| 摘要 |
A method of determining the position of a blockage ( 192, 392 ) in a passage ( 15, 313 ) having a first end and a second end. The method comprises blowing a sealing device ( 200 ) into the passage to form a seal adjacent the blockage ( 192, 392 ), then blowing a gas into the passage from the first end, making at least one measurement concerning the gas blown into the passage from the first end and determining a distance D between the first end and the sealing device using the at least one measurement.
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