Understanding the causes and prevention of spontaneous breaking in Tempered Glass
Tempered glass, known for its strength and safety features, sometimes breaks spontaneously without an obvious cause. This phenomenon can be perplexing and potentially hazardous, necessitating an understanding of its causes and preventive measures. In this article, we delve into the reasons behind spontaneous breaking and explore how these incidents can be minimized.
Causes of spontaneous breaking in Tempered Glass
1. Impact over time :
Tempered glass is susceptible to breaking if it is impacted in the same place repeatedly over time. Such impacts can accumulate tension in a specific area, causing the glass to break either immediately or at a later time.
2. Pressure points from metal fittings :
Pressure points created by metal fittings, such as screws in the profiles, can contribute to spontaneous breakage. These pressure points introduce stress concentrations that weaken the glass structure.
3. Continuous tensioning :
Defective assembly or improper installation can lead to continuous tensioning of the glass. This occurs when the glass is too tightly secured or when fixing points are not coplanar, causing undue stress.
4. Tight fit in the frame :
If the glass is fitted too tightly within its frame, it can lead to spontaneous breaking. The lack of adequate space for expansion and contraction creates stress, which may eventually cause breakage.
5. Poor edge finishing :
Finely finished edges are crucial for tempered glass. Poorly finished edges, including those with shaving remains, can be a weak point and contribute to spontaneous breakage.
6. Nickel sulphate inclusions :
Nickel sulphate inclusions within the float glass are another potential cause. These inclusions, though rare, can create weak points that lead to spontaneous breaking under certain conditions.
Probability and risk of spontaneous breakage
The probability of spontaneous breakage due to nickel sulphate inclusions is approximately 1 in 10,000. This risk is influenced by factors such as the thickness of the glass and temperature fluctuations. Despite the low probability, the consequences of spontaneous breakage necessitate measures to further reduce this risk.
Preventive measures : The heat soak test
To mitigate the risk of spontaneous breakage, a preventive measure known as the Heat Soak Test can be performed. While it cannot entirely eliminate the risk, it significantly reduces the probability of breakage.
What is the heat soak test ?
The Heat Soak Test involves heating the tempered glass to a temperature of approximately 400 degrees Celsius. The glass is maintained at this temperature for about 2-4 hours and then gradually cooled according to a calculated and pre-set temperature curve. During this process, any glass containing nickel sulphate inclusions is likely to break, thereby preventing its installation.
Benefits of the heat soak test
1. Increased safety :
By identifying and eliminating glass with nickel sulphate inclusions, the Heat Soak Test enhances the overall safety of tempered glass installations.
2. Reduced probability of spontaneous breakage :
The test reduces the probability of spontaneous breakage by a factor of 100, lowering it from 1 in 10,000 to 1 in 1,000,000. This substantial reduction in risk is crucial for applications where safety is paramount.
3. Enhanced durability :
Glass that passes the Heat Soak Test is more durable and reliable, making it suitable for critical installations where failure is not an option.
Best practices for preventing spontaneous breakage
1. Proper installation :
Ensure that tempered glass is installed correctly, with attention to avoiding continuous tensioning and providing adequate space within the frame for expansion.
2. Regular inspections :
Conduct regular inspections of tempered glass installations to identify and address potential stress points or defects that could lead to breakage.
3. Edge finishing :
Ensure that the edges of tempered glass are finely finished and free of any imperfections that could weaken the glass.
4. Use of quality materials :
Utilize high-quality glass and fittings to minimize the risk of introducing stress concentrations that can lead to spontaneous breakage.
Conclusion
Spontaneous breaking of tempered glass, while rare, can pose significant safety risks. Understanding the causes, such as repeated impact, pressure points, continuous tensioning, tight fitting, poor edge finishing, and nickel sulphate inclusions, is essential in mitigating these risks. The Heat Soak Test emerges as a crucial preventive measure, significantly reducing the probability of spontaneous breakage and ensuring the safety and durability of tempered glass installations.
By adhering to best practices in installation, inspection, and material quality, and by leveraging advanced testing methods like the Heat Soak Test, we can enhance the reliability and safety of tempered glass, making it a robust choice for various applications. At Glas Expert, we are committed to providing the highest quality tempered glass products, ensuring safety, durability, and peace of mind for our clients. If you have any questions or require further information, please do not hesitate to contact us.
