Keeping pace with high performing insulating glass products is a struggle for quality control, especially when it comes to insulating gas retention. The non-invasive testing method makes it possible to measure gas concentration of insulating glass unit on even double and triple glazing with the most coatings and lamination and deliver tested products to end-users.
Energy efficiency of insulating glass units
Glazing products today have higher and higher performance needs, and the requirements for better products are growing steadily. Today’s glass products carry a wide range of elements enhancing their properties. One main property is the energy efficiency in both heated and cooled buildings. The energy properties can be enhanced with various methods, such as coatings, multiple glass layers and inserting a medium in between. The medium can be normal air, vacuum, or specific gas – typically argon or krypton.
A common insulating enhancement in modern insulating glass (IG) unit is filling it with argon or krypton gas. The insulating gas is applied to the cavity either during the manufacturing process at gas press station, or manually to the ready-made units. The challenges are confirming the correct filling degree and ensuring that the initial gas concentration will remain inside the insulating glass unit (IGU). A gas escape could occur from improper sealing of the IGU, and this needs to be tested prior to shipping the IG to customers. Product liability for the insulating glass and window suppliers can last several years after the initial delivery of the product. Thus, they are looking ways to increase the security of the gas fill.
Even though clear standards do not exist in all areas, the industry and manufacturers have formed best practices to produce high quality insulating glass. The fact that small molecule gas is prone to leakage is a challenge, and thus manufacturers aim to ensure the maximum possible content of argon after the gas filling – typically 95% and over.
Insulating gas measurement methods
The actual argon measurement can be conducted either with an invasive or non-invasive method. The invasive method penetrates through the sealing of the IGU, and the gas sample is calculated automatically. These are generally affordable and robust technologies with good accuracy but require breaking the IG structure. In practice this means that the IGU cannot be delivered to the customer or retested.
Plasma emission spectroscopy for gas analysis
The non-invasive method allows measuring the glass without breaking the IGU. The most commonly used non-invasive method utilizes a spark that is ignited through the glass. Based on the color of the ionized gas, the argon content is calculated automatically. This method is fast and accurate and used widely on double glazed units as measuring can be done from monolithic glass side for the non-coated surfaces. The non-invasive method can be repeated as many times as the quality system or the end-user requires. The limitation of spark technology is that it can measure double-glazed units with just one low-e coating.
TDLAS technology in IG unit quality control
The breakthrough in measuring technology solves the issues attached to currently used methods to test insulating glass gas concentration. The laser based technology is capable to measure non-invasively double and triple glazing and through coatings and laminations.
The technology, called TDLAS, allows testing of complicated structures, such as energy efficient triple glazing. This brings the level of quality assurance of these high performing glazing units at pair with advanced product expectations. As the laser technology measures non-invasively the oxygen level, it can measure the percentage of any gas.
The technology applies modulated laser beam into the IG, and by measuring the reflection, intensity, and harmonic changes in signal it can determine the oxygen content inside the cavity. Oxygen concentration can be then converted into insulation gas percentage. The most used insulating glass gases are argon and krypton.
Gas analysis is a sales argument
Having gas content information from every piece of the unit produced can be used in efficient quality control of the production line. The laser-based system is possible to be installed on-line and connected to the production control software or to the control system of the production line. Quality control in today’s factory operations plays an ever-increasing role that is not only seen as eliminating the rejects but also as a sales argument.
