Tinker Air Force Base
Oklahoma City, OK

For more than a decade, the Navy's Best Manufacturing Practices (BMP) survey process has been a primary avenue for industry and government to present individual and distinctive success stories in management and manufacturing disciplines. For those organizations seeking to advance their overall manufacturing performance, the BMP program has provided validated and documented best practices. These practices, verified on-site by BMP survey team members, have served as a model for improvement in business and industry and as a tool to promote teaming.

In 1995, industry and government representatives discussed the idea of broadening the BMP program's scope to incorporate success stories submitted by industry. The objective was to find an efficient, cost-effective way to share a greater volume of information on the latest technology and business developments. Since the BMP program had a proven approach for sharing success stories, this seemed to be a logical expansion.

The practices in this report were submitted to the BMP Center of Excellence by Tinker Air Force Base, Oklahoma City, OK as an example of some of the latest developments in the environmental area. They are considered to be best practices or success stories, however, they were not validated by an on-site BMP survey team. Our goal is to help industry and government keep pace with the rapid changes taking place in the business, manufacturing, and environmental communities.

Today with nearly 22,000 civilian and military assigned to the base, logistics work is just part of Tinker's mission. After the arrival of the Navy, Tinker became one of DoD's premiere interservicing facilities. Not only is total support of America's defense systems a priority, but protecting and enhancing the environment is a top concern as well. Through the use of aggressive and innovative technologies, Tinker has become a national leader in pollution prevention.

Tinker's largest organization is the Oklahoma City Air Logistics Center (ALC), one of five depot repair centers in the Air Force Materiel Command. The ALC is the worldwide manager for a wide range of aircraft, engines, missiles and commodity items. The center manages an inventory of 2,267 aircraft which include the B-1, B-2, B-52, C/KC-135, E-3, VC-25, VC-137 and 25 other Contractor Logistics Support aircraft.

The Center also manages an inventory of more than 13,724 jet engines that range from the Korean Conflict vintage J33s (T33) to state of the art B-2 engines such as the F118. Missile systems managed by the center include the Air Launched Cruise Missile, Short Range Attack Missile, Harpoon and Advanced Cruise Missiles.

Commodities management includes responsibility for some 42,399 different exchangeable or commodity items.

TABLE OF ACRONYMS:
The following acronyums were used in this report:

Background: Although cadmium plating has been eliminated in the OC-ALC plating shop, there are still a great number of parts that must have old cadmium coatings removed. This process results in large amounts of cadmium contaminated strip solutions. To reduce this waste stream, a system was developed to rejuvenate the stripping solutions for reuse by selectively removing cadmium.

Description: The cadmium strip rejuvenation process uses an ion exchange column to selectively remove cadmium from contaminated strip solutions. A specially designed resin was developed that removes cadmium from the solution. When the resin can no longer remove cadmium, it can be rejuvenated with ammonia. The cadmium is then electrowinned (plated) from the ammonia solution. This pure cadmium can then be sold.

Results: This process allows the plating shop to reuse the stripping solution several times before disposal. When disposal is finally necessary, the solution will contain only trace amounts of cadmium making it less expensive to dispose. Finally by plating the cadmium out of the ammonia regeneration solution, the cadmium can be sold as a pure metal instead of disposed of as hazardous waste.

Background: CO₂ blasting is used to remove carbon, corrosion, and paint from jet engine components. In the past, these operations were accomplished by using solvents, acids, and caustics to chemically remove the material. This process required large vats of chemicals where parts would be soaked for several minutes to several hours.
Another use of CO₂ blasting is to replace traditional grit blasting. When grit blasting parts with internal cavities, it is necessary to mask the part to avoid grit entrapment. CO₂ blasting eliminates the need for masking, since the solid CO₂ sublimes to a gas upon impact.

Description: CO₂ blasting was installed in 1988 and is used primarily as a cleaning supplement. In this process, an operator works in an enclosed booth using a full face respirator by manually directing the CO₂ gun at the part. The gun propels CO₂ pellets at a high flow rate (8 pounds per minute). The cleaning is accomplished by the force of the impact which causes the solid CO₂ to sublime to a gas. The removed soils can then be collected. Smaller particles are removed from the air by a filtration system. Larger particles such as paint chips and carbon deposits are swept from the blast booth floor.

