| 摘要 |
PURPOSE:To detect the anomalous points, e.g., pin holes, etc., in particular, of a hollow pipe by a simplified method in which a conductive inner layer is formed in a thermoplastic extruded pipe and voltage is applied between the electrode of a sparking tester and the inner layer. CONSTITUTION:A pipe corresponding to an inner layer is molded by extruding a conductive resin from an extruder 4, land an outer layer 2 is formed on the inner layer by extruding a thermoplastic resin from an extruder 5 connected in tandem to the extruder 4. The hollow pipe 1 so molded is cooled in a water tank 6 while being pulled by a withdrawer 7, and the inner layer 3 is earthed and then passed through a linked ball type sparking tester 8. Since potential is given to the linked ball type electrode of the sparking tester 8 in such a way as to cause sufficient potential difference to occur in the inner layer 3, sparks take place at pin holes, if any, in the outer layer 2, and therefore, the pin holes can be easily detected. |
