Page 302 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition
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274                       Applied Process Design for Chemical and Petrochemical Plants







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               The woven fabrics have various yarn patterns for dif-   varies, but one promise  seems to be that higher  tem-
             ferent spacings between  the yarn fabrics  (Table 4-14).   peratures will be handled.
             There  is  a  wide  variety  of  choices  for  not  only  the
             materials  of  construction  but  the  tightness  of  weave   New  cartridge  designs  for  bag  houses  will  allow
             and the size of the yarn. All of these factors along with   improved servicing and cleaning techniques.
             the others noted earlier, make the selection of bag fab-
             ric  an  art  that  requires  manufacturer's  and  plant's   It is important to keep bolts, nuts and other poten-
             actual  field  tests.  Woven  fabrics  have  a  low  ratio  of   tially  loose  items  to  a  minimum  inside  the  unit,  as
             weave openings for yarn area and generally have a lim-   vibration  from  air/gas  flow  and  bag  cleaning  can
             ited  face  velocity for  air  flow  of  about  1.5 to  3.0  cu   loosen  nuts,  break  small  welds,  and  ultimately  tear
             ft/min/sq  ft [47].                                   holes  or  rip  bags.  The  bag  construction  is  likewise
                                                                   extremely  important,  since  loose  edges  and
               Newer  fabrics, not in common  use but in develop-   "unlocked"  seams  will  fray  and  tear,  allowing  fibers
             ment,  test,  and field  trials,  are  described  for higher   into the product dust. The bag construction must have
             temperature applications  by  Reference  [50]. Applica-   straight  seams  in  order  for  them  to  bend  and  flex
             tion  to  400"F--2100"F  are  potentially  available  using   properly on cleaning and/or  loading.
             ceramic  fibers  Nextel  312@, laminated  membrane of
             expanded  PTFE  on  a  substrate,  polyimid  fiber  P-84,   Cartridge filters may be single units or clusters in a sin-
             Ryton@ polyphenylene  sulfide,  and woven  fiberglass.   gle container  or canister. Figures 468 to  474 illustrate
             The heat  and  acid  resistance  of  these  new  materials   typical units. These may be designed to filter suspended
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