Abstract: Apparatus for use in a multi-stage system in which a fluid being treated is passed in succession through a first stage A, a second stage B, a third stage C, etc. includes a controlled system of valved interconnections that permits the direction of flow within each stage to be reversed while preserving the original sequence ABC . . . in which the fluid progresses from stage to stage. The stages may be reaction chambers in which chemical or photo-chemical reactions are carried out or the stages may be filters that need to be reverse-flushed at intervals. In accordance with the invention, a second set of inter-stage connections is provided, in addition to the original connections used for forward flow. In the second set, the inlet and outlet ports are located at opposite ends of each stage from the inlet and outlet ports used in the original connections.

Abstract: A replaceable wiper cartridge is described which is held captive within a shuttling scraper of a type known in the art which is pushed axially through a cylindrical reaction chamber intermittently to remove reaction products from the inside surface of the reaction chamber and from the outside surface of a smaller coaxial tube that extends the length of the reaction chamber. The replaceable wiper cartridge has an annular shape that is obliquely cut to permit a slight radial expansion to accommodate the smaller coaxial tube and to engage it in a tight sliding grip so as to scrape from the smaller tube any deposits.