INDEPENDENT TESTING OF SPARKLIKE LASER NON-DESTRUCTIVE INSULATING GLASS GAS FILL ANALYZER ased on a test report by TÜV Rheinland R&D Manager Kai Niiranen, MSc (Tech.); Development Manager Jarno Hartikainen, MSc (Chem.); Production Manager Ville-Petteri Säily, Eng. (Med.) INTRODUCTION Insulating glass units (IGU) have higher and higher performance needs, and the requirements in insulating gas (IG) market are growing all the time. A common insulating enhancement in modern IGU is filling it with noble gas such as argon or krypton. The challenges are confirming the final filling degree and ensuring that the initial gas concentration will remain inside the insulating glass unit. Different markets have different standards for gas concentration, but usually the gas content needs to meet or exceed 90% with a margin. A gas escape could occur from improper sealing of the IGU, and this needs to be tested prior to shipping the insulating glass to customers. Product liability for the insulating glass and window suppliers can last several years after the initial delivery of the product. Thus, glass and window suppliers are looking ways to test their units quickly and cost-effectively. Although invasive methods have their advantages, insulating glass industry specialist are looking for new ways to analyze the insulating gas fill. Sparklike Oy has developed a technology that allows the measurement of the IGU s gas fill without breaking the glass or having any extra components inside. The analyzer measures the IG gas concentration on double and triple glazed units. The measurement can be done through most coated and laminated glasses. However, window and door manufacturers use a plethora of different coating in their IGU s. Therefore, Sparklike Oy requested TüV Rheinland to perform a test in order to determine the argon gas concentration in insulating glass units by using a particularly challenging test specimen. This test specimen included samples with different constructions i.e. clear glass, strengthened glass and laminated glass with different coatings. The purpose of the test was to verify the results
from measurements done with Sparklike Laser Standard analyzer, by using gas chromatograph as a reference device. TüV Rheinland was selected, since they are a globally active independent test service provider. Since 1872, they have been developing solutions to ensure and enhance safety, quality and economic efficiency in various of markets by providing testing, inspection, certification, consultation and training services. 1. DESCRIPTION OF THE TEST EQUIPMENT SPARKLIKE LASER STANDARD AND GAS CHROMATOGRAPH Sparklike Laser devices are based on technology known as TDLAS (Tuneable Diode Laser Absorption Spectroscopy). y using this technology, the device measures oxygen and from there, the amount of argon, krypton or other insulating gas can be calculated. When measuring the gas concentration from inside the IG unit, the laser beam goes through the first pane and is reflected to the detector from the first surface of the second pane (when measuring a double IG). With a triple unit, the laser beam goes through two panes and is reflected from the third pane. To get the focused laser beam to the correct measuring point, the IG dimensions are first scanned. This is done by moving the focused laser beam through the IG and collecting the reflected signal in order to obtain accurate dimensions of the IG. This, in return, enables the calculation of the gas concentration(s). Different IG coatings have different transmissions. Opposite for transmission, is reflection. Simple equation for reflection is R = 1 T, where T is transmission. When measuring an IG unit with a low transmission on the first pane and high transmission (low reflection) on the surface where the beam is reflected to the detector, the measurement signal is small and the device accuracy can be reduced. The following figure 1 shows different low-e product transmissions versus wavelength, where the vertical red line indicates the laser (wavelength = 760 nm) used in the Sparklike Laser devices.
Low-e products transmission as a function of wavelength Figure 1 Float and different low-e coated glass transmissions. As we can see from the figure 1, different coatings have different transmission spectrum and the transmission depends on the wavelength. An ideal situation to get a good measurement signal response from inside of an IG unit is, to have a high transmission on the first pane and high reflection on the second pane on 760 nm wavelength. In this case when there is a strong signal, the device accuracy is higher. The Sparklike Laser device scans structures of IGU and from scanning information, the analyzer calculates thicknesses for the glasses as well as for the cavities. y using the measured dimensions, the device determines reflection surfaces and from the received laser signal, the gas concentration is quantified. When measuring triple glazed units, at first the device measures the average gas concentration of the cavities and then, the gas concentration of the first cavity. The first cavity is the nearest to the device s measuring head, and is later referred as side A. The side, on the other hand, refers to the second cavity. Furthermore, using the obtained results of the 1st cavity and the average results, the gas concentration for the 2nd cavity is calculated. In other words, since the result of the second cavity s gas concentration is computational, it is correlated to the accuracies of the 1st cavity and the average gas concentrations. The
concentration of the second cavity is calculated from the weighted average formula as follows: where x = # $ ' &(# ω & x & (1), x is the average gas concentration of the IGU W is the overall length of the spacers ω is the spacer length x is the cavity gas concentration where x * = + $-+. /. / 0 (2), x 2 is the second cavity gas concentration x 1 is the first cavity gas concentration ω 1 is the first cavity length ω 2 is the second cavity length As can be seen from the equations above, the role of the average error is more emphasized. The gas concentration can also be measured with a gas chromatograph, an invasive test device to analyse gas concentration within double and triple glazed insulating glass units. The gas chromatograph device used in this analysis was a type Varian CP-4900 micro GC with a 20-meter molecular sieve 5A PLOT column set at 30 C. The measurement uncertainty is determined +/-1 % (absolute). 2. DESCRIPTION OF THE TEST SPECIMEN In order to receive reliable results, Sparklike provided 12 pieces of test glasses (350x350mm) purchased from a Finnish CE marked glass manufacturer producing insulating glass units according to EN 1279-5 standard (evaluation of conformity). The samples consisted of 7 double and 5 triple glazed units with different types of glass and coatings. The insulating glass unit combinations were selected to be challenging and thus descriptive of the limits. This was important in order to better express the capabilities of Sparklike Laser Standard analyzer.
