Traditional Aqueous Parts-Cleaning Operations Work Great on Day One, but Rapidly Become Contaminated

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➤ B Y s tep h en D . te m ple , ran s o h o f f Cleaning you can count on Traditional aqueous parts-cleaning operations work great on day one, but rapidly become contaminated. Adding an ultrafiltration process to a parts cleaning system can dramatically extend and improve its performance. Traditional aqueous parts-cleaning operations can be inconsistent and costly. Machine shops and contract manufacturers dealing with a range of contaminants and heavy contaminant loads are finding they need something more. In many cases, adding an ultrafiltration (UF) system to an existing parts cleaning system can provide cleaner parts as well as dramatically lower maintenance and operating costs. This is not to say that traditional systems cannot be effective in certain situ- ations. For example, a shop can realize good bath life and part cleanliness when primarily cleaning with nonemulsified oils and when the system’s cleaning chemistry can effectively split the oil to the surface of the parts bath. This splitting allows removal via con- All images: Ransohoff ventional oil skimming or decanting Deerfield Manufacturing installed a 360 gal./day UF system that effectively turns methods. (A typical industrial parts over its wash tank every fourth day. washer includes a wash stage where most contaminants are removed, fol- rity and achieve optimal cleaning. The This is an inefficient and inconsistent lowed by rinsing and drying stages. result is that metalworking operations process, particularly for operations that Newer systems may include only a start out on day one with fresh water must meet stringent parts cleanliness single-stage wash with dry off.) and a new chemical charge to create specifications, such as in Six Sigma However, a more likely scenario for the cleaning solution. Assuming the manufacturing systems. Continuous most shops and manufacturers is that parts washer is functioning properly, dumping and recharging of the clean- they are dealing with water-soluble they will initially have clean parts, but ing fluid also adds considerable cost to oils, emulsifiable fats and oils and a cleaning performance quickly degrades the process. Replacing a full charge of high level of fine particulates. In these until parts are no longer being cleaned chemistry, reheating the solution and cases, conventional oil skimming and effectively. At that point, usually after associated labor costs add up quickly particle filtration methods are not suf- 1 week, a tank dump, refill and chemi- (see sidebar on page 52). ficient to maintain solution bath integ- cal recharge are required (Figure 1). Tank dumps are required when the

48 / APRIL 2007 CUTTING TOOL ENGINEERING cleaning you can count on cleaning solution is contaminated with excessive levels of emulsified or Standard Process—Dump is every 7 Days

soluble oils and fine particulate. No Level

amount of chemistry can overcome 10 an oily cleaning solution. Traditional parts cleaning systems often filter and 5 remove nonemulsified oils and particulates from 50 to 100 microns. Unfortu- 2

nately, this is not sufficient to maintain Grams/Liter Contamination consistent part cleanliness. Today’s manufacturing operations must meet three key objectives: part 7 14 21 28 quality, cost efficiency and process Number of Days consistency. The typical aqueous cleaning process does not deliver on Figure 1: Typical aqueous cleaning process without ultrafiltration. any of these objectives. tion. Once a UF membrane is fouled, ing. New membranes cost from $500 What’s the Solution? it must be taken out of service and to $1,500 each. Ideally, an initial cleaning solution cleaned. At worst, the UF membrane One of the primary challenges for charge remains stable, requiring only has to be replaced. parts washer filtration systems is the periodic chemical concentration checks However, many types and styles different types of contaminants that and additions. This goal is achievable of UF membranes have been proven end up in the system depending on the by implementing a properly designed effective at removing emulsified oils parts in production, workpiece materi- UF system. Most UF systems require a and fine particulate from parts washer als and coolants used. Contaminants fluid to pass through a polymer mem- solutions to a level of 0.05 microns and include a range of cutting, forming, brane under pressure or via vacuum are not prone to premature fouling and stamping or drawing fluids used during action, returning the cleaned fluid back failure. UF system suppliers should be manufacturing. In addition, particu- to the system. In many cases, UF de- able to guarantee at least 4 weeks be- lates can include chips and lapping grit vices can be retrofitted to an existing tween cleanings. Some suppliers have from machining processes. It is vital to parts-cleaning system. For small- to installed systems that operate for 6 select a UF membrane that can handle medium-sized applications, UF sys- months or more between cleanings. these different types of contaminants. tems have footprints from 4 to 8 sq. ft. Also, in a well-designed system, Some end users might be skeptical users should expect to replace the Three Key Considerations about UF systems. They may have membrane at least annually, though There are three key variables in a UF heard about or experienced UF system membranes in many applications have process: water quality, chemical recy- failures, primarily due to premature gone far longer before replacement. clability and chemical compatibility. fouling of the filtration membrane. Membrane cleaning or replacement is Water Quality: Untreated municipal Some operations have experienced relatively simple, and shops can typi- potable water, or tap water, cannot be fouling in less than one shift of opera- cally handle it on their own after train- used to feed and replenish the solution

