Industries And Manufacturing

Types of fire-resistant glasses

2011-12-16T05:43:00.000-08:00

The increased use of glazing in buildings, together with building code requirements in the fire-rated glass sector which have seen rapid changes, have lead to the development of new types of fire glasses.

Generally, any type of glass that can withstand the fire test and therefore resist passage of smoke, flames and hot gases, is considered "fire-resistant glass". These glasses are then further categorised and rated according to special criteria. Typically, the rating is based on how long a particular type and size of glass will withstand fire. Classifications range from 20 minutes up to 3 hours.

Ordinary flat glass cannot withstand extreme temperatures, and breaks at around 120° C. Fire-resistant glass must be able to withstand 870° C for a selected period of time and remain in its frame. Immediately following this extreme heat, the glass is exposed to ?The Hose Stream Test?. In this test, water is used to rapidly cool the hot glass to test its ability to withstand thermal change. The purpose of this test is to test a real situation in which water from a sprinkler system shatters glass intended to function as a barrier, and thus permits smoke and fire to spread and escalate to the next level.

The three most important factors in connection with the choice of fire-protection glass are:
- type of protection (class E- and class EI)
- duration of protection (e.g. 15, 30 or 60 minutes),
- frame construction to be used (wood, aluminum or steel).

Class E involves protection against smoke and flames while class EI also offers protection against fires spreading heat radiation.

On the market today they are several fire-resistant glass products such as wired glass, ceramic glass, fire-rated tempered and special laminated glass.

article source
http://www.glassonweb.com

Today’s challenges of automotive glass manufacturers

2011-12-16T05:42:00.000-08:00

Automotive glass manufacturers are forced to face great challenges daily. Especially now since world financial crisis had almost immediate impact on the industry. The slowing economy drives the new vehicle sales down with out exception in each continent. To Remain competitive, more than ever now all manufacturers from largest multinational corporations to smaller private companies are seeking ways to cut costs, improve efficiency and production yields – at least they should be, by now.

Ever rising energy prices are making each windscreens production cost higher and when we add on top of this all the costs arising from waste pieces, used working hours, and possibly extended development periods, the margin per piece simply comes smaller and smaller. Without continuous efforts to boost up the yield, productivity, efficiency, and quality, company will end up losing ground to its competitors. Well trained, professional and committed staff is a key factor when companies fight their way through these rough times.

THE PROCESS

From raw glass warehouse, to cutting table, grinding, washing, long pair powdering and short pair to printing, short pair is dried and finally glasses are paired again. After this so called “cold-end” of the process is done and the glass is half way in the process chain. It is amazing how much these processing methods still vary today. It is common to see glasses hand cut and separating powder applied manually while in the other hand larger more developed companies use completely automated production lines with robots and automatic measuring.

Although these companies are set to aim different markets, both can make profitable business. With out any deeper knowledge on the cold-end part everyone can understand that a lot can be done wrong and many to cut costs and improve efficiency. Automatic quality control monitoring is available for the manufacturing lines, but due to the costs the quality is still monitored by the operators. From these processes grinding and powdering can cause breakages and defects later, in and after bending process. Therefore it is important to monitor these processes carefully. After the “cold-end” the process chain continues with bending the most demanding process of the complete chain. After bending follows pvb assembly, vacuum and autoclaving. This article will focus more on the “hot-end” part of the process chain.

MANUFACTURING CHALLENGES - Bending the most important part of the process

Every day larger and more complex shapes in car windscreens come more common. Although every part of the process play their important role in the final product, it is clear that bending is the most important and demanding part. Without successful bending results the complete process fails. So called cielo and panoramic type windscreens with deep cross curvatures, tight wing shapes and small installation angle, together with thin, coloured, glass pair combinations create an “equation” that needs careful and professional care while it’s been developed into production. Bending these difficult windscreens with basic gravity bending furnaces is everything else than simple.
The key issue will be – How to achieve perfect optical quality. Challenge is obvious, even to meet the optical requirements of the ECE 43 regulations and it is common that the car manufacturer has its own standards. These manufacturer standards have a tendency to be far more demanding than the ECE optical regulations. Hand in hand with this optical challenge comes the complex shape. Deep cross curvatures are sometimes some what tricky to handle. The “profile” of centre section of the glass easily contains “flat” or “reverse” parts. In other words the cross curvature is not smooth and continuous, as part or parts of the windscreen is left “flat” or has “reverse bending”. These “flat and reverse” areas cause problems in “wiperbility” and in worst case these defects will cause reflections on the optical examination. Due to the challenging characteristics of the windscreen and quality requirements the bending trials can get uncomfortable while the perfect heating configurations and tooling settings are being searched for long periods of time and often without any encouraging results. After a while the work can come into a halt. Correct heating configuration and advanced tooling are highly important, but it is also necessary to realize that good optical quality cannot be reached if the process chain from cutting until final inspection is not in order.
The latest model serial gravity bending furnaces are equipped with wide range of features, but still the challenge is real. The biggest advantage on new furnaces is the well improved heating element controls and endless possibilities of adjustments. In fact so many that an average shift operator does not know half of the parameters and the functions behind. Older furnaces have their limits when it comes to producing the windscreens for latest car industry innovations, and we are not talking only about the physical limitation set by the chamber size. Coloured, thin glass pair combination and a complex shape can prove out to be impossible to manufacture without up to date machinery. Unfortunately investing into a new furnace can be too expensive.
Similar challenges are faced with coach, special vehicle and bus windscreen manufacturing. Biggest challenge for this segment of windscreens is the wing and corner shapes. Today most of the single chamber and serial furnaces for larger windscreens are equipped with bottom heating and position/out put power controls. These technical features enable faster and uniform heating for both short and long glass pair and a precise heating radiation control only to the areas where the radiation needs to be applied. Bottom heating further eliminates possible optical defects. Large windscreens with long and tight wing shapes together with deep cross curvature are difficult to bend to the final shape. Deformations on edge shapes and reverse bending are common problem when the glass has been forced to its shape. To achieve competitive results advanced mould tooling is very important. Advanced mould tooling allows perfect control of the windscreen from the beginning of the bending process until the very end. With different mechanical solutions the mould and glass can be controlled so that no external manipulation of the glass is necessary. Such control of the glass and mould eases reverse bendings and shape deviations on the corner areas.

Generally, with both; serial and single chamber furnaces, complex bus and special vehicle windscreens are bent manually using only the basic automatic functions such as automatic heating element configuration during the bending and final bending. Other functions weight controls, slight adjustments on temperature balance and finally release to cooling (Glass Ready) are all controlled by the operator(s) during the process. Manual operating is time consuming but in some cases cannot be avoided, simply because the technology available today does not make it possible. Since the process is controlled manually it is obvious that certain level of skill is a must to successful operation. The bending is very unforgiving, and one mistake can be fatal to the end product. Well trained and committed staff is major factor in this process and the yield levels and quality can be improved to a completely new level with continuous and efficient development of the bending practises

QUALITY - a true strength

ECE 43 regulations determine the basic guide lines regarding the checks on conformity of production, but it leaves a lot for the manufacturer it self to decide how to measure and control the end product. When compared the manufacturers ARG windscreen manufacturing quality control measures vary widely from next to nothing to basically thorough 100 % inspections. For example: Some companies are checking all windscreens immediately after bending with the checking fixture and document the shape and size variations carefully while others still are not using no checking fixtures at all. In OEM segment the practice does not vary so widely although clear variation on quality control measures is still there. Strict quality control measures after each process are easy way to improve the yield levels and save costs when only the good parts are processed. Once again the production line staff is in a key role – they must be committed to the perfect quality idea.

INDEPENDENT EXTERNAL VIEW – way to easier solutions?

In every aspect of the business, companies are using consulting, coaching, training and advising when their own internal development and technical departments face a situation when there’s simply no new ideas and the work comes to stand still. Most of the times the external view is sought even before the actual stand still situation is faced. In these situations external professional view, can probably pin point the weakest spots and determine worst “reefs” to be avoided. Problems can be caused simply because the matters are looked from “too close proximity” and instead of seeing the complete picture, everyone is focused into one minor detail, “thinking inside the box”. Thinking outside of the box normally generates innovative and novel ideas. Sometimes neutral external “variable” can change a lot. Broader view, different approach, professional experience, and purely neutral opinions based only to the facts gathered, can lighten up the situation for all, in completely different perspective. Doesn’t really matter if it is a technical problem or matter of working practises – the “external variable” can be a way to easier solution.

In technical problems the working pattern is very much like doctor and patient relation. The reasons are sought according to the patient’s report of the symptoms. Doctor examines the process and after analysing the observations he explains the cause and consequences and suggests possible treatments. All this is done under professional confidentiality. Since the automotive windscreens manufacturing process chain still contains a lot of “manual” and “automated manual” work it is clear that the skills and commitment of the manufacturing staff play a crucial role on the continuous development. Both multinational corporations or private companies targeting the local markets need “tools” to overcome and improve their daily practises. Efficient and necessary “tool” can be change of attitude, practical training, technical advising or possibly new machinery, but sometimes hiring help out side is necessary to define the correct solutions.

article source
http://www.glassonweb.com

What makes glass transparent?

2011-12-16T05:40:00.000-08:00

Glass is something we use every day, a transparent material produced by melting a mixture of sand, calcium, oxide, and other raw materials and then cooling the resulting product. But have you ever wondered what makes glass transparent? Why can we see through window and not through the frame that enclose it?

In general most liquids and gases like water, air, natural gas, cooking oil, or rubbing alcohol are transparent, while solid materials like wood, metal, ceramics, etc. are opaque. That is because of a difference between the molecular structure of solids, liquids and gases. When a substance is in its solid state, molecules are ordered in a regular lattice just like bricks stacked neatly on top of one another, being virtually impenetrable for light waves. The molecules of an substance in the liquid stage are disordered and are not rigidly bound. This causes the disordered stacking of the molecules, creating gaps and holes that allow portions of light waves to pass through. The greater the gaps in molecular organization the easier it is for light to pass through. As glass in neither liquid nor solid, because its molecules are motionless (like a solid) but random in configuration (like a liquid), glass exists in a solid yet transparent state.

article source
http://www.glassonweb.com

Why a hose stream test is critical for testing fire glass

2011-12-16T05:39:00.000-08:00

The options in fire-rated glass have expanded greatly in recent years. Where architects and designers were once limited to traditional wired glass in relatively small sizes, today they can choose from a range of glazing that offers superior fire protection and the chance to incorporate entire walls of glass without compromising safety.

This is no small feat: To achieve a fire rating of more than 20 minutes, heated glass is subjected to a mandatory hose stream test as specified in test standards such as the National Fire Protection Association’s (NFPA) Standards on Fire Test for Window and Glass Block Assemblies. While some have questioned the ongoing necessity of the hose stream test, the NFPA standards clearly state: “The hose stream test provides a method for evaluating the integrity of constructions and assemblies and for eliminating inadequate materials or constructions. The cooling, impact, and erosion effects of the hose stream provide important tests of the integrity of the specimen being evaluated.”

Why should architects, glaziers and building code officials be aware of the importance of the hose stream test? Because one manufacturer now sells a 60-minute “fire-rated” product that does not and cannot pass the mandatory hose stream test.

To the unsuspecting eye, a 45- or 60-minute fire-rated label on the glass that says “…without hose stream…” may not raise suspicions – unless you know that the hose stream is a mandatory procedure required by North American test standards. To selectively decide what portions of required test procedures one chooses to complete can be dangerous.

Fire-Glass Testing The hose stream test is part of a series of tests that begins with heat testing of the glass. Manufacturers seeking a fire rating take their products to an independent testing facility, such as Underwriters’ Laboratories. The lab installs multiple pieces of the glass in a frame and wall assembly, which is then placed in a large furnace. A fire is then ignited on one side of the widow assembly, with temperatures attempting to replicate a “real world” fire. Following a standard time/temperature curve, at five minutes temperatures approach 1,000 F. and are nearly 2,000 F. at 180 minutes. The length of time the glass remains intact in the furnace will correspond to the final fire rating it receives (ranging from 20 minutes to 3 hours).

The goal of this testing is to determine how long the glass can remain in place and be expected to act as a barrier to a real life fire. If glass fails under the intense heat and vacates the frame, the flames and deadly smoke will be free to travel throughout a building.

If glass successfully survives the fire test and the manufacturer is seeking a rating greater than 20 minutes, the glass is immediately put through a second type of test. While the glass and framing system is still hot from the furnace, it is sprayed with water from a fire hose at a pressure of at least 30 PSI.

Most glass cannot tolerate drastic temperature differences such as this. If one area of the glass and framing system is hot while another is cool, it creates stress on the glass, known as thermal shock. Since part of the glass is expanding and part is contracting at the same time, the glass will shatter and vacate the frame.

