Water pressure test method for leak detection

Indirectly measuring pressure difference (positive or negative pressure) using the pressure drop method

It is mainly used for the sealing test of valves and pipe fittings, the leakage test of stainless steel welded products, and the micro-leakage test of aluminum alloy die-casting products. The principle is similar to the pressure drop method, but this method is better. Inject gas of a certain pressure into the sealed workpiece cavity, and inject gas of the same pressure into the standard tank. After standing for a period of time, observe the pressure in the standard tank and the workpiece, and observe the tiny pressure difference on the differential pressure sensor caused by the leakage. According to the output change of the differential pressure sensor, the leakage amount of the measured object is quantitatively calculated by the airtightness detector. When the external environment and the work itself are different, the existence of reference materials will minimize the impact of the test. It overcomes the shortcomings of the above methods and improves the detection efficiency, accuracy, and reliability.

Waterproof leak detectors are suitable for testing occasions with low requirements. For example, in IP-level waterproof tests, such as in outdoor electrical products, this method is to pressurize one side of the cavity and the other side (cavity) to collect leaked gas and minimize the volume of the cavity as much as possible to increase the pressure change rate under unit leakage.

The flow detection method of the waterproof leak detector equipment uses the instantaneous loss flow method to perform the airtightness test on the product to be tested. The main airtightness detection principle is that the sensor directly detects the leakage rate of the product and displays it in real time, which can basically save the leakage test accumulation time in the original pressure leakage test method. This product has a fast leakage test speed and can directly display the leakage unit, which is suitable for products with requirements for test efficiency. The measurement signal of flow measurement is irrelevant to the test volume, unlike pressure measurement, where the measurement signal decreases as the test volume increases. This is an advantage during calibration; the measurement signal directly corresponds to the gas flow through the leak calibrator, and the calibration process no longer needs to know the exact test volume, nor does it need to consider determining the leakage rate. Volumetric flow method is generally not used for leak detection but for flow control, such as monitoring the free channel in the gas system before using the same measuring element (differential pressure sensor) for pressure drop leak testing. In the mass flow detection method, the test signal is not only irrelevant to the test volume but also irrelevant to the test pressure, but directly corresponds to the standard leakage rate Std cm³/min, unlike the pressure drop method measurement, which needs to calculate the allowable leakage rate.

Waterproof leak detector manufacturers generally do not use the volumetric flow method for airtightness detection but for flow control, such as monitoring the free channel in the gas system before using the same measuring element (differential pressure sensor) for pressure drop leak testing.

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