process was unworkable at the time. Before the development of float glass, larger sheets of plate glass were made by casting a large puddle of glass on an iron surface, and then polishing both sides, a costly process. From the early 1920s, a continuous ribbon of plate glass was passed through

3366-541: The hot end handles the manufacture proper—the forehearth, forming machines, and annealing ovens; and the cold end handles the product-inspection and packaging equipment. Batch processing is one of the initial steps of the glass-making process. The batch house simply houses the raw materials in large silos (fed by truck or railcar), and holds anywhere from 1–5 days of material. Some batch systems include material processing such as raw material screening/sieve, drying, or pre-heating (i.e. cullet ). Whether automated or manual,

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3432-411: The interior cools and contracts it creates tension. Even cooling is achieved by annealing . An annealing oven (known in the industry as a lehr ) heats the container to about 580 °C (1,076 °F), then cools it, depending on the glass thickness, over a 20 – 60 minute period. The role of the cold end of glass container production is to complete the final tasks in the manufacturing process: spray on

3498-429: The logic of this given the cost in carbon of (1) not using regenerators and (2) having to liquefy and transport oxygen is highly questionable. Sulfur oxides are produced as a result of the glass melting process. Manipulating the batch formula can effect some limited mitigation of this; alternatively exhaust plume scrubbing can be used. The raw materials for glass-making are all dusty material and are delivered either as

3564-446: The mould that produced the container. This is done by reading the mould number on the container, which is encoded (as a numeral, or a binary code of dots) on the container by the mould that made it. Operators carry out a range of checks manually on samples of containers, usually visual and dimensional checks. Sometimes container factories will offer services such as "labelling". Several labelling technologies are available. Unique to glass

3630-403: The new "stock units" are labelled, warehoused, and ultimately shipped. Glass container manufacture in the developed world is a mature market business. World demand for flat glass was approximately 52 million tonnes in 2009. The United States, Europe and China account for 75% of demand, with China's consumption having increased from 20% in the early 1990s to 50%. Glass container manufacture is also

3696-416: The opening, but the body of the container is initially made much smaller than its final size. These partly manufactured containers are called "parisons", and quite quickly, they are blow-molded into final shape. The "rings" are sealed from below by a short plunger. After the "settleblow" finishes, the plunger retracts slightly, to allow the skin that's formed to soften. "Counterblow" air then comes up through

3762-551: The past. This method gives the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass. Most float glass is soda–lime glass , but relatively minor quantities of special borosilicate and flat panel display glass are also produced using the float glass process. The float glass process is also known as the Pilkington process , named after the British glass manufacturer Pilkington , who pioneered

3828-408: The physical and chemical properties of the glass. The raw materials are mixed in a batch process, then fed together with a controlled proportion of cullet (waste glass) into a furnace , where it is heated to approximately 1,500 °C. Common float glass furnaces are 9 m wide and 45 m long and have capacities of more than 1,200 tons of glass. Once molten, the temperature of the glass

3894-415: The plunger, to create the parison. The baffle rises and the blanks open. The parison is inverted in an arc to the "mould side" by the "neckring arm", which holds the parison by the "finish". As the neckring arm reaches the end of its arc, two mould halves close around the parison. The neckring arm opens slightly to release its grip on the "finish", then reverts to the blank side. "Final blow", applied through

3960-467: The risk and consequential product liability of using a component (the reused container) of unknown and unqualified safety. How glass containers compare to other packaging types ( plastic , cardboard , aluminium ) is hard to say; conclusive lifecycle studies are yet to be produced. Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin , although lead and various low melting point alloys were used in

4026-411: The same off the site again as finished product. Water is used to cool the furnace, compressor and unused molten glass. Water use in factories varies widely; it can be as little as one tonne water used per melted tonne of glass. Of the one tonne, roughly half is evaporated to provide cooling, the rest forms a wastewater stream. Most factories use water containing an emulsified oil to cool and lubricate

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4092-469: The surface, as the pressure was relieved. Denis Papin suggested in 1691 that the working time in a diving bell could be extended if fresh air from the surface was continually forced under pressure into the bell. By the 19th century, caissons were regularly used in civil construction, but workers experienced serious, sometimes fatal, symptoms on returning to the surface, a syndrome called caisson disease or decompression sickness . Many workers were killed by

4158-506: The technique (invented by Sir Alastair Pilkington ) in the 1950s. As with all highly concentrated industries, glassworks suffer from moderately high local environmental impacts. Compounding this is that because they are mature market businesses, they often have been located on the same site for a long time and this has resulted in residential encroachment. The main impacts on residential housing and cities are noise, fresh water use, water pollution, NOx and SOx air pollution, and dust. Noise

4224-436: The temperature change. On exiting the "cold end" of the kiln, the glass is cut by machines. Today, float glass is the most widely produced form of glass, with a multitude of commercial applications. Due to both its high quality with no additional polishing required and its structural flexibility during production, it can easily be shaped and bent into a variety of forms while in a heated, syrupy state. This makes it ideal for

4290-430: The tin bath is provided with a positive pressure protective atmosphere of nitrogen and hydrogen . The glass flows onto the tin surface forming a floating ribbon of even thickness with perfectly smooth surfaces on both sides. As the glass flows along the tin bath, the temperature is gradually reduced from 1,100 °C until at approximately 600 °C the sheet can be lifted from the tin onto rollers. The glass ribbon

4356-437: The vaporized water turns to liquefied water. Cooling the air as it leaves the compressor will take most of the moisture out before it gets into the piping. Aftercooler, storage tanks, etc. can help the compressed air cool to 104 °F; two-thirds of the water then turns to liquid. Management of the excessive moisture is a requirement of a compressed air distribution system. System designers must ensure that piping maintains

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