#AskGlaston Episode 6: How to reduce glass breakage and eliminate hot spots?

You have been excellent again and sent us many interesting questions. This latest #AskGlaston episode will cover three of your questions:

  1. How to reduce breakage in the quenching section?
  2. What is the lifetime of a tempering line? How about the electric system?
  3. How to eliminate hot spots from tempered glass?

Watch our video response here. I hope you’ll get new insights, share those with your colleagues and raise your quality level. Keep your questions coming, and we’ll keep answering them!

How to reduce breakage in the quenching section?

The most common reasons for glass breakage in the quench are:

  • Too low glass temperature when it exits the heating section
  • Poor glass pre-processing quality, including cutting or edge work

Both can be easily corrected. Remember to follow the glass exit temperature from the pyrometer or temperature scanner that is installed after the heating section. This always gives a good indication of the glass temperature.

The pre-processing quality is more of a process issue. Service your pre-processing equipment properly and use the right tools to ensure good results.

What is the lifetime of a tempering line? How about the electric system?

Glaston has several tempering lines working around the world that have been in production for over 30 and even 40 years. So the lifetime of a tempering line can be several decades if it’s serviced properly.

The lifetime of the electrical systems is shorter. Their development phase has shortened so much that also the recommended, and sometimes mandatory, upgrades come at a faster pace than before. Just 30 years ago, a control system upgrade might have taken place after 15-20 years of operation. Today, the average lifetime is estimated to be 5-10 years, and sometimes even faster. It is important that your supplier is able to upgrade the control system so that you don’t end up in a situation without any support for your line.

How to eliminate hot spots from tempered glass?

The main reasons for hot spots are either that the glass has been too hot or there are defects in the ceramic rollers. Many times, it is a combination of both. Also the incorrect heating profiles can cause hot spots if some part of the glass has more contact with the rollers than others.

The first thing to try is always to bring the temperature down. This should usually work. If there is a consistent pattern of hot spots, check the rolls and clean them. If you experience hot spots with a large or otherwise difficult glass piece, try doing a temperature profile to keep the glass heating more evenly in the heating section. It is common that in full loads of thick glass, the leading and trailing edge of the loading absorb more heat, which then creates hot spots. Reduce the temperature profile at the loading and unloading ends of the heating section to avoid overheating the glass edges.

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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.