| 摘要 |
Apparatus for cleaning pipelines of finite length with a liquid has a shuttle valve with a body having a liquid admitting inlet, a liquid discharging outlet and two hollow couplings connectable to the ends of a pipeline which requires cleaning. The body confines a shuttle which is reciprocable between two positions in the first of which liquid flows from the inlet to one of the couplings, through the pipeline between the couplings into the other coupling and then into the outlet. When one or more spherical or otherwise configurated cleaning elements in the pipeline cause the shuttle to assume its other position, the liquid flows from the inlet to the other coupling, through the pipeline into the one coupling and then into the outlet. The apparatus and/or the pipeline is likely to be damaged if the pressure at the inlet reaches a certain value and/or when the raised pressure of the liquid causes the shuttle to strike against the body with a greate force as a result of abrupt movement from the one end position to the other end position or in the opposite direction. Therefore, the inlet contains a pressure relief valve which opens and establishes a path for the flow of liquid from the inlet to the outlet around the shuttle when the liquid pressure in or at the inlet reaches or exceeds a preslected value.
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