Liquid penetration type flaw detecting method and device

As a pretreatment of liquid penetration, a surface in water to be detected is covered while sealing it with a detachable detection box for liquid penetration flaw detection, water in the detection box is sucked to the outside of the detection box using a jet pump by way of an air vent tube connected to the upper portion of the detection box while opening to the atmosphere on the water surface. Air bubble pumping is caused by using air bubbles jetted from the jet pump to a water draining tube connected to the exit of the jet pump. The surface to be detected and the inside of the detection box are dried by a high frequency induction heating coil after the draining of the detection box. In addition, the inside of the flaw present on the surface to be detected is dried to promote cavitation. Then, liquid penetration type flaw detection can be conducted easily even in water at a depth of 10m or more by using a simple local water draining mechanism, and if flaws are present on the surface to be detected, remaining water is removed to make the penetration of the penetration liquid satisfactory thereby improving the effect of the flaw detection. (N.H.)