When designing a new building, we have to comply with a whole series of requirements regarding fire safety that are imposed by EU legislation. Construction materials used for partitions must meet the criteria of specific fire resistance classes, which for some architects can feel as a brake on their freedom of design. A glass partition can provide a solution here, given that even for the top fire resistance classes, a transparent solution is possible using glass. EU legislation
EU legislation distinguishes a material’s reaction to fire and it’s resistance to fire. A material’s reaction to fire indicates how a material will respond to fire. A distinction is made between fire-resistant materials, inflammable materials and flammable materials. Materials are divided into seven Euroclasses: A1, A2, B, C, D, E and F, where A is the best classification. The following glass products are included in the list of materials that are assigned to class A1 without testing being needed: float glass, patterned glass, heat strengthened glass, thermally toughened glass, chemically toughened glass, glass with an inorganic coating, and wired glass. Continue reading →
There are typically four different glass types used in glazing products: From weakest to strongest they are: Annealed, Heat Strengthened, Tempered and Laminated.
1. Annealed glass is your basic non-impact glass type. It is used in applications where the required wind load is not so high and safety requirements are not a concern. When annealed glass breaks, it breaks in sharp chards.
2. Heat Strengthened glass is also a non-impact glass. It undergoes a “heat treatment” that increases it’s strength to twice that of annealed glass. It is used in similar applications to annealed glass but where the required wind loads are much higher. When heat strengthened glass breaks, it also breaks in chards.
3. Tempered glass is your basic impact glass. It undergoes a more aggressive “treatment” that increases it’s strength to four times that of annealed glass. It is used in “small missile” impact applications typically installed 30 feet or higher above ground and in safeguard applications. When tempered glass breaks, it breaks into very small cubes.
4. Laminated glass is your typical impact glass. It is a combination of two (usually) of the three previously mentioned glass types that are “laminated” together with an interlayer between them. It is typically used in “large missile” impact applications installed up to 30 feet above ground. When laminated glass breaks, it breaks based on it’s glass type make-up but is held in place by the interlayer…similar to a car’s windshield.
Here’s an interesting article by Rick De La Guardia on how to design safely with glass for today’s threats. This article was featured in US Glass Magazine. (Click on the article image to read more and download the entire edition)
Here’s an interesting find from Glazette.com. This article claims about a new type of glass tempering, called Chemical Strengthening. It is also claimed in the article that these glasses are 6 to 8 times stronger than annealed glass, where as toughened glass is only 4 to 5 times strong. Most amazing fact is that these glasses could be cut after tempering unlike toughened glasses. However, the breakage pattern for these glasses remain almost the same as annealed glass, which obviously affects its acceptance in terms of safety.
Insulated glass unit (IGU), also known as Double glazed unit (DGU) consists of two glass panes separated by dry air with an aluminum spacer. IGU has been in use in many countries since 1960s, except in the middle-east and Asia, … Continue reading →
In my previous post on Glass Tempering or Toughening Process, I had mentioned how the process is executed and the physics involved (Refer Back). Also a brief mention how the toughened glass quality is assessed after it breaks, this is very important because safety is the reason for we spend on tempering. There are also other issues in terms of quality when glass is tempered. These are mainly optical distortion, roller marks, waviness and bend, edge strength, coating burns, fragmenting, burns, spontaneous breakage, etc.
High Optical Distortion
Quality of tempered glass mainly depends on the quality of equipments used and the quality control procedures adopted. Optical Distortion , is mainly a blurred appearance in images when seen through the glass, as well as on the reflection on the glass. This quality issue in tempered glass is common to all types of glasses. Even though minor levels of optical distortion is present in most of the tempered glasses, but it gets magnified when the quality is that poor and the glass is applied on high rise building facades. The minor level optical distortion is inherent on tempered glass, considering the fact that glass nearly reaches it’s softening point as it is heated up to a temperature of 726 degrees, and also the fact that this glass moves in rollers, therefore it is also called roller wave distortions. Such distortions could be easily identified in reflective and low-e coated glasses. Roller wave distortions could be easily controlled by adopting suitable technology and quality control procedures (use of forced convection furnaces instead of radiation furnaces). Continue reading →
There are major defects happening with laminated glass, if the process is not executed properly. Most prominent of such problems is de-lamination. This happens mainly due to the poor bonding between the glass and PVB sheet. In my previous post on laminated glass basics, I had mentioned about the clean facility requirement for lamination process, if this is not followed in the facility, there are chances for dust to stick on to the PVB and at a later stage, resulting in de-lamination. Waviness in the glass is also another reason for de-lamination: waviness in the glass can happen mainly due to poor quality tempering and even in annealed glass which has high amount of inherent waviness. De-lamination mainly occur at the edges where chemical bonding is weaker. De-lamination may also happen when the unit is over exposed to water, mason errors (like improper cutting), applying poor quality sealants, etc. Continue reading →
Laminated glass is made by sandwiching Poly vinyl butryl (PVB) sheet in between two pieces of glass. Laminated glass offers more safety because when the glass breaks, it keeps sticking on to the PVB sheet in the middle. Apart from … Continue reading →
Annealed float glass when breaks is a safety hazard, just because it breaks into sharp pieces and can injure. Imagine, if an annealed glass applied to a window in the 6th floor of a building, and if it breaks by … Continue reading →