What causes glass to break inside the heating oven of glass tempering furnace?

During the production of tempered glass, operators may experience glass breakage inside the tempering furnace, which is known as furnace explosion and is an abnormal situation in tempered glass production. Because glass breaks inside the tempering furnace, it usually needs to be cooled and cleaned, which usually means significant economic losses for glass deep processing factories.

Tempered glass blast furnace is a production anomaly that all processing enterprises want to prevent, but it is difficult to prevent. Below we will discuss which factors are related to this issue:

1. the quality of float glass

Glass undergoes a rapid heating process in a tempering furnace. During this process, the glass is subjected to thermal stress, and because glass is a brittle material, some small cracks will rapidly propagate under the effect of thermal stress, causing the glass to break. Just like when a piece of paper is pulled taut, with just a small crack, the paper immediately breaks open from the crack.

The main factors that have a significant impact on the tempering furnace in the original film are stones, bubbles, and microcracks. During the tempering process of glass with a thickness of over 12mm, furnace explosions are often caused by defects in the original sheet. In addition to purchasing high-quality raw materials, it is only necessary to strengthen the inspection before entering the furnace.

2. Cold processing quality

Cold processing leading to steel furnace explosion refers to the occurrence of cracks such as edge grinding, drilling, and slotting that cause steel furnace explosion. During the process of glass tempering, the edges experience the greatest thermal stress and are also the easiest places to break. Tempered glass must be ground to eliminate cracks caused by cutting edges.

The situation of drilling, slotting, and edging is the same, and it is also necessary to eliminate cracks at the hole or groove position, otherwise the glass may also break from the crack during the heating process.

3. Tempering process

Tempering process is also one of the reasons for furnace explosion. There are two main reasons for improper processing: rapid heating and uneven heating.

Heating too quickly is primarily related to high temperature settings and excessive convection settings. Heating too quickly can cause the glass to heat up too quickly after entering the furnace, resulting in high thermal stress on the glass and causing it to burst. Generally speaking, the thicker the glass and the larger the surface, the slower the heating speed should be. The explosion fragments caused by rapid heating are generally in the form of small fragments.

Uneven heating primarily refers to the different heating rates of the upper and lower surfaces of glass when heated in a tempering furnace. Heating quickly at high temperature while heating slowly at low temperature. In this case, the glass will warp inside the tempering furnace, ranging from slight white marks on the roller conveyor to direct breakage of the glass by hitting the roller conveyor or heating element.

Uneven heating is very common on LOW-E glass, and temperature and convection conditioning are the primary methods to avoid it. Directly investigating the state of the glass inside the furnace is a useful way to avoid it.

4. Abnormal equipment

The explosion caused by abnormal equipment is caused by the transmission system, commonly including silicon rod jamming, abnormal length measurement, and abnormal transmission encoders and frequency converters. In addition, the uneven temperature in the area caused by the breakage of some heating wires or the failure of convection fans can also easily lead to furnace explosion.