Introduction
In the production and quality control process of flexible packaging bags, sealing integrity is a key indicator to ensure the quality and safety of the contents. As a non-destructive testing equipment, the seal tester can effectively locate the small air leakage points of the packaging bag, which is of great significance for preventing deterioration and pollution caused by leakage. This article will systematically explain its working principle, test method, result analysis and related technical points.
How it works:
The seal tester is mainly tested by the pressure decay method or the vacuum attenuation method. The basic principle is that the flexible packaging bag to be tested is placed in a specific test chamber, and a stable pressure differential is established and maintained inside and outside the packaging bag by the equipment. If there is a leak in the bag, gas will flow through the leak point, causing a change in pressure or volume in the test chamber. By monitoring this change through high-precision sensors, it is possible to determine whether the bag is leaking and locate the leakage point through auxiliary means.
The pressure change process can be described by the following relationship: pressure within the system when there is a leak P Over time t The rate of change is related to factors such as leak pore size. Its simplified model can be expressed as:
ΔP/Δt ∝ Q
Among them,ΔP is the amount of pressure change,Δt is the time interval,Q is the leakage rate. The leakage rate is related to the pore size, differential pressure and gas properties.
Test method steps
The standard testing process typically includes the following steps to ensure the reliability and repeatability of test results.
1. Sample preparation: Select representative flexible packaging bag samples to ensure their surface is clean and dry, with no visible wrinkles or damage.
2. Equipment Setup: Set test parameters such as test pressure, holding time, leakage threshold, etc. according to the material, size, and expected leakage level of the packaging bag.
3. Install the sample: Properly seal and connect the opening end of the bag to the tester interface, or place the entire bag in a vacuum chamber to ensure the tightness of the test chamber.
4. Start testing: Start the equipment, and the system automatically completes the stages of vacuum extraction (or pressurization), pressure holding, and monitoring.
5. Result judgment and positioning: The device automatically judges "pass" or "fail". For failed samples, the leakage can be pinpointed by applying a foaming agent (such as a neutral detergent solution) or by immersing the bubble in water.
Key influencing factors
The accuracy of the test results is affected by a variety of factors, which the operator needs to pay attention to and control.
| Packaging materials and structures | The flexibility, breathability, and heat seal strength of different materials can affect leak performance and detection sensitivity. |
| Ambient temperature and humidity | Temperature changes can cause gas volume changes, and humidity can affect the properties of certain materials. |
| Test parameter setting | The test pressure, holding time and leakage rate judgment standards should be reasonably set according to product requirements. |
| Equipment calibration and maintenance | Regularly calibrate pressure sensors and timing systems to ensure the equipment is in good condition. |
| Operational standardization | Procedures such as sample installation, surface cleanliness and test chamber sealing must be strictly followed. |
Analysis and application of results
The test results are not only used to determine whether individual packages are qualified, but also for process control and quality improvement. Through statistical analysis of leakage samples, the common locations of leakage points (such as heat sealing edges, material seams, bag pinholes) can be traced back to the production process, optimizing the bag-making process, adjusting materials, or checking the wear of equipment molds. Regular tightness testing is an important part of packaging process validation and continuous monitoring.
Technology development outlook
With the improvement of sensing technology and automation, seal test technology is developing in the direction of higher sensitivity, faster detection speed and more intelligence. For example, automatic visual positioning of leakage points can be achieved in combination with image recognition technology, or integrated production lines for online inspection. At the same time, the standardization of test methods is constantly being improved to facilitate the comparability of test results between different laboratories and equipment.
References
1. General Principles for Flexible Packaging Sealing Performance Test Methods, National Packaging Standard Compilation.
2. Research on the technology of pressure decay method for detecting small leaks, Journal of Detection Technology and Instruments.
3. Principles and Applications of Packaging Leakage Testing, A Review of International Packaging Technology Research.
4. Advances in Non-Destructive Packaging Testing Technology, Journal of Materials and Testing Engineering.