Following the previous discussion, let's now explore the second testing method, La2: the steady-state air pressure test for non-abrasive fine dust.
This test is designed to evaluate how equipment performs under conditions of fine, non-abrasive dust exposure. Before starting the test, the specimen must be inspected visually, dimensionally, and functionally according to the relevant specifications. This ensures that any initial defects or issues are identified before the test begins.
The test dust used must be dry, fine, and non-abrasive. It should pass through a square mesh with an opening of 75 mm and a wire diameter of 50 mm. To ensure consistency, the dust is heated at 80°C for two hours to remove moisture, and it must not be reused more than 20 times during the entire testing process.
The airflow within the dust chamber must be directed vertically, either upward or downward, and must not form laminar flow. The air velocity needs to be sufficient to create a uniform distribution of dust particles throughout the chamber. Additionally, the relative humidity inside the chamber must remain below 25% to prevent condensation or moisture buildup that could affect the test results.
The test specimen should be placed in the chamber in its original, non-packaged state, with the device turned off and ready for use. Based on the operating conditions of the specimen, an appropriate air pressure condition should be selected from section 5.(1)b.(b). If the device experiences temperature cycling during operation, test category 1 is applied; otherwise, test category 2 is used.
In test category 1, a vacuum pump is connected to the specimen’s drip hole (or a new hole is drilled if necessary), and the internal air is extracted before introducing the dust into the chamber for a specific duration determined by the residence time in section 5.(1)b.(d). For test category 2, the dust is introduced into the chamber and left for 8 hours.
If specified in the relevant standards, measurements should be taken during or after the test. After the test, the specimen is placed in a container until all dust settles. It is then allowed to rest under standard atmospheric conditions for two hours to return to normal environmental conditions before performing visual, dimensional, and functional inspections.
Before final measurements, the surface of the specimen may be cleaned according to the applicable specifications, ensuring no damage is done to the device during the cleaning process.
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