How do environmental factors affect the glass tempering process?

If your processing plant is located in an area where the temperature is colder during the winter and warmer during the summer, you have most likely experienced the impact of the outside air temperature when running your glass tempering line. In this post, I’ll cover the main things to consider to take better control over your glass tempering process in all environmental conditions.

Usually, the tempering process utilizes outside air for creating the required tempering pressure. The air temperature has an impact on the tempering effectiveness, which is scientifically called the heat transfer coefficient. The lower the air temperature, the better the tempering effect. The difference is not huge but can be meaningful especially with thinner glass of 3 or 4 mm. For example, when the outside temperature is -20 °C or +35 °C, there is a clear difference in tempering results. In temperatures of +35 °C, many processors may face difficulties to temper even the thinnest glasses. However, when the outside temperature is -20 °C, the fragmentation pattern occurs easily. This proves that the temperature has a clear effect on the tempering process.

There are several things to consider regarding temperature. In the end, it will help you make sure that your glasses are always tempered properly and that your energy is utilized in the most optimal way.

Here is a 5-step guide to overcome most challenges with varying outside air temperatures:

1) Make sure you have the capability to process the thicknesses you need – always

As number one, make sure your tempering line is suited for its purpose. I have been in several discussions where the glass processor’s existing tempering line had difficulties in getting the glass tempered during the hottest days of the year. If this was known by the processor at the time of the glass tempering line investment – fine. But sometimes this issue is revealed only later. And in this case, it is simply a question of an incorrect dimensioning of the blowers and quenching unit.

One solution to overcome this challenge in thin glass tempering, such as 3 mm, is to use compressed air technology for quenching instead of relying on the blowers and outside air. This technology is called the boost unit. It utilizes compressed air, which is always the same temperature. The compressor pressurizes a tank, which then releases the required pressure and air volume when the glass is heated and enters the quenching section. This system works in the same way despite any variations in outside temperature and thus provides a very stable solution for thin glass tempering.

So, when investing in a glass tempering machine, make sure the line is capable of doing what you need it to do under all circumstances. Remember to ask your supplier about this.

2) An operator’s tempering process know-how is crucial

A warmer outside temperature requires higher pressure settings than a cooler air temperature. This means the operator needs to make changes to the tempering settings as the temperature varies. If, for example, the operator makes a fragmentation test in the morning when it is +10 °C and then the temperature warms up to +25 °C during the day, there is a risk that the glasses being processed during the day are not fully tempered. Since this is the last risk you want to take, it is important that your tempering line’s operator knows the impact of the outside temperature and how to adjust the process accordingly.

There is also a more fail-safe approach to do this: consider automation.

3) Consider automation

The easiest solution for dealing with outside air temperature variations is to utilize automation. As an example, all Glaston tempering lines include the possibility to utilize an option that takes the outside temperature changes into account and makes all needed adjustments based on the measured temperatures – automatically.

4) Utilize the tempering process energy for optimal energy efficiency

Many times, the tempering air is taken from outside. However, it can be taken also from inside. In locations where there are wide temperature variations, the best solution is to have air intake from both inside and outside.

For example, during cold winter times, you can mix the inside air and the outside air by using plates that control the air flow. In the winter, you can utilize the air after tempering to heat the factory. This will save energy, reducing your heating bill, and will stabilize your tempering process.

5) Make sure the air quality is adequate

There are some geographical areas with sudden storms or even sand storms. In these cases, it is important to have filters on the air intakes so that no larger objects, like sand or large dust piles, are collected within the tempering line.

When you follow the steps listed above, you can feel confident that the changes in your surrounding environment will have little or no impact on your production. What’s more, keeping this list in mind, you can even take advantage of the changes in the outside temperature conditions.

In other words, the glass you process can always be tempered with the proper quality, while your electricity bills can be minimized. Important things, right?!

Do you have other concerns or questions regarding the impact of the environment on your tempering process? Shoot us a question and we’ll do our best to help you.

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About the author

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Miika Äppelqvist

Encourages transparent solutions in buildings and ways of working. Seven years of experience from being a glass-man in product management, sales and projects with a focus on glass heat treatment. Believes helping is the best marketing any company can do. Father of two toddlers and a wannabe sportsman with an internal love of ice hockey.