Metal Finishing Guide Book


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Fig. 5. Five-stage belt-type iron phosphating machine (see Table III for details). 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 prior to disposal to the sewer. In some cases, where the potential discharge of cleaners 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 additional information, or consultants are available to assist in your decision-making process. Fig. 6. Three-stage drum-type washer with blow-off (see Table IV for details). 813

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