Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Fig. 5. Five-stage belt-type iron phosphating machine (see Table III for details). rinse stages are 30 seconds; thus, they are each sized at 2 ft in length. Good design practice dictates that the approaches and exits should be two times the tunnel width; therefore, they should be 4 ft long. The drains should be three times the tunnel width, minimizing spraying and carryover contamination; therefore, they are 6 ft in length. Special consideration for drain lengths may be necessary for long parts or slow line speeds. The hot air blow-off will require three minutes of drying time, so size that at 12 ft. You also must have 1 ft between washer and hot air blow-off fan for ventilating. ENVIRONMENTAL CONCERNS Most washer systems require waste treatment of the effluent from the system pri- or to disposal to the sewer. In some cases, where the potential discharge of clean- ers and phosphates to the sewer are significant, a self-contained treatment system is required. Most municipal waste treatment authorities have a list of chemicals they can accept and in what concentrations. Check with the local authorities for addi- tional information, or consultants are available to assist in your decision-mak- ing process. Fig. 6. Three-stage drum-type washer with blow-off (see Table IV for details). 193

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