FDS Glass Corporation                       
Glass Tempering Furnace

                Grid-Array Forced Convection Tempering System

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AF-1 Glass Tempering Furnace










Heating Section with Forced Convection System


                     The structure of heating section is of a double-layer box type covered by thermo-insulating material. The use of new insulation material (a kind of porcelain-oriented thermal insulating board with anti-airflow erosion characteristic) on the nner surface of heating chamber successfully ensure no crumb falling down from the insulation material surface. Inside the heating section, there is a conveyor system with high temperature resistant ceramic rollers, which are manufactured by VESUVIUS, HALDENWANGER, etc. The adoption of synchronous cog belts for conveyor of ceramic rollers greatly improves drive accuracy, which decreases the glass scratch problem caused by roller speed difference and the faults caused by glass position change, then increases glass productivity and optical quality. The heating elements are installed in both upper layer and lower layer of this section, which is of an integrated part with spiral type resistance erected on ceramic part and can be easily replaced. Each heating zone is controlled by an independent thermo couple and PID loop. Both conveyor rollers of the loading table and heating section are moving synchronally at forwarding the glass into the heating chamber. The front door closes after the glass batch enter into the heating chamber. The number of glass oscillating strokes is calculated by the control system automatically, so that the glass will be evenly heated. The upper section can be lifted up under cooling down situation, for purpose of maintenance. The heating elements are in matrix layout arrangement. The ceramic rollers of the furnace are provided with special capsulated bearing, for purpose of avoiding pollution. The device of SO2 is composed of a gas bottle (supplied by the Buyer), an air pressure reducing valve, flow meter and pipes (inside and outside), etc. By using this device, a thin film is formed on the surface of the ceramic rollers which can reduce the friction between the glass surface and the ceramic rollers. This will reduce or prevent the white haze phenomenon problem. In case of a main power breakdown, the glass will be evacuated from the heating chamber by using of UPS emergency driving system, or additionally with the help of a crank by which the rollers are to be moved manually.

 

Main features:

        1 Perfect combination of matrix radiation heating system and grid-array forced convection heating system, fully satisfy the processing demand of Low-E glass and other high quality glass.

         2 High temperature convention fans are made of aerospace material (superalloy) by special welding process. The rotation speed of each convection fan motor is controlled by one frequency inverter. Its well-sealing performance and effective thermo bridge blocking technology, which provide stable and efficient engine to the forced convection system, assure the life time of these fans as well as their stability.

         3 Bilateral convection fans, even and smooth air circulation and bilateral hot air blowing units well ensure the steady air pressure and flow in the heating chamber. The use of stronger power for convection fans in upper part, well balance the conduction heating from ceramic rollers in bottom part, which well ensure the uniform and symmetrical heating in whole chamber, as well as keep the glass flat since its entering into the heating chamber.

         4 The grid-array arrangement of radiation heating elements and convection blowing units complement each other. This ensures the even heating coverage in whole heating chamber and successfully overcomes the problem of leopard spots caused by uneven heating.

        5 The use of anti-oxidation and anti-deformation heat resistant alloy, plus the use of advanced manufacturing technology, ensure the durable performance without distortion of inner air circulation system. 



 

Rubber rollers: The rubber covered roller was coated with wear-resistant, heat resistance, silicon-free and anti-static material. The upper main line is higher than the side aluminum shielding to bring great convenience of the loading and unloading the glass.

 
 

 Lighting system: It is convenient to check the quality of the float glass and also the optical quality of tempered glass. Arch shape cover of the lighting system will make broken glass to be easily cleaned.

 
 

Bilateral convection fans, even and smooth air circulation and bilateral hot air blowing units well ensure the steady air pressure and flow in the heating chamber. The use of stronger power for convection fans in upper part, well balance the conduction heating from ceramic rollers in bottom part, which well ensure the uniform and symmetrical heating in whole chamber, as well as keep the glass flat since its entering into the heating chamber.

 
 

Main driving system is Servo control with “U” type synchronous belt driving system. It reduces the glass scratch damage between different speeds of the rollers. The life of the ceramic rollers has been extended. The no-aperture structure has been adopted in the main driving system, easy to disassemble.