The hose stream test is a critical way to measure how glass will respond to temperature differences. The glass must remain intact in order to pass and offer protection.

Interestingly, it doesn’t have to be a fire hose to prove the point. One manufacturer tested a 20-minute rated product with a simple garden hose. While the hot glass was able to withstand approximately 1,500 F., it quickly shattered when the light spray was applied.

Continuing Need for Hose Stream Test
Why is the hose stream test important? In the case of a real world fire, there’s a good chance glass and framing systems that have been exposed to the heat of flames will also be subjected to water from a fire hose, sprinklers or fire extinguishers. If the glass can’t withstand thermal shock, it will fall out of the frame, leaving an opening for fire or smoke to spread.

In the United States, all fire-rated glazing products with ratings greater than 20 minutes are required to pass the hose stream test (Canada requires the hose stream test for all ratings). Building and fire codes are very clear on why the hose stream test is critical, and in recent years, proposals to eliminate the test have been soundly defeated.

Last year, the manufacturer marketing a product that cannot pass the hose stream test sought to eliminate the hose stream test requirements from two portions of the fire-rated glass test standards in the International Code Councils’ (ICC) building safety and fire prevention codes. The ICC’s Fire Safety Code Development Committee, comprised of code officials, fire marshals and other experts, rejected these proposals after careful review of the issues presented in open public hearings. In its rejection of one of the proposals, the Committee stated that removal of the hose stream test requirement “…would reduce the level of life safety which the code has generally required and provided.” In its decision on the other proposal, the Committee noted that the issue has been debated a number of times and that “it has always been defeated.” (2006 ICC Public Hearing Results, FS121-06/07 and FS107-06/07). By its actions, the ICC has repeatedly validated the importance of the required hose stream test for life and property safety.

When choosing fire-rated glazing materials, it is critical to make sure that the product in question meets or exceeds all the testing standards. Otherwise, you may be taking a serious risk or increasing your liability. For openings with fire ratings of greater than 20 minutes, always insist on glass that has passed the mandatory hose stream test, and beware of products that acknowledge they have not passed the required test. There’s no need to compromise when life and property safety could be at stake.

About the author:
Jerry Razwick is founder and president of Technical Glass Products (TGP), a distributor of specialty glass and framing as well as architectural products. He has been a glass factory agent in foreign and domestic markets for over 25 years. Mr. Razwick has served on the Industry Advisory Committee for Underwriters Laboratories, Inc. and is an active member of AIA, CSI, NGA and GANA

article source
http://www.glassonweb.com

Windows of the future

2011-12-16T05:28:00.000-08:00

We spend millions of dollars every year to heat our homes and businesses. That is why it is so important to understand the role that windows play in how buildings use energy. In older homes, windows are often one of the largest sources of heat loss in winter due to their low insulating ability and high air leakage rates. Windows are also generally the major source of unwanted heat gain in the summer. As a result, windows are typically net energy losers, and can be responsible for 25 to 50 percent of the energy used to heat and cool homes. However, improved windows, combined with proper consideration of their placement and other details, can result in windows that provide a net energy gain.

Windows

Windows were once little more than holes cut in walls to let light and air into rooms. Today they bring beauty and light, warmth and cooling breezes into homes while providing a sense of openness and space.

On the down side, windows can also let in the winter chill or the summer heat. They can make a home drafty, uncomfortable, and energy inefficient. Fortunately, modern windows make the most of the benefits of windows while minimizing the drawbacks. Single-pane glass has been replaced by multi-panes separated by insulating materials. Frames are made of new, more energy efficient materials. Even the glass itself has been coated to reflect heat.

Windows of the future

New technologies are producing increasingly energy efficient windows. Already on the market are “super-windows”, boasting triple layer designs, with two low-E coatings and spaces filled with mixtures of argon or krypton gases. A new generation of windows, however, is being called “smart windows” because they adapt to changing conditions.

A few “smart windows” are already commercially available, and others are being developed in research labs. These windows change properties - like their shading coefficients and visible transmittances - in response to either an electric charge or an environmental signal such as a change in light level. Depending on the mechanism that initiates the change in the window, these “switchable glazings” fall into four categories: electrochromic, liquid crystal, thermochromic, and photochromic.
By GlassOnWeb editorial staff

Photochromic Windows: See The Difference

Sunlight Reactive Thermo Windows are the ultimate “smart” window. They are perfect for any application, architectural or residential.

Photochromic glass automatically changes from a clear glass to a tinted glass with the rays of the sun. There is no electricity or knobs required. As the sun sets, the glass will lighten up returning to it’s clear state. This will continue each time the sun is shining on the glass without fatigue unlike film tints and coatings. It also costs a fraction of the price of other smart windows currently available on the market.

Other glass reflects the harmful ultra violet rays that go back into the Earth’s ozone and are a great contributor to the global warming problem. Photochromic glass absorbs the UV rays helping to protect our planet. In doing this, it reduces the heat transferring into the building and reduces energy consumption and air conditioning costs.

In architectural applications, the automatically tinting glass will create privacy on sunny bright days. It will also protect expensive office furnishings with it’s 100% UV protection and stop the glare on computer screens and projectors. It can be made in a variety of colours making each application unique.

In residential applications, homeowners will be able to enjoy the sight out of their windows, protect their furnishings, and save on their energy costs all without curtains or blinds.

With Sunlight Reactive Thermo windows, as the glass changes from light to dark with the sunlight, you can see the difference.

For more information Please visit our website at:www.photochromicwindows.com

By Christopher Crawford

World Demand for Flat Glass

2011-12-16T05:26:00.000-08:00

According to a study from the Freedonia Group, production of flat glass is projected to increase 5.2 percent per year through 2008 to 48.3 million metric tons, of which around 34 million metric tons will be high quality float glass.

Construction markets will grow the fastest based on expanding global fixed investment: consequently, demand in the already dominant architectural glass sector will register the best gains.

The market for architectural glass is forecast to grow 5.4 percent per year through 2008 to US$53 billion: it will benefit from the greater use of value-added glazing products (such as laminated, tempered, mirrored glass, and, above all, double-glazed insulating glass units, which have become more and more popular in developed countries).

Asia will continue to offer strong annual gains, with growth especially strong in China and India. The US market for fabricated flat glass is forecast to outpace the global average, although actual gains in metric tonnage and square meters are expected to remain slightly above the average. Western Europe will continue to post the weakest sales growth, hindered by below average economic growth.

article source
http://www.glassonweb.com

Windscreens Go Deeper, Wider, Steeper, Spherical

2011-12-16T05:23:00.000-08:00

Breaking new ground with designs that are original and appealing is a daily challenge for car designers. One limitation on their creativity may be the constraints placed by the materials used in the design.

New glass technologies have brought significant advances in design; windshields have gone from being flat to curved, and now they can be spherical with wrap-around corners. Many practical issues still pose a challenge; visibility during the day and at night, comfort and safety, to name a few.

As a result, car designers today are including more and more glass in their cars. They are looking for aerodynamic efficiency, driving comfort and safety, as well as optimum structural stability and an attractive appearance. This has led to higher and wider windscreens, and steeper inclinations. And more glass overall in the car body.

TECHNOLOGY

For deep sags (> 30 mm), it has almost been the rule to use a press bender. This is certainly justified in long OEM series, but for short OEM series and replacement windscreens, it reduces manufacturing flexibility. Glassrobots has designed its innovative, reliable TFA FuzzyBend™ range of windscreen bending furnaces to be flexible enough for short and long runs in OEM and ARG production. With the new TFA 3evolution™ furnace, windscreens with sags of up to 32 mm are also produced with the reliable Glassrobots gravity bending control method. Using the TFA 3evolution™, it is possible to manufacture these windscreens, which manufacturers used to think required a press bender. Windscreen manufacturers can then decide whether they do short, long or replacement series. With the TFA 3evolution™, they at least have the right furnace.

The tooling for a press bender is also very expensive, which makes it uneconomical and unsuitable for producing replacement windscreens. Since more and more new windscreen models are being produced, it was time to design a reliable and flexible furnace for this ARG market.

Complex, wrap-around corners, increased cross-bending and larger glass sizes are typical features of modern windscreen design.

The outstanding, distortion free quality and dimensional accuracy of the end product, as well as the higher capacity, derive from the following innovative features of the TFA 3evolution™ furnace:

• New enhanced bending programme based on percentage control of heating elements with the proven and patented FuzzyBend™ control system

• Bottom heating elements with individual control for different models

• Special second level heating zone

• Customised heating elements for making the most demanding windscreen shapes

• Optimised arrangement of moving parts

All this is backed up by the experience and proven technology of Glassrobots, such as:

• Vertically Adjustable Heating Elements, VAHE™, to focus heat in difficult areas in the bending section

• 5-part heating elements in the bending sections, instead of the normal 3-part elements

• Temperature Balancing System, TBS™, consisting of an extra pyrometer in the bending sections, guarantees symmetrical heating. The glass temperature is measured systematically and if variations are detected, the control system automatically adjusts the heating pattern.

• Side Heaters enhance the heating of the side areas. They are normally installed in the pre-bending and bending sections.

• MirrorPattern™ (patent pending) eliminates the negative effect in mixed production of thermal inertia from the heating pattern for the previous glass.

• GlassButler™, remote diagnostic software that enables our technicians to be in direct contact via a modem link with the client’s process computers.

• Condition Monitoring and Maintenance System, CMMS™, a preventive maintenance feature that minimizes downtime and maximizes hours of operation.

RECENT DELIVERIES

Trakya Cam Sanayii A.S. Oto Cam Fabrikasi, a member of the Sisecam Group in Turkey, acquired its second car windscreen bending furnace from Glassrobots in just two and a half years. Sisecam is the biggest glass producer in Turkey. The Sisecam Group, one of the first public enterprises in Turkey, is quoted on the Istanbul Stock Exchange.

Gilan Glass Industries, Iran, is one of the largest OEM suppliers in Iran. They have one plant operating in Rashd in northern Iran. Capacity requirements have increased, and GGI is building a new plant in southern Iran. To better serve OEM car suppliers, GGI chose the new Glassrobots furnace, with an option for a second one.

The innovative details characteristic of Glassrobots furnaces were the main reason why these clients chose aGlassrobots furnace. And there are more to come, with windshield manufacturers queuing up for this fantastic product.

FUTURE INNOVATIONS

Much has been achieved, but even more remains to be done, to satisfy the ever-increasing demands of windscreen benders, or ultimately the car designers and makers. Future models will probably make even greater demands on the bending and laminating process. The use of solar-control glass, heated windscreens, integrated antenna systems, advanced display systems etc. is becoming more common, but research on these and other issues is going on all the time.

It is not just windshields that are undergoing considerable changes in design. Windscreens today may even continue directly into a roof window that is also laminated. Some car models now have laminated side lites. These provide better sound insulation, improve security against break-ins and safety in roll-over accidents, and of course give a wide range ofcolour options. But they cost five times more for the carmakers.

In order to meet future requirements and develop the new technology for them, the windscreen processor and furnace manufacturer have to work together and come up with new ideas to give them an edge over the competition. The key factors in success will continue to be cost efficiency, process quality and control and, above all, product quality.

article source

http://www.glassonweb.com

Photos: Glassrobots Oy
Last review: July, 2008

Windshield Lamination Process Secrets

2011-12-16T05:19:00.002-08:00

The complex nature of lamination defects; individual processing conditions, and different materials create a situation where the only working solutions are individually adjusted processing parameters.

I was inspired writing this article after I concluded that majority of my windshield production related cases included findings causing lamination defects and encouraged further more after seeing lines performing under conditions that were not supposed to produce even one good piece of laminated glass. In my experience the producers sometimes over look the conditions that contribute to reduced lamination process performance. The lamination process is in key-role in complete windshield production unit performance and it’s results and quality are directly linked with bending and pre-processing activities. In this article I will review the lamination process and most common lamination defect.

LAMINATION PROCESS

Lamination defects are typically within the top 5 waste (scrap) reasons in production of laminated windshields. Dominating lamination process in production of windshields contains the following process cycle:

PVB Assembly -> 2. Vacuum conveyor (cold and hot)-> 3. Autoclave

Alternatives are existent such as vacuum boxes, but the processing principles remain. The entire process seems simple, however following the basic guide lines of clean environment work and common processing parameters alone is not enough to maintain and improve the production yield levels. Without perfectly adjusted processing parameters the process can result with high number of re-autoclaved and waste pieces due to lamination defects. Waste created at this stage of production chain is particularly expensive and re-autoclaved pieces create workflow to unnatural direction. Furthermore re-autoclaved pieces are especially harmful for productivity as the autoclave is typically the bottleneck in laminated glass production lines, due to the limited capacity and long process cycle taking up to 4 hours.

