Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 90 of 707

chemical surface preparation ADVANCEMENTS IN SOLVENT RECOVERY VIA CARBON ADSORPTION BY JOE MCCHESNEY PARTS CLEANING TECHNOLOGIES, BOWLING GREEN, KY For solvent users who have switched from chlorinated or fluorinated, or other solvents to nPB, now you can obtain an engineered solution to recov- er fugitive emissions, address worker health and safety concerns, and reduce operational cost. How? Technology exists today for degreasing systems using n-propyl bro- mide (nPB) solvent to meet all of the above statements. The old adage that solvent cleans better, faster, and in more restrictive places than water can ever reach is still true. The fact that today's clean- liness specifications for critical cleaning cannot have any contaminants residue or rinsewater residue on the end product drives some users to remain with solvent or switch to solvent for certain applications. With the use of solvent cleaning, comes the issue of emissive losses and worker exposure limits. (The levels of enforcement by the EPA and OSHA vary according to the solvent being used and will be subject to future changes.) nPB HISTORY Due to environmental regulation changes over the past decade, some sol- vents were eliminated from being used for vapor degreasing while oth- ers were regulated by the amount of pounds/kilograms annual usage and/or operator exposure limits such as Threshold Limit Value (TLV). In an effort to find suitable, cost-effective substitutes, solvent users and manufacturers started replacing "eliminated solvents," or those perceived to have future risks, with a wide variety of fluids. One of these fluids that gained considerable market exposure in a rela- tively short period of time is nPB. With performance characteristics simi- lar to the "eliminated" trichloroethane (1-1-1 or TCA) and combined with the ease of transition into degreasers that were already in place in the field, nPB is a good fit for most degreasing systems whether old or new. Past: many users switched from chlorinated/fluorinated to nPB. Present: EPA issues SNAP ruling on nPB. Future: nPB exposure limits? nPB solvent has found general industry acceptance as a replacement fluid for other chlorinated compounds that are being phased out or face more stringent regulations by the U.S. EPA as well as OSHA. 89

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