How it works:
Vacuum attenuation is a non-destructive quantitative leak detection technique based on the ideal gas equation of state and pressure change measurement. During the test, the test sample is placed in a dedicated test chamber. The instrument first evacuates the test chamber to a preset reference pressure level, then isolates it from the vacuum source and enters the testing phase. If there is a leak in the sample, external gas will enter the test chamber through the leak hole, causing the absolute pressure in the chamber to rise in a way that can be detected by high-precision sensors. The leakage rate of the gas can be calculated by measuring the appreciation of pressure over a specific time interval and based on the known test chamber volume. The process can be described by the following relations:
ΔP = (Q * t) / V
Among them, ΔP represents the pressure change value during the detection stage, Q represents the leakage rate, t is the detection time, and V is the net volume of the test chamber. This method has high sensitivity to small leaks, and the test results are not significantly affected by the morphology of the product contents (liquid, powder, solid).
System composition
A typical vacuum attenuation tightness tester consists of the following subsystems: a high tightness test chamber, a vacuum generation module, a high-resolution pressure sensor, a data acquisition and processing unit, and a human-computer interface. Its performance depends primarily on the resolution of the pressure sensor, the overall tightness of the system, and the stability of the algorithm. To ensure test accuracy, the instrument needs to be calibrated for standard leakage holes prior to testing. The technical parameters of the main concerns are shown in the table below:
| Pressure sensor resolution | It can reach the order of 0.1 pascals |
| Detects the smallest leakage rate | Typically in the range of 10^-5 to 10^-3 mbar·l/s |
| Test cycle | Seconds to tens of seconds, depending on the method settings |
| Test cavity volume adaptation | It needs to be configured or calibrated according to the sample size |
Applications:
This method plays a key role in packaging seal quality inspection across multiple industries due to its non-destructive, quantitative, and adaptable characteristics. Typical application scenarios include, but are not limited to:
Food packaging: Used to detect the sealing integrity of canned food, vacuum packaging bags, coffee caps, beverage caps and other products to prevent spoilage caused by leakage.
Electronics packaging: It is used to detect the sealing of the shell of smartphones, smart watches, sensors and other devices to meet the verification requirements of their dustproof and waterproof ratings (such as IP ratings).
Daily chemical and chemical product packaging: Ensure the tightness of packaging bottles and cans of liquid products such as shampoo and engine oil to prevent leakage and volatilization of contents.
Medical Device Sterile Barrier System (Non-Pharmaceutical): For example, testing the tightness of the initial packaging of blister blisters and Tyvek bags of sterile medical devices is an important guarantee for maintaining the sterility of products.
Advantages and limitations
The main advantage of vacuum attenuation is that it provides objective quantitative leak rate data, the testing process is fast and often does not damage the sample, allowing for 100% in-line testing. It is suitable for rigid and semi-rigid packaging as well as aseptic barrier systems with headspace.
At the same time, this method also has certain limitations. For flexible packaging, test interference can occur due to package collapse during vacuuming. If the packaging contains volatile substances or has no headspace (e.g. completely filled with liquid), the test gas may not be air, which will affect the accuracy of the calculation. Additionally, the initial investment in the instrument versus the cost of tooling and fixtures required for different product sizes are factors to consider.
Standard compliance
The application of vacuum attenuation method should refer to relevant international, national or industry standards. For example, in the field of food and medical device packaging, this method has been included in some standards as one of the approved leak detection methods. When establishing a test method, users need to perform adequate method validation, including but not limited to: repeatability and reproducibility studies, correlation with standard leaks, and confirmation of detection capabilities at different leak sizes. Rigorous validation is the basis for ensuring reliable and comparable test results.