TYPICAL LAMINATION DEFECT

Defect known as “bubbles” is probably the dominating lamination defect caused by air left between the glass sheets. This lamination defect is controversial: the bubbles do not appear every time when a little air is left between the laminate or when gapping between the glass pairs is monitored. The defect seems to arise when few contributing factors are existent. The fact that there seems to be no single dominating factor that ultimately creates this defect makes the elimination difficult.

The “Bubble”-defect appears in different sizes and locations. Typically the defect appears as “bubble”-areas in the very edges of the glass, while also larger individual bubbles appear: both in edges as well more towards to the middle section.

Larger “bubbles” appearing in the very edge of glass can be commonly fixed with re-autoclave cycle adding clips that help sealing the glass edges. However larger bubbles in the inner parts of the glass, typically between the glass corner and mould hinge line can be impossible to fix.

WHY BUBBLES APPEAR?

There are several conditions in each processing stage that can affect the lamination performance.

Pre-Processing

Cutting size variations will cause severe difficulties in positioning of the glass pair in the lamination. Default in positioning of glass pairs in PVB assembly will cause unwanted gapping between the glass sheets.
Extensive amount of separating powder will cause minor surface variations in the glass pairs inner surfaces reducing adhesion of the PVB and glass.
Poor washing water characteristics can affect the adhesion. Therefore the hardness of the water is monitored.
Gapping between glass pairs created during bending process is also potentially increasing the risk of defects. Gapping between the glass sheets created due to temperature difference between the glass sheets or mould issues will contribute to appearing bubbles. Gapping affect is very product dependent, however gapping < 0,8 mm is usually not considered to cause “bubbles”. In any case gapping is a contributing factor and together with other contributing factors will create circumstances where the “bubble”-defect is more likely to appear.

Lamination process conditions:

Lamination clean environment conditions; temperature, and relative humidity should be in suitable levels.
PVB storage should also maintain correct temperature and relative humidity.
Cold-Suction of the laminate is also in important role. The cold-suction time should be sufficient enough to relive almost all the air from the glass before the edges are sealed.
Usually most common reason for appearing bubbles is processing default in the very beginning of the heat treatment (hot-vacuum) enabling the glass edge to close too early.
The hot de-airing phases heating should be conducted gradually and evenly so that the glass edges do not seal before all air is relieved from the sandwich

Autoclaving process

The autoclaving process is the final real treatment process of a typical windshield that will define the lamination and end product quality. The process temperature and pressure curves can be controlled in great detail with modern autoclaves. Correct temperature and pressure set points are required to gain perfect results. With wrong set points the bubbles can appear days after the process.

HOW TO PREVENT BUBLES DEFECT?

Start with perfecting the pre-processing activities; cutting size, washing water quality control, bending process controls and quality. Follow to lamination activities controlling and measuring all the actions carefully: Releasing the PVB, careful positioning at assembly, sufficient cold-vacuum, controlled heating in hot-vacuum, correct actions with vacuum ring assembly and disassembly, and finally perform perfectly adjusted autoclave process with correct heating and pressure curves. When all production activities are well documented, staff performs according to production instructions and process parameters are repeated to perfection the identification of all variations is considerably easier. Safety Glass Experts provides services to study your current production activities performing a complete production Present State Evaluation. The evaluation will provide you complete, objective, external experts assessment and findings of your production current status. This information enables efficient approach solving any production defects, reducing waste, improving efficiency and line personnel know-how.

CONCLUSIONS

Processing conditions and used materials vary; therefore the followed process guidelines must be adapted to individual situations. Lamination process conditions must be well controlled to enable adjustments and identification of process variations when defects appear. Lamination process includes various minor details that potentially affect the results and results are linked with bending and pre-processing quality. Mastering these details is essential. Manufacturers suffering from any lamination difficulty will receive immediate solutions through our Remote Expert Service or on-site visits conducted by our experts.

Safety Glass Experts International Oy Ltd
Talviseisaus 2 D 8
FI-20400 Turku Finland
Phone: +358 400 979 300
Fax: +358 2 6518 2539
Email: info@sge.fi
Web: www.sge.fi
All graphics, photographs, and text appearing in this article belong to Safety Glass Experts International Oy Ltd. Redistribution or commercial use is prohibited without express written permission.

Photos: http://www.sge.fi
Last review: January, 2011

Glass Manufacturing)..Installing Channel Glass )

2011-12-15T14:34:00.000-08:00

A Popular daylighting system for interior or exterior glass walls, channel glass – such as Pilkington Profilit™, available from Technical Glass Products (TGP), Kirkland, Washington – provides a sleek, modern look for commercial or industrial buildings and homes. The glass is available in a variety of colors and textures with varying translucency, allowing for the passage of natural light without loss of privacy. This very versatile product can be installed vertically or horizontally and is available in lengths up to 23 feet, with either tempering or filming options available to meet impact safety requirements.

Because of the shape of the system, it can achieve very tight radiuses or can be used in serpentine applications. Intermediate vertical mullions are generally not required for vertical installations. Additional benefits include strong thermal performance, sound transmission control and adaptability to seismic code requirements.

Given the distinctive nature of channel glazing, some specific guidelines must be followed for proper installation. While not difficult or complex, the steps differ from more traditional glazing materials. The following guidelines provide general instructions for installing the product in exterior vertical applications. As with any specialty glazing, consult the supplier’s documentation for specific installation instructions, including procedures for horizontal or interior installations.

Preparing the Structural Opening
Prior to fitting, the supporting structure must be checked to ensure that it is square, plumb and in plane. The support jambs must be plumb. All surfaces should be checked to ensure that they are suitable for attachment and conform to the contract documents.

Measuring and Attaching Aluminum Frames
Measure the opening sizes and cut the head, sill and jamb sections. Miter or cope and butt the joints at the head. Cope and butt joints at the sill.

When measuring the frames, take into account the caulking bead clearance requirements and shim with the appropriate-sized horseshoe-type plastic glazing shim. Expansion properties of the aluminum frame should be taken in to consideration. Consult the supplier for specific details.

To attach the aluminum frames to the structure, place all fasteners approximately 12 to 18 inches on center (300 to 450 mm), or as recommended by the engineer of record. Fasteners should be located no closer than 6 inches from the corner joints. Couple frame members exceeding 24 feet in length with an expansion joint material as supplied by TGP. The specific type of fastener required depends on whether the supporting structure is concrete, steel or wood. Refer to manufacturer’s table for typical types of fasteners for the various applications.

At all head/jamb mitered corner joints, install aluminum corner keys and internally seal corners with approved silicone. At sill/jamb coped and butted corner joints, a screw boss is provided for corner assembly. After assembly, care must be taken to internally seal all joints.

Cut and fit plastic inserts into the head, jamb and sill sections of the frame. The vinyl inserts at the jamb should be fitted to the full daylight height of the opening and clip securely into the frame. The horizontal head and sill vinyl comes pre-cut to length to match the glass sizes and should be place intermittently (to match glass placements) in the sill and head of the frame. Finally, insert foam baffles into exterior weep holes.

Cutting channel glass Tempered glass and annealed (at customer’s option) glass can be provided cut to length. If glass is desired, or required, to be cut on site, the following procedures should be followed:
• Place the glass channel on a flat surface, preferably cushioned with felt or other suitable materials. With the flanges pointed upward, channel glass channels can be cut by hand or by special saw. There should be a minimum glass bite allowance of ¾ inches (20mm) for the head and jamb and ½ inches (13mm) for the sill. The flange cut (jamb) channels must have a bite or at least ¾ inches (20mm).

To cut by hand:
• Use a cutting template or straight edge to ensure a straight cut.
• Begin by scoring the flange furthest away, starting at the corner and working upwards; return back to the corner of origin and start the cut across the face of the glass and continue up the flange closest to the cutter in one continuous motion.
• Make a light glancing blow to the top edge of the flange opposite the cut on each side of the glass channel.
• Place the glass-cutting tool under the glass channel and apply light pressure to the flanges of the glass to snap it cleanly across the cut line.
• Ensure that the ends of the channels are free from chips, cracks or bad cuts (pay particular attention to the quality of the cut at the corners, there should be no notches or shark’s teeth in this area). Seam the ends of the glass with a disc or belt sander specifically designed for glass edging, taking special care to smooth any irregularities caused by cutting.

Installing Glass Before installation, clean all internal surfaces of the glass with an alcohol-based glass cleaner. Apply the 166 flange gaskets on each flange of every channel. The gasket application is most effective if the material is stored in a shaded location prior to installation. The gasket should be held ½ inch from the end of the flange on one end and flush with the edge of the flange on the opposite end (e.g. a 96-inch channel would have a 95-½ inch 166 flange gasket). The recessed portion of the gasket is always applied to the bottom end of the channel.

Installation of the glass channels can begin at either the center point of the opening or at either end. Shop drawings are typically provided to indicate starting point and number of channels to be used for a specific elevation. Consult TGP for the size of joint between the channels. Typically, these joints are 1/8 inch, but the size can sometimes vary depending on the requirements of the contract documents. The jamb channels at either end of the glazed opening must have a minimum glass coverage of ¾ inch (20mm), or as otherwise specified. The flange cut/jamb channels are typically inserted prior to the installation of the last full-size channel.

Pocket glaze the channels by inserting into the plastic liners located in the head and then lowering the glass down onto the corresponding plastic insert located in the sill. Suction cups are typically used to aid with this procedure. To ensure that the spacing between the channels is consistent, place 1/8-inch plastic shims at the head and sill of each channel as it is being installed.

Sealing the System
Prior to the application of any sealant, check glass joints for consistency and plumb. Install special channel glass shims across internal and external joints and seal all glass-to-glass and glass-to-aluminum joints with approved silicone sealant. For 1/8-inch glass-to-glass caulk joints, it is not necessary to use backer rod. The caulk joint at the perimeter of the frame should be packed with the properly sized backer rod and the approved, specified sealant should now be applied to the perimeter joint.

Although the installation process for channel glass such as Pilkington Profilit involves some specific steps and techniques that differ from standard glass, experienced glaziers can install the product without hassle using these basic guidelines.

By Ms. Tysen Gannon and Mr. Peter Alberini
Tysen Gannon is the product manager for Pilkington Profilit, a channel glass offered by Technical Glass Products (TGP), Kirkland, Washington. Peter Alberini is the technical sales manager for TGP. www.tgpamerica.com 1-800-426-0279

Glass Manufacturing)..Glass Tempering: Issues and Concerns)

2011-12-15T14:32:00.001-08:00

Tempered glass has traveled a long distance, since inception of its production by vertical method, transition to sophisticated horizontal tempering equipments and now tempering of the most sophisticated glass types and designs, but this journey was not as smooth as it sounds, glass processors faced a plethora of problems during this transition stages (and a chunk of them are still facing). We will examine various issues related to glass tempering in this article.

Typical problems occurring during the heating process
Heating is the most typical stage of glass tempering; a lot depend on this stage to bring out the product of high standard. Quality of tempered glass is very much influenced by the heating process used in the furnace. Non-uniform heating causes deformation of the glass in the quenching process. The most common problem is caused by rapid heating of the lower surface of the glass due to conduction of the heat from the ceramic rollers. The resulting expansion of the lower surface bows the glass edges upwards and the glass moves on the rollers like a boat, resulting in damage called “centre line haze”. Other non-uniform heating results include overheated edges, which cause deformation known as bistable saddle and may result in breaking of edges during the heating process.

Coated Glass- A challenge for processors
The continuing move towards better energy efficiency in buildings is providing a strong push for the application of coated glass. Sputtered (off-line) low-E or solar control coatings are becoming standard in countries where climates are sunny the whole year or cold in winter and warm in summer. For glass processors with traditional technology this has meant a need to adopt somewhat slower tempering processes because of longer heating time. At the same time processors are hard pressed to boost their production capacity without compromising the aim for outstanding quality with all glass types.

Problems are far more severe when processing coated Low-E and reflective glasses. In addition to the problem of conductive heat from the rollers, the coating on the upper surface of the glass reflects the radiation from the upper heating elements, whereas the lower heating elements heat the glass twice, because the radiation from below penetrates the glass and is reflected back from the coated upper surface.

Uneven heat distribution may in turn occur when variable loads are run into the furnace one after another. When it enters the furnace, the cold glass absorbs the heat from the roller bed. Due to thermal inertia, the previous glass leaves the area where it has been oscillating cold, and consequently the next batch enters a roller bed which may have excess heat on the edges and a cold area in the middle. This can be partly compensated by adjusting the cross-sectional heat so that it only heats the loaded area.

Non-uniform heating may also result in cold streaks in the direction of the glass. Here the uneven temperature caused by the resistance elements gives rise to iridescence which is most clearly seen in a polarisation test, but may also be visible to the naked eye.

