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Clearing the air (and water) on metalcleaning.

At IMTS '92, DuPont took a survey of attendees to gage their knowledge of the then-proposed labeling requirement for products or components made with, cleaned by, or containing ozone depleting substances (ODS). Not even half the respondents knew of the existence of the law and its likely impact on their operations.

Judging by the more recent rush to find substitutes for cleaning systems, metalworkers have learned something in the meantime. For example, they have learned that their favored universal solvent cleaning agent, 1,1,1-trichloroethane (methyl chloroform), would carry an increased tax of 21.1 cents per pound in 1993, escalating to 53.5 cents per pound in 1995.

More important, they also learned that after 1995 that tax won't matter, because production of 1,1,1-tri as well as CFC-113 will end, and the ODS solvents won't be available at any price.

Here are the EPA's final rules on the labeling requirement:

* The amended Clean Air Act requires labeling of products made with or containing Class I (CFCs and 1,1,1-tri, also called methyl chloroform) and Class II (HCFCs) ozone depleting substances.

Warning labels are scary. They must be square or rectangular, with or without a border. Maybe it's the WARNING in capital letters, followed by a statement that says the product is made with an environmentally damaging material appearing in a strong contrast against its background. Black on white or red on white present strong contrasts and are good. Yellow on white or dark blue on green will not do, advises the EPA.

* All products made before May 15, 1993, are exempt from the labeling requirements if the manufacturer is able to show within 24 hours, upon request, that its products were made before that date.

* If a manufacturer purchases a product from a supplier that labels its product "manufactured with," the manufacturer does not need to incorporate that information into a label on its final product. In other words, manufacturers need only label their products according to whether the soon-to-be banned ODS products are used in their own direct manufacturing processes.

Finally, the EPA has not backed away from the May 15th deadline, but it has announced that the regulation will be "selectively enforced" for a nine-month period, from Feb 11, 1993, the date the rule was published in the Federal Register.

Not on my products

The new labeling requirement has caught the attention of major consumer products manufacturers. Some have made it company policy that their products will not carry such labels and acted to remove the offending materials from their cleaning systems, says Carl Lawson, senior product manager, NAPCO Inc, Terryville, CT, a manufacturer of water-based cleaning systems.

There is some incentive in the rule for that decision. A company, including its divisions, branches, or facilities that achieves a total use reduction of methyl chloroform (MCF) and/or CFC-113 used as solvents in its manufacturing processes of 95% or more over its 1990 use is exempted from the labeling requirement for its products manufactured with MCF and/or CFC-113.

Larger companies, with the corporate staff to support such efforts and the capital resources to fund it, are making the changeover from vapor degreasing systems to aqueous or semi-aqueous systems more easily than their smaller brethren.

Smaller companies, like contract machining operations, often do not have the support staff needed to spearhead the analysis, engineering, procurement, and installation required in selecting the cleaning processes that they need. They must rely on trade associations, suppliers, and an organization like the Center for Emissions Control in Washington for translation of EPA rules and regs into an agenda for action.

With the impending ban, manufacturers face a problem they never had to deal with before, namely, choosing which detergent to clean parts, and how to best dry and protect them for the next customer, whether internal or external. CFCs were a miracle solvent that did a remarkably good job of removing water-miscible dirt or oil-soluble dirt, regardless of how heavy or light. The part came out free of residue and essentially dry, and all the manufacturer had to worry about was applying a corrosion protector.

Sizing up your processes

"Metalworkers have to look at the entire manufacturing process today, in their own plants and in those of their suppliers and customers," explains William Sluhan, president and CEO of Master Chemical Corp, Perrysburg, OH. "It used to be a relatively simple thing for the manufacturer at the beginning of the process to finish work on a casting or on barstock, apply a corrosion inhibitor, and send it along to his customer. The protectant would be removed so that it wouldn't contaminate any of the cutting fluids on his machines, and the process would be repeated. The process is more complicated today. Manufacturers will have to evaluate their decisions on cleaning processes and protectants based on how they affect their customers, or they could lose a customer," says Mr Sluhan, whose company has specialized in water-miscible cleaning systems for more than 40 years, pioneering the recycling of cutting and grinding fluids.

