Metal Finishing Guide Book


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Improvement of Manufacturing Operations The implementation of recovery and quality maintenance methods and systems for both process water and process baths can help improve the performance of plating and surface-finishing baths and, in turn, the quality of the finish and the products that are produced. Such action will also help to reduce the amount of rejects and reworking of parts. Both aspects benefit production and quality control and will reduce operating costs and increase the value of fabricated products. Total Avoidance of Sludge Disposal For this scenario, justification for investment in recovery is based on the obvious desirability of eliminating generations of hazardous waste residuals. Stringent economic quantification is difficult in this case because of the uncertainty associated with determining long-term liability costs for future landfill disposal; nevertheless, there is powerful emotional appeal attached to the avoidance or minimization of long-term liability. Evaluating Strategies The first of these strategies is clearly the most conservative. It is easily applied and is the strategic analytical technique, which has traditionally been used by many metal finishers. The rapid escalation of sludge disposal costs makes point source recovery techniques, which were unattractive a few years ago, very enticing now. The second strategy is legitimate but must be analyzed and applied with caution. There is a tendency to assume that recovery can be a complete substitute for treatment. Careful consideration must be given to potential downtime of recovery equipment; the generation of excess waste if the units are overloaded; the treatment of side streams such as regenerate waste or blowdown from the recovery process; accidents such as tank overflow, heat exchanger failure, spills or drips of chemicals, etc., plus unanticipated sources of regulated pollutants. An example of the last-mentioned caution would be the presence of zinc ion contamination in the drag-out from alkaline cleaners, acid dips, and chromate dips in a zinc plating line. Too often attention is focused on recovery of the dragout from the main plating tank, with no recognition that effluent quality may be unsatisfactory simply as a result of minor contributions from various other sources. When considering this strategy, the absolute minimum provision for unrecovered waste should be the determination of the minimum holding and treatment capacity needed to cope with the volume of unanticipated accidents or upsets. The third strategy is the most efficient and productive way of converting waste treatment capital into waste minimization and production control efforts. Many examples today prove that the incorporation of pollution control and maintenance equipment into plating operations helps to significantly reduce batch dumps of process baths. Controlled bath maintenance limits bath impurities that cause plating quality problems and thus improve fabrication while reducing manufacturing cost. In many cases, short duration ROI objectives can be realized. The fourth strategy is the most risky and the most difficult to support by facts. It is a rare situation where the generation of sludge can be completely eliminated, even in a theoretical sense, especially if such unanticipated occurrences as just discussed are considered. In summary an investment in recovery technology and equipment should be supported by a hard, quantifiable economic analysis and supported by adequate 598

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