The glass itself may also cause problems in heating. Radiant heat is differently absorbed in printed areas of the glass than in plain glass. The same applies to shaped glass lites.

These problems may adversely affect the shape or flatness of the end-product, its optical qualities or the surface of the glass. Uniformity in heating is achieved by compensating the temperature difference by profiled heating; hence the key importance of having the option of profiled heating.

Convection for coated glass and speed
"Heat is transferred to the glass in three different ways: by radiation, conduction and convection. Regardless of the type of furnace, these three ways of heat transfer are always present. They can be further analysed into the following parts:

1. Radiation

Direct radiation

Indirect radiation

2. Conduction from the ceramic rollers .

3. Convection – It can be classified in three categories.

Natural convection.

Assisted convection by using compressed air.

Forced convection.

The extent to which each of these contributes to the heating process depends upon the type of furnace, the type of glass and the phase of the heating process. In traditional furnaces the main source of heat transfer is conduction from the rollers (in the initial phases of heating) and then radiation. In full convection furnaces, the heat predominantly transfers through convection. Convection must play a major role if coated glasses are to be heated effectively.

In order to overcome these problems, machinery manufacturers are on the constant lookout for new solutions that are based on the use of convection. Convection is seen as a must for any production line where coated glass is made. As well as helping to improve the quality of the end product, convectional heating has another important advantage over radiant systems, namely heating speed.

Tempering systems based on radiant furnaces heat up the float glass at speeds of about 40 sec/mm of thickness. With convectional heating, heating times can be reduced to 25-30 sec/mm of thickness, increasing output and productivity by up to 40-50%! As Low-E and other coated glass types require much longer heating times in a radiant furnace, productivity is increased even more. "(quoted from the article Convection gives the advantage, by Juha Karisola)

Disadvantages of Forced Convection
There are three negatives of forced convection tempering. First, it is difficult to control the convection currents inside the furnace and requires proper design in the equipment and operator skill. Secondly, forced convection tempering consumes about 10% more electricity due to indirect heating through air-jets. Additionally, forced convection machines are also more expensive to buy as well as maintain.

Edge Quality and Toughned Glass Edge quality plays an important role during fabrication, shipping and installation of float glass products in automotive and architectural applications. The tempering process induces transient tensile stresses during early portion of tempering both on the surface and edges of float glass. Depending on the temperature and viscosity of glass these stresses may or may not be relieved by viscous relaxation before the permanent beneficial stresses begin to build in. In view of good quality of float glass the temporary tensile stresses can be sustained by the surfaces but not necessarily by the edges. Indeed, the edge quality which depends on the type of edge finish is inferior to that of tin and air side surfaces. Consequently, premature fracture may initiate at these edges if the combination of temporary tension and flaw severity is unbearable. Such a premature breakage occurs when the glass temperature is not high enough and the quench rate is too high. Glass breakage during tempering cuts down productivity and at the same time reduces glass quality.

Chinese Processing Machinery- Boon and Bane
No doubts that China is the most vibrant economy of the world, this day and Chinese glass industry is giving sleepless nights to the glass producers and processors worldwide, but alas this vibrant economy and its machinery producers have failed significantly when it comes to glass tempering machines, you can count on your fingers a few quality machine manufacturers ( I bet you wont exhaust even one hand ), but ironically Chinese tempering machines are mushrooming in every corner of the world, be it the most sophisticated market of North America , Western Europe or the developing countries like India, Vietnam or African countries. These Cheap machines are finding the market in most unlikely places, I mentioned this matter to a few glass processors in my country and invariably the answer was lower initial cost, however none of the processor mentioned that there is a problem with quality (though the plant managers have a different story to tell).

One doesn’t have to look very far, the way tempering machine manufacturers mushroomed in China, in a very short span of time tells the story itself. Look back five years back, there were five manufacturers of tempering machines in China, today you can count three dozens, and majority of them with hardly any R & D and selling at a cost nearly one third of European manufacturers . Though the lower initial cost has helped a lot of processors and new processors have bought these machines and has added to the volume of processed glass but in majority of the cases at the cost of quality. In my country has high as 75% of the tempering machines used are of Chinese origin.

By Seema Gahlaut

article source
http://www.glassonweb.com

Glass Manufacturing).Glass-Ceramics )

2011-12-15T14:32:00.000-08:00

Ordinary glass is non-crystalline. Glass-ceramics however, are manufactured through the controlled crystallization of a specially formulated glass.

For the production of glass ceramics, a high density of crystalline nuclei is generated in the molten glass, either by the droplet phase-separation mechanism or by the addition of nucleating agents such as titanium, zirconium, or phosphorus pentoxide. After the nucleation process is carried out for a predetermined time, the crystals are allowed to grow to maturity at an increased temperature. It is also named crystallite glass.

Glass-ceramics are useful in thermally hazardous conditions. This 'glassy' material contains crystalline lattices, which give it specific properties. Glass-ceramics are commonly used in thermally hazardous environments, such as in cookware. With lower density like aluminium, glass-ceramics are also used in high precision equipment such as high speed cutting reamers and to cover radar appliances on rockets because some types have the property of near-zero expansion. Some others have a high physical strength and can be machined like metals.

Good resistance to erosion and pressure, as well as excellent hardness, also makes glass-ceramics widely used in industrial purposes. Moreover, glass-ceramics are very good electrical insulators.

article source
http://www.glassonweb.com

Glass Manufacturing)..Furnace Technology - development standstill)

2011-12-15T14:31:00.001-08:00

The global recession has created severe problems for the automotive industry. Since the rapid downturn, car windscreen original equipment manufacturers (OEMs) have been forced to lay off employees and even close factories. Warehouse stocks of passenger car windscreens do not need replenishing; furthermore, the weak automotive replacement glass (ARG) market, along with decreasing OEM orders, are not offering enough demand to keep larger production lines in operation. The recession has caused a decrease in the demand of personal vehicles, growing demand for public transportation. Also the need for special vehicles which are used to harvest crops and manage forests has remained steady. These factors ensure the relative stability of this segment of the safety glass market.

A brief review of bus and special vehicle windscreen manufacturing techniques will show that, despite the continuing need for the glass products, the industry’s production technology has not been significantly improved in a decade. There are considerable opportunities to advance the state of the art.
Production Technology
Gravity bending is the only available method for larger, complex, bus and special vehicle windscreen manufacturing. It is amazing, that heat is the most important factor producing these windscreens efficiently, but the technology is still infact very undeveloped. Today these windscreens are produced mainly in infrared-radiation-heated single-chamber and serial furnaces. In the past, furnaces were equipped with longer heating elements controlled in single rows; currently, the heating element rows are divided into three or even six individually controllable parts which enable more accurate heating. The first automatic serial furnaces were introduced in the 1980s. The furnaces produced in the new millennium are highly automated, featuring temperature-controlled bending with multiple pyrometers, heat balancing, adjustable heating elements and power rates, bottom heating, temperature-controlled glass support, and mold/glass movement controls. Most of these technical features were invented before 2000.

Automation of basic furnace functions frees the operators to concentrate on glass loading and other tasks. It also improves efficiency by reducing the work force and decreasing human errors that might affect yield. For example, modern furnaces include a glass center support system, probably introduced during the 1970s, that replaced an outmoded “aluminium stick” system built into the mold. The newer support system is mounted into the mold wagons to reduce pre-bending breakage. Originally manually controlled, the support system’s movement is now determined by the user interface temperature-based settings. Automation allows the operator to control the glass bending according to visual observation; the glass wing can be bend to into its final form only after it reaches the optimal temperature. Bending with automated controls is probably the only viable method for forming complex bus and special vehicle windscreens without any external manipulation.

Furnace Characteristics
Single-chamber furnaces remain the most common manufacturing units for several reasons. Investment costs are low compared to those for serial furnaces; one-hour cycles accommodate short production series with frequent mold changes; construction facilitates multiple views into the heating chambers and improves ergonomics for operators who can work from a standing position; and simple construction and mechanics guarantee reliable operation. However, single-chamber furnaces definitely have drawbacks. For example, production capacity is small; on average, these furnaces produce only five to eight parts per eight-hour shift. To facilitate greater production capacity, several single-chamber furnaces must be utilized, requiring extensive floor space. In contrast, serial furnaces require less floor while offering similar production capacity than multiple single-chamber furnaces. Single-chamber furnaces are also not energy-efficient. The heating elements require the same amount of energy for each production cycle, while the hot air released by the cooling process is wasted. Compared to single-chamber furnaces, serial furnaces are much more energy efficient since the lower track’s cooling energy can be harnessed to heat the glass on the upper heating track and also the heat mass left into the chamber can be utilized, in continuos serial production.

Both single-chamber and serial furnaces are produced with open and closed wagons. In the single-chamber furnaces, a closed wagon provides the option of pre-heating, assuming a special preheating section is available. This enables shorter cycle times because while the bending chamber is busy, the loaded wagon can be preheated. The disadvantage of a closed wagon is that it often limits working space for loading, unloading, mold tuning, and maintenance during operations. In contrast, an open wagon allows free access to the wagon platform during the loading actions. The windscreen cooling rate is sometimes faster with an open wagon. Due to its construction, an open wagon can also perform better from the windscreens edge compression qualities, since the glass edges are exposed to cold air flow immediately after the final bending. This air flow coming from the bottom of the glass can eliminate possible delamination problems.

Production Problems
Although furnaces in use today are equipped with modern automation, the process-related problems associated with the older, fully manual furnaces persist. For example, variation in the final product is unavoidable, especially with larger windscreens, since repeatability depends completely on operator actions. The final bending of the large windscreens is still handled manually by an operator controlling the furnace with the user interface. It is very difficult to reproduce the same center sag and edge size when these are estimated visually from a distance and with a limited view into the furnace. Glass temperature can be used only as a reference, since the bending conditions still vary.

Another enduring processing issue involves the practice of “sticking” as a way to externally manipulate the glass into its final shape. This method leaves marks that appear as dips, black stripes and lines in the inner surfaces of the windscreens. “Sticking” method enables production of more complex shapes with simple mould tooling and furnace technology and amazingly is in common use by leading European manufacturers. A while a go other manufacturers were simply not able to produce large complex shapes, but this is now changing. New companies in the industry are not using such a method, instead they are determined to produce all the glasses with out any external manipulation. This means careful employment of all the up to date furnace systems and superior mould technology.
Development Opportunities
Future development should advance the state of the art by improving process controls and making the process further automated leaving only the loading, minor process supervision, process fine tuning, and unloading to the operators. Further research should be conducted with the goals of ensuring energy efficiency, increasing output capacity, improving quality, and addressing ergonomics issues. Windscreen manufacturers’ internal research has led to innovations in mold construction and tooling, process controls, and glass shaping, making it possible to develop and produce the windscreen for the vehicles available today. Recently, some interesting trials have been conducted with high frequency microwaves (HFM), which allow both faster and more precise localized heating of glass. It will be interesting to see what the future furnace technology will offer.

article source
http://www.glassonweb.com

Glass Manufacturing)..Extinguishing the Myths of Fires, Sprinklers and Glass)

2011-12-15T14:31:00.000-08:00

Fire sprinklers in a glazing publication? The topic may seem unrelated to the glass industry, yet in reality, what you know about sprinklers may significantly impact the way you glaze a building for fire safety and protect you from liability issues. There are essentially two ways to provide fire protection in a building: active systems and passive systems. Active systems, such as sprinklers or fire extinguishers, rely on components or people to move into "operation mode" when a fire starts. Passive systems are made up of components such as fire-rated glass that offer a degree of fire protection with no activation required.

Currently, there is a great deal of debate as to how active and passive systems should interact. Is one method preferable to another? Should they be used together or separately?

It is well documented that sprinklers, when working properly, can provide life- and property- saving benefits during a fire. And systems that incorporate both sprinklers and fire-rated glazing materials have tested positively.

However, some fire sprinkler manufacturers are now suggesting that fire-rated glazing is unnecessary if a sprinkler system is in place. Their theory is that if a fire starts, the sprinklers will activate and bathe the glass surface with water. This will keep the glazing system in place, where it will continue to offer fire protection. Consequently, they have begun recommending the use of tempered and heat-strengthened glazing materials in conjunction with their sprinklers.

Is this practice safe? Closer examination will show that it may be based on dangerous and unrealistic assumptions.

Fire-Rated Glass and Fire Protection

Fire protection is a critical issue in the United States. In 1996, a fire was reported every 15 seconds, a fire injury every 20 minutes and a fire-related death every 2 hours, according to the National Fire Prevention Agency (NFPA). Financial losses caused by fires reach nearly $9 billion each year.

