| 摘要 |
<p>PROBLEM TO BE SOLVED: To safely conduct the connection construction work by inserting at least three balloons at positions where gas is shut off and introducing inactive gas into a plurality of partition chambers formed among each balloon to exhaust gas in a second partition chamber when balloons are inserted into a pipe and gas in a gas pipe is shut off. SOLUTION: When a pipe passage position at which work is done is shut off from a direction of gas flow 2, three balloons 4 are inserted in gas shut-off positions, and partition chambers 12, 13 are formed among each balloon 4. Next, inactive gas is introduced into the partition chamber 13 adjacent to a shut-off zone, 14 through an inactive gas pouring pipe 7, and gas in the adjacent partition chamber 12 is exhausted from a gas exhaust pipe 8. At this time, pressures of a gas pipe on upstream side 11, each partition chamber 12, 13, a shut-off zone 14, and a gas pipe on downstream side 17 are measured by pressure gauges 21 to 23 to keep a pressure in the partition chamber from which gas is exhausted at a lower pressure than other pressures. Consequently, gas on the upstream side is extracted from the partition chamber 12 to eliminate a gas leakage into the shut-off zone 14 so that the work in the shut-off zone 14 can be done safely.</p> |
