The vacuum attenuation method sealing instrument is a specialized equipment for high-precision detection of packaging sealing, widely used in quality control of industries such as food, medicine, and daily chemical. The core principle is to determine whether there are defects in the packaging by monitoring the leakage rate (i.e. pressure decay rate) of the sample in a vacuum environment. The following elaborates on the usage details from three aspects: preparation before operation, key steps, and precautions, to assist in accurate detection.
1、 Preparation before operation: Basic support is essential
1. Environmental and equipment inspection: Testing should be conducted in a stable laboratory environment with temperature (23 ± 5 ℃) and humidity (≤ 80%) to avoid temperature and humidity fluctuations that may interfere with the accuracy of the pressure sensor. Before starting up, check whether the power cord and air pipe connection of the instrument are stable, and confirm that the oil level of the vacuum pump is within the scale range. If it is insufficient, add the specified model of vacuum pump oil.
2. Sample pretreatment: The packaging to be tested should be intact and undamaged, with a clean and dry surface (especially to avoid residual liquids or powders blocking the air vents). For soft packaging (such as composite film bags), customized fixtures should be used to secure the sample to the sealed cavity during testing, to prevent misjudgment due to air leakage caused by looseness.
3. Parameter pre setting: Based on the sample type (rigid/flexible packaging) and standard requirements (such as GB/T 15837-95), set the target vacuum degree (usually -90kPa to -95kPa), holding time (usually 30 seconds to 2 minutes), and qualified threshold (upper limit of pressure attenuation value) on the touch screen interface. It is recommended to verify the rationality of parameters through blank experiments during use.
2、 Core operating steps: Standardized execution to ensure accuracy
1. Sample clamping: Place the sample in a sealed chamber, slowly close the lid, and observe whether the sealing ring is fully embedded in the slot to ensure the tightness of the chamber. If it is a bottle container, it is necessary to use an adapter to tightly connect the bottle mouth with the sealing chamber, and if necessary, apply a small amount of Vaseline to enhance the seal.
2. Vacuumization and stabilization: Click the "Start" button, and the instrument will automatically start the vacuum pump to extract air from the chamber to the set vacuum degree. During this process, attention should be paid to whether the pressure rise curve is smooth - if there is a sudden rise or the plateau period is too short, there may be pipeline blockage or initial sample leakage. After reaching the target vacuum degree, the system enters the pressure holding stage and records the real-time decay data of pressure over time.
3. Result judgment: After the pressure holding is completed, the instrument automatically calculates the pressure attenuation and compares it with the preset threshold. If the attenuation value exceeds the threshold, it is judged as unqualified (prompt "NG"); Otherwise, it is considered qualified ("OK"). Some models can generate pressure time curves for easy tracing of leakage trends.
4. Repeated verification: For samples suspected to have critical values, it is recommended to repeat the test 2-3 times to eliminate the influence of accidental factors (such as the escape of small bubbles) and improve the reliability of the results.
3、 Key considerations: Details determine success or failure
-Avoid human interference: Do not touch the instrument or shake the workbench during the testing process to avoid additional pressure fluctuations caused by vibration; Gloves should be worn during sampling to prevent sweat from contaminating the surface of the sample.
-Regular maintenance: Clean the vacuum filter screen weekly, calibrate the air pressure sensor monthly (using standard weights or third-party measuring instruments), check the tightness of the vacuum pump belt quarterly to ensure long-term stable operation of the equipment.
-Special scenario response: For high barrier material packaging (such as aluminum-plastic composite film), the holding time can be appropriately extended to amplify minor leaks; If there is a drastic change in atmospheric pressure in the environment (such as thunderstorm weather), the reference pressure needs to be recalibrated before testing.
The precise use of vacuum attenuation sealing instruments relies on strict control of every detail in each step. By standardizing operations, regular maintenance, and targeted parameter adjustments, the accuracy of testing results can be effectively improved, providing reliable guarantees for product quality.