A long-established principle for fire protection in buildings is "compartmentation," the use of physical barriers (such as fire walls and fire-rated glass) to limit the spread of fire and smoke. According to the NFPA 1994 Life Safety Code Handbook (section 6-1.1.1), "lack of compartmentation and rapid fire development have been primary factors in numerous multiple-fatality fires." Building codes attempt to achieve compartmentation by requiring the use of products that meet specific test criteria, such as fire-rated doors, walls and glazing materials. These products are tested at independent laboratories, and if appropriate, receive a listing for a designated period of time.

Specific test criteria have been established for fire-rated glazing materials. Fire-rated glass is installed in a door or window frame system and mounted in a test furnace. Fire near the surface of the glass creates temperatures of nearly 1,000 and 1,638 degrees Fahrenheit at 5 and 45 minutes, respectively (as a reference, standard tempered glass cannot withstand continuous temperatures in excess of 500 degrees Fahrenheit). This test is designed to simulate a real fire. For a successf

ul test, fire and smoke are not permitted on the side of the glass away from the fire.

Glazing tested for more than a 20-minute rating undergoes a fire hose stream test. The water impact from the fire hose tests the structural integrity of the heated glazing, frames and door components as well as the ability of the assembly to withstand thermal shock without collapsing. Thermal shock can occur in a fire when water from sprinklers, fire extinguishers or fire hoses impacts the assembly. The glazed assembly must be able to withstand the fire hose stream test without creating openings for passage of fire and smoke. If the glazing and other materials in the assembly pass the fire and hose stream tests, they can be relied on to achieve the desired compartmentation.

Sprinklers & Non-Fire-Rated Glass

But what about non fire-rated glass? If sprinklers are installed nearby, isn’t that adequate fire protection?

The answer may be a resounding "no." True, some tests indicate that non-fire-rated glass will remain intact if a fire does not originate near the surface of the glass, if the sprinklers and supporting systems are operational and function early in the fire, and if they completely and continuously bathe the surface of the glass.

However, other tests indicate that fires occurring near the surface of the glass cause heat stress in the glass, which may then break and fall from the framing system even if the sprinkler operates properly. Since it is nearly impossible to predict where a fire will begin, it is unrealistic and even dangerous to assume that it will occur far from the glass surface.

The "Hospital for Sick Children" test in Toronto supports the above findings ("Fire Resistant Wall Assemblies with Glazing," SFPE Bulletin, July 1987). A fire test facility was developed at Canada’s National Fire Laboratory to determine the fire resistance of non-fire-rated window assemblies protected by automatic sprinklers. The source of heat was a propane burner located across the room from the glazing (approximately 7 feet from the glass surface). Sprinklers were carefully positioned to ensure uniform water coverage. In eight tests conducted with sprinklers on the fire-exposed side of the glass, the sprinkler activation time averaged only 32 seconds. When using tempered glass, the glass "remained intact for the duration of all tests in which sprinklers were located inside the burn room."

These tests indicate that sprinklers activated early by a large fire occurring away from the glass surface, before stress builds up in the glass, may allow the glazing assembly to stay in place for the duration of the 2-hour test.

The results of these tests are limited, however, because some test conditions were modified and the fires were never initiated near the glass surface. In short, the tests did not simulate a "real world" fire situation. For example, the water flow rate from the sprinklers was adjusted if dry spots formed on the fire-exposed face of the glass. In real life, such dry spots on the surface of hot glass cause heat stress and can be a principal cause of glass fracture.

For a sprinkler and glass assembly to operate successfully, it is vital that the sprinklers activate early, covering the glass completely and continuously. The dry spots in the test indicate that the glass surface was not completely covered with water. Adjusting the sprinkler water flow to cover these spots may artificially prolong the endurance of the glass. In a real fire, no one would be available to "adjust" the water flow.

Furthermore, and critically important, the heat source was located several feet away from the glazed assembly-- the most ideal situation for the glazing to survive. In real life, fires can and do ignite near the surface of the glass.

Another factor to examine is the sprinkler activation time. The test used special "quick response" sprinklers that responded two to three times faster than standard sprinklers. The sprinklers also activated early due to artificially high temperatures in the room, thus cooling the glass faster than normal. In addition, the sprinklers were located on the side of the glass exposed to the fire.

The authors of "Fire Resistant Wall Assemblies with Glazing" point out some of these test limitations. They note that "the location and response time of the sprinkler must be such that activation will occur before the glazing reaches critical temperature levels....Should sprinkler activation be delayed so that the temperature of tempered glass is in the range of 250 C. (approximately 482 F.), glass failure could possibly occur."

In 1995, Factory Mutual Research Corp. observed tests to determine whether a non-fire-rated window assembly and sprinkler "system" could provide protection equivalent to that of a fire-rated assembly. Using specially designed sprinklers, researchers found that tempered or heat- strengthened glass systems survived if the fire started far away from the glazing (approximately 8 feet) and if the sprinklers activated very early.

However, in subsequent tests in which the heat source was placed adjacent to a non-fire-rated glass system, the glass failed in less than 5 minutes. As a result, Factory Mutual declined to offer a passing grade to the system for use in general fire-rated locations.

Tests were conducted at Lawrence Livermore National Laboratory (LLNL) in 1986 to specifically examine how well non-fire-rated (tempered) glass and sprinklers would perform when the fire source was close to the glass surface. Two fires (250 kW and 40 kW) were used. In the test using the large fire, the sprinklers activated early and the glazing remained intact. But both tests using the smaller fire resulted in glass fracturing and falling from the test assemblies in less than 4 minutes. In other words, the glass failed before the sprinklers even activated.

What the LLNL tests seem to indicate is that tempered glass may perform adequately when exposed to relatively large fires that cause the room temperature to rise fast enough to fuse (activate) sprinklers before high stresses can be generated in the glass. However, when a fire is concentrated in an area near the glass surface and is not large enough to activate sprinklers early, sufficient stresses can be generated to shatter the glass. Who can rely on fires always being large enough to activate sprinklers before the glass is thermally stressed?

Similar tests were conducted at Underwriters Laboratories (UL) when a sprinkler manufacturer wanted to test its specially designed sprinklers with a non-fire-rated glazing "system." When the heat source was placed close to the glass, the glass failed in three of the four tests. In two of those tests, the sprinklers activated first, but the glass could not withstand the "thermal shock" of water hitting the hot surface. The test report states that in all three tests, "...large pieces of glass fell to the floor" after an average of only 4 minutes. UL did not give the manufacturer a listing for the sprinkler and glass wall syst

em.

In support of a sprinkler and non-fire-rated glazing system, some suggest that fire could be kept away from the surface of the glass by using a 36-inch-high pony wall (Canadian Construction Materials Centre Evaluation Report, CCMC 12752-R, June 24, 1996). In this report, the CCMC reviewed UL test results regarding the Central Sprinkler’s Model WS Sprinkler System. It concluded that this particular sprinkler model complies with CCMC’s Technical Guide for Sprinkler-Protected Glazing Systems, Masterformat 15335, dated April 12, 1994, if used in accordance with the limitations and conditions stated in the report.

The pony wall indeed has limitations. First, it does not prevent flammable objects such as desks, file drawers, coat racks, etc., from being placed near the glass. Second, the window "sill" created by the pony wall is an attractive location for storage of flammable materials such as books and papers. Some sprinkler installation instructions state that "all combustible materials shall be kept 2" (50.8mm) from the face of the glass." After occupants move into a building, not only is it difficult to enforce this provision, but it is also unrealistic to think they will not place flammable objects near the windows.

How do curtains, blinds or other window coverings affect the performance of sprinklers? When these materials are placed between the glass and sprinkler, the water is unable to cool the glass, thus causing the glass to fail early on. Recognizing this fact, one manufacturer states in its literature: "Blinds or curtains must not be between sprinkler and glass." But that is not practical.

Sprinkler heads can be located up to 12 inches away from the windows they are trying to shade or cover, while blinds and curtains in offices, schools, hospitals and other commercial facilities are generally located very near the surface of the glass. And who is to ensure that subsequent building tenants will be aware of this critical warning? Again, this is unrealistic and unenforceable.

Sprinkler Limitations

Another concern with a "sprinklers only" approach to fire protection is that protection depends on the system operating. If the sprinklers don’t operate, fire protection literally goes out the window. Fire-rated glazing, on the other hand, is a passive system that provides protection without requiring any other system or activity.

Sprinklers are generally reliable, but they are not infallible. Last summer, a headline in the August 13, 1997, edition of USA Today read: "Widely Used Fire-Sprinkler Often Fails." After a particular brand of sprinkler failed to operate properly during some fires, UL conducted further tests. In those ongoing tests, the newspaper reported that this particular sprinkler model had a 31 percent failure rate. This reminds us that while sprinklers usually are reliable sources of fire protection, they can and do fail. Therefore, it is not a good idea to rely solely on the proper operation of sprinklers with a non-fire-rated system.

Confusion also exists concerning how sprinklers are listed. Some manufacturers imply in their literature that if a sprinkler head has a laboratory listing when tested by itself, it will also provide adequate fire protection when combined with a non-fire-rated glazing system. Tests seem to prove that this is not always the case.

Safe Solution

There is no question that sprinklers offer a valuable line of defense in fire situations. Sprinklers operating early in a fire have proven to reduce damage from fire and smoke, and they can reduce the amount of heat transfer through the glass by as much as 90 percent. However, combining sprinklers with non-fire-rated glazing provides questionable fire protection at best. Too many conditions must operate perfectly for this system to work consistently-and an actual fire acts differently than one under laboratory conditions. Also, fires originating near the surface of the glass can cause the glass to collapse within minutes even if the sprinklers work perfectly.

If a client requests that you supply tempered or heat-strengthened glass in lieu of fire-rated glazing because sprinklers are being used, remember that you could be held liable. Be sure to ask these important questions:

* What carries the listing-the sprinkler and glass "system," or only the sprinkler head?

* Can the risk of a fire close to the glass surface be eliminated?

* If the sprinklers fail, will the glazing offer any type of fire protection?

* Can the glass withstand thermal shock if the sprinklers come on after a fire starts?

When it comes to fire protection and life safety, too much is at stake to leave things to chance. The best way to provide fire protection is to use sprinklers in conjunction with listed fire-rated glazing materials that have passed the fire hose stream test.

Jerry Razwick is president of Technical Glass Products, Kirkland, Wash., factory agents for a variety of fire-rated glazing products.

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Glass Manufacturing)..Furnace Technology - development standstill)

2011-12-15T14:30:00.000-08:00

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Glass Manufacturing)..Explore glass chemical composition )

2011-12-15T14:29:00.002-08:00

Almost all commercial glasses fall into one of three basic categories. These categories are based on chemical composition. There are numerous compositions, all distinct, even if fused silica is always present.

Glass is by definition an amorphous solid material made by fusing silica with a basic oxide. Glass is called amorphous because it is neither a solid nor a liquid but exists in a vitreous, or glassy, state. Architectural glass is made from three principal raw materials, easily found in nature: silica, lime and sodium carbonate. The secondary materials are used to give special properties to glass or to facilitate the glass-making process. By mixing secondary materials with the basic raw materials in the right percentage different types of glass are obtained, which can be categorized into three broad categories:

Soda-lime glass:
This is the most common commercial glass (90% of total production), and also the least expensive. The chemical and physical properties of soda-lime glass are the basis for its widespread use. Soda-lime glass is primarily used for bottles, jars, everyday drinking glasses, and window glass. It usually contains 60-75% silica, 12-18% soda, and 5-12% lime. Soda-lime glass is resistant neither to high temperatures nor sudden thermal changes, nor to corrosive chemicals.

Lead glass:
As the name already indicates, lead glass has a high percentage of lead oxide (at least 20% of the batch). Lead glass has a relatively soft surface, making it especially suited for decorating using grinding, cutting, and engraving processes. This glass will not withstand high temperatures or sudden changes in temperature.

Borosilicate glass:
The third major group, borosilicate glass, is any silicate glass having at least 5% of boric oxide in its composition. It demonstrates greater resistance to thermal changes and chemical corrosion. Thanks to its properties, borosilicate glass is suitable for use in industrial chemical process plants, in laboratories, for ampoules and vials in the pharmaceutical industry, in bulbs for high-powered lamps, etc. Borosilicate glass is also used in the home for cooking plates and other heat-resistant products.

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Glass Manufacturing)..Advances in the manufacturing of toughened laminates )

2011-12-15T14:17:00.001-08:00

The last three years have seen an increase in demand for toughened laminates with several high profile projects requiring both the structural strength and integrity that only a toughened laminate can provide.

Mr. John Gilleeney, Technical Director - Manufacturing of the South African company AGI takes an interesting approach to toughened laminates in his GPD Case Study. ?My case study covers two projects using toughened laminate glass. The first project was for balustrades on the Nelson Mandela Bridge in Johannesburg, and the second project was for the gorilla enclosure at the National Zoological Gardens in Pretoria,? he explains.

