Leakage detection must be carried out before screw vacuum pump is put into operation. If the operation is not correct, the vacuum pump will be damaged. The following points shall be considered when detecting leakage: First, it is necessary to find out whether the test piece can bear positive pressure and how much pressure it can bear, so as to determine whether the extraction leakage test method and the gas that can be filled with pressure can be used. Before detecting the leakage of screw vacuum pump, the weld shall be carefully cleaned to remove welding slag, oil stain and dust. The light at the leak detection part shall be sufficient, the bottom of the sink shall be dark, the water shall be clean and transparent, and there shall be no steam and fog on the water surface. The test piece shall be inflated first and then put into water. Otherwise, if there is a large leak, water may enter the container under inspection and the small hole may be blocked by water. Before putting them into the water, please use the monitoring method to check whether there is a large leakage, and then put them into the water after eliminating the large leakage, otherwise it will affect the detection of small leakage. When the screw vacuum pump specimen is placed in water, bubbles may appear on the surface of the specimen. If these bubbles are erased or punctured and the bubbles no longer appear, it can be judged that there is no leakage. Where bubbles are initially generated. If bubbles appear regularly and continuously, there will be leakage where bubbles are generated. The inspected part shall be kept stable in the water and observed after the water surface is flat. The inspection position of screw vacuum pump shall be as close to the water surface as possible. If any leakage is found, mark it in time. If there is a large leak, check the small leak after repair. In short, the screw vacuum pump can only be put into use after passing the leakage detection; Otherwise, unnecessary damage will be caused for future use.