www bzfxw com BRITISH STANDARD BS EN 1279 3 2002 Glass in building — Insulating glass units — Part 3 Long term test method and requirements for gas leakage rate and for gas concentration tolerances Th[.]
Gas leakage rate
The gas leakage rate, Li, for gases with concentrations higher than 15 %, and also for air, measured as described in clause 5 shall be
For insulating glass units, the initially measured Li values are significantly higher than the actual Li values expected after 10 years of natural aging Consequently, the limiting value should not be utilized for calculating gas concentration throughout the unit's lifespan Refer to annex B for further details.
For sealants made from polysulfide, polyurethane, silicone, or polyisobutylene, measuring the gas leakage rate of argon (Ar) can serve as a substitute for assessing the leakage rates of sulfur hexafluoride (SF6) and air.
Tolerances on gas concentration
For tolerances on gas concentration, refer to EN 1279-6.
Dew point and moisture penetration index
For testing and requirements on dew point and moisture penetration, refer to EN 1279-2.
Edge seal strength
For the requirements on edge seal strength, refer to EN 1279-4.
Additional requirements for other gases than argon, sulfurhexafluoride and air
For those requirements, refer to annex A.
Principle of testing
In the test, the gas leakage rate at 20 °C is measured after subjecting the test specimen to a climate as specified in
EN 1279-2 with the following modifications:
– the number of cycles is reduced to 28; and
– the time at a constant temperature of 58 °C is reduced to 4 weeks.
To measure the gas leakage rate, a unit is placed in a gastight container, and the amount of gas that leaks over a specified time is recorded Following this measurement, the gas concentration within the unit is analyzed to calculate the gas leakage rate.
Apparatus
Climate exposure equipment
Test apparatus for the climate exposure as specified in EN 1279-2.
Container for gas leakage rate measurement
To measure the gas leakage rate, a hermetically sealable controlled temperature container must be utilized This container should accommodate the unit under test while minimizing stress, ensuring that the residual volume is kept to a minimum Additionally, it is essential that the sealed edge zones of the unit are exposed to the flow of purging gas.
To measure the amount of ambient air entering a container or the leakage of its constituents, a blank test should be conducted using a solid glass body that closely matches the dimensions of the test specimens.
A container is considered sufficiently tight if the amount of gas measured during testing does not exceed 10% of the mass of gas that leaks from the test specimen.
The container shall have fittings for introducing specific gases and for taking gas specimens.
For glass units featuring at least one outer pane composed of organic material, it is essential to account for gas diffusion through these panes in the measurement process.
Gas analysis equipment
A gas analysis equipment shall be used which is capable of: a) analysis of the gaseous constituents essential to the insulation function of the glass unit, for concentrations of
50 ã 10 -6 ; b) determination of percentages by volume of gas of up to 100 % within ± 3 % (relative).
These tasks shall not necessarily be performed using the same equipment.
Gas sampling device
A device shall be used for taking gas specimens from the glass unit, ensuring that the result is not distorted by ingress of air, segregation phenomena, or similar.
Test specimens
Preparation of test specimens
The test specimens shall consist of two panes of 4 mm clear float glass in accordance with EN 572-1 and
According to EN 572-2, the dimensions of the test specimens must be 502 mm in length (with a tolerance of ± 2 mm) and 352 mm in width (also with a tolerance of ± 2 mm) The nominal gap should be 12 mm, or as close to this measurement as feasible if not manufactured to specification Additionally, the test specimens must accurately represent the system description outlined in prEN 1279-1.
If gas leakage occurs through the plastic in glass/plastic units, glass will be replaced with plastic.
The design of the insulating glass unit, including the type and quantity of desiccant and gas, must adhere to standard production specifications unless otherwise agreed It is essential that the panes of the test specimen remain flat during sealing Additionally, the temperature (T in K) and absolute pressure (P in hPa) must be accurately measured to the nearest 1 K and 3 hPa, respectively, during the sealing process.
The test specimens have to be manufactured in such a way that the gas concentration meets ci = ci,o (+ 10 % to - 5 % absolute), for each gas when gas mixtures are used.
For the production of the test specimens, EN 1279-6 is mandatory.
Number of test specimens
At least six test specimens shall be prepared of which at least two shall be tested as described in 5.4 after climate exposure.
It is advisable to conduct additional tests on gas-filled specimens prior to climate exposure Gas leakage can be assessed on subsequent units at least four weeks after they have been filled and sealed This approach helps to optimize testing costs and timelines effectively.
