Original Date: 01/26/1998
Revision Date: 01/18/2003
Best Practice : Advanced Metal Finishing Processes and Facility
Corpus Christi Army Depot (CCAD) operates a new metal finishing facility, one of the most advanced metal finishing facilities in the Department of Defense (DoD) (Figure 2-1). The new metal finishing facility consists of 18 process lines with 25 processes including electroplating, conversion coating, anodizing, metal stripping, aqueous cleaning, passivation, aluminum vacuum coating, nitrogen implantation, stress relief, and organic finishing. The previous plating facility was an old structure, outfitted with small tanks and uneconomical scrubbers and ventilation systems. CCAD’s Advanced Metal Finishing Facility’s new design and modernized equipment have reduced operator labor by 20%, water consumption by 90%, and hazardous waste disposal by 90%.
The new metal finishing facility has greatly improved safety and productivity and has provided the capability for environmental compliance. Safety has been improved by adequately segregating and storing cyanides, automating the black oxide process, and providing enhanced ventilation for fume control. Processes became more effective by using straight lines for material flow, sizing tanks for new weapon systems, and providing better laboratory support. These improved efficiencies resulted in increased productivity and expansion capability. Environmental compliance was facilitated as follows:
Ground water protection was enhanced by closed loop water usage. By constructing the metal finishing processes on the second floor and the wastewater treatment and storage system on the first floor, the risk of a hazardous waste spill was essentially eliminated. Furthermore, there were now four layers of spill protection, and all gravity drains from the building were disconnected. Water reuse resulted in substantial water conservation. Deionized water was produced on- site and spray rinsing/double and triple counter current rinsing were used.
To comply with air quality requirements, a mesh pad was used for the chrome scrubber, and acid/alkaline scrubbers were used. For blasting operations, a centralized dust collection device was used. A backup generator was installed as an emergency response measure.
Waste minimization was implemented. Concentrated and diluted waste waters were segregated, and a diluted waste water stream was continuously treated. The concentrated waste water was treated as a batch.
The advanced metal finishing facility has provided enhanced safety, improved productivity, and environmental compliance capability. New technology such as aluminum vacuum coating shows good promise; however, it will take some time until it is universally accepted in the DoD system. Lessons learned in operation of this facility include:
Too many alarms were designed, and only critical alarms should be audible. A centralized computer for heating, ventilation, and air conditioning is needed.
No air agitation of chrome plating tanks is needed.
Figure 2-1. Advanced Metal Finishing Facility
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