Spontaneous explosion is one of the features of tempered glass. Usually it occurs during tempering, storage or using without being exerted any mechanical external force. But how this happens and how to prevent it?
The following reasons account for the spontaneous explosion of tempered glass:
1. The glass has a poor internal quality such as stone like impurities, nickel sulfide particles, bubbles, etc.
2. The scratches, nick, deep micro cracks left on the glass during glass processing due to improper operation may lead to stress concentration or spontaneous explosion.
3. The uneven stress distribution due to uneven heating or cooling is likely to cause spontaneous explosion.
4. The higher stress inside the glass and the higher tempering level, the higher percentage of spontaneous explosion it will has.
Those above mentioned are common cause.
Therefore, the following points should be concerned during the production:
1. Both the internal and external quality of the glass should be strictly inspected and none of the defective glass is allowed to put into the furnace.
2. There should be no huge temperature differential between the top and bottom glass surface during heating; also the air pressure between the top and bottom glass surface should be kept as even as possible.
3. Glass should be tempered under the optimized heating temperature, heating time and tempering pressure to avoid excessive tempering stress.
The spontaneous explosion rate of the tempered glass would be greatly reduced if the above items can be followed.