Why does tempered glass self explode?



Every summer, most parts of the country enter the "barbecue mode", and summer is also a period of high incidence of tempered glass self explosion. What exactly is the cause? Today we will explain it in detail，  Glass product  .

The self explosion of tempered glass is characterized by the phenomenon of broken tempered glass without external direct action. During the processes of tempered processing, storage, transportation, installation, and use, self explosion of tempered glass may be induced.



Reasons for self explosion of tempered glass



01. Impurities present



Part of the glass is semi tempered or simply thickened, and there are more impurities, stones, and air in the glass, which become weak points of the glass. The crack propagation that accompanies stones is very easy to occur.



02. Nickel sulfide (NiS) and heterogeneous particles



Tempered glass cannot be controlled to self explode, which may also be caused by the presence of NiS particles or other heterogeneous particles inside the glass. The germination and propagation of cracks in glass are mainly caused by residual stress generated near the particles. This type of stress can be divided into two categories: one is the phase change stress during the phase change expansion process, and the other is the residual stress generated by the mismatch of thermal expansion coefficient.



03. Improper installation



During the installation process, if the installation gap is small or the glass is in direct contact with the frame, the expansion coefficient between the glass and the frame is different under sunlight, which can easily cause squeezing pressure on the edges or corners of the glass, leading to the cracking of tempered glass.



04. Natural factors



Strong typhoons and other wind disasters lead to the failure of wind pressure resistance design, which can cause the rupture of tempered glass.



Factors affecting the risk of self explosion of tempered glass



(1) The effect of tempering stress: The stronger the tempering stress, the easier it is to self explode



(2) The impact of particle size on self explosion sources: The larger the particle size, the easier it is to self explode



(3) The influence of particle position of self explosion source: the closer the particles are to the middle layer, the more likely they are to self explode



(4) The impact of temperature: The greater the temperature change (rise or fall), the more likely it is to self explode



(5) The influence of external loads: the greater the force on the glass, the easier it is to self explode



How to Identify Self Explosion of Tempered Glass



Firstly, check whether the initiation point (the cracks in tempered glass are radial and have starting points) is in the middle of the glass. If it is at the edge of the glass, it is generally because the glass has not undergone chamfering or edge grinding treatment or there is damage to the glass edge, causing stress concentration and gradual development of cracks; If the initiation point is in the middle of the glass, check if there are two small polygons forming a pattern similar to two butterfly wings (butterfly spots) at the initiation point. If there are black small particles visible to the naked eye around the edges of the two small polygons (nickel sulfide stones), it can be determined that they are self exploding; Otherwise, it should be caused by external forces. The typical feature of glass self explosion is butterfly spots, with glass fragments distributed radially, with two glass blocks resembling butterfly wings in the center of the radiation, also resembling an "8" character.