| 摘要 |
<p>PROBLEM TO BE SOLVED: To avoid a risk where a tube is deformed or damaged by making lower the pressure difference between the pressure of fluid flowing into the first end part of a duct and that inside the tube than an excessive pressure that the tube can withstand. SOLUTION: Both end parts 31 and 32 of a tube 3 are blocked by a plug, sealing, or the like for making airtight, and an air penetration valve is mounted to one of the end parts. Then, a compressor for supplying a pressure Pi to a blowing/propulsion device 1 is used to give an air pressure to the tube 3. The tube 3 inflated to a pressure Ps that is lower than or equal to the pressure Pi and is maintained constant throughout an entire laying process. An excessive pressureΔP, that is directed from the outside to the inside of the tube 3, can be minimized by the rough pressure Ps for the pressure Pi, namely by inflating the tube 3 to a pressure that is extremely close to or equal to the pressure Pi and making the excessive pressureΔP lower than the value of an external pressure that the tube 3 can withstand at all times.</p> |