 
 
The high temperature convection fans are allocated on one side of the furnace. The blowers are made of aerospace material (superalloy) by special welding process. The motors of the convection fans are speed controlled by inverters. The addition of air distribution devices inside ventilation circuit ensures that the air pressure and flow are evenly distribute on both left and right sides when air is entering from only one side by convection fans. More powerful configurations of convection fans balance the heat transfer effect from ceramic rollers at the bottom and achieve the entire heating uniform and symmetry inside the whole heating section, which finally ensure that the glass sheets are flattened totally since entering into the heating section.
This Grid-Array forced convection tempering furnace is suitable for tempering flat glass to high standards, coated glass (including temperable soft coats), and cast glass. The heating speed is remarkably improved.
 

QUENCHING SECTION:
The blast heads are divided into upper and lower parts. The nozzles are made of aluminum alloy, and the distance between glass and upper/lower nozzles can be adjusted according to the quenching demand for different kinds of glass.

In among the blast heads, there are a lot of rollers conveying the glass sheets forwarding.  When the glass sheets come

out the furnace, the rollers here will move synchronously with the rollers in the furnace, to transit the glass sheet into

quenching section. Then, the glass sheets will move back and forth with the rollers, to keep evenly quenching. While the

glass is oscillating in the quenching section, the quenching parts are oscillating in transversal direction, the main

purpose is to decrease the glass stress and evenly quench in this section. Meanwhile, the blower will immediately blow

the air on the surface of the glass through air ducts. The air pressure and flux is decided by blower speed, which is

controlled automatically by the control system. The rollers are spirally rolled with Kevlar band.

Lifting of the quenching section: The upper and lower of the quenching section can be lifted by motor separately by

using the encoders. The distances between the quenching sections and glass can be adjusted by the computer.

Special steel rollers in Quenching section: customized of one-time cold-drawing steel bars which have excellent

character of anti-deformation. They replace the normal steel or ceramic rollers and combine both advantages of them.

They play the very important role in guaranteeing the super flat glass producing.



 

Removable air pressure block: During the quenching procedure, the air pressure in the down side of the glass will definitely higher than the top side because the air must be partially blocked by the rollers in the down side. When tempering the very thin glass, this unbalance of the air pressures between top and down side will cause the thin glass sheet to be “floating” over the rollers, which will consequently affect the final quality of the tempered glass. The air pressure block can be used to balance the air pressures, further to secure the glass quality  When make a thick glass, the removable air pressure block can be moved away from the glass sheet for realizing the better quenching result lighting in the quenching section: Linear fluorescent lighting device is location alongside the roller transfer level which

makes the observation of the quenching to be easier.

Observation windows: They are elaborately designed with a flexible device which can be easily stopped at any vertical

position, safe, convenient and functional.

Quenching parts oscillating in transversal direction: to evenly quench the glass and decrease the glass stress inside.




Organ Shape air pipe and Diversion structure: Organ shape air pipe make air flow completely unblocked whenever th equenches are moving vertically or horizontally. Diversion structure design makes the air pressure evenly in each point.


Lighting in the quenching section: Linear fluorescent lighting device is location alongside the roller transfer level which makes the observation of the quenching to be easier.


 Loading table

The loading table is composed of rubber-covered steel rollers. Each roller is driven by a belt pulley on the drive side, except the first roller which is non-driven. The loading table is equipped with a pneumatic actuated castor balls table with vertical movement, allowing the easy positioning of the glass. When the glass is put onto the rollers, the glass will be automatically conveyed to the entrance of heating section where it will be at ready-to-enter-furnace position and then conveyor rollers stop moving. It will send the glass into the heating section once the computer gives enter instruction.

The loading table is equipped with several non-driven lateral rollers which are used to load large glass sheets from lateral working side of loading table.

 

Main features

1.New type rubber covered steel rollers: High strength, beautiful appearance and durable.

2 Lighting system: It is convenient for the operator to check the glass optical quality; Arch shape cover over the lighting system will make the cleaning of cullet easily.

3 Rollers speed control: The transmission speed of conveyor rollers is controlled and adjusted by inverter (frequency control), which ensure the consistency of transmission speeds of loading section, heating section and quenching section. The transmission speeds of loading & unloading conveyors can be adjusted at any time, which is helpful to improve the productivity.