| 摘要 |
A pipeline having a plurality of outlets spaced along its length is connected to a controllable supply of liquid under pressure. A transversely expandable and collapsible bladder is fixed in position within the pipeline interior and extends along its length to overlap the locations of the outlets. Air or other compressible gaseous material is provided within the bladder at a pressure less than the supply liquid pressure, causing the bladder to be expanded to substantially fill the interior of the pipeline when it is emptied of liquid. When the connection between the liquid supply and lateral pipeline is open, the bladder is collapsed within the pipeline to permit passage of liquid to the outlets. When the connection is closed, the pressurized bladder is permitted to expand and thereby expel liquid remaining within the pipeline through the outlets. Longitudinally spaced compressible plugs are located between the outlets to prevent gravitational flow of liquid during draining of the pipeline.
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