John Gilleeney will give details on the lessons learned, advances made and the significant reduction in quality losses and, of course, recommendations based on hands-on experience.

The steps to better yield
The first step for the successful manufacture of toughened laminates is to cut and process the glass as accurately as possible. This is especially important when the toughened laminate panel has holes, as was the case with the glass panels used on the Nelson Mandela Bridge: ?Any deviation in the position of the holes, results in the dilemma whether to line up the edges or the holes, and often a compromise has to be made. Good processing also reduces furnace losses, which is important when trying to produce matched sets.?

Step 2 is to toughen the glass as flat as possible. Some deviation from absolute flatness is inevitable, hence the need to produce matched sets so that the glasses can be ?nested? together.

Some of the factors affecting the direction or degree of roller wave are common knowledge, e.g. glass orientation through the furnace, furnace settings, glass type and substance, and the influence of glass coatings. ?We learned from our recent experiences that there are other factors which, while being obvious, are not always taken into account. For example, the loading position of glass on the furnace bed plays a role. My presentation will discuss these other factors and how we significantly reduced our losses during the production of the Mandela Bridge laminates.?

The third step is the assembly of the laminate. AGI found that it was preferable to use a single layer of PVB. ?For this reason, where possible, we have changed from using two layers of 0.76mm to a single 1.14mm Butacite interlayer.?

For de-airing AGI use either a nip roll or a vacuum bag process. ?The nip roll has a lower manufacturing cost but a higher risk of producing a reject. The higher manufacturing cost of vacuum bagging is justified for multi-laminates or where the laminate does not have a symmetrical construction.? AGI used nip roll de-airing for the Mandela Bridge, while for the gorilla enclosure they provided matched sets of 4 x 10mm toughened glass panels to Rene Turck and Associates, a company that specialises in producing special laminates by a vacuum bag de-airing process. They produced 20 large panels (3000mm x 1100mm) without any losses.

?The autoclave cycle also plays an important role and we have benefited from putting a step into our cycle, which maintains a lower pressure until a pre-determined temperature has been reached. Then the cycle continues to reach the maximum temperature and pressure. This has reduced the incidence of edge bubbles due to blow in.?

A mixture of good elements
Having once participated in the GPD, the conference concept was familiar to John Gilleeney: ?I have also been following the glassfiles.com website, where many of the discussions have dealt with problems related to the production of toughened laminates. That made me think that a case study built on our project experiences would attract the interest of glass processors.? He points out that hearing what actually happens in the factory may benefit scientists, too. He also advocates including both scientific and practical presentations in the conference program: ?A good mixture of presentation with different views improves mutual understanding between the various parties in the glass business.?

AGI BRIEFLY
AGI is the holding company of a group of South African and international companies that manufactures glass and aluminium systems and distributes, as wholesalers, a comprehensive range of both value-added glass products and aluminium systems to a world-wide customer base.

AGI (formerly Africa Glass) was established in 1980 by its present Chairman, Alex Barrell, and has developed from an 80m² site in Johannesburg into an organisation that operates from 54 sites located throughout Southern Africa, in the United Kingdom, Germany, Denmark and the United States of America. Today the Group employs over 1,500 people and has supplied markets in more than 40 countries.

Since the purchase of the first toughening furnace in 1995, AGI has experienced a steady increase in demand; in 2001 two additional furnaces came on stream with a fourth furnace being added in 2004. AGI is now the largest manufacturer of architectural toughened glass products in Southern Africa. AGI?s involvement with PVB laminates is relatively recent. Since the acquisition of their first autoclave in 2001 their market share has grown, making them the second largest manufacturer of architectural PVB laminates in Southern Africa.

The synergy between the glass and aluminium divisions is personified by the successful development of a hurricane resistant sliding glass door, which has passed the stringent Dade County, Florida test for hurricane resistant glazing.

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Glass Manufacturing)..Treatment Technologies)

2011-12-15T14:17:00.000-08:00

GlassOnWeb dedicates the weekly focus to a technical article titled "A Sealed System for Heatable Glass - A New Product; the article is written by Prem Boaz, President of Glass Products Consulting LLC in Port Orange, Fla..

THE NEED FOR A NEW PRODUCT STRATEGY

In 1967 when the heated back wind shields were launched the following conditions were in place:

The price of silver was $3.00/oz. (Now about $40.00)
The ceramic frit binding the silver was high in lead
The volatile organic compounds emitted during the process was not yet an issue
The electrical terminals were soldered with an alloy high in lead ( expensive indium replaces lead)
Laminated back wind shields were offered only on high priced cars.

New Product Description

Copper replaces % 83.0 of silver.
Soldering electrical terminals and related use of indium is eliminated.
PET film is the carrier of the heating elements.
Fabrication process uses established production processes such as flexography roll to roll printing , nano silver material and roll to roll electroplating.
Grid line width as low as 0.2mm is feasible.

HEATED GLASS CONSTRUCTION

Heating grids and busbars are printed on a PET film using Nano silver as the bait layer.
The electrical conductance of the grid is then built up to a required value with copper using an electroplating process.
The PET is then included between two PVB films and this assembly is laminated between two glass panels.
PET film is prepared with conductive grids and busbars as in (1) along with radio antenna if required
An obscuration non-conductive black band along the edges is added as a second print.
The heating grids are printed on a PET film as in (1) and this film is laminated to a glass panel with a PVB film on the grid side. This is applicable to heated/insulated glass units where the PET is on the inside facing a low-e coated surface.

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PROCESS STEPSStep 1. The PET film is passed through a roll to roll Flexography or screen printing process where the required grid pattern is printed using Silver Nano particles in specially prepared water base.

Step 2. The PET film is then passed through a continuous Copper plating process. The thickness of the copper is controlled to provide the required electrical conductance of the grids.

Step 3. The templates are cut off from the continuous PET roll.

Step 4. The electrical contact tabs are located in place with a dab of conductive epoxy. The purpose of the epoxy is to keep the plasticizer from PVB seeping in between the tab and the busbar.

Step 5. The assembly is completed with the layers of PVB.

Step 6. The completed assembly is mated with the glass panels and autoclaved.

SEALED GRID HEATING SYSTEM
(THE THRE BASIC SYSTEMS DESCRIBED HERE)

Heated/insulated glass units
Electrically heated automotive windshields (windshield wiper rest area)
Electrically heated laminated rear windshields

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A full de-icing is preferred in the wiper rest area to prevent the blades from scraping over ice dams. For this reason the grids are placed 0.25” apart.
Grid width is kept at .005” for aesthetic reason.

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The grids are kept apart by 1.25 to 1.5 inches to heat a large area with minimal energy. Partial clearing is still adequate for rear view.

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CONCLUSIONS

With the reduction in dependence on Silver metal, the heated windshield (wiper rest area) is now an economically feasible option.
The laminated back windshield with it’s inherent advantages such as “break in” resistance, noise reduction, etc., is more attractive since the cost of silver has been minimized.
A low cost option of heated/insulated windows is now available.

The author Prem BoazPresident of Glass Products Consulting LLC. Specialist in ceramic coatings on Automotive windows and other related issues as below: o Windshield retention to car body. o Ceramic-paint specifications and automotive requirements. o Decorative as well as functional applications o Ceramic material as well as application process ( Screen printing) Specialist in Electrically heatable windows and related issues as below o Conductive ceramic compositions o Screen print applications o Design to meet car requirements o Specifications and test methods o Terminal design and attachment techniques o Solder process specialist.

Glass Manufacturing)Architectural Glass: 6 Glazing Technologies to Consider )

2011-12-15T14:16:00.000-08:00

Glazing can take several forms in a building application including curtain wall, operable windows, storefront, skylights and architectural glass. And while glazing has myriad properties that would be essential to consider from a building occupant, owner or architectural perspective, the ones called out specifically in energy codes and standards are u-value (also commonly referred to as u-factor) and solar heat gain coefficient (SHGC).

Essential Glazing Factors

U-value represents the thermal transmittance, or heat transmission through a unit area of material or construction assembly and the boundary air films, induced by unit temperature difference between the environments on each side, measured in Btu/hr-sq ft-°F.

SHGC is the ratio of the solar heat gain entering the space through the fenestration area to the incident solar radiation. Solar heat gain includes directly transmitted solar heat and absorbed solar radiation, which is then reradiated, conducted, or convected into space. The fenestration area (at least as far as ASHRAE 90.1 is concerned) refers to the total area measured using the rough opening and including the glazing, sash, and frame. So when the standard calls out an assembly maximum, it’s not just center-of-glass values we need to take into consideration.

Glazing and Cooling Loads

Oftentimes, decisions regarding building glazing can contribute upwards of 20% of the required cooling load of a building. In buildings where energy-efficiency is critical, both increasingly strict energy code requirements and green building rating systems, are forcing the specification of high performance envelope components to becoming more and more critical.

Therefore, specific window performance information (such as u-factor and shading coefficient/solar heat gain coefficient) are becoming more important aspects of project construction documents. And several high performance window design strategies are available on the market today to maximize efficiency while maintaining visual characteristics. Essentially a window’s energy efficiency is dependent on its framing, glass and operation.

Frames can conduct heat, and since they’re oftentimes metal this heat can be significant, so aluminum frames should always have a thermal break (an insulating plastic strip between the inside and outside of the frame and sash) to reduce heat loss and frame u-factor. Composite, wood, fiberglass and vinyl are also available options (but typically relegated to residential use). They all have pluses and minuses with regard to cost, maintenance and longevity as well (more information at http://www.energysavers.gov/your_home/windows_doors_skylights/index.cfm/...).

Operation is another aspect that’s often a moot point in commercial buildings since glazing is mostly fixed (meaning it doesn’t open). Some operations (awning, casement, and hopper) have lower air leakage rates than others and double hung or sliding), which should be taken into consideration for operable windows.

Finally, the big variable, glass type… there is no ‘one size fits all’ glass for every application. Final selections for the same building might even differ by orientation or location in the wall assembly. Factors like orientation, climate, and building design all play their part here. And since glazing technologies can be combined there are many types available. The main technologies can be separated into six main categories, as described below:

Six Glazing Technologies to Consider

Gas Fills: In glazing assemblies with multiple panes, adding a gas fill helps improve the thermal performance of the assembly by providing additional resistance to heat flow over standard air to decrease a window's u-value. Gasses utilized are inert (don't react readily with other elements), commonly argon and krypton. Argon is less expensive, but Krypton has better thermal performance.

Heat-absorbing tints: Such tints change the color of the glass to absorb a large fraction of the incoming solar radiation, reducing SHGC, visible transmittance and glare. Some heat can still pass through by conduction and radiation, however, which means that tint does not lower a window's u-value.

Insulated glazing: Insulating glazing refers to windows with two or more panes of glass (such as double-glazed or triple-glazed). Insulation is achieved through spacing the glass panes apart and hermetically sealing them to form a single unit with an air gap, which helps resist heat flow. This lowers both the u-value and SHGC.

Low-emissivity (Low-E) coatings: Such coatings control heat transfer through windows with insulated glazing.

A microscopically thin metallic or metallic oxide layer is deposited directly on the surface of a glass pane. These coatings reduce the infrared radiation from one pane to another, lowering the u-value of the window (but can also lower the visible transmittance). Low-e coatings are available for high, moderate or low solar gain. The low-e coating should be applied to the outside pane of glass to keep heat out and to the inside pane of glass to keep heat inside the house. Windows produced with these coatings typically cost 10-15% more but reduce energy loss by as much as 30-50% compared to non-coated windows.

Reflective coatings: Reflective coatings are usually composed of thin, metallic layers, such as silver, gold or bronze. These coatings reduce the transmission of solar radiation, while blocking more light than heat. As a result visible transmittance and glare are significantly reduced with a lesser reduction in SHGC.

Spectrally selective coatings: These coatings are a special type of low-e coating that filters out 40-70% of heat normally transmitted through insulated glazing, while at the same time allowing the full amount of light to be transmitted.

Such coatings reflect particular wavelengths (like infrared) but remain transparent to others (like visible). This results in both a low u-value and low SHGC with high visible transmittance.

By Sarah Gudeman, LEED AP, EIT, Morrissey Engineering, Inc.

Source: www.green-buildings.com/content/781972-architectural-glass-6-glazing-technologies-consider

Glass Manufacturing )..Borosilicate glass )

2011-12-15T14:15:00.000-08:00

Borosilicate glass is a high silicate glass with at least 5% boron oxide bow handle threaded rod with a triangular shaped handle.

Borosilicate glass is a particular type of glass, better known under the brand names Pyrex and Kimax. It was first developed by German glassmaker Otto Schott in the late 19th century and sold under the brand name "Duran" in 1893. After Corning Glass Works developed Pyrex in 1924, it became a synonym for borosilicate glass in the English-speaking world.

