The production process control and quality inspection of gas-filled insulated glass.
With the vigorous implementation of energy-saving policies and regulations and the gradual popularization of building energy-saving knowledge in some developed countries, people's demand for insulated glass with high energy-saving configuration is also increasing, and the large-scale production of low-emission coated glass has brought market growth. The relative increase in quantity makes it possible to continuously increase the effective demand for high-performance insulated glass, so low-emission coated insulated glass is more and more widely used. However, the application of low-emissivity glass also brings two problems that we have not encountered before: using an off-line low-emissivity coating to make insulated glass, the requirements for sealing life become more prominent; after using low-emissivity glass to solve the problem of thermal radiation, the reduction of the heat convection in the hollow glass cavity becomes very urgent.
Filling the insulated glass with inert gas helps to improve the sealing life and reduce the problem of thermal convection at the same time, and the initial gas concentration and air tightness necessary for the gas-filled insulated glass are the basic guarantees to solve these two problems. This article focuses on the related issues involved in increasing the initial concentration of gas-filled insulated glass, such as the production process control and product quality inspection of gas-filled insulated glass, aiming to help those who have been inflated with insulated glass but the concentration is less than 90% and those who are considering the use of insulated glass. Manufacturers of glass inflatable equipment choose the correct inflatable equipment.
The quality inspection of gas-filled insulated glass
Generally speaking, the inert gas used in gas-filled insulated glass is argon, which is colorless, odorless, and non-toxic. Its molecular weight is 38% heavier than air, and its thermal conductivity is smaller than that of air. Since the density of argon is higher than that of air when the insulated glass is inflated, the argon filling (inlet) air hole is at the lower end, and the air outlet (exhaust) air hole is at the upper end, to replace the air in the insulated glass and achieve the required argon gas concentration.
The inflation process of insulated glass is essentially the process of transferring the flowing gas from one motion state to another state, and the inflation quality is related to whether the gas produces laminar flow (laminar) or turbulence (turbulence). Therefore, the discussion of the quality of the insulated glass gas can not be separated from the discussion of the basic concepts of laminar flow and turbulent flow.
Figure 1 The argon-filling inflation process of insulated glass
Laminar flow is the layered flow of fluids. At this time, there is no essential difference between the Newtonian viscous stress of the fluid in motion and the mechanical mechanism of the solids resisting each other's sliding motion. The basic characteristics of turbulent flow are vorticity, irregularity, randomness, diffusion, and dissipation. randomness. The turbulent flow contains ordered large-scale vortex structures, as well as disordered and random small-scale vortex structures. The random pulsation of turbulent physical quantities is the result of the combined action of these vortices of different scales.
At present, the inflatable quality of insulated glass in some developing countries is not high, which is largely caused by the turbulent flow during the inflation process. It is assumed that the sensor of the inflatable equipment only recognizes the concentration of the inert gas collected at the exhaust hole of the insulated glass, and the inert gas concentration finally given by the laminar flow and turbulent flow of the gas-filled insulated glass also meets the standard requirements, and people cannot distinguish the insulated glass with the naked eye. The concentration trend of the noble gas after diffusion. If the initial concentration of this kind of gas-filled insulated glass is detected online by the high-voltage discharge method, the obtained concentration will be higher than the actual concentration after diffusion. If the manufacturer judges that the product with the turbulent flow is qualified and delivered to the customer or sent to the laboratory for testing, the actual concentration after diffusion will be lower than the concentration at the beginning of the test. Such gas-filled insulated glass with significantly varying concentrations can confuse manufacturers because the seal of the product is not defective and the product is only tested for the initial concentration.