This process is used primarily for two purposes. The first is for spot or touch up cleaning. When a part is not completely cleaned in the chemical cleaning line, the CO₂ blast unit is used to clean the soiled area. This results in reduced chemical usage. It also allows the part to be processed faster, since it does not have to be reprocessed through the chemical cleaning line

CO₂ blasting is also used in replace of grit blasting on parts with internal cavities. Internal cavities must be masked before grit blasting to prevent grit entrapment which could cause damage to the engine. Since CO₂ sublimes from solid to gas, cleaning can be accomplished without grit entrapment and without masking. This results in reduced hazardous waste from masking and quicker processing times.

Background: High Velocity Oxy-Fuel (HVOF) Flame Spray is the newest generation high energy thermal spraying process. HVOF is currently approved for the application of wear/erosion coatings and thermal barriers on exhaust nozzles, combustion chambers, and compressor blades. HVOF is currently being prototyped as a chrome replacement on a series of parts.

Description: The main advantage of HVOF over other thermal spray processes is the high impact speed that is obtained by the molten droplets of metal. This high impact speed produces very dense, hard coatings. Many of the properties of HVOF coatings are similar to that of chrome plate. In addition, HVOF coatings can be applied in approximately 45 minutes compared to over 48 hours for the same thickness of chrome. Waste water is virtually eliminated because there are no rinse waters involved. Masking waste is also eliminated because the masking will consist of bolt-on sheet metal masks. Finally, HVOF is very flexible because one machine is capable of applying over 23 different coatings. The properties of HVOF are being compared to the requirements of different parts to determine prototype candidates. These prototype parts will then be coated and tested in an engine to validate the new coating.

Results: This process allows the plating shop to reduce the amount of chrome plating that is done. It is hoped that HVOF will eliminate approximately 30% of the chrome plating work load. This reduction in chrome plating will also reduce waste water treatment and hazardous waste disposal.

Background: Pressure spray washers are used for general parts cleaning and degreasing. The spray washers have been used to eliminate both perchloroethylene and Freon degreasers, PD-680 solvent cleaning, and some hand cleaning processes.

Description: Six pressure spray washers are currently in use. The washers are essentially very large 'dishwashers' in which parts are loaded, the door is closed, and the switch is set to a preprogrammed cycle. The spray washers offer several advantages over conventional degreasing. First, spray washers remove both grease and soils whereas a degreaser will only remove the oils. Second, the detergent is biodegradable and produces no organic vapors. The spent solution can be discharged to a waste water treatment facility instead of being disposed of as hazardous waste. Third, the spray washers eliminate worker exposure to solvent vapors making the workplace safer and more enjoyable. Finally, the spray washer technology is sustainable, because the biodegradable detergents will not compromise the environment for future generations.

The spray washers have successfully replaced perchloroethylene and Freon degreasing. It has also replaced some PD-680 solvent cleaning and hand solvent cleaning operations. In addition to meeting all the cleaning requirements of the previous processes, the pressure spray washers have also decreased process times and increased worker safety.

Results: The pressure spray washers have eliminated the use of 25,000 pounds per year of CFC-113, 220,000 pounds of perchloroethylene, and 8,000 pounds of PD-680. They have also resulted in quicker processing times and increased worker safety. Continued use of the pressure spray washers will identify additional uses which will result in less hazardous material usage and exposure.

Background: The Solvent Recycling System is used to distill solvent for reuse. The system allows the paint shop to use the solvent several times before final disposal. The solvent, acetone, is used to clean the paint spray guns. In the past, the solvent was used until its cleaning ability was diminished. At that point, it was transferred to a barrel for disposal.

Description: One Solvent Recycling System is currently in operation. The system boils the solvent (acetone) under vacuum. The solvent vapor is then condensed resulting in a pure solvent that is suitable for reuse in the cleaning operation. The paint solids and sludge are then disposed of in barrels.

New solvent is added to maintain the solvent level. When the solvent is no longer adequately cleaned, the entire solvent bath is replaced.

Results: The Solvent recycling system allows the solvent to be reused for over one month. Before implementation, the solvent was replaced on a weekly basis. This system allows the Paint Shop to use less chemicals and dispose of less hazardous waste.

