Metal Finishing Guide Book


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Access considerations. Design mist eliminators for ease of removal for inspection, cleaning and replacement. Mist eliminators should be encapsulated to prevent potential bypass. Access doors should be provided for an operator to inspect the packed bed section, sump area, pump area, and liquid distribution section. The access for the sump area should be above water level to prevent leak points. View ports should be provided for easy inspection of internals. (Borosilicate glass works best as a window; it resists fading, unlike clear PVC or Plexiglas, and withstands the heat of the high-intensity lights.) Locate widows between the water line and packing bottom, at the packed bed section, and at the liquid distribution section. Utilize slide shades to keep light from entering the scrubber where possible. TECHNIQUES FOR REDUCTION OF BIOLOGICAL GROWTH Following are some guidelines to reduce bacterial growth, which could impede scrubber function: ��� Acid wash the unit periodically or shock it with sodium hypochlorite (5% solution) to destroy algae and other biological organisms. ��� Use a chlorinating or brominating system to destroy algae and other biological organisms. ��� Use UV light devices for disinfecting supply and recirculation liquid. ��� Segregate VOC exhaust from scrubbed exhaust. Field experience indicates less evidence of growth with non-VOC exhaust. ��� Segregate all sources of phosphoric acid or other phosphates that feed algae and scrub them with a strong caustic solution at a pH of 10 to 11. ��� Field experiences suggest reduced growth in polypropylene constructed units versus FRP construction. Porosity and pin holes tend to be breeding areas, which are common in FRP units. ��� Utilize sliding shades over all clear view doors to prevent light from entering the unit. CONCLUSION This article touches on just a few common causes of reduced efficiencies in scrubber systems. Proper design of a high-efficiency scrubber system requires much more than just a pump, vessel and spray header. Routine preventative maintenance schedules are important to avoid compounding problems and costly downtime. Reputable scrubber manufacturers can provide periodic preventative maintenance inspections and follow-up reports that allow for trending of system parameters and early recognition of arising problems. For more information on wet packed bed fume scrubbers, please visit 623

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