| 摘要 |
PURPOSE:To check defects in a valve stem of a valve gear without disassembling this valve gear by detecting the reaching time of an ultrasonic wave till this wave out of an ultrasonic probe reaches where should be after being reflected by contours of the valve stem, and diagnosing whether anything goes wrong with the valve stem or not. CONSTITUTION:In a valve stem in a valve gear controlling a full-close position by means of torque seating, such a possibility that a crack might occur in a valve stem back seat part is high. In the valve gear in this type, there are provided a valve box 1 and a valve cover 2, and both these elements 1, 2 are coupled with bolt and nut. The valve stem 4 is one that transmits driving force out of a driver 5 to a valve element 6 which is connected to a lower end of the valve stem 4. In this connection, this valve element 6 is set up in space between the valve box 1 and the valve cover 2 free of lifting motion. An uotrasonic probe 9 is set up on top of the valve stem 4, an an ultrasonic wave being emitted out of this ultrasonic probe 9 is scanned in an inner part of the valve stem 4 vertically toward the side of the valve element 6, while the reaching time of another ultrasonic wave (bottom echo) being reflected by a bottom surface of the valve stem 4 is read out, and if this reaching time is longer than the specified time, it is so judged that something goes wrong. |
