The Plating Department at the Corpus Christi Army Depot designed a new finishing facility to help it meet new environmental regulations...
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An infrequent traveler deplanes at concourse B of the Dallas-Ft. Worth Airport clutching the ticket for his connecting flight. He assumes a quick walk will bring him to his next gate. After all, isn't the connecting flight with the same airline? It may be the same airline, but it is leaving from concourse D. After a lengthy, anxious walk past many directories and beleaguered passengers, he arrives at his gate. So much for a hop, skip and jump.
That is how one may feel when entering the Corpus Christi Army Depot (CCAD) and Naval Air Station, except there are no directories: only street signs, an occasional building number and, if it's a newer building, a sign identifying the building. Two large, white, steel structures resembling tremendous screened-in birdcages occupy a field in front of several buildings. Perched in the background are the enormous "birds": Blackhawk, Apache and Chinook. You start recognizing the people standing outside the buildings and realize you are going in circles. Eventually I drove down the right street, and, fortunately, my destination is one of those new buildings with a sign.
CCAD is the Army's only facility for the repair and overhaul of rotary wing aircraft. Its mission is to overhaul, repair, modify, retrofit and modernize all types of Army and most DoD (Department of Defense) rotary wing aircraft. It also provides hands-on training for Reserve, National Guard, active duty and friendly foreign military personnel. CCAD also furnishes additional depot maintenance support, including on-site maintenance teams, crash damage analysis, chemical, metallurgical and technical support.
One of the "newest" support shop areas at CCAD is the Advanced Metal Finishing Facility, supported by Jim Holiday, chemical engineer, and Jerry Smith, chemist. The spacious, bright, clean plating facility is a direct contrast to the shop it abandoned two years ago. "The best way to describe the old shop," stated Mr. Smith, "is that it was a 1940's design built in the 1970's and crammed into a tiny area."
The old shop design did not allow for linear process flow. Platers would have to jump the line with a rack of parts to use the rinse water. "There was a lot of cross contamination," noted Mr. Smith, "particularly in the rinses." Platers used one rinse for several different plating baths. "It was a safety and environmental nightmare," Mr. Smith commented. "We would replace at least 12 plating baths each year due to dragin contamination and poor water quality."
"We used this situation, upcoming environmental regulations and the new weapon systems coming in as leverage when requisitioning a new facility," said Mr. Holiday. "Most of the Vietnam vintage craft, like the Huey, are being phased-out."
The old shop was 40,000 sq ft. The new shop has 126,000 sq ft. The old shop had 12 process lines with small tanks, including acid tanks situated next to cyanide containing tanks. The new shop has 18 separate lines with greatly enlarged tanks that can handle 670- lb, eight-ft-long, 24-inch-wide helicopter rotors and four-by-12-ft aluminum aircraft skins. The old shop had no secondary containment except on the cyanide baths. The new shop has four levels of containment in addition to monitors on all solutions. Also, there are no gravity drains from the building, and all floors are sloped with sumps. The sump systems also have audible and visual monitors if the liquid level rises above a certain point.
The old building had a basement below the plating shop that extended four to five ft into the ground. Four to five feet below the basement level were exhaust chambers for drawing out exhaust air. These exhaust chambers continued in a row toward the scrubbers, which were about 14 to 16 ft underground. "Our water table here is 12 ft in dry season and three ft in the wet season," noted Mr. Holiday. "The basement was always wet, and the soil is a sand/clay mixture with high permeability."
There are 14 KCH Services' exhaust systems in the new building: seven acid/alkaline, three chromium, two cyanide and two general exhaust. Three of the KCH systems are mesh-pad systems for scrubbing chromium plating fumes. (The chromium-plating vent at the tank provides 6,000 to 9,000 cfm.) The seven acid/alkaline scrubbers use a water purification cell that recirculates 80 gpm of water. The old method was to simply treat and release the scrubber water. All scrubbers are housed indoors to reduce corrosion. CCAD has retained a contractor, National Chemical, who performs monthly cleaning and preventive maintenance on all scrubber and exhaust systems.
Another significant change from the old shop to the new was the water. In the old shop, DI water was used only to make up the initial plating baths and for solution replenishment; a futile effort considering all of the cross contamination. Tap water was used for the rinses. "The water in this part of Texas," explained Mr. Smith, "is high in chloride, calcium and magnesium. So it is not very good rinse water for plated parts."
In the new shop, DI water is used for everything: solution makeup, rinse tanks and solution replenishment. Water saving techniques were also implemented. Double and triple counter-current rinses (depending on application need) were installed on all lines. Water from the first rinse feeds back into the process tank. All rinse tanks feature computer-controlled push-button timers. When an operator activates a rinse, it cascades for a programmed number of minutes and then automatically turns off. Rinse tanks also have hand-held spray rinses so the metal finishers can ensure that even intricately shaped parts are well rinsed.
