LEAK POINT DETECTING METHOD FOR UNDERGROUND BURIED CONDUIT

摘要

PURPOSE:To easily detect a leak point of the conduit which is buried under the ground from on the ground by closing both ends of the conduit in an inspection section, and pressing liquid in the enclosed conduit and raising its internal pressure. CONSTITUTION:A partition valve 2 is closed at one end side of the conduit 1 which is buried under the ground and a partition valve 3 is also closed at the other end side to enclose the conduit 1 between both the partition valves 2 and 3. Then the same liquid as liquid in the conduit 1 is injected into the enclosed conduit 1 to raise the internal pressure. Consequently, the leakage increases and the liquid in the conduit begins to flow toward the leak point 4. Therefore, the flow of the liquid in the conduit increases in flow velocity toward the leak point 4 at the periphery of the leak point 4 and the direction of the flow is inverted at the leak point 4. The leak point is detected by detecting the velocity and direction of the liquid in the conduit 1 while moving the detection terminal 5 of a Doppler type ultrasonic flowmeter in the laying direction of the conduit. When the velocity of the liquid direction and the change of the flow direction are detected, the leak point is present on the conduit at the position.