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Aqueous component cleaning and degreasing systems can be operated manually or can be installed as part of an automated work cell.
Goodrich has installed two MecWash AVD systems (one shown here) and 12 Midi systems for environmentally sound cleaning of its aerospace components.
Parts are loaded into baskets before feeding them into the aqueous component cleaning and degreasing systems. Clean parts meet the exacting standards of Goodrich's customers.
Aqua-Save units can be installed with the aqueous cleaning systems to continuously purify all of the wash and rinse, allowing the water to be reused indefinitely.
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Advances in technology have pushed precision machining to extraordinary ends. The aerospace, defense and medical industries all increasingly rely on machined parts produced to demanding levels of quality and consistency that were never possible before. As a result, all three of these industries are also scrutinizing their cleaning systems more than ever before. Surface preparation has always been an integral part of the manufacturing process, but in the highest-value manufacturing applications, the importance of cleaning has dramatically increased.
Yet cleaning technology faces challenges apart from the machining technology, because even though modern cleaning technology is capable of similarly impressive results, meeting the cleanliness standards alone is not the only pressing consideration. Health, safety, and environmental policies also present challenges. Particularly in aerospace, defense and medical industries, the demand on the cleaning system is not just about results but also compliance.
Global aerospace company Goodrich (Charlotte, NC) faced this. To comply with its own progressive health, safety, and environmental policies, Goodrich had long sought to eliminate the use of solvents in its cleaning process. As a move in this direction, the company wanted to test the performance of several different water-based cleaning systems in one of its facilities. In 2007, as part of this research and discovery, Goodrich took delivery of a MecWash AVD (aqueous vapor degreaser) on a trial basis. The machine is available in North America through Godfrey & Wing (Aurora, Ohio).
This cleaning system was developed specifically for the medical, aerospace and defense industries, designed to remove most contaminants including resins, greases, zinc stearate, lapping pastes and polishing compounds. Instead of solvents, the aqueous system does this by harnessing the high thermal energy of boiling water, allowing it to effectively clean and degrease parts that solvent systems may struggle with.
Operating at more than 212°F in a sealed system, the AVD breaks down and removes heavy contamination in minutes. Subsequent vacuum drying reduces the entire required cycle time to less than five minutes. The high operating temperature also allows the aqueous cleaning solution to penetrate smaller cavities, pores and other openings that otherwise might be unachievable in lower-temperature aqueous cleaning machines.
Immediately after installation, Goodrich subjected the cleaning system to aerospace industry ASTM tests using standard "five-starburst" TAM panels. When cleaned with trichloroethylene, these TAM panels would expose three, sometimes four, starbursts. However, the aqueous-based unit consistently exposed five starbursts, meaning the system consistently achieved more effective cleaning results than was previously realized with solvents.
According to Goodrich Senior Materials Engineer Tony Roots, "The new system performed this important quality task to a higher level than [TCE], and did so using a much more environmentally acceptable aqueous solution." Goodrich proceeded to test the system's effectiveness in more general component cleaning of pumps, valve bodies, and other parts. Again, the aqueous-based system performed equally well or better than the company's solvent-based degreasers.
Since the testing process, Goodrich has installed 14 MecWash machines at four different sites around the country. Two of them are the AVD, but most are larger aqueous component cleaning and degreasing systems permitting increased customization. With their high-volume ultrasonic flood and spray wash cycles, these larger systems allow up to 260 gallons of water per minute to flow through their wash chambers. This high flow rate contributes to the systems' effectiveness in penetrating extremely dense part loads. Both kinds of systems can rotate in clockwise and counterclockwise directions. In addition, their rotational speed and oscillation can be programmed specifically to the task required of them.
Environmentally Responsible
The MecWash cleaning systems are designed to be "environmentally friendly," but that is a relative term. In the case of the AVD and related systems, here's what that means
The first step toward environmental responsibility in cleaning, of course, is to eliminate harsh solvents. Aqueous or water-based cleaning systems have been around for years. The problem, however, has been that they could not achieve the same results as solvent-based systems. But that concern has been addressed with this type of system. Combining rotational cleaning methods with options for sophisticated ultrasonics, flood wash and rinse, dedicated jetting, vapor degreasing, and vacuum-dry technologies, modern cleaning systems allow high-level component cleaning with aqueous-based detergents.
The second step is to drastically reduce the amount of water used in cleaning through recycling of the wash water. Accomplishing this means installing cleaning machines as closed systems, with 100% of the water required for washing the parts remaining within the system. The same water can be reused again and again.
But there is a drawback here. Even in closed systems, there comes a time when the contamination of the wash and rinse waters reaches a level where it must be changed. The operator must shut down the washer, remove all of this contaminated water to be hauled away, and then refill the closed system with new water from the tap. All of this must occur before restarting the machine and cleaning any additional parts. Of course, this change-over process is time-consuming. More important may be the hard costs, because over time, this process creates thousands of gallons of discharge that must be dealt with at direct expense to both the operator and the environment.
That leads to the third step—zero discharge of the wash or rinse water. By attaching a water purifier to any of the high-performance cleaning systems, all of the wash and rinse can be continuously purified. Hence, these wash and rinse waters can be reused indefinitely.
With a water purifier (the MecWash unit is called "Aqua-Save"), the only waste these cleaning systems create is the grease, oil, and solids removed from the given parts during the cleaning process. This waste is captured and filtered out into a separate container and represents less than 5%, by volume, of the total amount of the cleaning solution used. Thus, for every 100 gallons of aqueous cleaning solution used in the cleaning system, the amount of waste created should fit easily into a five-gallon bucket. PC
MecWash Cleaning Process |
Designed to serve the aerospace, defense and medical industries, each model in the lineup of MecWash systems is customizable to meet the specific demands required of it by a given application. However, considering the stringent cleaning requirements of the industries they serve, their technical configurations, one model to the next, are often similar. The major point of difference between the AVD and other systems in the line is the AVD’s use of superheated water. Otherwise, the systems employ a similar cleaning process, which is detailed here.
The first step in the cleaning process is to submerge the batch of components to be cleaned in a total immersion bath of hot water mixed with cleaning chemistry (A). With the AVD, this water is superheated to a temperature above the boiling point of 212º. While submerged, the batch can be programmed to rotate in either a clockwise or counterclockwise direction, or both.
The second step is the engagement of ultrasonic transducers into this rotating total immersion bath (B). The ultrasonic implosion of millions of air bubbles creates cavitation of massive proportion per liquid ounce of wash solution. The length of time the operator desires to employ these ultrasonic transducers can be selected on a per-batch basis.
After the purge of this wash water, the next step in the process is the total immersion of the component batch in a chamber full of rinse water, free of any detergent (C and D). After the purge of this rinse water, each system can be programmed in a fifth step to include a subsequent total spray rinse using more than one hundred spray nozzles at a preset PSI strength (E). For larger components with very complex construction, here is when a sixth step could be added—dedicated jetting to guarantee the absolute cleanliness of every deep blind passage and the deepest of drilled holes (F).
In the final step, after the purge of all rinse waters, the batch is blown with hot air (G) and then vacuumed with powerful suction devices to ensure the absolute dryness of every individual component or surface (H).
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William L. Westbrook is North American product manager for Godfrey & Wing Inc., a global manufacturer of engineered equipment, products and services for vacuum impregnation and surface preparation. To learn more about the MecWash line of parts cleaning equipment and water purifiers, call (330) 562-1440 or visit godfreywing.com.
