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How To Avoid The Cracking of Fused Cast AZS Sidewall

The service life of the sidewall refractories is one of the most important factors that determines the life of the glass furnaces. The cracking of the sidewall refractories shortens the life of the glass furnaces and causes glass defects. Thus, it is important to avoid the cracking of sidewall refractories. The sidewall of the float glass furnaces usually employs fused cast AZS block.
fused cast AZS
AZS 33#, 36# and 41# are the most widely used refractories in the sidewall of the float glass furnaces. They can be divided into straight block, wedge block and knife type block. 
 
Fused cast AZS block is a kind of brittle material. Due to its thermal properties, AZS block, especially AZS 41# and knife type block, tends to crack during the preheating of glass furnaces. When the method is not proper or power failure occurs during the preheating, the sidewall will surely crack. Therefore, it is important to avoid cracking of the sidewall during the preheating. 
 
Reasonable rate of temperature increase
For AZS block, when the rate of temperature increase is under 15℃/h, crack formation can be avoided. However, in the practice, sudden climb or drop of temperature may happen. It should be avoided. 
 
Reasonable time to turn on the sidewall cooling fan
In current, there are two ways: 1) turn on the cooling fan when the temperature of glass furnace is 500℃; 2) turn on the cooling fan when the temperature of the glass furnace is above 1400℃ and the glass phase begins to separate out. With the second way, the stress produces by cooling fan can be absorbed, but it requires that the air volume should be as small as possible when turning on the cooling fan and can be precisely controlled. 
 
Reasonable temperature of the sidewall
When the cooling fan is turned on under 500℃, insulating is not necessary, while a layer of insulating material should be added when the cooling fan is turned on above 1400℃. Make a reasonable heating curve and control the rate of temperature increase strictly, especially to avoid the sudden climb of temperature. Control the air volume of cooling fan at a low level which can effectively reduce the cold shock of cooling air. 
 
With the above ways, the cracking of fused cast AZS sidewall during the preheating of the glass furnace can be effectively reduced or even avoided and the life of glass furnaces can be effectively prolonged. 

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