Borosilicate glass is the oldest type of glass to have appreciable resistance to thermal impact and higher temperatures, also has excellent resistance to chemical attack. In this glass structure, the first to carry the Pyrex trademark, some of the SiO² is replaced by boric oxide.

Borosilicate glass has a low coefficient of thermal expansion and is, thus, suited for telescope mirrors and other precision parts. Also, because this glass can withstand thermal shock, it is used for oven and laboratory ware, headlamp lenses, and boiler gage glasses. Most borosilicate glasses have better resistance to acids than do soda-lime glasses, but poor resistance to alkalis. Glass fibers used in reinforcing plastic compounds are a modified borosilicate glass.

Chemical Composition
SiO2 = 80.6%

B2O3 = 13.0%

Na2O = 4.0%

Al2O3 = 2.3%

Physical Properties
Coefficient of expansion (20°C–300°C) 3.3 x 10-6 K-1

Density 2.23g/cm3

Refractive index (Sodium D line) 1.474

Dielectric constant (1MHz, 20°C) 4.6

Specific heat (20°C) 750J/kg°C

Thermal conductivity (20°C) 1.14W/m°C

Poisson’s Ratio (25°C – 400°C) 0.2

Young’s Modulus (25°C) 6400 kg/mm2

Optical Information

Refractive index (Sodium D line) = 1.474

Visible light transmission, 2mm thick glass = 92%

Visible light transmission, 5mm thick glass = 91%

Critical Temperatures

150°C - When working above this temperature care should be taken to heat and cool Borosilicate glass in a slow and uniform manner.

500°C - The maximum temperature that Borosilicate glass should be subjected to and then only for short period of no longer than a few minutes.

510°C - Temperature at which thermal stress can be introduced to Borosilicate glassware.

565°C - Annealing temperature. When uniformly heated in controlled conditions, such as a kiln or oven thermal stress’s can be removed.

820°C - Softening point at which Borosilicate may deform.

1252°C - Working point, the temperature that glassblowers need to attain in order to work Borosilicate glass.

Working Temperatures

Borosilicate glass retains its mechanical strength and will deform only at temperatures which approach its strain point. The practical upper limit for operating temperatures is much lower and is controlled by the temperature ditterentials in the glass, which depend on the relative temperatures of the contents of the equipment and the external surroundings.
Provided borosilicate glass is not subjected to rapid change in temperature, creating undue thermal shock, it can be operated safely at temperatures up to 450°F (232°C). The normal limiting factor is actually the gasket material. The degree of thermal shock (usually defined as sudden chilling) which it can withstand depends on many factors, for example: stresses due to operating conditions; stresses imposed in supporting the equipment; the wall thickness of the glass, etc. It is therefore undesirable to give an overall figure but, as a general guide, sudden temperature changes of up to about 216°F (120°C) can be accommodated .
At sub-zero temperatures, the tensile strength of borosilicate glass tends to increase and equipment can be used with safety at cryogenic temperatures.
Further development in glassmaking continues to create new glass-ceramics that outperform borosilicate glass in various ways.

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Glass Manufacturing)..Chinese Glass Industry )

2011-12-15T14:12:00.000-08:00

China's rapidly increasing demand for glass was stimulated by its two-decade high economic growth, especially the continuously rising demand in the automobile and construction markets

A country that is showing great vitality and fast economic growth. China entered into the WTO, Beijing will host the 2008 Olympic Games and the World Expo 2010 will be held in Shangai: numerous events have accelerated the swift development of Chinese glass industry.

The Chinese authorities said that the economy has grown by 9.5% in 2004. The China's demand for glass has considerably increased as well, and the Chinese glass industry has risen consequently. The total flat glass demand will increase 11.5% annually to 360 million weight cases in the year 2005.

In the next five years, both production and demand will continue to grow. The Chinese automobile industry will increase its demand for glass and will lead the industry in growth. The Chinese construction industry will remain the largest market for glass. Insiders forecast that the architectural and automotive glass market can rise by 10 per cent every year.

Source: GlassOnWeb.cn

Glass Manufacturing)..Pollution Prevention and Control)

2011-12-15T14:11:00.000-08:00

China's rapidly increasing demand for glass was stimulated by its two-decade high economic growth, especially the continuously rising demand in the automobile and construction markets

The Chinese authorities said that the economy has grown by 9.5% in 2004. The China's demand for glass has considerably increased as well, and the Chinese glass industry has risen consequently. The total flat glass demand will increase 11.5% annually to 360 million weight cases in the year 2005.

In the next five years, both production and demand will continue to grow. The Chinese automobile industry will increase its demand for glass and will lead the industry in growth. The Chinese construction industry will remain the largest market for glass. Insiders forecast that the architectural and automotive glass market can rise by 10 per cent every year.

Source: GlassOnWeb.cn

Glass Manufacturing)..City Hospitals Sunderland - NHS Foundation Trust)

2011-12-15T14:10:00.000-08:00

“NOT just one of the best in the country – but possibly the world” is how Dave McNicholas, Unit Manager, describes the new state of the art ICCU at Sunderland Royal Hospital which opened April 11th.

Client: Royal Sunderland Hospital, NHS Trust
Architect: HDP Architects
Contractor: Lumsden & Carol Contractors
Project: High Dependency ICCU
Date: Project completed March 2011

The unit is part of a new £28m ward block at the hospital and is seen as a model of excellence within the NHS as it includes hi-tech technology, incorporating the most advanced electronic patient monitoring systems available.

The Integrated Critical Care Unit (ICCU) includes high dependency single bed units, isolation single bed units and general post-operation single bed units.

Project Brief

Extension of the Sunderland Royal Hospital to increase patient capacity from 970 to 1108. A 138 bed ward extension to provide much needed supplementary care facilities for the hospital. A new high dependency Integrated Critical Care Unit (ICCU) to separate theatre staff and nursing staff to eradicate the chances of contamination spreading between the two

sections.

LC SmartGlass

LC SmartGlass toughened panels were used to create a state of the art partitioning system along the corridors of the ICCU. The double doors entering each ward are fitted with LC SmartGlass toughened door panels allowing for patient privacy and dignity at the flick of a switch, while also permitting care staff to effectively monitor patient activity. Through continued studies it has been proven that sheer, easily cleaned surfaces are essential in hospitals in order to reduce the risks associated with the spread of super bugs such as Clostridium difficile (CDIFF), Methicillin-resistant Staphylococcus aureus (MRSA) and Vancomycin-resistant Enterococcus (VRE).

A recent American study by the Cleveland Veterans Affairs Medical Centre in Ohio found that curtains which hang between patient beds in hospitals can become contaminated with drug-resistant bacteria and may be playing a role in the spread of these germs in hospitals.

The study showed that CDIFF, MRSA and VRE can be found on hospital privacy curtains. More worrying, researchers found that these bugs transfer onto the hands of people who handle the contaminated curtains, suggesting that health care workers who operate these may be spreading bugs. The study found that 43 percent of privacy curtains were contaminated with VRE, 22 percent of them harboured MRSA and four percent tested positive for CDIFF.

LC SmartGlass provides the ideal surface to combat these deadly infections and eliminates the need for traditional blind systems which are difficult to clean and high risk in terms of harbouring dirt and bugs.

Principle

When the electrical supply is switched on, the liquid crystal molecules align and the LC SmartGlass panel instantly clears. When the power is switched off the liquid crystal molecules are randomly oriented scattering light and the LC SmartGlass becomes opaque (private).

LC SmartGlass can be tailored to suit varying healthcare applications with requirements such as fire rated, x-ray proof and impact resistant glass.

“This is one of the most carefully designed intensive care units in the country”. It gives patients and their families the reassurance that they are receiving the best possible treatment in the most modern of settings, with the latest equipment and the most highly trained staff”.

“Our first objective is the patient. The new unit has been developed to ensure that they have the benefit of the very best ICCU service that is available anywhere in the NHS”.

Dave Mc Nicholas, ICCU manager

“This is one of the best ICCUs in the world, the state of the art equipment and staff are truly excellent. Any patient treated here will be guaranteed first-rate treatment that is leading the way in critical care.”

Graham Howard, City Hospitals Sunderland NHS Foundation Trust

For more information on SmartGlass Medical visit www.smartglassmedical.com.

All photographs are courtesy of HDP Architects

Glass Manufacturing)..Coated Architectural Glass )

2011-12-15T14:09:00.000-08:00

Michael Elstner, state certified Engineer & Master Glazier

Head of the INTERPANE Consultancy Service (IBC)

Glass is the dominant building material in modern architecture. It creates visual accents and offers multiple technical features like glass for thermal insulation, solar protection, and sound proofing, as well as a design component, safety glass, or as a part of solar plants. The industry nowadays offers glass with customised technical data for every application possible. In architecture, a special emphasis is often placed on energy-saving building methods, particularly in view of the rising energy and raw material costs which are the greatest challenge of our times. Due to the wide diversification of the technical features, tailor-made technical glass consulting is becoming an increasingly important service in architectural glazing. This paper describes the historical context as well as the evolution of glass as a material and its applications in windows and facades, with a description of its most important building-physics values.

The history of glass

Flat glass has been used for around 2000 years as a space-enclosing component and is, therefore, one of the oldest artificial building materials. Due to ongoing developments concerning manufacturing and finishing methods, it is now also one of the most advanced building materials and it characterises modern architecture today. Since it can now fulfil nearly any requirement of modern building envelopes, the conflict between the fundamental human need for protection from the outside world, on the one hand, and the openness to light, on the other hand, has now been overcome.
Flat glass was produced using casting, crowning or cylinder techniques until industrialization. These handcrafted methods were eventually superseded by sheet glass and polished plate glass production methods that were applied until the 1960s. The disadvantage of the machine glass processes was that the glass was distorted and uneven. The grinding and polishing steps that were necessary for the production of high-quality plate glass were a cost driver. Both methods were improved over the years, but it was impossible to eliminate the fundamental disadvantages. In order to cover the increasing demand for high-quality flat glass, new methods were required. At the beginning of the 1950s, the English company Pilkington Brothers invented an industrial solution and enabled high volume production of large plate formats, along with a consistently high quality at a relatively low price: This is known as the automatic float process and as a result, glass became a mass produced product that anybody could afford. As a result of the oil crisis in the 1970’s, the criticism of glass architecture increased. Uncoated flat glass at this time was a waste of energy. An ecological and economical milestone for higher energy efficiency was the production of thermal insulating and solar control coatings using thin-film technology.

Why is a coating applied?

Single glazing, which was standard until the middle of the 1970, is responsible for large thermal losses (Ug Ø ≈ 5.8 W/m2 K). Double glazing then became more common, with its improved Ug value of about 3.0 W/m²K. It was not until double glazing technology was combined with modern thin film technology to create transparent coatings on glass that the specific energy losses could be halved yet again. In contrast to metals, which re-radiate about 2 to 10 percent of the absorbed energy, i.e. which have a low emissivity value, ε, glass does not possess this favourable property. More than 80 percent of absorbed heat is emitted via the glass surface (ε ≈ 0.85). In order to combine the transparency of glass with the excellent emission properties of precious metals, thin metal films are deposited onto the glass. These are transparent to sunlight but simultaneously reduce the emissivity of the glass surface very effectively. Extremely thin silver films with a thickness of about 1/100,000 mm (= 10 nm) are optimal. Colour-neutral, coated insulating glazing was first introduced by INTERPANE to the market at the beginning of the 1980. A vigorous market campaign, including the distribution of basic coated glass as a semi-finished product, ensured that iplus was soon widely disseminated. Today, thermally insulating glazing (low-e glazing) with a Ug value of ø 1.1 W/m²K is accepted as the state of the art. With triple glazing, Ug values down to even 0.5 W/m²K can be achieved. This means thermal losses that are only a tenth of those for single glazing!

The Structure of low- emissivity and solar control coatings

Different coating materials are deposited onto glass to produce functional coatings. These provide adhesion, thermal functions, cover and protection, forming a complex system. The optical properties are achieved by applying the interference principle, which is familiar from antireflective coatings on camera and spectacle lenses. The ipasol solar-control coatings are similar to the others in principle, but have a significantly more complex coating structure. The desired properties regarding solar and thermal radiation are obtained with additional absorbing and/or reflecting components

Fig 1: Example: Structure of a simple Low- E coating on glass
Coating technique

At INTERPANE, in-line sputtering in vacuum chambers is used as the coating technology (Fig. 2). The pressure in the sputtering chamber is reduced to about one millionth bar (app. 10-3 mbar). The glass pane is transported from the input chamber through a transfer chamber to the sputtering chamber, where the coating process actually takes place. In order to obtain homogeneous coatings, the glass is transported under the coating devices at a constant speed.

