What Is The Air Forced Convection Piping System for Glass Tempering Furnace And Its Role During Heating Process of Glass Tempering Oven

LV Series Glass Tempering Furnace With Force Convection System is one of our newest products. It is used for producing the tempered glass for architecture, automobile, and other industries. Compared with the common (traditional) tempering furnace, this equipment not only has the performances of the common (traditional) tempering furnace, but the higher production efficiency, better surface quality, etc. it is especially for processing the top grade glas, such as, Low-E glass, coated glass, and so on.

The heating oven of the common (traditional) glass tempering furnace is divided into upper part and lower part for heating. The upper part and lower part is divided into several small zones further according to the size of the heating oven. Each heating zone has its thermocouple forming an independent control loop.

For the traditional glass tempering furnace, the lower side of the glass is heated by following two ways:

1. Ceramic rollers conduct heat to the glass.

2. Heating elements in the Lower part radiate heat to the glass.

The main heating way is the ceramic rollers conducting heat. The upper side of the glass is heated by only one way: heating elements in the upper part radiate heat to the glass. The different heating way for the upper and lower side of glass results in that the heating speed is also different: the upper side is slow and the lower side is fast.

There are two general resolvents for this matter:

a. Reduce the distance between the glass and the heating elements in the upper part;

b. reduce the heating temperature of the lower part and increase the heating temperature of the upper part. However, if the distance between the heating elements and the glass are too close, the glass surface quality will be affected, so the second way is usually took.

When tempering the Low-E glass, Coated glass, the film should be up towards in case that the film being scratched. But on the other hand, the film has a high reflection index, therefore a great deal of heat is reflected back. Thus, the heating speed of the upper side is lower than that of the lower side greatly. The only way is to reduce the heating speed of the lower side, increase that of the upper side and prolong the heating time to make the heating symmetrical. But it will lead to a lower production efficiency.

According to the above analysis, we think, because the upper side of the Low-E glass, Coated glass is heated by only radiation, the heating time has to be prolonged. On the other hand, the above method for balancing heating the upper & lower side of the glass will reduce the heating ability and efficiency of heating system in the lower part.

Based on the above analyse, we can increase the heating efficiency greatly by keeping the lower part heating way unchanged and changing the upper part heating way. So we equip the upper part of the heating oven with force convection system.

This system can blow the circle hot air which from the upper part heating elements to the glass upper side closely. Thus the heating way of the upper part is changed from the single radiation to radiation & convection. The heating speed of the glass upper side is increased greatly.

In the meantime, the temperature in the heating oven is more symmetrical and the glass is heated more evenly.

But for the traditional glass tempering furnace, the edges and center of the glass is over heated. Since the heating efficiency is increased, the heating time is shorted and the heating speed is higher of 25%. That is to say, the heating time is reduced from 40s/mm to 30s/mm and the production efficiency is increased 25%. The time for glass swing in the heating oven is reduced and the possibility of the wave, pockmark is also reduced. The glass surface quality and flatness is increased greatly.

This forced air convection system is especially suitable for processing the glass which two sides absorb the heat at different speed, such as the Low-E glass, Coated glass

The force convection system consists of transmission motor, convection blower, air-entering pipe, air-exiting pipe, etc. each motor is equipped with one inverter. By adjusting the rotated speed of the motors to control the convection quantity, thus the effect proportion on the glass upper side between the convection and radiation can be kept in a suitable range. The advantage is that it can both increase the heating speed and keep the advantage that the heating temperature in each zone can be adjusted separately.

The detailed structure and airflow cycle principle of the force convection system, please refer to the attached drawing.