Miscellaneous Mechanical ComponentsDOE-HDBK-1018/2-93FILTERS AND STRAINERSThe flush source is then opened and the flow goes into the outlet of the strainer or filter, throughthe strainer or filter, and exits the inlet to the backwash drain or waste tank, carrying the debriswith it.SummaryThe important information in this chapter is summarized below.Filters and Strainers SummaryA cartridge filter may be a single cartridge or multi-cartridge filter. Thecartridges are cylinders that usually consist of a fiber yarn wound around aperforated metal core. The liquid being filtered is forced through the yarn andthen through the perforations in the metal core to the filter outlet, which can beat either end. This type of filter is used to remove fine particles in any flowcondition. Radioactive systems may use these because they are inexpensive andeasy to replace.Precoat filters consists of a filter housing that contains a bundle of septums,(vertical tubes, on which the filter medium is deposited) usually made ofperforated or porous metal (normally stainless steel), porous stone, or porousceramic material. The filtering medium fibers may be finely divided diatomite,perlite, asbestos, or cellulose. Diatomite, the least expensive medium, is used tofilter liquid waste that will be discharged from the plant. Cellulose is generallyused for processing water that will be returned to the reactor, because diatomitecan allow silica leaching.A deep-bed filter is based on a support screen (decking), which is mounted a fewinches above the bottom of the tank. The screen is perforated to allow water toflow through it. A coarse, aggregate layer of crushed rock or large lumps ofcharcoal is placed on top of the screen, and the deep bed itself (2 to 4 feet ofgranular anthracite or charcoal) is placed on top of the aggregate. This type offilter is frequently used in raw water treatment.The bucket strainer is literally a bucket to catch debris. The bucket can beremoved for cleaning by loosening the strongback screws, removing the cover,and lifting the bucket out by its handle. It is usually used in systems expected tohave larger debris. Rev. 0ME-05Page 47
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