"It's an all-encompassing issue for manufacturers," says James McEachen, vice president and GM of Midbrook Products Inc, Jackson, MI. "It goes beyond just replacing some solvent cleaning equipment and moves backward into the manufacturing process. It involves looking at every step of the process and rethinking what kinds of coolants and lubricants are being used with that product and how it's being presented to the end user or customer."

Working with aqueous and semi-aqueous systems is very different from the past practice, says Mr McEachen. "It's not a form, fit, and function replacement. It just typically doesn't work that way. You have to worry about rinsing, about spotting, drying...things that were pretty straight-forward when you were working with a solvent cleaner."

Where do you start?

Parts and processes, says Mr McEachen. The solution to cleaning problems--all the way through recycling of fluids and disposal of any waste--depends on parts and processes. What causes contamination? What types of lubricants are used? How large and complex in geometry are parts? Is it a milling operation, forming, or grinding?

The two big questions that need answering are what is clean and what is dry. The answers to those questions have far-reaching implications. However, cleanliness standards are currently being defined by only about 5% to 10% of the market, and it's usually the larger companies who have done so, says Mr. McEachen.

An even more subjective area of concern is dryness. It's a function of the next process in the manufacturing cycle or that of your customer. It makes a difference, for example, if the part is going to be plated or painted and has to be absolutely dry or not. Making the proper distinction in the level of dryness required can lead to oversizing or undersizing a project if the proper targets are not established at the outset, Mr McEachen warns.

Paul F Wilson, product manager, Allied-Kelite Co, Melrose Park, IL, says that, in the long run, it will cost less to use aqueous systems. Level of cleanliness is especially important for cleaning parts such as electronic parts and components, production parts with micro holes, refrigeration coils, hydraulic cylinders, and gaging equipment. Residues can and do interfere with them. "The cleaning product selection process must consider parameters such as soil, surface, method of application, surface condition required, use of liquid or powder, chemical restrictions, and waste treatment," he says.

Choosing productivity

James Schleckser, division director of Ultrasonic Cleaning at Ney Ultrasonics, Bloomfield, CT, points to four levels of productive capability for aqueous, semi-aqueous, and water-miscible cleaning systems:

* The dishwasher or agitation-type system is basically a single tank with a platform agitator or sprayers for cleaning. Level of investment required is low--in the $10,000 to $20,000 range--as is productivity. Parts handled tend to be fairly simple in configuration, without a lot of deep undercuts or holes.

* Baths, for clean, rinse, and dry cycles, have higher productive capability with baskets in every station. Price ranges from $25,000 to $50,000.

* A series of baths with robot loading provides still higher productivity. Add price of the robot.

* In-line conveyorized systems are especially good for automotive, sub-component manufacturing, and high-volume PC board shops. It's a spray system, so parts have to be fairly simple in configuration. Price ranges from $150,000 to $250,000.

Highly complex parts with a lot of tapped holes and channels to clean will require full immersion systems with ultrasonic assists. Products like these fall into the category of precision cleaning. They are precision fabricated parts with tight tolerances, high surface finishes, and complex geometries, such as hydraulic products or precision instrumentation and scientific apparatus and medical components, where there is interior tapping and passage ways.

To aid in selecting the right chemistry, Ney Ultrasonics uses a chemistry decision tree, which narrows choices based on metals cleaned. Mr Schleckser points out that if a precision cleaning level of cleanliness is not needed, a solvent/solvent process can be a cost-effective way to handle intermediate or in-process cleaning. The solvent/solvent approach goes back 30 years,--prior to the adoption of the now-offending CFCs--when mineral spirits or some other organic chemicals were used as a rinsing agent.

Cleaning choices

Everyone agrees that selecting the right chemistry is of critical importance in metal cleaning. Aqueous cleaning formulations tend to be very contaminant-specific and do not handle multiple soils well, says DuPont. In addition, many metal parts are incompatible with either straight water or the highly acidic or alkaline cleaning solutions, making waste water treatment more difficult. Spot-free drying is a concern. Aqueous systems can run between $30,000 and $200,000 in equipment, with maintenance baths and water treatment adding to capital cost.