Construction and appearance
The visual examination of test specimens will focus on several key criteria, including the construction quality of the insulating glass unit, the presence of damaged edges, edge cracks, fractures, specking within the cavity, the congruence of panes, and any other visible defects.
Procedure
Determination of internal volume of a test specimen
To measure the clear distance between opposite spacers, s₁ and s₂, use a gauge graduated in millimeters, ensuring accuracy to the nearest 1 mm For the clear distance between the inner pane surfaces, s₃, measure at mid-length on the four edges of the test specimen to the nearest 0.1 mm and calculate the mean The internal volume, V₍ᵢₙₜ₎ in mm³, is calculated by multiplying s₁, s₂, and s₃.
Climate exposure
The climate exposure outlined in section 5.1 must be conducted on four test specimens, starting no earlier than one week after their preparation Following the climate exposure, the specimens should be stored in conditions that allow for air circulation around the edges, maintained at a temperature of (23 ± 2) °C and a relative humidity of (50 ± 5) % for a minimum of four weeks and a maximum of seven weeks, prior to measuring the gas leakage rate as detailed in section 5.4.3.
To ensure proper air circulation around vertically stored units, it is essential to use at least two blocks that are a minimum of 20 mm high, with each block covering no more than 30 mm of the edge.
Measuring the gas leakage
Measure gas leakage from a minimum of two test specimens at a temperature of (20 ± 1) °C following climate exposure Allow the specimens to remain in the container until the mass of gas that has leaked can be quantitatively determined in àg/h, utilizing the gas analysis equipment specified in section 5.2.3.
Gas leakage measurements must be conducted repeatedly until a stable set of values is obtained Stability is defined as achieving a standard deviation of less than 0.25 µg/h over the last four measurements, which should be spaced at least one day apart Additionally, at least one measurement must exceed the value of the preceding measurement (refer to annex C).
Analysis of gas
Determine the volume fraction in percent of the gaseous constituents essential to the insulation function of the unit, using the gas analysis equipment described in 5.2.3.
Take a gas specimen for this analysis from the cavity of the unit after the last measurement of the gas leakage rate.
Evaluation
Calculate the gas leakage rate, Li, according to 3.3.
In a collaborative inter-laboratory test conducted across four laboratories, a uniform production of four to eight units was subjected to specific climatic conditions as outlined in section 5.1 Following this exposure, the gas leakage rate was assessed in accordance with section 5.4.3 and annex C, revealing a standard deviation of 20% for all individual measurements.
The test report shall evaluate the test in detail and shall include the following summary:
Name, address and logo of the test laboratory.
Insulating glass units - Evaluation of the gas leakage rate and gas concentration measured according to prEN 1279-3
For details, see the test report
Reference to test report for moisture penetration index according to EN 1279-2:
Gas leakage rate Li, (in %⋅a -1 ):
NOTE 1 If for certain gases the gas leakage rate Li is not relevant, fill in the cell for Li "NR" (= not relevant)
System conforms: YES NO (Delete whichever is not applicable)
NOTE 2 For comparisons of gas leakage rates of different insulating glass unit systems, the standard deviation indicated in clause 6 of EN 1279-3:2002, should be taken into consideration.
Durability of the gas and interaction with insulating glass components
The durability of the gas must be evaluated to ensure it meets the requirements for the intended applications, along with assessing its interactions with insulating glass components.
Effect on thermal- and sound insulation
For most insulating glass unit types, the thermal transmittance U-value and/or the weighted sound reduction index
Rw(C/Ctr), depending on the gas concentration, shall be determined.
This standard stipulates that the thermal transmittance and sound reduction of insulating glass units must remain stable throughout their operational lifespan Specifically, the U-value should not increase by more than 0.1 W/(m²K), and the reduction in sound insulation, measured as Rw(C/Ctr), should not exceed 1 dB.
Those requirements are fulfilled under one of the following two conditions:
1) When gas filling improves the U-value by a maximum of 0,4 W/(m²K) and when gas filling improves the
Rw(C/Ctr) index by a maximum of 5 dB.
The U-value and Rw(C/Ctr)-value for publication are:
Up = U(ci,o) and R w,p (C/Ctr) = Rw(C/Ctr)(ci,o).
When gas filling enhances the U-value by over 0.4 W/(m²K) or increases the Rw(C/Ctr) index by more than 5 dB, it is essential to verify that the difference between the internal and external U-values, U(ci,f) - U(ci,o), does not exceed 0.1 W/(m²K).
