The reason why tempered glass undergoes homogenization treatment is because tempered glass, as a safety glass, still has a certain risk of self explosion. After homogenization treatment in a homogenizing furnace, the self explosion rate of the finished tempered glass can be reduced to less than one in ten thousand, greatly improving the safety performance of the tempered glass.

Process principle

The nickel sulfide inside tempered glass, as a non vitreous material particle, has always existed in the glass and is the main factor leading to self explosion of tempered glass. Nickel sulfide is brought into the glass by impurities in the raw materials used for producing glass, such as quartz sand and silica powder. Some nickel sulfide particles undergo a period of time, and their crystal structure changes from α State transition to β Status, in this α one β During the transformation process, the volume of nickel sulfide particles expands significantly. This process of volume expansion creates strong internal stress on tempered glass, causing it to self explode.

(Note: Not all nickel sulfide can cause glass self explosion. Nickel sulfide located in the compressive stress layer and nickel sulfide that cannot reach the critical diameter will not cause glass self explosion.)

Due to the crystal transformation of nickel sulfide, the volume increases, leading to self explosion and the production of radioactive cracks locally, as shown in the following figure. If the glass still remains inside the frame after being broken, a butterfly shaped pattern feature can be easily found at the starting point of the breakage. From the "butterfly spot" generated in the glass fragments after self explosion, at a 45 degree angle, it is easy to see a small black spot placed in the "butterfly" at the center of the glass plate, right between the cracks, and the direction of the self exploded glass cracks is scattered from the center to the surrounding areas.

The homogenization treatment of tempered glass by secondary heating and annealing(also known as hot dip treatment)is recognized as an effective method to solve the problem of self explosion.Heat the tempered glass again to around 290±10℃and keep it warm for a certain period of time before slowly cooling down,so that the nickel sulfide particles in the tempered glass complete the crystal phase transformation in homogeneous treatment.This allows the glass that may self explode to be crushed in advance in the factory,effectively reducing the self explosion rate of tempered glass after leaving the factory,improving the yield,and reducing the adverse effects of transportation,installation,and subsequent process rework caused by self explosion.

At present,the main method for homogenizing tempered glass in China is to use a forced convection electric heating hot dip furnace.Most of the existing tempered glass homogenization furnaces have heating boxes located at the top or back of the furnace body.A fan is used to transport hot air through the air duct to the tempered glass that needs to be homogenized in the furnace,and the hot air is sucked back into the fan through the gap between the tempered glass.It is continuously repeated to heat the tempered glass to the rated temperature and maintain a constant temperature for a long time,in order to achieve the purpose of detonating the tempered glass with the risk of self explosion.

Preparation work

(1)Before conducting maintenance,the main power supply of the homogenizing furnace electrical cabinet must be turned off and a warning sign must be hung.

(2)Wear a safety helmet,mask,and gloves,and wear a safety rope when climbing onto the furnace.

(3)When maintaining the electrical cabinet,the operator must hold a certificate and be on duty.

(4)When improving the equipment,it is necessary to follow the equipment user manual and manufacturer's guidance,and after completion,conduct inspections to ensure that the equipment continues to meet safety requirements.

Furnace inspection and maintenance

After years of use,there is a certain gap in insulation effect between the homogeneous furnace and the new furnace,so it is necessary to regularly maintain the furnace body.

(1)During the hot dip treatment of glass,check the sealing of the furnace door.If there is any air leakage in the furnace door,replace the sealing cotton of the furnace door after the furnace is shut down.Please do not touch the furnace body during the inspection process to prevent burns.

(2)Check if the insulation cotton on the top of the furnace pipeline is loose or damaged,and if there is any looseness at the pipeline connection during shutdown.Directly exposing pipelines to the air will take away some of the heat energy,leading to an increase in electricity consumption.

(3)Regularly use a laser digital tachometer to measure the speed of the cooling circulation fan at power frequency.If the speed is too low,it will cause insufficient heat exchange of the circulating fan in this area,resulting in lower temperature in this area compared to other areas.After stopping the furnace,it is necessary to adjust the cooling circulation fan belt.

(4)The cooling circulation fan's impeller,impeller shaft,and bearings are constantly in a high-temperature and high-speed state,which is prone to failure.The bearings need to be regularly lubricated with high-temperature lubricating oil.Check if the wind turbine is deformed,if there are any abnormal noises or excessive clearances in the bearings,and replace them in a timely manner if any problems occur.

(5)Regularly inspect the gas pipe and gas pipe joints during shutdown,as the gas pipe will accelerate aging and rupture in high-temperature environments.

(6)Timely clean the scale in the cooling water tank to ensure the normal operation of the cooling water circulation system.

(7)Manual damper solenoid valve switch,check the working status of the solenoid valve and cylinder.In high temperature environments,the sealing ring inside the solenoid valve and cylinder is prone to damage,resulting in the damper not being able to open.This problem is not easily detected during the production process,and the time for the glass to cool down will be extended.

(8)Check the stainless steel sealing plate inside the furnace body.If any screws fall off,they must be fixed in a timely manner to prevent the sealing plate from falling off and damaging the glass during the production process.

(9)Check the heating tubes and high-temperature wires of the furnace body.Under high-power conditions,the wiring terminals of the heating tubes and high-temperature wires are prone to oxidation and heating,leading to burning of the wiring terminals.Regular replacement of wiring terminals is required to ensure good contact between the high-temperature wire and the heating tube.

Regularly observe the temperature control curve

(1)The homogenization treatment stage of tempered glass is divided into three stages:heating stage t,constant temperature stage t2,and cooling stage t3.

(2)By observing the current or historical records of each temperature control curve,the temperature situation in the region can be analyzed.When the temperature is relatively low compared to other areas,stop the furnace and check the thermocouples and heating tubes.When the temperature is relatively high compared to other areas,check if the solid-state relay is faulty.

(3)The temperature curve of the furnace body can only be qualified in the best condition,so that the quality of the glass meets industry standards.

Epilogue

After hot dip treatment,tempered glass reduces the probability of self explosion,improves the quality of tempered glass,and solves the problem of glass self explosion in the construction industry.Only by understanding and familiarizing oneself with the operation and maintenance of equipment in any state can the performance of the homogenizing furnace be more stable and provide guarantees for normal production.

Fuyuan tempered glass homogenization furnace

The above is an introduction to the working principle and inspection and maintenance of a homogenizing furnace,hoping to help everyone better understand.Foshan Fuyuan Glass Technology Co.,Ltd.is a professional manufacturer of homogenization furnace equipment.Fuyuan homogenization furnace effectively prevents self explosion of tempered glass,ensuring quality.Welcome to consult!

Source:Architectural Glass and Industrial Glass,Li Fan from Zhongshan Grant Industrial Co.,Ltd.,Wang Yong from Tianjin Nanbo Engineering Glass Co.,Ltd.,Jubo Information,and online materials

Address:No.1 Sanhe Road,Gaoming District,Foshan City,Guangdong Province

Contact information:

13702975894 Mr.Hu

13709659484 Miss Li