Figure 2 The sensor of the inflatable insulated glass argon-filled equipment
When the gas-filled insulated glass produces turbulent flow, part of the air in the insulated glass cavity cannot be replaced by the filled argon gas, so the initial concentration of the gas-filled insulated glass with the turbulent flow is difficult to meet the requirements specified in the standard. In addition, the turbulent flow generated during the inflation process makes the air still exist in the center of the hollow glass cavity. When turbulent flow occurs in the insulated glass, the concentration detected by the insulated glass exhaust hole sensor should generally be higher than the turbulent air in the center of the insulated glass cavity, and the complete diffusion of the insulated glass inert gas requires 6~8 Hours. If this method is used for online detection, the measured concentration is significantly higher than the actual concentration after diffusion. Therefore, we cannot use this detection method as an online detection method for gas-filled insulated glass. Otherwise, when turbulent flow occurs in the gas-filled insulated glass, it will bring the wrong perception to the inspectors. Therefore, it is necessary to measure after the gas-filled insulated glass is placed for 6 to 8 hours, to get the correct concentration figure.
According to the survey, the initial concentration of some manufacturers' self-inspected gas-filled insulated glass is above 90%, but the actual concentration after diffusion is significantly lower than 90%, and some even less than 70% after third-party measurement. By visual inspection of these gas-filled glass seals with widely varying concentrations, it was difficult to find any seal defects, so we deduce that one of the reasons for this phenomenon is due to turbulent flow.
However, this detection method is an after-the-fact detection of product quality. After the gas-filled insulated glass is placed for 6 to 8 hours, the second sealant is cured. If the concentration of the gas-filled insulated glass does not meet the requirements, it is time-consuming and laborious to rework the gas-filled insulated glass. In addition, if the aeration method is not improved, there is still no guarantee that the aeration concentration of the reworked product will meet the requirements. The use of ordinary inflation methods, namely natural inflation, inflation, and forced air extraction, will inevitably lead to turbulence. Even if the glass randomly inspected and tested meets the concentration requirements, unless we have real-time monitoring numbers for each glass during the inflation process, we will also There is no certainty that an entire batch of gas-filled glass will pass.
It can be seen that unless the inflating equipment we use can effectively avoid the occurrence of turbulent flow, or always maintain a stable laminar flow during the inflation process, we cannot rule out the authenticity of the online detection of the concentration. Further, under this condition, the correct method for us to ensure the concentration of gas-filled insulated glass is to control the production process of gas-filled insulated glass, not the quality control of the product.
The production control of gas-filled insulated glass
The production process control of gas-filled insulated glass is to ensure that the production process of gas-filled insulated glass is in a controlled state, focus on controlling the factors that directly or indirectly affect the quality of the process, and formulate and implement a control plan to ensure the quality of the process. Argon is a colorless and odorless gas, and its aeration concentration is not easy to measure. The current test methods can be roughly divided into two types: the sensor compares the gas collected from the exhaust hole with the set gas concentration to judge whether it meets the requirements; the sensor compares the gas collected from the exhaust hole with the set gas concentration. The gas concentration is dynamically compared and real-time curves such as concentration, pressure, and flow rate are given, which can be judged not only from the concentration but also from the shape of the curve to judge the actual concentration of the gas. Comparing the two types of current test methods, the second method is the description of the entire aeration process, which is currently the most advanced production control method for real-time monitoring of the aeration process.
Figure 3 The entire aeration process could vision from insulated glass argon-filled production line
The quality control of the concentration of gas-filled insulated glass is characterized by ex-post, which belongs to the detection of unqualified products. The production control of the European insulated glass standard EN1279-6 refers to the measurement of the concentration of the gas-filled insulated glass after lamination, which should be understood as the quality control or detection of the product, rather than the real production process control. In this standard, the sampling inspection of the initial concentration of gas-filled insulated glass stipulates that when there are less than 100 pieces of gas-filled insulated glass per shift, one piece shall be randomly checked. The argon gas in the gas-filled insulated glass needs about 6 to 8 hours to be completely diffused. Therefore, the detection of the initial concentration of the gas in the insulated glass can only be carried out after the gas is completely diffused. It is only after 6 to 8 hours that the inert gas is completely diffused and then tested, which can only be judged whether the product is qualified or not. If the result of this sampling test is overall unqualified, it is too late to discover the problem. The main reason for the low initial concentration of gas-filled insulated glass is the turbulent flow phenomenon during the gas-filled process. The significance of the production control of inflatable insulated glass is to monitor the entire inflation process in real-time, to effectively avoid the turbulent phenomenon that may occur during the inflation of the insulated glass, and to improve and ensure the stability of the inflation quality.