Fig. 2: Schematic diagram of the continuous operating coating line with high-performance sputtering (in-line method).

Fig. 3: Schematic cross- section of a cathode chamber to deposite thin films by the magnetron sputtering procedure

Fig. 4: Surface processes during sputtering
The coating procedure itself is shown schematically in Fig. 3: For sputtering, plasma is created in a vacuum chamber by applying a high voltage between a cathode and an anode. The plasma forms when atoms of the inert gas, argon, are introduced into the chamber and are transformed into heavy, positively charged argon ions by collisions with electrons. The plasma can be recognised by its typical coloured appearance, similar to that in fluorescent tubes. The strong electric field created by the high voltage accelerates the heavy, positively charged argon ions toward the cathode. A so called "target", which consists of the coating material (e.g. silver), is mounted on the cathode. The incident high-energy argon ions knock material out of the target, which is then deposited as a thin layer on the glass (Fig. 4). Oxygen may be additionally introduced into the chamber as a reactive gas to form chemical compounds with the atomised target materials.
Important building-physics values
Ug-value according to EN 673
Heat transmittance through a surface by conduction, convection and radiation is expressed by its U value according to European Standards. This was formlerly known as the K coefficient in some contries. The thermal transmittance (U value) specifies the heat flow per unit time through 1 m2 of a building component for a temperature difference between the adjoining room and the outdoor air of 1 Kelvin. Thus, the lower the U value, the better is the thermal insulation. The units for specifying a U value are W/m²K. The Ug value is determined by calculation according to EN 673 or by measurement according to EN 674. Under the same boundary conditions, the calculation and measurement procedures result in comparable U values. The ASHRAE/NFRC yield a slightly worse (higher) U value than the European standards (approx. 0.1-0.2 W/m2K). The ASHRAE/NFRC U Value is separated into winter and summer conditions.
Emissivity ε according to EN 673
The emissivity value, ε, describes the radiative property of the surface of a body. With respect to the thermal insulation of insulating glazing, the lower the emissivity value, the better is the U value. In the past, the U values of glazing were always measured in a test rig – today, reliable calculation procedures are available (EN 673). One of the values needed for the calculations is the ε value. The emissivity value is determined by measuring the infrared reflectance of a building component surface. It is assumed that the angle of incidence is almost perpendicular to the considered surface and that radiation of different wavelengths is used for the measurement. The reflectance value R determined in this way is converted into the emissivity value using the formula
ε = 1 – R
As it is not possible, from a metrological point of view, to measure with an angle of incidence of 0°, measurements are generally made with an average angle of incidence of ≤ 10°.
Normal emissivity εn according to EN 673
The determination of the normal emissivity value εn according to EN 673 is based on the measurement procedure described above, where 30 wavelengths between 5.5 µm and 50 µm are evaluated. The mean value is determined from these individual results, with the spectral distribution of thermal radiation at + 10 °C being taken into account. The result is designated the “normal emissivity value εn”.

Declared emissivity εd according to EN 1096
The declared value of the emissivity, εd, is the nominal value of the normal emissivity specified by the manufacturer of the basic glass.

The solar factor (SF) or g-value according to EN 410

The solar factor is the total energy transmittance (or solar heat gain coefficient) of glazing for solar radiation in the wavelength range between 300 nm and 2500 nm. The solar factor is significant for HVAC calculations (heating, ventilation, air-conditioning) and is expressed in %. The solar factor is the sum of the direct solar energy transmittance τe and the secondary internal heat transfer factor qi describing long-wave radiation and convection.

g = τe + qi

b-factor or shading coefficient (SC)

The “average transmittance factor b” (also called the shading coefficient SC) is the decisive factor for calculating the cooling load. The b-factor is the ratio of the solar factor of the evaluated glazing unit to the solar factor of a conventional double-glazed window, according to German VDI 2078 (edition July 1996).

Internationally (USA- ASHRAE, NFRC or UK- CIBSE) the shading coefficient is the ratio of the solar factor of the evaluated glazing unit to the solar factor of a 3 mm single glazing.

In some contries the shading coefficient is separated into long-wave and short-wave components, whose values are derived in exactly the same way, by comparing with the same property of a 3 mm clear float. The short wavelength shading coefficient (SWSC) is the direct solar energy transmittance e divided by 0.87. The long wavelength shading coefficient (LWSC) is the secondary internal heat transfer factor qi, again τe divided by 0.87. Both together give the same result as described above. Drawing international comparisions it is more common to determine the SC by dividing the solar factor by 0.87.

Colour rendering index Ra according to EN 410

Colour rendering is very important for physiological perception and for psychological and aesthetic reasons. The colour effect in a room is influenced by the spectral distribution of the incident daylight. The maximum value that can be taken on by the general colour rendering index Ra is 100. This value of 100 is attained in glazing-types where the degree of spectral transmission within the visible spectral range is absolutely constant (e.g. ipawhite: Ra,D 100 up to a glass-thickness of 8 mm uncoated). In terms of lighting technology, general colour rendering index-values of Ra > 90 indicate a very good level of colour rendering, and index-values of Ra > 80 indicate a good level thereof. The Ra,D-value describes colour recognition by daylight firstly within the room and secondly outdoors, as viewed from indoors through the window. In a comparable way, the Ra,R-value characterizes the colour rendering of the glazing for outdoor reflections. The colour rendering characteristics of glazing are established by means of the general colour rendering index Ra in accordance with EN 410. Used as the basic reference illuminant is the normal illuminant D 65.

Light transmittance τV according to EN 410

The light transmittance τV is the ratio of the visible light (380 to 780 nm) that is transmitted through glazing, weighted by the sensitivity of the human eye. The light transmittance is indicated as a percentage and can be influenced by the glass thickness, for example. Due to the varying iron oxide content of the glass, slight fluctuations are possible. A single-pane of clear float glass has a light transmittance of approximately 90% in the spectral range of the visible light (the 10% loss being mainly due to reflection). An INTERPANE insulating glass consisiting of two float glass panes, has a light transmittance of 82%. iplus neutral E has a light transmittance of 80%. The reference value of 100% corresponds to a wall opening without any glazing. The light transmittance of the glazing should be selected appropriately for the building and the environment.

Energy absorption αe according EN 410

In addition to transmission and reflection, absorption is the third process determining radiation transport through glass. Radiated energy is converted by absorption into thermal energy. This causes the temperature of the absorbing glass pane to increase. If the absorption is ≥ 50% for horizontal glazing and ≥ 55% for vertical glazing, INTERPANE recommends fully toughened or heat-strengthened glass. This recommendation is based on a typical location without any static/severe shadow on the glazing. For specific applications, however, an analysis of thermal glass breakage risk is recommended. The Interpane Consultancy Service (IBC) would be pleased to assist you.

Transmission
+ Reflexion
+ Absorption
--------------------
= 100 %

Selectivity characteristic S

The selectivity index serves to indicate the ratio of the degree of light transmissivity τV to the degree of total energy transmittance g. A high selectivity index expresses a favourable ratio.

Thermal effect of insulating glass with a low-E coating

The heat flow through insulating glazing is determined by the following components:

radiation exchange between the panes according to the emissivity of the pane surfaces for thermal radiation
heat conduction by the gas in the gas-filled space
convection of the gas in the gas-filled space

Fig. 5: Heat flow through insulating glass

In conventional, uncoated double glazing, about two-thirds of the heat flow is due to the radiation exchange between the panes due to the high emissivity of the glass surface. Only one third is caused by conduction and convection of the air in the space between the panes. The low emissivity coating reduces the emissivity from εd ≈ 0.89 for uncoated glass to, for example, εd ≈ 0.03 for iplus E. Thus, the radiation exchange is suppressed almost completely. The heat flux due to conduction and convection in the gas-filled space remains unchanged. Thus, a low-emissivity coating based on silver, such as is used in iplus E, reduces the Ug value of double glazing from approximately 3.0 W/m²K to 1.4 W/m²K. If, in addition, the air in the space between the panes is replaced by an inert gas such as argon, which has a lower thermal conductivity, the Ug falls by a further 0.3 W/m²K to 1.1 W/m²K.

Outlook

The developments centred on the material glass are not merely restricted to classical features, such as energy-saving and solar protection, but also set out to improve and change its strength and look. Nature is often used as a model, such as in the case of the lotus effect, or those products that are offered that can control light and energy transmission flexibly and independently from the user. Innovative solutions for decorative facade glazing are also very popular with the planners. In this context a new range of coatings is now available. So called “design coatings” such as ipachrome. This coating can be be applied partially or extensively and it opens creative opportunities for the design of buildings. The multi-layer system ensures that the glass is as reflective as a conventional silver mirror.

Since product diversity continues to grow, glass technical consulting for architects, planners, and clients in building projects is in high demand among glass processing companies. The INTERPANE Consultancy Service (IBC) in Plattling, which is located in Bavaria, Germany, assists national and international architects, engineers, planners, fabricators, and institutional building clients either by phone or on-site. Apart from architectural and technical consulting for window and facade builders, the IBC also offers training courses and co-ordinates the national and international cooperation of architectural consultants and clients. The IBC can be reached via phone at +49 (0) 9931 950 229, fax +49 (0) 9931 950 236, or e-mail ibc@interpane.com.

8. References
[1]INTERPANE: Design with glass 7th Edition, 2007.

Michael Elstner, state certified Engineer & Master Glazier
Head of the INTERPANE Consultancy Service (IBC)
INTERPANE Glasgesellschaft mbH, Plattling, Germany
phone +49 172 85 14 519, michael.elstner@interpane.com

Glass Manufacturing)..Glass solarization )

2011-12-15T13:51:00.005-08:00

Glass solarization is a phenomenon which occurs when certain types of colourless, transparent glass are exposed continuously to the sunlight. This exposed glass develops a pink or violet color. When bottles and fragments have this color they are usually referred to as "desert glass". However scientists and experts prefer the term solarized glass.

The main ingredient in the majority of glass types is silica, usually introduced as a raw material in the form of sand at the beginning of the glassmaking process. Although silica itself is colorless, most sand contains iron as an impurity which produces a greenish color in the glass. By adding various ingredients to molten glass, it is possible to offset this and produce water-white glass. The dioxide manganese (pyrolusite) is used to "decolorize" this glass containing impurities.

Solarization of glass occurs when pieces of colorless glass containing manganese oxide are exposed to ultraviolet light for long periods of time, causing the manganese to become photo-oxidized. This converts the substance back into an oxidized form which, even in rather low concentrations, imparts a pink or violet color to glass. The ultraviolet rays of the sun can promote this process over a matter of a few years or decades, thus accounting for the color of desert glass.

Due however to improvements in the industry, nowdays most clear glass uses much purer raw materials that do not react to solar rays.

article source

http://www.glassonweb.com

Glass Manufacturing)..Glass Market in India )

2011-12-15T13:51:00.004-08:00

When entrepreneurs talk about business, China immediately comes to mind. Many firms wish to corner a share of its huge market. Glass industry businessmen are no exception. But India, a place where “glass sells like crazy”, is another country they can bet on: here, according to the Master Guide to Indian Glass, the demand for flat glass has increased at an average annual rate of 12% to 15% for the past 2-3 years and, over the long term, is expected to grow at around 3.8% per year. The demand for processed glass has also grown by more than 30% annually in recent years.

The construction and automotive industries are the most important consuming sectors: almost 80 million square feet of land in India is earmarked for shopping malls. Nowadays, taking climate, safety, sound attenuation, energy conservation and aesthetics into consideration, builders are opting for more glass in their construction. The glass revolution is also taking place in the automotive industry which is predicted to grow following an 8% cut in excise duty on vehicles and the easy availability of flexible automobile loans.

It goes without saying that the rapid increase in demand during the 1990s, in addition to provoking a cutback in exports, charmed some international firms which now are the major producers of float glass (Gujarat Guardian Ltd., Asahi India Glass Ltd., Triveni Glass Ltd., Saint-Gobain Glass India Ltd...). Close to them there are about 27 domestic companies which have been forced to expand their capacities and diversify into new areas in order to remain competitive.

Totally, the flat glass industry grew by about 80% between 2000 and 2006, resulting in a compound annual growth rate of 10.1%. The per capita consumption of glass, which was 0.41 kg in 1999, reached 0.76% kg in 2006.

Anyway, it isn’t all “peaches and roses” in India : problems like the overcapacity of raw glass (and a projected surplus of processed glass), Chinese competition (in spite of anti-dumping duties) and the lack of codes of standards threaten Indian glass industry. As far as overcapacity concerned, analysts say that the supply will far exceed demand at least until 2009. Excess capacity, increased competition and the development of a regulatory framework are the real future challenges for the Indian glass industry.

article source
http://www.glassonweb.com