by: Cheryl Salerno
Pages: 12-17; October, 2000

Currently, Raytheon's missile systems business unit produces missiles and weapons systems for the US Navy, Air Force, Army, Marines, and allied nations. The product lines include Air-to-Air, Strike, Surface Navy Air Defense, Land Combat, and Projectile missiles, as well as submunitions and advanced programs. Parts consist of metal and nonmetal components (copper, aluminum, titanium, steel, composite, printed wiring board assemblies), which are cleaned prior to such subsequent operations as powder painting, bonding and conformal coating. The facility also cleans printed wiring board assemblies following soldering.

“Missiles are manufactured at relatively low production rates,” states Paul Fecsik, Senior Process Engineer, Raytheon Missile’s Environmental Health and Safety department. “Components often have very unique cleaning requirements, beyond the simple removal of oil and dirt. As a result, we must often create or adapt an existing cleaning process for our needs. With such low rates, we also must pay close attention to the cost of cleaning per part.”

At AFP 44, cleaning is definitely not a one-size-fits-all process. Because a variety of parts come through the facility, a variety of cleaning equipment and chemistries have been integrated throughout the plant, including: aqueous cleaning systems, ultrasonic cleaning units, isopropyl alcohol (IPA) vapor degreasing, IPA hand wiping, high purity water cleaning (for flux removal), paint gun cleaning, and other proprietary cleaning processes relating to optics and cleanroom activities. AFP 44 also employs grit blasting techniques to remove heat treated scale and plastic bead blasting to remove paint and specialty coatings.

Maverick missile airframe refurbishing is one of the main processes carried out at AFP 44. The process entails paint stripping, cleaning, and powder coating of the frames prior to rebuild. For this type of cleaning, technicians use an automated aqueous cleaning especially built for the airframe with a popular aqueous chemistry in a 125-gallon tank. General parts cleaning is accomplished with a very large automated aqueous cleaning system which carries parts through 550-gallon tanks in standard baskets using the same chemistry. The operator can select one of two wash chemistries based on substrate as well as a variety of wash sequences. A capability also exists for a final rust inhibitor dip when required.

Targeting Pollution Prevention Opportunities
AFP 44 is unique in its designation as a site for USAF-funded pollution prevention initiatives, called P2 projects.

“They have a wide variety of P2 projects completed, others in the works, and new ones coming on-line,” says Richard B. Lantis, Project Engineer, ASC/ENVC, Wright-Patterson Air Force Base, OH. “AFP 44 was chosen because of the good working relationship we at Aeronautical Systems Center (ASC) and Headquarters Air Force Material Command (HQ AFMC) have with the Raytheon employees. Raytheon has always been eager to support the pollution program initiatives and is very creative in the solutions they provide.”

This aggressive P2 program at AFP 44 includes four areas of concentrated effort:

• The Hazardous Material Elimination segment looks at ways to use new technologies to eliminate the use of chemicals and other materials that may be considered environmentally unfriendly.
• The Chemical Recycling program is aimed at improving methods by which chemicals can by recycled and reused right in the production areas.
• The Hazardous Waste Reduction program is designed to find new ways to reduce the use of chemicals and to thereby eliminate the need to treat these substances.
• The Water Recycling program investigates new technologies that allow the water used in manufacturing to be recycled.

The process of developing environmentally friendly substitutions for standard manufacturing processes is not a simple endeavor. According to Fecsik, that process begins with a diligent investigation of promising new alternative technologies.

“We then need to determine what type of certification testing will be required to obtain missile program office approval to change over to it,” he explains. “This can often be cost prohibitive, involving a full re-qualification of a missile system or major component, which most likely means the existing cleaning process is spelled out on a drawing. However, we can and do make process changes during already planned missile testing for upgrades, etc. Since we have gotten rid of ozone depleting compounds, we also need to prove that the new process, while greener, will also be better, cheaper, and faster.”