Rw(C/Ctr)(ci,o) - R w (C/Ctr)(ci,f) ≤ 1 dB (A.2)
The U-value and Rw(C/Ctr)-value for publication are:
Up = U(ci,o) and R w,p (C/Ctr) = Rw(C/Ctr)(ci,o).
And when a) is not fulfilled, the following calculation shall be carried out: b) Up = U(ci,f) - 0,1 W/(m².K), and/or (A.3)
Rw,p(C/Ctr) = Rw(C/Ctr)(ci,f) + 1 dB (A.4) withci,f = (ci,o - 5) (1 - 0,22⋅Li,m) (A.5) where
Li,m is the maximum gas leakage rate in percent as measured according to this standard, plus 5 % relative.
In case of gas mixtures, only the gas(es) with the maximum influence on the U-value and/or Rw(C/Ctr)-value shall be considered.
Assessment example with krypton gas filling
– insulating glass unit with a cavity width of 8 mm, two panes of 4 mm, one coated with an emissivity of: ε = 0,1
– measured krypton leakage rate: LKr,m = 0,5 %⋅a-1 (= 1,05⋅LKr)
– demonstrated argon leakage rate: LAr < 1,0 %⋅a-1
Answer to 4.1: The gas leakage rates satisfy the requirements.
Answers to 4.2, 4.3 and 4.4: In this example, the requirements are assumed to be satisfied.
Answer to A.1: Krypton reacts chemically similar to argon No special investigations are necessary.
Answer to A.2: The krypton gas filling improves the U-value by more than 0,4 W/(m²K), however the
Rw(C/Ctr)-value improves by less than 5 dB.
In accordance with condition 1) of A.2, the weighted sound reduction index for publication Rw,p(C/Ctr) is equal to
For the U-value, check against to condition 2 a) of A.2:
– increase in U-value (calculations according to EN 673):
That increase is greater than 0,1 W/(m².K), so that condition 2)b) of A.2 is performed.
– the U-value for publication shall be:
Up = 1,54 - 0,1 = 1,44 W/(m²K) and rounded to one decimal Up = 1,4 W/(m²K)
Relationship between artificial and natural ageing with regard to thermal and sound insulation
A study assessed the gas leakage rate of insulating glass units installed in buildings for a decade, revealing that the measured values were ten times lower than those of similar units tested under DIN 52293 standards after artificial ageing Furthermore, a comparison of this artificial ageing process indicated no significant differences in gas leakage rates.
Based on this experience, it can be inferred that insulating glass with a gas leakage rate of Li < 1.0 %⋅a⁻¹, after undergoing artificial aging as per the standard, is expected to lose less than 5% of its gas content over a 25-year period when installed in a building To ensure a conservative estimate, it is assumed that the gas leakage rate in buildings may double every year.
Over a span of 10 years, a unit with a nominal argon concentration of 90% and a potential real concentration of 85% maintains a gas concentration exceeding 80% after 25 years Assuming that the U-value improves by 0.4 W/(m²K) with 100% argon filling, this indicates a deterioration in performance.
The calculated value of ∆U is less than 0.04 W/(m²K) with a cAr,o of 90%, leading to a final U-value rounded to 0.1 W/(m²K) Additionally, similar conclusions apply to sound insulation, as insulating glass units meeting these standards are expected to exhibit no significant changes.
Determination of the gas leakage rate by gas chromatography
Principle of method
The test method described below is one method for measuring the gas tightness according to clause 5 Other methods can be adopted.
If one follows this method, it should be followed strictly in order to achieve the correct result.
The test method is specifically designed for gas-filled insulating glass units constructed from inorganic materials It measures the gas leakage, denoted as mi, in mass per hour, to calculate the gas leakage rate Li, which is expressed as a percentage by volume per year (%⋅a⁻¹), in accordance with clause 5.
The test specimen is contained within a slightly larger container, allowing for the measurement of gas leakage Helium is used to transport the leaked gas to a gas chromatograph equipped with a thermal conductivity or electron capture detector, where the mass of the leaked gas is accurately determined.
Equipment
Full container
The container in Figure C.1 consists of:
1) a lower part made of metal;
3) a mat made of foam plastic, 3 mm thick, with dimensions according to the test specimen;
The lower part of the container features a flat inner bottom measuring approximately 360 mm in width and 510 mm in length, designed to minimize residual volume after the installation of the test specimen With an inner height of 22 mm, the walls may include ledges for securing the test specimen without obstructing the gas stream at its edges Additionally, the walls are equipped with two bore holes for the supply and extraction of purging gas, and an annular groove may be present to facilitate the flow of a protective gas stream.