The old shop used 100,000 gpd of water on average. Only 12,000 gpd flows through the new shop.
Finishing processes at the Advanced Metal Finishing Facility include: black oxide; zinc phosphate; manganese phosphate; DOW 7 Process (Mg); DOW 9 Process (Mg); Alodine; zincate; titanium, chromic acid and sulfuric acid anodize; derusting, Nital etch; stainless steel passivation; silver, copper, nickel chloride, nickel sulfamate, electroless nickel, chromium and cadmium plating.
Plated parts vary from a 10-cu-in CH-47 hydraulic housing worth $80,000 to an eight-ft shaft for a CH-47 Chinook helicopter. In addition to traditional finishing baths, CCAD also offers aluminum vacuum coating, nitrogen implantation, powder coating and heat treating using Grieve Corp. ovens.
The chromium plating tanks have multiple rectifiers so different parts can be plated simultaneously. Chromium tanks also feature 12 inches of freeboard to help with fume control. Instead of air agitation, CCAD uses Flo King Filter Systems' four-in-one filter systems. There are 300 Flo King systems throughout the shop.
Original plating processes were written to military specifications or federal specifications. Recently, however, the government decided to retire many of the specifications and use available commercial and industrial specifications instead. Because of this, Mr. Smith designed CCAD's plating processes around AMS (aerospace material specification) or ASTM (American Society for Testing and Materials) specifications. "Many of the ASTM and ASM specifications were derived from MIL specs anyway," noted Mr. Smith. "Specifications dictate the performance and quality of the finish; however, they do not specify how to apply the finish."
The new 2,000-sq-ft lab ensures that the finishes meet specs. "The old lab was basically a hole in the wall," laughed Mr. Smith. "The new lab is fairly standard with an atomic absorption spectroscopy system, ion chromatograph and automated titration system. The lab follows a specific plating solution analysis schedule. Plating bath samples are drawn, analysis done, and the results are logged and compared to historical records. "We write up work orders that typically include the following: chemical additions, solution filtration, or solution disposal," explained Mr. Smith.
These work orders are then passed on to the shop's chemical maintenance team. During its shift, the team adjusts the plating baths and returns the completed work order, indicating all actions taken.
In addition to process testing, the lab also uses a Singleton salt fog chamber to test corrosion resistance. The chamber is automated so lab personnel need not come in on weekends or holidays to keep it filled with water. Salt fog numbers for some of the plated finishes are 197 hrs for cadmium; 200 hrs for anodized finishes; and 2,000 hrs for painted parts.
The central computer features automatic process timers to control process start and stop, monitor temperatures, liquid-levels, and rectifiers. Platers also have access to the computers to monitor plating line operation and process parameters. Operators have the power to get into programs and change parameters.
The waste treatment system, however, is operated and maintained by an outside contractor, National Chemical. National Chemical provides Total Site Management that encompasses all aspects of the plating shop's industrial wastewater treatment. This is a total turnkey service. The company provides comprehensive daily services, including system maintenance, daily sampling, equipment readings, equipment normalization, chemical deliveries, real-time monitoring and daily normalization of ultra-pure water systems using up-to-date computer normalization software. The plating shop produces about 1,200 lb of sludge every one to two weeks.
Other improvements at the Advanced Metal Finishing facility include a computer tracking system that provides documentation for those "disagreements" the plating shop occasionally had with its customers. Before the tracking system, the plating shop would sometimes plate parts that were not supposed to be plated or did not need to be plated. Parts were "dumped" on the shop and pigeonholed in an open area above the old shop. The new computer tracking system ensures that those days are over. Parts are inspected, tagged, tracked and returned to the proper customer.
The shop also has a small machine shop for making racks and fixtures. Mr. Holiday plans to use the lathe for buffing nameplates and other small decorative items plated at the shop. The Advanced Metal Finishing Facility provides plating services for other DoD facilities in South Texas; however, it would be interested in plating commercially as well. The only problem is that the military has a non-compete agreement with industry in the area. If a commercial shop in the area offers sulfuric acid anodizing, for example, CCAD cannot bid on the job.
Although the CCAD is an enormous, confusing place, the Advanced Metal Finishing Facility is not. Jerry Smith and Jim Holiday made sure the plating lines followed a linear path. They provided for DI water in all plating operations. They designed the facility so that there was no danger of an environmental mishap. They planned the move for nine months. They left an out-of-date plating facility and moved into one they designed to take the military into the next millennium.