The following tables number 1 and number 2 summarize the test specimen for double and triple glazed units. Sample numbers 7, 9 12 represent triple glazed units and samples 1 6 and 8 represent double glazed units. The samples configurations are based on the information label on the glass. Different configuration elements are being separated with vertical line ( ). Furthermore, all the configurations are listed moving from side A to side. Further explanations for different configurations can be found at the end of this article (Appendix). Sample Side # A Configuration / information from label on glass Side 1 A Optiwhite 4mm 12mm alu optiwhite S1N 4mm 2 A Optiwhite S1N 4mm 12mm alu Optiwhite 4mm 3 A 4 A Strenghtened LowE 4mm (t) 16mm alu Lam 3+3 0,38 Suncool 70/40 4mm 12mm alu Strenghtened 4mm 5 A Float 4mm 6mm alu float 4mm 6 A Float 4mm 12mm alu Strenghtened 4mm 8 A Lam optiphon 6+6 1,14 20mm alu LowE 6mm Table 1: The test specimen for double glazed units. Sample # Side A 7 A 9 A 10 A 11 A 12 A Configuration / information from label on glass Lam 4+4 0,76 12mm alu float 6mm 15mm alu LowE 6mm Lam 4+4 1,52 12mm alu float 6mm 15mm alu LowE 6mm Lam 4+4 0,76 12mm alu float 6mm 15mm alu Strenghtened LowE 6mm (t) LowE 6mm 12mm alu LowE 6mm 12mm alu float 6 mm ASCND06 16mm alu float 6mm 15mm alu LowE 6mm Side Table 2: The test specimen for triple glazed units.
3. TEST METHOD The test took place on the June 8th, 2016. The insulating glass units were tested with non-destructive method by using Sparklike Laser Standard device. In order to compare the results between two measurement approaches, the same insulating glass units were tested also with an invasive method, by using a gas chromatograph. First, all the samples were measured 5 times from both sides: from A to and from to A with Sparklike Laser Standard. This was done to see how much the measurement signal intensity change affects the final result when measuring through different glass types, structures and coatings. During the second phase of the experiment, the gas concentration of the same test specimen was measured with a gas chromatograph. With a vial punched through the edge seal, 3 gas samples were taken and analyzed for argon/oxygen and nitrogen concentration for each of the 12 tested IGU s. The last 2 gas sample values were used for evaluation, according to TÜV Rheinland process. 4. TEST RESULTS This chapter presents the measurement results side-by-side for the nondestructive and invasive test methods. Furthermore, the results are divided according to insulating glass types, presenting separate tables for double and triple glazed insulating glass units. The tables number 3 and 4 present the average results of argon concentration in percentage. For both tables, the results received by using Sparklike Laser Standard device are indicated with the word Laser and the results gained by using gas chromatograph are labelled GC. The following table number 3 demonstrates the argon gas concentration of double glazed units with the following sample numbers: 1 6 and 8.
Sample # 1 2 3 4 5 6 8 Sparklike measured % Argon from side Laser GC A 96.0 94.8 95.3 A 85.1 83.4 83.1 A 94.3 94.4 95.4 A 86.7 87.8 87.5 A 89.6 90.0 88.8 A 92.4 92.1 90.5 A 91.5 90.8 90.5 Table 3: Argon gas concentration, double glazed units As can be observed from the above table, Sparklike Laser Standard device was able to analyse IGU gas concentration from both sides for all the 7 test samples. The following table number 4, demonstrates the argon gas concentration of triple glazed units with the following sample numbers: 7, 9 12. Sample # 7 9 10 11 12 % Argon Cavity Sparklike measurement from side A from side GC 1 82.1 83.6 82.2 2 67.3 64.9 69.1 Average 73.9 73.3 75.7 1 83.7 82.5 84.1 2 72.9 73.5 75.4 Average 77.7 77.5 79.4 1 84.6 85.4 85.2 2 83.2 81.2 82.9 Average 83.8 83.1 84.1 1-78.6 78.0 2-84.6 87.8 Average - 81.6 82.6 1 86.2 88.3 86.8 2 82.3 80.1 82.3 Average 84.3 84.3 84.3
Table 4: Argon gas concentration, triple glazed units The expected accuracy was met with most of the tested triple glazed insulating glass units, measured from either side. Challenges and greater deviation than normal were caused by surfaces with high reflectivity where a significant amount of laser beam (wavelength = 760 nm) output power is lost. Therefore, the measurement signal received when measuring the insulating glass, was too small to be analysed accurately. The average gas concentration result for each triple glazed unit is generally more accurate than result measured from a single gas filled spacing because of the longer absorption length. This can be observed from the results displayed in the previous chapter. As mentioned above (Chapter 1), the second cavity results are calculated from the average and the 1st cavity gas concentration results and are, therefore dependent of their accuracy. This can be seen in the second cavity results for the sample number 7. CONCLUSION The test shows that every sample was measured successfully using the Sparklike Laser Standard device. One IGU sample out of 12 samples was measured from one side, due to high reflection. In other words, the results obtained with Sparklike Laser Standard device are fully comparable with GC in 11 out of 12 samples. As was mentioned in the first chapter, when measuring an IG unit, which has low transmission on the first pane and low reflection on the second, the received measurement signal is small and therefore the device accuracy is reduced. However, that was the case with only one IGU sample. Therefore, the test report from TüV Rheinland shows that Sparklike`s new measurement device makes it possible to test even the most complex insulating glass structures nondestructively. APPENDIX *Optiwhite = Pilkington Optiwhite *Float = float glass *Optiphon = Pilkington Optiphon *Lam 4, Lam = laminated