1 Lower part 6 Purging gas in and out
2 Metal foil 7 Protective gas in
Ring container
The ring container features a metal frame and two masks made from self-adhesive metal foil or sealant-coated sheet metal It includes two bore holes: one for the supply pipe and another for the extraction of purging gas To minimize the residual volume after the installation of the test specimen, the dimensions of the ring container and the test specimen must be carefully aligned.
5 Purging gas in and out
Cooling trap
The cooling trap is designed with a metal tube shaped into a U or spiral, filled with a specific adsorbent It features two interchangeable containers: one containing liquid nitrogen and the other holding water at a temperature of (95 ± 5) °C This setup allows for the adsorption of gas at the low temperature of liquid nitrogen, which can then be rapidly released when exposed to the higher temperature of hot water.
Gas chromatograph
A commercial gas chromatograph (GC) equipped with a thermal conductivity or electron capture detector, along with an integrator and recorder, is essential for analysis The system includes a calibrating loop of about 1 ml connected to the gas chromatograph, utilizing helium as the carrier gas.
Connecting pieces
The pipes, valves and adapters as illustrated in Figure C.3, should be so tight that the leakage rate during testing with helium is not more than 0,000 1 lPas-1.
Solvents
For cleaning the test specimen surface, ethanol and isopropanol are recommended.
Purging and carrier gas
Helium with a purity of 99,999 6 % parts by volume.
1 Calibrating gas 4 Integrator 7 Cooling trap
2 Purging gas 5 Carrier gas 8 Calibrating loop
3 Flow meter 6 Gas chromatograph 9 Container
V1, V2 and V3: valves, for valve positions, see Table C.1.
Table C.1 — Overview of valve positions
The process involves several key functions: a) purging the system, b) filling the calibration loop with the calibration gas, c) achieving the concentration of the calibration gas through cooling, d) measuring the gas concentration, e) determining the concentration of contamination via cooling, f) assessing the concentration of the gas specimen based on standing time, and g) evaluating the concentration of the gas specimen through cooling.
Calibrating gas
Helium using a volume fraction of 1 % of the relevant gases, for example nitrogen, oxygen, argon and sulphurhexafluoride, is recommended if the calibrating loop has a volume of approximately 1 ml.
Preparation of test specimens
Test specimens must adhere to section 5.3, ensuring that all sealant residues, labels, and contaminants that could affect gas exchange are eliminated The surfaces of the test specimens are thoroughly cleaned with a solvent, taking care to avoid any contact with the sealant.
Procedure
Connection of the apparatus
The apparatus is connected as shown in the gas pipe plan (see Figure C.3).
Installation of the test specimen
To ensure effective purging of the test specimen, install it so that the periphery is completely accessible, leaving only the area between the two purging holes sealed with a suitable sealant like butyl For a full container, apply high vacuum grease to the contact surfaces of the lower part and the metal foil, then place a flawless metal foil on the test specimen and sealing face Position the mat centrally on the metal foil to ensure it is compressed by the cover during tightening, thereby minimizing the residual volume In the case of a ring container, cover the gap between the test specimen and the frame with masks, ensuring an overlap of at least 15 mm, and press the upper and lower masks together with the frame.
Temperature
To accurately measure the gas leakage rate, maintain the temperature at (20 ± 1) °C by either regulating the room temperature or placing the test specimen container in a water bath Ensure the ring container is fully submerged in the water bath for optimal results.
Calibration
To ensure reliable quantitative and qualitative results, it is essential to monitor the retention time, separation performance, and sensitivity of the gas chromatograph on a daily basis Utilize a calibrating loop with a defined volume, such as 1 ml, to direct the calibrating gas into the analysis system Additionally, the integrator must have sufficient resolving power to accurately evaluate the signals detected.
Adjust the gas chromatograph parameters according to the operation, as the volumes of gases such as nitrogen, oxygen, argon, and sulfur hexafluoride in the calibration gas are comparable to the volumes of the gases being detected, allowing for effective control during calibration.
Measurement of the gas leakage
The sensitivity of a thermal conductivity detector is normally insufficient to analyse the gas specimen quantitively in a direct way, so the following steps for concentration should be performed:
– concentration in the container by standing time: interruption of purging and closing of the container;
The concentration in the cooling trap is achieved through the adsorption of gas specimens, calibrating gases, or contaminants present in the purging gas This process utilizes appropriate adsorbents at liquid nitrogen temperatures to ensure effective cooling and separation.