But above all other considerations, a substitute process must first guarantee one thing: it can get the job done.

“There are a number of challenges in researching and implementing new environmentally-friendly cleaning and recycling technologies, including technician training, shortening payback periods, etc.,” Lantis remarks. “However, the most critical one is that any new process must not jeopardize Raytheon's primary mission—that is, producing high quality, reliable missiles for the Army and Navy as well as the Air Force.”

According to Fecsik, the final destination of components cleaned at the AFP 44 facility makes efficiency testing a critical part of evaluating any substitute technology. This evaluation is extensive as well as specific.

“As a retired Air Force Reserve pilot, I can relate to the fact that a missile only gets one chance to work,” he remarks. “You can’t take it back for warranty service if it doesn’t work like a car or computer. Fortunately, there are extensive testing procedures that a missile goes through at various build levels to screen out faulty components that may get traced back to a cleaning problem. Actually, this is very, very rare.”

Recycling Initiatives Offer Improved Methods
Recycling represents a significant portion of the P2 projects carried out at AFP 44. As Fecsik notes, Raytheon puts a great deal of emphasis on reusing the chemistries and water that go into cleaning.

“For recyclers, the work is much easier as we are not changing the actual cleaning process,” he explains. “But we do have to prove that the recycling system is not changing the chemistry or having any adverse effects. We also have to compare the cost of replacing the chemistry (makeup through waste treatment) with that of purchasing and operating a recycler.”

According to Fecsik, investigations into new recycling technologies have offered benefits that extend well beyond environmental considerations.

“The recycler, if it works, always seems to be the best way to go,” he states.

One recent recycling project carried out at AFP 44 involved the implementation of recycling systems for aqueous alkaline cleaning solutions and associated rinse waters. When trichloroethane vapor degreasers were removed from the metal finishing and paint areas of the AFP 44 plant back in 1994, technicians found that wastewaters from the new aqueous cleaning chemistries were putting a heavy organic loading on the downstream wastewater treatment processes. Traditional filtration and oil decanting equipment that came along with the automated aqueous cleaning system in the metal finishing line was not adequately removing manufacturing oils from the solution. This resulted in a rapid and undesirable buildup of oil and cleaning chemistry in the 550-gallon rinse tank and the need for frequent dumps.

Seeing the wash unit as yet another pollution prevention opportunity, Raytheon looked into improved options for recycling both the cleaning solution and the associated rinsewaters for wash units in the metal finishing as well as the painting areas of the operation. Based on the cost of chemical and that of wastewater treatment, Raytheon showed a clear payback on implementing more efficient recycling systems and received funding from the USAF’s pollution prevention budget for the project.

Raytheon met with its chemical supplier as well as its aqueous cleaning equipment suppliers to investigate various methods by which oils could be removed from the wash and rinse tanks. Other recycling equipment suppliers were also identified and consulted. A recycling system was ultimately selected from one of the original equipment supplier lines.

Raytheon enlisted the help of the National Defense Center for Environmental Excellence (NDCEE) for full-scale testing of the first built recycler in its demonstration factory in Johnstown, PA. A test plan was jointly written between the Air Force, Raytheon, the NDCEE, the recycling system supplier, and the chemical system supplier to provide a fair evaluation of the recycling system’s performance.

New System Includes Storage Component
The recycling system contained three subsystems: an aqueous cleaner recycler portion; a rinsewater recycler portion; and a water makeup plus storage unit.

The Aqueous Cleaner Recycler
In the aqueous cleaner recycler portion of the system (Figure 1), the wash solution first passes through a 5-micron cartridge filter and then into a wash concentrates tank on the recycler. A decant unit continually removes a small portion of the oils.

The solution is then pumped through a 0.1-micron ultrafiltration membrane constructed of sintered stainless steel with a titanium oxide coating. The three types of contaminants removed at this stage are hydraulic test oil, machine oil (with cutting fluid), and rust preventative oil. The permeate is sent back to the cleaning tank.

