Metal Finishing Guide Book


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method does not alter the solids-holding capacity of depth-type cartridges, as most of the carbon will stay on the outer surface layer; however, carbon removal is not easily accomplished. TIPS ON FILTER INSTALLATION Filtration equipment should be installed as close to the plating tank as possible in an area that affords access for servicing. Equipment that is not easy to service will not be attended to as frequently as Fig. 8. Suction or dispersion required, and the benefits of filtration will piping system with strainer and not be maximized. The suction line should siphon breaker. Drill a hole 2 in. always have a larger diameter than the disbelow working solution level as a charge to avoid starving the pump (e.g., 1 siphon breaker to prevent in. versus in. or 2 in. versus 1.5 in.) Where solution loss due to unforeseen damage to piping, pump, and so it is necessary to install the equipment on. Chlorinated polyvinyl more than 10 to 20 ft away, check the chloride with screwed pump suction capabilities and increase the connections offers maximum size of the suction piping (1.5 in. instead of flexibility and ease in installation 1 in., or 2 in. instead of 1.5 in.) to offset the and may also be used on the pressure loss. return line by eliminating the Hoses made of rubber or plastic should be strainer and replacing it with a checked for compatibility with the different longer length of pipe that is open solutions. Strong, hot alkaline and certain along the full length. acid solutions such as chromium are especially aggressive. The use of chlorinated polyvinyl chloride (CPVC), polypropylene, or other molded plastic piping for permanent installation is becoming more common. Some plastics are available with socket-type fittings, which are joined with solvents. Their chemical inertness and temperature capabilities are excellent. Iron piping, lined with either rubber or plastic, is ideal but usually limited to use on a larger tank capable of justifying the investment. It should be pointed out that whenever permanent piping can be used in and out of the tank a more reliable installation will exist, since there is no shifting to loosen fittings, and collapsing or sharp bending of hoses is eliminated. The suction should be located away from anode bags, to avoid their being drawn into the line and causing cavitation. Strainers on the suction are always advisable. It is also desirable to drill a small opening into the suction pipe below the normal solution operating level on permanent installations so that, should any damage occur to the system, the siphon action or suction of the pump will be broken when the level reaches the hold (Fig. 8). This provides added safety during unattended operation. Whenever automatic equipment is operated, some provision must be made to protect against unforeseeable events that could cause severe losses. This includes some form of barrier or removable strainer to prevent the suction of parts into the pump. The addition of a pressure gauge is strongly recommended to determine the initial pressure required to force the solution through the filter and also to determine when the filter media needs to be replaced. 688

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