The measurement consists of six steps:
Step 1: Purge (see Figure C.4) the volume between test specimen and container with purging gas.
1 Purging gas (no 2 in Figure C.3)
2 Container with test specimen (no 9 in Figure C.3)
Figure C.4 — Purging - Valve position a) (see Figure C.3 and Table C.1)
Step 2: Calibrate the detector system by the calibrating gas:
– take a defined amount, e.g 1 ml, of gas by the calibrating loop (see Figure C.5);
– turn the valves to position (c) of Table C.1;
– enrich the purging gas by cooling (see Figure C.6);
– turn the valves to position (d) of Table C.1;
To analyze the calibrating gas effectively, it is essential to drive it off and separate it using a carrier gas (refer to Figure C.7) This process allows for the control of resolving power and peak shape, enabling the determination of the calibrating factor for each gas.
1 Calibrating gas (no 1 in Figure C.3)
2 Calibrating loop (no 8 in Figure C.3)
Figure C.5 — Filling the calibrating loop with calibrating gas C
Valve position b) (see Figure C.3 and Table C.1).
1 Purging gas (no 2 in Figure C.3)
2 Calibrating loop (no 8 in Figure C.3)
3 Calibrating gas in cooling trap; cooling trap with liquid nitrogen (no 7 in Figure C.3)
Figure C.6 — Concentration of calibrating gas by cooling
Valve position c) (see Figure C.3 and Table C.1).
1 Carrier gas (no 5 in Figure C.3)
2 Cooling trap with water of (95 ± 5) °C (no 7 in Figure C.3)
3 Gas chromatograph (no 6 in Figure C.3)
Figure C.7 — Driving off, separation and detection of the adsorbed gas
Valve position d) (see Figure C.3 and Table C.1).
Step 3: Inspect the purging gas and the pipe system by cooling, enriching, driving off, separating and detection of the contaminants in the purging gas (see Figure C.8) Gas flow duration during this inspection is similar as for gas leakage measurement.
1 Purging gas (no 2 in Figure C.3)
2 Cooling trap with liquid nitrogen (no 7 in Figure C.3)
Figure C.8 — Concentration of contaminants by cooling
Valve position e) (see Figure C.3 and Table C.1).
Step 4: Concentrate the gas specimen by standing time (see Figure C.9), purge the gas specimen with purging gas and concentrate it by cooling (see Figure C.10), followed again by purging (see Figure C.4).
1 Container with test specimen (no 9 in Figure C.3)
Figure 9 — Concentration of gas specimen by standing time
Valve position f) (see Figure C.3 and Table C.1).
1 Purging gas (no 2 in Figure C.3)
2 Container with test specimen (no 9 in Figure C.3)
3 Cooling trap with liquid nitrogen (no 7 in Figure C.3)
Figure C.10 — Concentration of gas specimen by cooling
Valve position g) (see Figure C.3 and Table C.1)
Step 5: Drive out the gas specimen by warming the cooling trap, separation and detection (see Figure C.7). Evaluate quantitatively the gas leakage rate by following steps 2 and 3.
Step 6: Repeat steps 4 and 5 until a sufficiently constant values, is reached In addition repeat steps 2 and 3 daily.
Sufficient constancy is achieved when the standard deviation of the last four measurements is below 0.25 àg/h, with measurements taken at least one day apart Additionally, at least one measurement must exceed the previous one.
Conditions for measuring gas leakage rate:
– purging time: 5 h up to 3 days;
– purging gas flow: about 50 ml/min for purging; 100 ml/min for enriching by cooling.
Blank test
Periodically check the system's tightness using a blank test by installing a glass plate of similar dimensions to the test specimen in the container, and measure according to the guidelines outlined in section C.4.5.
Result
Evaluate the gas leakage rate mi, in àg/h, from the measured volume, àl/h, in relation to temperature and pressure.
1 Mean value of measurements 4 to 7; standard deviation less than 0,25 àg/h
3 mean value of measurements 5 to 8; standard deviation less than 0,25 àg/h
Figure C.11 — Either the measurements 4 to 7 and measurements 5 to 8 is acceptable
[1] DIN 52293, Prüfung der Gasdichtigkeit von gasgefülltem Mehrscheiben-Isolierglas.
[2] prEN 13022, Glass in Building - Structural sealant glazing.
[3] ETAG 002, Guideline for European Technical Approvals for Structural sealant glazing systems.