Information Services #31 50 / APRIL 2007 CUTTING TOOL ENGINEERING Deerfield cuts parts cleaning costs by 85 percent

eerfield Manufacturing Inc., Mason, Ohio, produces device with a patented UltraFilic pancake-style membrane. Dstamped and drawn automotive sheet metal components. It is integrated in a small package for mounting directly on The company’s previous aqueous parts cleaning operation was top of a 55-gal. drum, which also serves as the concentra- costly to operate, required frequent operator intervention tion tank. and created quality problems. Deerfield Manufacturing required a 360 gal./day UF system Process Engineer Joe Carter wanted to improve the quality that would effectively turn over its wash tank every fourth and consistency of the company’s parts cleaning operation day. The filter’s spinning disc minimizes membrane fouling while reducing operating costs. Deerfield operated a dual- while producing positive filtration down to 0.05 microns. stage aqueous parts washer with two 1,200-gal. tanks. The The installed cost of Deerfield’s UF system was $14,000, but system processed a high volume of heavily contaminated it has extended bath life by a factor of eight or more, with parts, and both tanks had to be dumped and recharged the company dumping its tanks every other month instead of weekly. Every Sunday, a maintenance technician (being paid every week. (Deerfield’s bath life could be further extended overtime wages) dumped the tanks, cleaned out the system, with the purchase of a similarly sized UF system for its rinse refilled it and added a full charge of chemistry (approximately tank or a larger UF system turning the tank over every day). 40 gal. each) to the two tanks. Since Deerfield does not have Deerfield already had its own in-plant reverse osmosis water in-plant waste treatment, it paid a waste hauler 25 cents/gal. supply. Had Deerfield needed to add an in-line RO filtration to dispose of the wastewater. Weekly system operating costs system working off in-plant line pressure and producing 15 were nearly $2,000 (Table 1). gal./hour (rated for its UF system), total system cost would have increased by about $2,500 to $3,000. Table 1: Weekly Costs Without Ultrafiltration Deerfield’s annual parts cleaning operating costs decreased from more than $100,000 to $15,000 (Table 2). The UF sys- Spent solution haulage, 2,400 gal. @ 25 cents/gal. $600 tem paid for itself in less than 3 months and has eliminated Chemistry to recharge two tanks, 80 gal. @ $8.45/gal. $676 the operation’s part cleanliness quality problems. Premium-time labor expense, 8 hr. @ $55/hr. $440 Utility cost to reheat cleaning solution and water usage $225 Table 2: Annual Cost Savings with Ultrafiltration Total weekly expense $1,941 Spent solution haulage reduction, 105,000 gal. @ 25 cents/gal. $26,250 Reduced chemical usage, 3,500 gal. @ $8.45/gal. $29,575 The continuous dump and recharge routine cost Deerfield Premium-time labor expense reduction, 350 hr. @ $55/hr. $19,250 more than $100,000 annually while producing an unaccept- able level of part cleanliness quality and consistency much Utility cost and water usage savings $9,845 of the time. Deerfield looked at several alternatives and Total annual savings $84,920 ultimately purchased a Waste Wizard point-of-use UF system manufactured by GE Osmonics, Minnetonka, Minn., which Solution recycling with ultrafiltration, like that used at was retrofitted to Deerfield’s existing parts cleaning system. Deerfield, is a proven, reliable process. It can solve key qual- Deerfield purchased the UF system from Ransohoff, Cincin- ity and cost problems associated with parts cleaning at many nati, which also installed it. metalworking operations. The Waste Wizard incorporates a spinning disc antifouling —S. Temple

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52 / APRIL 2007 CUTTING TOOL ENGINEERING cleaning you can count on filter maintenance to parts cleaning cling—reduced chemical usage. effectiveness. Problems typically start One such recyclable chemistry is bath in a UF parts cleaning system. once the parts cleaning bath reaches a Ever-Cycle Ultra, produced by Ranso- Use of tap water will lead to excessive level of 1,400 ppm TDS. Water from hoff. This product will pass fully in- buildup of minerals and hard water a typical untreated municipal water tact through a 0.05-micron membrane. salts in the solution that not only dam- supply is in the range of 250 to 350 Other suppliers produce similar prod- age the UF membrane, but also nega- ppm TDS. ucts. The chemical components of tively affect cleaning chemistry, part As a result, UF parts cleaning opera- these specialty formulas are, in most quality and system maintenance. tions require high-quality water, such cases, well-guarded trade secrets. In traditional parts cleaning, bath as reverse osmosis water or deionized Also, an ideal UF system chemistry water is dumped each week, so using water. Many UF packages include fil- should produce a protective coating hard water is generally not a problem. tration systems that convert municipal on the membrane surface. This can However, in a recycling-based parts water into RO or DI water. prevent premature fouling and extend cleaning process, where the cleaning Chemical Recyclability: The second membrane life. The coating proper- solution is not dumped for 6 months or key variable in an effective UF system ties of these chemistries provide the more, hard water is a serious problem. operation is using a chemical solution membrane with an ultraslick surface, A typical parts washer bath has that is truly recyclable (able to pass which helps prevent contamination an evaporation rate of up to 10 per- intact through membranes with pores from adhering to and ultimately foul- cent and possibly more for each 8- at least 0.05 microns in size). If the ing the membrane surface. Ever-Cycle hour shift. Minerals and hard water chemical solution is not recyclable, Ultra is one of the chemical products salts don’t evaporate, so each gallon the UF membrane will filter out key that can produce this coating. of makeup water makes the problem constituents of the cleaning chem- Keep in mind that there are situ- worse. It doesn’t take long for the bath istry, requiring continuous additions ations in which a specific cleaning to be overcome with a high level of to maintain proper concentration and chemistry may be necessary to achieve total dissolved solids (TDS). This can chemistry integrity. This defeats one of process objectives and that chemistry compromise system operations, from the primary benefits of solution recy- may not be recyclable. If this is the

