Airless Cleaning Aerospace Case Study Process Efficiency With Airless Cleaning In addition, LeFiell is an employee-owned company with 85 percent of the company stock showing up for work in the morning. All 143 employees are aware of costs; and they expect to see value for capital outlay and for effort expended. Rather than viewing cleaning and environmental compliance as necessary evils, LeFiell took a systems approach, revising their build process to fit a work cell concept and using an airless cleaning system to sharply reduce build process time, achieve superior contamination control, maintain high product quality, and exceed environmental goals. Time for a Change The manufacturing process requires careful attention. Many of the tubes are long (12 to 40 feet); and some have a rectangular cross section. As precision components, these tubes must have no entrapment of contaminants and no flaws. Oil-based chlorinated waxes are required for the high-pressure draws of high strength materials including titanium, aluminum, stainless steel, and other high-temperature alloys. Cleaning is mandatory to assure structural integrity. The heavy, waxy oils must be completely removed prior to heat treatment. Heating at 1900oF to 2000oF is indeed a crucible both literally and figuratively. Even small amounts of residual solvent can result in obvious, visual discoloration after heat treatment. The experienced eyes of many of the engineers can readily detect subtle visual changes that could result in intragranular (IGA) problems. In addition to careful visual inspection, LeFiell has a sampling plan that involves microscopic evaluation of sample mounts at 400X and 1000X. Prior to adopting an airless system, LeFiell had been using perchloroethylene (PCE) in an early 1990s vintage open-top vapor degreaser. In addition to the equipment requiring increasing, repeated levels of repair, there were environmental drivers. LeFiell is located in Southern California, with very stringent state-wide environmental constraints. Additionally, it is in the South Coast Air Quality Management District (SCAQMD), the district with perhaps the most stringent regulatory requirements in the U.S. While the degreaser was state-of-the-art when purchased, it was time for a change. Aqueous cleaning would seem the obvious solution; and where performance is acceptable, LeFiell has adopted aqueous processes. Aqueous processes were evaluated extensively; none were effective in removing the waxy lubricant. Sometimes, the oil or lubricant can be changed to allow other cleaning agents. In many processes, a water-based lubricant can be adopted. However, none were found that met LeFiell's process requirements. In addition, corrosion of the tubes has to be avoided at all costs to assure strength and ability to bond. Systems Approach The company chairman chose the cleaning system based on his 38 years of experience in manufacturing. There were several important considerations in choosing a cleaning system. While it was clear that solvent cleaning was required, an open-top degreaser was not considered. In addition to the stringent environmental requirements, the company did not want the cleaning operation remote from the heat treating operation. Building a separate, self-contained room for an open-top degreaser, then adding the engineering and employee protection controls, seemed cumbersome. The airless system selected by LeFiell from Tiyoda Manufacturing (Torrance, CA) has a number of features important for an exacting, heavy-duty process. All stainless steel construction was considered crucial to equipment longevity in a harsh processing environment. Don Averill, Director of Facility and Safety, comments that the execution of the mechanical and control systems is excellent. The controls are UL approved; and all entities are well-labeled and identified for ease of maintenance and operation. Overall, the equipment appeared to be thoughtfully designed. Equipment design, a cooperative effort between the supplier and LeFiell, is an impressive example of successful coordination within a global village. Because no equipment supplier had the size and configuration required, it was necessary to custom-design the cleaning system. The system had to be able to handle 20 feet of tubing; it had to have an 18-inch chamber diameter; and it needed to contain 420 gallons of chlorinated solvent. George Ray, Chairman and CEO, comments that given the exacting and unusual process requirements, equipment design became a collaborative engineering effort between LeFiell in California and the equipment supplier in Japan, coordinated by the U.S. vendor representative. The build process was expedited because the equipment manufacturer actively listened to LeFiell's suggestions and incorporated the appropriate modifications. Implementation With the older open-top system, the main issue was the need for constant repairs. With the new airless system, as with most automated, sophisticated manufacturing systems, the key is preventive maintenance. This involves attention to the details of the maintenance process. For the last 2.5 years, LeFiell has had a program of autonomous maintenance. This involves an ongoing interaction between management, operators/fabricators, and the maintenance department. Good preventive maintenance does not happen without extensive employee training; LeFiell invests in training. Employees take one week from their production schedule for classroom training in the new equipment; and sufficient people are trained so that, even with some changeover in personnel, there is good in-house knowledge of the equipment. Tiyoda coordinated a detailed employee education program for LeFiell and did not limit the number of employees who could attend the training sessions.
