| 摘要 |
PURPOSE:To detect the position of a pinhole in the barrier by providing a directional ultrasonic wave receiver in a tank space, generating a differential pressure between the inside and outside of the barrier, and receiving an ultrasonic wave generated when a fluid passes through the pinhole in the barrier. CONSTITUTION:A cargo tank 2 for liquefied gas is provided in an LNG carrying vessel 1 and this consists of a primary barrier 3, secondary barrier 3', and tank external wall 3''. A primary heat insulation space 4 and a secondary heat insulation space 5 are evacuated by a vacuum pump 10 to lower than the atmospheric pressure. This negative pressure produces the difference pressure between the inside and outside of the primary barrier 3 and if there is a pinhole in the primary barrier 3, an ultrasonic wave is generated when a liquid passes through the pinhole. The directional ultrasonic wave receiver 7 installed at the inside of the primary barrier 3 is operated remotely to find the direction in which the display value of the received ultrasonic wave is maximum, thereby detecting the pinhole as the leak position of the primary barrier 3. |