The inflatable method of insulated glass
From the perspective of the degree of integration with the insulated glass production line, the inflation technology is divided into online inflation and offline inflation; from the perspective of production automation, the inflation technology is divided into automatic inflation and manual inflation. Generally speaking, online inflation means that the inflation process is performed on the insulated glass production line, and the inflation process is completed after the insulated glass is framed and before lamination (such as Lisec production line, Bystronic production line, Jinan LIJIANG Glass production line), with a degree of automation. It has the advantages of high, short inflation time and stable concentration, but the disadvantage is that the waste of inert gas is large; manual inflation is performed offline after the insulated glass is laminated, before or after the second sealant is applied. Generally speaking, the characteristics of ordinary manual inflatable equipment are slow inflation, high gas consumption, and low concentration. Both inflatable methods require production process control. For example, some glass manufacturers in Europe use the online panels press inflatable insulated glass production lines to monitor the online inflation process in real-time.
Video 1 The inflatable method of insulated glass processing flow
There are three main ways to inflate manual inflatable equipment: natural inflation, simultaneous inflation and exhaust, and program-controlled inflation and exhaust simultaneously (see the table below). The flow rate of the natural charging method is generally about 5 liters/min, the flow rate of the simultaneous charging and exhausting mode is between 12 and 18 liters/min, and the flow rate of the program-controlled charging and exhausting process mode can be as high as 90 liters/min.
When choosing inflatable insulated glass, the first factor to consider is the stability of the inflatable quality of the equipment. The key to improving the concentration of inflatable insulated glass is whether the inflatable equipment can avoid turbulent flow during the inflation process, and monitor the inflation process in real-time. The characteristics of the natural inflation method are that the equipment investment is small, but the inflation speed is too slow, the inflation concentration is not fully guaranteed, and the gas consumption is large, which is not suitable for the production of a large number of inflatable insulated glass. The second method is that inflation and forced pumping are performed synchronously. Although the inflation speed is increased and the inflation time is shortened, forced pumping can easily lead to turbulence in the gas flow in the cavity. When the sensor detects the inert gas and judges that At the set concentration value, inflation stops. This method cannot effectively avoid the occurrence of turbulent flow during the inflation process, so the concentration value may not be the true concentration of the gas-filled glass, that is, the concentration after complete diffusion. The third method is program-controlled inflation and pumping. Its essence is to intelligently control the inflation process. Through real-time monitoring of the inflation process, the inflation speed is greatly improved, and the possible turbulence during the inflation process is avoided. the specified aeration concentration.
When considering the selection of gas-filled insulated glass equipment, three aspects of concentration, time, and gas consumption must be considered at the same time. The ideal state is that the selected inflatable equipment can not only achieve the required concentration stably but also has a short time and low gas consumption. The intelligent control rapid inflation equipment can meet the requirements of 3 aspects at the same time. In this sense, intelligent control rapid inflation equipment is no longer manual inflatable equipment in the traditional sense. It is closer to the online automatic inflatable equipment in terms of technical characteristics, but the gas consumption is small.
To increase the concentration of gas-filled insulated glass, some other details need to be paid attention to. If the insulated glass needs to be placed vertically when it is inflated, it should be placed on the ground as short as possible. insulated glass cannot be placed horizontally to inflate.
The summary
The production process control of gas-filled insulated glass is an important guarantee for increasing the gas-filled concentration, and the quality control of gas-filled insulated glass is an after-the-fact inspection, which is an auxiliary means to ensure the initial gas-filled concentration. Comparing the two methods, the production process control of gas-filled insulated glass is more important. Turbulence is an important reason for the low quality of the insulated glass inflated. Using the intelligent control rapid inflation method can not only ensure that the laminar flow during the inflation process reaches the initial concentration specified in the standard, but also has the advantages of fast inflation speed and small consumption of inert gas.
In addition, the insulated glass production equipment with an intelligent rapid inflation function is cost-effective and can monitor the online inflation process in real-time. It has the advantages of small investment and durability. It is an argon gas inflation method for insulated glass suitable for the current glass deep processing market. It has a wide range of application prospects.
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