| 摘要 |
Filtering apparatus includes two or more passages (2) acting in parallel, each having an extended filter (12) which passes through inlet and outlet ports (48, 49), flowable preferably sealed by solidified plugs of the flowable substance such as a polymer being filtered. The flow of such substance to one passage can be terminated so as to permit filter advance under conditions of zero pressure drop, whilst flow through the other passage continues. Filter advance can be assisted by extrusion of a sealing plug in the outlet port under the pressure of such substance from the other passage which is still filtering. In additional or alternative mode, flow into a passage is terminated and a secondary outlet (20, 21) in that passage is opened. This creates a counterflow under the pressure of substance from the other passage, which cleans the filter. The secondary outlet can be sealed by a plug which is extruded during counterflow. An alternative valve for the secondary outlet, which can also be used in a diverter valve for controlling the input of substance to the two passages, has a side passage (26) in which is formed a plug of solidified substance, and means (27) for pushing the plug into the flow substance.
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