The cleaning specification for this line required that the permeate have no more than 10 parts per million (ppm) of combined contaminating oil at a 1-gallon-per-minute (gpm) minimum flow rate. Concentration levels of the original cleaning solution had to remain at 90 percent.

The reject is returned to the concentrate tank, which must be closely monitored and dumped to prevent fouling of the membrane. A “clean in place” system allows for cleaning of the membrane at temperatures up to 160º F (which can tolerate 0-14 pH solutions). This system was gauged so that the “clean in place” process returned the fouled membrane back to a permeate flow at least 90 percent as strong as the original flow rate (per specification).

The Rinsewater Recycler
The rinsewater recycling portion of the system (Figure 2) sends the rinsewaters directly to the rinse concentrate tank, where a decant unit continually removes a portion of residual oil. The water then passes through a 5-micron cartridge filter and next through a 0.005-micron ultrafiltration (UF) membrane. The permeate is then sent to a 0.0006-micron traditional reverse osmosis (RO) membrane, which delivers permeate containing 0 ppm of contaminating oils and less than 20 ppm of total dissolved solids (at >1 gpm flow rate). The UF reject (mostly cleaning chemistry and a very little oil) is returned to the wash tank while the RO reject is returned to the rinse concentrate tank.

The Makeup Water Portion
Polished city water had traditionally been supplied to AFP 44 via a water and wastewater treatment plant. With the recent shutdown of this facility, Raytheon required its newly purchased recycling systems to include water makeup units. City water (with ~400 ppm of total dissolved solids) is now sent through a 5-micron cartridge filter and then a carbon cartridge filter (Figure 3). A 0.0006-micron RO membrane polishes the water and delivers permeate to an 80-gallon hold tank for use in both the wash and recycling units. RO reject is sent directly to the sewer.

Looking in New Directions
P2 projects like the one described are important to AFP 44 because they accomplish several objectives. First, they allow Raytheon to remain in compliance with various local, state, and federal environmental regulations. But such projects offer far greater benefits to Raytheon and the USAF.

“They reduce the cost of maintaining compliance and allow dollars to be available for further facility mission improvements and technology acquisition,” states Tom Chanda, Chief, Pollution Prevention, who represents HQ AFMC/CEVV, an Air Force branch that provides funding for P2 projects. “Finally, they are a good public relations tool—that is, these activities demonstrate to the local community that the plant is an asset and not a liability.”

According to Fecsik, the success realized at AFP 44 in terms of pollution prevention initiatives has provided momentum for investigations into other alternative techniques.

“We are currently looking for a good non-VOC replacement to IPA vapor degreasing,” he stated. “We’re also investigating the use of a non-MEK paint gun cleaning chemistry as a follow-up to our existing aqueous cleaner chemistries, which may offer improved cleaning. In addition to this, we’ll be implementing a CO2 snow unit for optics cleaning and lasers for paint and other coatings stripping within the next year.”

To reduce water consumption, the company has begun using Russian-developed electroflotation equipment in its paint spray booth. This cellular application uses charged particles to float organics so that they can be skimmed and removed. The process allows the company to continuously recycle 125 gallons of water, with no discharge to the sewer and only evaporative losses. Raytheon also uses a number of parts made from proprietary composites that do not require cleaning at all.

For manufacturers who, like Raytheon, remain on the lookout for new, environmentally friendly substitutions for current cleaning technologies, Fecsik offers this advice:

“Be sure you clearly understand the cleanliness requirements and end function of the hardware you clean before changing the chemistry, changing the cleaning system, or attaching a recycler. Do your homework in terms of overall cost savings. Production areas want to be compliant and greener, but you have to look at the bottom line to stay afloat. Lastly, do not replace a VOC with some other hazardous air pollutant [HAP] or vice versa.”

Sound advice from professionals who make missiles that not only keep the nation safe, but the earth as well.

Paul Fecsik assisted in writing and reviewing this article.