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CUTTING TOOL ENGINEERING APRIL 2007 / 53 cleaning you can count on case, an end user should probably seek Ultrafiltration—Turning Tank every Day other filtration alternatives because UF Ultrafiltration—Turning Tank every 2 Days will not work effectively. Chemical and Process Compatibil- Standard Process—Dump is every 7 Days ity: The third key consideration for UF Level 10 systems is chemical and process compatibility. Not all cleaning chemicals 5 are compatible with UF membranes, and different UF membranes require different chemistries. Also, most mem- 2 branes only operate effectively within Grams/Liter Contamination certain pH and temperature ranges. Most traditional parts cleaning sys- 7 14 21 28 tems use alkaline-based cleaners with Number of Days a pH range from neutral (7) to alkaline (11). For UF system cleaners, chemis- Figure 2: Comparison of contamination levels in a typical aqueous cleaning system tries in the neutral to near-neutral range and a cleaning system with UF. are the most effective. They typically cost about twice as much as conven- manufacturers can realize significant and temperatures up to 140° F. How- tional chemistries on a per gallon basis. chemistry cost reductions by using UF ever, there are metallic membranes However, in systems that recycle their systems. available that can withstand virtually cleaning fluids, chemical usage can be Keep in mind that cleaning chemi- any pH and temperature. They are just 10 percent of that required by tra- cals must be compatible with UF mem- considerably more expensive than traditional cleaning systems. As a result, branes. The typical membrane can ditional UF membranes, though. despite higher initial costs, shops and withstand pH ranges between 3 and 10

Information Services #42 Information Services #76 54 / APRIL 2007 CUTTING TOOL ENGINEERING Selecting the Right System (Turnover is the amount of time it lower operating and maintenance cost An effective, industrial-scale UF takes to run the entire contents of inherent in a UF system, make them system for use in a typical aqueous the wash tank through the filter.) a smart investment for many types of parts washer usually costs between n What is the recommended time metalworking operations. q $8,000 and $35,000. Prices vary de- between cleanings? pending on the size of the system, n How often will the membrane About the Author the type of membrane used, and if need to be replaced, and what is Stephen D. Temple is a cleaning indus- prefiltration or incoming water treat- the replacement cost? try professional with over 35 years of ment is required. Some areas of the n What is the expected level of so- experience in parts cleaning and solu- United States have municipal water lution clarity? tion recycling. He has served in vari- that does not require pretreatment. Figure 2 shows the impact a success- ous senior technical and executive Also, shops and manufacturers would ful UF installation can have on a parts level capacities during his 35-year be well served to select a UF system cleaning process. Tank dumps can be career with the Ransohoff Division of supplier that extends a “try it before virtually eliminated or, at a minimum, the Cleaning Technologies Group LLC, you buy it” arrangement or provides a greatly reduced. Chemical and utility Cincinnati. He can be reached directly written performance guarantee. costs are significantly lower (see side- at (513) 870-1719 or by e-mail: stem- While considering any UF system, bar on page 52), and most importantly, [email protected]. For more infor- potential buyers should ask the follow- a shop or manufacturer has a consistent mation about the company’s products, ing questions: process that continuously produces the visit www.ransohoff.com or enter #310 n Is the UF membrane compatible same high level of part cleanliness, on the Information Services card. with the soils and contamination eliminating contamination spikes. level of my specific application? Parts cleanliness—typically mea- For more information, n Is prefiltration required, and is it sured in total residual particulate visit “Archived Articles” included in the purchase price? weight, particle size or level of organ- at www.ctemag.com and n How often will the wash tank ics left on the parts—will most always enter the keywords need to be turned over? This will be improved with the addition of a “parts cleaning.” dictate the size of the system. UF system. This, combined with the 8

Information Services #4 CUTTING TOOL ENGINEERING APRIL 2007 / 55