Posts

Feasibility Study

Image
Feasibility Studies Stewart Engineers can help you quantify risks and ensure financial feasibility before investing in glass manufacturing . Investing in float glass is challenging for new entrants. How can you verify the viability of an idea when there are many small glass importers making gathering market data tricky? There is a broad range of quality, and therefore cost, available in glass industry equipment making a cost benefit analysis difficult. About Stewart Engineers Stewart Engineers is a privately held and family-owned company led by glass industry experts. Our company headquarters is in Wake Forest, North Carolina with branch offices in Kyzylorda, Kazakhstan and Altendorf, Switzerland. Les Stewart founded Stewart Engineers in 1986. We have served the glass industry since our inception with engineering and glassmaking equipment. We have a deep understanding of the glass industry due to our expertise and experience in the glass industry. Our knowledge enables us t...
Read more

Glass Manufacturing

Image
Glass Manufacturing Stewart Engineers builds high-quality float glass manufacturing facilities around the world. We use our considerable experience in float glass to design and build float facilities that maximize profit. Technologies like the StewartFloat® tin bath and AcuraCoat® CVD system combined with Stewart’s international project management and procurement experience result in float facilities that are built on schedule, on budget, and on quality. Beyond the initial project metrics, Stewart Engineers delivers a total solution by providing highly automated and robust solutions along with glass manufacturing process and business operations training. Stewart Stewart Engineers specializes in helping new entrants to float glass manufacturing understand what they need to succeed. Determining ideal tonnage, staffing, product mix, glass recipes, and other critical design decisions can be tough for groups entering the float glass market. A feasibility study is th...
Read more

Make CVD Part of your Future

Image
Make CVD Part of your Future Glass manufacturers began to use CVD for online coatings in the 1960’s. Pilkington was the first to develop a marketable product, Reflectafloat. Over the lifetime of the product, it was made in both the tin bath and the lehr. Reflectafloat is a reflective product that doesn’t have Low-E properties; it is still used in developing glass markets. Pilkington licensed the Reflectafloat technology to some of their float bath licensees but never made it widely available. Stewart Engineers was founded and committed to developing CVD so independent glass manufacturers could have access to the technology. With a concerted effort from the entire engineering staff, Stewart Engineers commissioned its first CVD system in 2005. Pilkington and AGC continued development of new CVD coatings, and then in 2006, Pilkington was acquired by Nippon Sheet Glass (later known as NSG). Stewart Engineers, NSG, and AGC all continued with CVD development in the 2000’s with St...
Read more

History of Glass

Image
History of Glass How to turn Sand into Glass The raw material from which glass is made is silica, the most abundant of all the earth's minerals. Milky white in color, it is found in many forms of rock, including granite. And as every beach in the world has been formed by water pounding rocks into tiny particles, sand is the major source of silica. When you examine a handful of sand, any grain that is semitransparent - rather than black, red, yellow or some other definite color - is a grain of silica. Sand also contains other minerals, but silica is the main component because it is hard, insoluble and does not decompose, so it outlasts the others.   Pure silica has such a high melting point that no ordinary fire would convert it into glass. Today, lime and soda are combined with silica to produce soda-lime glass, used for making bottles, window panes, flat glass products, and cheap drinking glasses. When glass cools, its structure does not return to the crystalline s...
Read more

Glass Manufacturing - Cutting & Packing

Image
Float Glass Cutting and Packing The final online manufacturing process for float glass is the Cutting and Packing line. The cutting and packing conveyor is immediately downstream of the annealing lehr . It is comprised of special roller sections that are capable of transporting glass product without damage. All cutting equipment and conveyor sections along the length of the conveyor are computer-operated and capable of handling "Jumbo" size (full ribbon in width, longer than ribbon width in length), "LES" size (full ribbon in width, ribbon width or less in length), and "SS" sizes (less than full ribbon in width, less than full ribbon width in length). The various pieces of equipment on the cutting and packing line are: X and Y Cut Conveyor Acceleration Conveyor Score Snapping and Packing Conveyor Conveyor Control System Strain Measurement Station Main Line Ribbon Disposal Examination Booth Longitudinal Cutting (Y-cut) Cross Cutting ...
Read more

