Innovative Water Management Solutions
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Innovative Water Management Solutions
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Aqueous PCB Chemical Cleaning:
When chemical cleaning agents are added to the aqueous process, both machine and water management techniques increase in cost and complexity. Because saponifier, or any other chemical additive, is costly, it is desirable to recirculate the chemistry by closing the prewash drain and directing the flow back to the wash tank. Thus, the prewash and wash combine to make one larger wash section. In addition to the cost factor, cleaning chemistry can be highly ionic in composition, so it cannot be left on the circuit boards and it will have an immediate, detrimental effect on media tank longevity. Different equipment manufacturers have different techniques to minimize dragout of cleaning chemistry from the wash section to subsequent downstream sections, but one of the most effective is to utilize an interstage rinse between the wash and recirculating rinse. Sometimes called chemical isolation, this section floods chemistry off the board and uses an airknife for a “squeegee” effect. The cleaner will have not one effluent stream, as in the straight aqueous process, but three: · Wash tank - when the tank is drained · Interstage rinse - ongoing, approx. 1 gpm · Rinse – ongoing process stream of 3-5 gpm The rinse stream, in effect, becomes a straight aqueous process loop and can be recycled by conventional means. The interstage rinse stream will have residual chemistry and, possibly, some lead content. In some municipalities, the level of contamination is low enough that this stream can be sent to drain. Where regulations are more stringent, this stream (and the wash stream) must be treated by drain media to remove heavy metals (Check out REsys ETS). (Note that some local regulations will require additional pH treatment, or possibly evaporation to achieve compliance. Local regulations must always be understood when specifying a water management system). The same argument for RO pretreatment of incoming water applies to aqueous cleaning chemistry (see the Open Loop application page). Potential benefits of RO are augmented since purified water is supplied not only to the ongoing rinse process stream, but also to the interstage rinse.
For more information please contact Brian Maheu @ 800-873-7379 or bmaheu(at)resysinc(.)com |
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REsys, Inc.
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