Background: Twin-wire thermal spray is used to deposit metal on jet engine parts and aircraft components. In the past, this operation was done by using nickel electroplating to deposit a layer of metal on the part. The new process decreases the processing time and provides a coating that has equivalent properties.

Description: Twin-wire flame spray has allowed OC-ALC to eliminate half of the nickel plating work load and its associated wastes. This process change was accomplished by challenging past practices. The flame spray coating and nickel plate are not the same, but the flame spray met all of the performance requirements for the application.

In addition to meeting performance requirements, the flame spray process produced less waste and required less time. A part can be coated with flame spray in less than one hour, while plating normally takes many hours. The only waste produced by the process is the water and metal sludge from the particulate filter. This is much less than the millions of gallons of nickel contaminated waste water that is generated from nickel plating.

Resluts: This process has resulted in reduced chemical usage, reduced waste generation, and quicker processing times. Twin-wire flame spray has reduced the purchase of nickel by 11,400 lb. The hazardous waste disposal associated with nickel plating has also been eliminated. Finally, the new process allows parts to be processed quicker reducing the cost and time of repairs.

Background: Zinc-Nickel Plating is an environmentally acceptable alternative to cadmium. Cadmium was used in the past to provide sacrificial corrosion protection to steel and high strength steel. Cadmium is the most toxic chemical used in the plating shop and was therefore targeted for substitution. Cadmium tank plating has been eliminated through the use of zinc-nickel alloy plating, Ion Vapor Deposition of Aluminum (IVDAl), and cadmium brush plating.

Description: Zinc-Nickel Alloy Plating is currently in use as a replacement for cadmium plating. It offers three times the corrosion protection of cadmium and is more erosion resistant. Zinc-nickel plating has been used extensively in the automotive industry for many years, and recently this technology has been accepted by the aerospace industry as a replacement for cadmium and nickel cadmium coatings.

OC-ALC has been using zinc-nickel plating since 1991 resulting in a 25% reduction in cadmium plating. This process compliments IVDAl, because it can be applied to all geometries including inside diameters.

Results: Technology transfer from the automotive industry identified zinc-nickel as an alternative process to cadmium. This process has resulted in a 25% reduction in cadmium plating and is a key process in the elimination of cadmium tank plating at OC-ALC. The elimination of cadmium tank plating also eliminated the cyanide associated with cadmium plating.

Background: The Water Jet is used primarily to remove rubberized coatings from engine casings. It is also capable of stripping abradable thermal spray coatings, fiberglass, paint, sealants, adhesives, and aluminum vane wraps. Modifications to the system would allow it to strip virtually all thermal spray coatings.

In the past, rubberized coatings were removed from engine cases in a two-step process. First, the case was soaked in methylene chloride for several days. The case was then removed from the solvent, and the rubber was scraped away using a putty knife. Currently, thermal spray coatings are removed in a chemical process.

Description: Two Water Jets are currently in operation. The first is a small unit with a maximum part diameter of 36 inches. It was installed in 1987 and is operated by securing the part onto a turntable and manually directing the nozzle at the area to be stripped. The lid is then closed and the cycle is started. The machine delivers 10 gallons of water per minute at a pressure of 10,000 PSI. This unit is used to strip rubberized coating from engine cases and to remove aluminum vane wraps from the TF30 Inlet Guide Vanes.

The second machine, installed in 1993, is larger and uses robotics for nozzle placement. This machine operates at 20,000 PSI with a flow rate of 20 gallons per minute. The increased pressure allows a wider range of materials to be stripped, including abradable thermal spray coatings. Modifications to the system to allow operation between 30,000 and 50,000 PSI would add the ability to strip most thermal spray coatings. In this machine, the operator again secures the part to a turntable; however, the nozzle placement is computer controlled. The nozzle movements for each part can be programmed and saved for future use.

In both systems, the stripped materials are filtered from the waste stream. The water is then discharged to the Industrial Wastewater Treatment Plant. The Water Jet technology is patented by Mike Patry and Herb Barringer, OC-ALC engineers. The equipment is manufactured by Automaker.

Results: The Water Jets have eliminated the use of 2,360 gallons per year of methylene chloride. They have also resulted in quicker processing times and increased worker safety. The modification to allow higher operating pressure would further reduce hazardous chemical usage.