| 摘要 |
The start (5) of the closed tubing (2) is hermetically-sealed, connected internally to a valve (6) and secured to a spool (4). Pressurized gas is fed in through the valve to fill and pressurize the tubing. Internal pressure is maintained. Downstream of production, the tubing enters a freezing unit, where the gas is solidified, forming a plug seal filling the internal cross section. At the same time, the tubing is wound onto the spool. Preferred features: The gas is frozen sufficiently to form an axial, gas-tight plug. The gas can be frozen in three separate chambers of the freezing system, spaced along the production line. This forms three gas-tight plugs. Each is effective only over a limited time scale. The gas is carbon dioxide. Before and after each freezer, the tubing is heated. Gas is supplied through a rotary joint (8) in the hollow core (7) of the spool (4). Its pressure is given by: P = A /* D /* W/R<2> , A being a constant dependent on the tubing material, D the tubing diameter, W the wall thickness, and R the radius of curvature. The tubing is closed at its end during unspooling, internal gas pressure being maintained.
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