Benefits Time: By allowing integration of cleaning and heat treatment into the process, adopting the airless system has saved significant amounts of time and has resulted in a much more effective process. The airless system with work cell manufacturing has contributed to an impressive 50 percent reduction in overall process time (sheet metal to shipped parts) from 20 weeks to 10 weeks in some cases. The older automated open-top degreaser required 45 minutes per cycle. The new airless system requires one hour, in part because of the extra purge cycles to minimize solvent loss. While systems with more rapid cycle times are available, the tube configuration, the environmental requirements, and the location of the cleaning system in the plant made an airless system the appropriate choice for LeFiell. When the open-top degreaser was in use, the cleaning system was located in another building at a considerable distance from the heat treatment furnace for reasons of space, environmental concerns, safety issues, and employee comfort. The airless system allows the cleaning and heat treatment steps to take place in close proximity, within 20 feet of each other. This saves approximately 60 percent in travel footage, and improves the production flow. Previously, employees sometimes had to wait for the rain to stop to transport parts. Performance/Contamination Control: With the open-top system, parts were cleaned in PCE and then stored, often for several days, prior to heat treatment. Now, tubes are cleaned in an airless system with trichloroethylene (TCE); and tubes move immediately from the cleaning basket to the oven. One important factor in contamination control is to avoid introducing soils. Cleaning the tubes immediately prior to the next process step minimizes the potential for contamination. In addition, the airless system with TCE results in more effective cleaning at a lower temperature than would be possible with PCE. PCE has a KB number of 90 with a boiling point of 121oC. TCE has a higher KB number (129) and a lower boiling point (87oC). The KB number provides a rough indication of solvency for hydrocarbon-based materials; higher numbers indicate greater solvency. While a higher boiling point can mean enhanced cleaning action, there is the increased potential of having some soils burn on, leaving a residue that is difficult to remove. TCE has proven more effective for LeFiell. Worker Comfort: Safety and regulatory requirements aside, a compact work cell containing an open top degreaser would have been impossible at LeFiell, simply from the standpoint of employee comfort. The airless system minimizes employee exposure to the cleaning agent. There may be less overall employee exposure with the airless system than there would be to open systems with more benign aqueous or semi-aqueous cleaning agents. Flexibility/Worker Cross-Training: The airless system has allowed flexible, lean manufacturing. Workers are cross-trained to do both cleaning and heat treatment. The evolution from specialized departments with a hierarchy of workers to more encompassing groups with more flexible, sophisticated workers is important in responding to changing production levels and changing product. Regulatory Drivers, Solvent Conservation: Regulatory compliance is facilitated with an airless system. While automating an open-top degreaser expedites parts handling and reduces solvent loss, the airless system has proven far superior in solvent containment. Adoption of the airless system has reduced solvent consumption to less than one-tenth of previous usage. It is far easier to stay within SCAQMD permit limits; and the company no longer has to deal with the Federal Toxic Chemical Release Inventory (SARA Title 313 Form R). Conclusion About the Authors
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LeFiell, a fabricator of precision tubular components, is a small, 70-year-old company that respects the past but continuously adopts more effective manufacturing techniques. In a tribute to the past, the sign and distinctive furnace gantry tower, visible from the nearby freeway, has been declared a city landmark. However, management is proactive and actively seeks out improvements. 
LeFiell took a systems approach to improve process flow, maximizing efficiency and product quality. Management coordinated the purchase of a new heat treatment system with a new cleaning system to set up the cleaning and heat treating as a work cell. 