Glass Manufacturing - Annealing Lehr

Image
Float Glass Annealing Lehr What is a lehr? A glass annealing lehr oven- often just referred to as a 'lehr', is a long, temperature controlled, kiln. Lehrs are typically 6m wide and 120m long, with an adjustable temperature gradient through which the glass passes. In the case of containers and tableware, the product is transported on a conveyor belt and for flat glass on a special roller conveyor. Adjustable electric heating elements and air heat exchangers are located in the lehr to maintain a consistent temperature profile across the width of the glass ribbon. Why is a lehr used? If the glass ribbon were to cool in ambient temperature air, the surfaces would cool much more rapidly than the internal body of the glass. This temperature gradient would cause the surface to be in severe compression, which will cause the glass to break spontaneously as the stresses exceed the strength of the glass. What is annealing of glass? After the formed glass ribbon leaves ...
Read more

Glass Manufacturing - Glass Forming

Image
Glass Forming Forming Technology Flat glass is manufactured using one of three processes: the sheet process, the plate process, or the float process. The float glass process has, almost entirely, replaced the sheet glass and plate glass processes. Sheet Glass The sheet glass process began with the mechanically drawing cylinder process, where large glass cylinders were made to be split and flattened into plates, and has developed into continuous vertical drawing processes. These processes depend on the stretching and cooling of viscous glass, and their produced glass typically has a desirable bright and transparent "fire finish" due to the surfaces of the glass ribbon cooling down without contact with solid forming elements until they are relatively hard. However, in stretching the molten glass, small differences in viscosity due to chemical and thermal in-homogeneity give rise to thickness variations in the glass ribbon which cause undesirable optical distortions. P...
Read more

Glass Manufacturing - Batching

Image
Glass Materials and Batching Glass contains three major categories of constituents - formers, fluxes, and network modifiers. Silicon dioxide (SiO2), or sand, is used as the former and basic constituent with soda ash (Na2CO3) as the flux. Lime (CaCO3) and dolomite (CaCO3MgCO3) are network modifiers that stabilize the chemical properties of the glass. Batch Plant Storage The batch plant receives the delivery of raw ingredients for glass making. Delivery of these ingredients varies from site-to-site, particularly when the plant is installed in a country where some of the ingredients are imported rather than domestic. The types of materials can be divided into two principal groups: bulk ingredients including sand, cullet, soda ash, limestone, etc., and "small ingredients" - various combinations of minor ingredients that are used to change physical properties of glass including color, transparency, and refraction. Batch plant storage systems are almost entirely dep...
Read more

Glass Manufacturing - Melting

Image
Glass Melting Process Melting The typical melting furnace is a Six Port Cross Fired Regenerative furnace with a capacity of 500 tons per day. Cross fired regenerative furnaces have been built for very small and very large melting areas. The smallest units may be uneconomical, although in certain cases they may provide the only technologically possible route. The major sections of the furnace are melter refiner, working end, regenerators, and ports, and are constructed of specialized refractory material with an outside steel framework. The largest units are found in flat glass manufacture , where furnaces with total areas of 500m2 and above are found. The typical 500 ton melter has an area measuring 23m x 9.5m (218.5m2) with a glass depth of 1150mm. The batch mixture is delivered to the melting furnace where the batch is heated to approximately 1580oC (2875oF). Insulation, special airflow features, and combustion air heating enable the furnace to operate at maximum fuel e...
Read more

Selecting the best float glass coating technology

Image
Glass Coating Technology Comparison A variety of techniques are available to deposit thin films onto flat glass. The most widely used of these for producing high-quality functional coatings can be subdivided into two classes: Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD). PVD processes include many approaches of which sputtering is one, and is also the one most widely used for glass. Sputter coatings are generally referred to as "soft coat glass" and are applied using PVD processes. Pyrolytic coatings are applied using CVD methods and are referred to as "hard coating". Both coating methods have advantages and disadvantages. It is essential to consider the performance and handling factors that best meet product and manufacturing needs when evaluating which system is right for a glass manufacturing facility . A Stewart Engineers AcuraCoat® CVD Under-Coater for on-line pyrolytic CVD glass coating. Disadvantages and Advantages of Magnetr...
Read more