Check whether the locating surface of the fixture is tight. After the workpiece and the locating surface of the fixture are tight, the pressure difference is within a certain range. If not, the pressure difference exceeds the range and an alarm signal is output. The equipment stops running. As shown in the figure, three points are gas inspection holes.
The air tightness of parts in large quantities is checked by barometer. The method is to seal the parts to be checked and then open the valve. When the pointer of the pressure gauge reaches the specified pressure, close the valve. If the pointer of the pressure gauge does not move, the seal is qualified. A worker has to test thousands of pieces in one shift.
mainly depends on whether there is leakage in the pressure-maintaining stage after sealing, using the soaking and bubbling method or directly using the flowmeter.
Extended information:
Introduce compressed gas into the closed container, then observe the leakage, and judge whether the sealing performance of the tool is qualified according to the observed phenomenon. The principle is as simple as that, and there are many methods. ?
bubble method: gas with a certain pressure is introduced into the closed workpiece cavity, and the workpiece is immersed in water (or other liquid) to observe whether bubbles overflow. Or apply soapy water on the surface of the workpiece to observe whether there are bubbles. ?
pressure drop method: introduce gas with a certain pressure into the closed workpiece cavity, stand for a period of time, check the pressure of the gas again, observe whether the pressure has decreased, and judge whether there is leakage according to the pressure change. ?
pressure difference method: gas with a certain pressure is introduced into the closed workpiece cavity, and gas with the same pressure is introduced into a standard tank, and the pressure difference between the standard tank and the workpiece is observed after standing for a period of time. This method is more accurate than the pressure drop method, and it can eliminate the pressure deviation caused by the change of ambient temperature. ?
flow method: gas with a certain pressure is introduced into the closed workpiece cavity. After a period of time, the flowmeter starts to measure and keep supplying gas continuously. Observe the gas flow rate for a certain period of time, and judge whether the leakage amount meets the requirements according to the flow rate. This is suitable for the situation that the workpiece is allowed to have a certain leakage. ?
halogen gas leak detection method: a halogen gas with a certain pressure is introduced into a closed workpiece cavity, and a halogen detector is used to detect whether there is halogen gas leakage outside the workpiece. ?
helium leak detection method: helium with a certain pressure is pumped into a sealed workpiece cavity, and then a helium mass spectrometer is used to detect whether there is helium leakage around the cavity of the workpiece. This method is currently used for high-precision leak detection. Compared with the previous methods, the accuracy is much improved, and of course, the cost is high. ?
Baidu encyclopedia-air tightness test