Quality management in the production of insulating glass: what role does the gas fill rate play, Nils Hirschfeld?

Gas content measurement service

Nowadays, multi-pane insulating glass should last at least 25 years. In order for insulating glass units (IGUs) to retain their required U-value, manufacturers must ensure that the gas content in the cavity between the panes of glass remains as high as possible throughout the life cycle of the product. Nils Hirschfeld, product manager at Technoform, uses the latest measurement technology to investigate the causes of gas leakage. In this interview, he explains the significance of the thermally optimized edge bond for the gas fill rate and why it is worthwhile for manufacturers to continuously refine their quality management processes. 

Nils, you have often been seen around Technoform lately with a measuring device on wheels that you pull behind you like a trolley. What is that all about? 

The case contains a Sparklike Laser Portable™, the latest generation non-destructive measuring device which is used to determine gas fill rates for double- and triple-glazed insulating glass units. The whole system is based on so-called Tunable Diode Laser Absorption Spectroscopy (TDLAS) which sends, in the case of double glazing, a laser beam through the first pane of glass and it is then reflected back by the first surface of the second pane of glass to the detector. The laser beam determines the dimensions – in other words, the whole construction – of the IGU and calculates the concentration of noble gas in the cavity between the panes of glass based on the residual oxygen content in the cavities of the IGU.  
When carried out regularly, TDL absorption spectroscopy enables changes in the gas concentration to be detected and documented easily and with very little effort throughout the life cycle of the product. The measurement carried out directly after production provides the manufacturer with important information on the quality of his products, methods and processes. Information on the durability of the edge bond can be obtained by checking the gas fill rates of insulating glass units already installed. Technoform wants to improve the quality and durability of insulating glass with warm edge and help manufacturers to continuously refine their quality management in respect of gas filling in the cavity between the panes of glass (and more).

Short film on how the Sparklike measuring device is used

Today, insulating glass elements are made using the latest processes and technologies. You would think that they would be completely sealed and that no insulating gas could escape. So why do you focus on the gas fill rate and gas leakage so much? 

Insulating gases such as argon, krypton or xenon are extremely volatile and in the long run, not even the best edge bond seal would be able to stop these escaping. However, gas leakage can be slowed down over the life span of the glass if all the edge bond components are optimally coordinated. That is what we focus on and where very large insulating glass elements which are exposed to climatic or mechanical loads are concerned, it’s an extremely important topic. That is why at Technoform, we do not only look at our product – the thermally optimized hybrid spacer – but we also want to take responsibility for the whole glass edge bond. After all, what’s the point of having the best spacer if it doesn’t interact optimally with sealants, desiccants and other glass edge bond components? 
Comparatively high gas leakage is often found in insulating glass elements which were installed 20 years ago or more. It’s no wonder when you think that back then, edge bonds were not at the level that we have today. Also, requirements weren’t as stringent as they are today. Warm edge systems like the ones produced by Technoform have played an important part in enabling the energy efficiency of the glass edge bond to be increased to the level that it is at today.  
I am particularly interested in the behaviour of today’s systems throughout the product life cycle. We have started a long-term study in order to find out more about the factors that influence the quality and durability of the glass edge bond and we have already tested and documented nearly 1100 units to date. The knowledge that we have gained should help us and our partners – the insulating glass manufacturers, designers and window manufacturers – to continue to further develop their know-how regarding their products. 

We are in the process of carrying out a long-term study in order to find out more about the relationships in the edge bond and the long-term behaviour of various Warm Edge systems.
Please contact us if you want your products to be included in the study.

The Technoform field study on the gas fill rate and quality of argon-filled multi-pane glazed units was only started in 2019. But you have already tested nearly 1100 units using Tunable Diode Laser Absorption Spectroscopy. Have you seen any results yet? 

It’s still too early for any reliable statistical assessment, we need to collect data over a longer period of 10 to 15 years for that. However, we have already observed that insulating glass manufacturers are managing the gas fill rate of their products well, which is good news. Nevertheless, we see approaches to improve the durability as well as to further refine the quality management in the entire value chain with regard to the gas fill rate, in order to proactively minimize the risks of gas leakage which will gradually reduce the energy performance of insulating glass units. Modern test methods like TDLAS enable us to check quality on an ongoing random basis and identify weak points.  
By doing this, materials and processes can be continually improved, creating added value for the end consumer. I see this as a major opportunity for manufacturers to make the best possible preparations for the future. After all, it’s quite possible that at some point, gas fill rate measurements using mobile measuring devices will be carried out as standard, as part of building inspections or warranty testing, for example. Insulating glass manufacturers should prepare for this in good time, and we are happy to support our customers with our experience and know-how. 
Nils, thank you very much for the interesting interview! 

Suggested reading

Would you like to learn more about quality assurance and sustainability aspects at Technoform?

Then read Sparklike Oy's interview with Sebastian Plettenberg.

For more information on the gas fill rate in insulating glass units, read our specialist article here in the Technoform blog soon.

Any questions?