New semi-aqueous chemistries are hydrocarbon-based agents with polar and non-polar components for a balance of selective solvency. Soils are dissolved in the cleaner and washed away in the subsequent water rinse, where the organic soil--the hydrocarbon portion--separates from the aqueous effluent, limiting waste discharge. Because of their chemical properties, however, thorough rinsing in at least two separate steps must be undertaken for complete removal of the solution.

Capital investment in semi-aqueous systems ranges from $30,000 for a simple, batch-process dishwasher type solvent and rinse system, to $60,000 to $100,000 for an automated batch-process ultrasonic tank, to $250,000 for a complex, automatic conveyorized in-line spraying system. Water treatment will add another $20,000 to $50,000 in upfront costs, says DuPont.

Manufacturers who cannot use aqueous or semi-aqueous systems for one reason or another can still select from closed loop solvent cleaning and recycling systems. Hahn & Kolb, Chandler, AZ, has introduced the PERO solvent cleaning and recycling system. It is able to use solvents that are still acceptable and deliver a high degree of cleanliness for parts that are complex, including screw machine products, small stampings, and aerospace-type products.

Matching equipment

One major difference of the aqueous and semi-aqueous chemistries is the need for greater mechanical agitation to perform cleaning, according to Jeffrey R Hilgert, director of marketing for Branson Ultrasonics Corp, Danbury, CT. This can take the form of agitation, sprays, or ultrasonics.

Ultrasonics works because it is an erosive process that is localized at and packs a lot of energy into the point of cleaning. When ultrasonic energy is applied to liquid, cavitation--the formation and collapse of thousands of vacuum bubbles--results. The energy released forces the cleaning agent into even the tiniest crevices and holes, where sprays and mechanical agitation typically can not reach.

"Once the chemistry has been selected and the cleaning process (wash, rinse, dry) has been worked out, the hardware is relatively simple," according to Branson's Mr Hilgert.

That being the case, why haven't more metalworkers changed over? Metalcutters have made the change-over faster than stampers, most agree. One of the reasons is the nature of stamping compounds. They tend to be viscous, physical lubricants more than chemical lubricants. It's more difficult to find detergent-type cleaners that will do a good job of removing them from the part than it is for machined parts. Chip makers have pretty much changed to water-based and/or water-soluble synthetic coolants in their machining operations.

Equipment manufacturers see lengthening leadtimes for delivery of cleaning equipment and systems. As many as 100,000 pieces of cleaning equipment, typically with a lifespan of eight to 10 years, will have to be replaced in a compressed timeframe over the next three years. Though most equipment makers say that leadtimes are holding in the 10- to 14-week timeframe, some point out that as the 1995 deadline approaches, leadtimes could lengthen to 26, 36, or even 48 weeks.

Rinse water cleaning

What happens to rinse water after cleaning takes place is of critical concern in adapting to the new cleaning systems. What you are left with is one or more contaminated baths of soil and chemistry. And it's not virgin material, either, having been mixed with a number of possible soils. Waste will be contaminated with soap solutions, oils, and metal particles.

Many metalworkers look at this as trading one problem for another. Now they have to go to another system that creates problems of its own.

But there are devices out there to close the loop and handle that problem. Cleaning processes, including carbon absorption, ultrafiltration, and membrane filtration techniques, are used to restore the water to a usable condition and to isolate and skim off oils, particulates, and soils.

Change to one fluid simplifies cleaning

When the Schlage Lock Co, San Francisco, CA, decided to eliminate the use of chlorinated solvents and replace its vapor degreasing equipment with a more environmentally acceptable cleaning process, the company embarked on a journey that all metalworkers have faced or will face in the not-too-distant future. The Schlage facility located in San Francisco manufactures door hardware components from brass, bronze, cold-rolled steel, and stainless steel for assembly at other Schlage facilities.

Schlage is not unlike many other metalworking companies, both large and small, in that it does not have the internal resources or expertise to make the change. The company turned to environmental engineering and fluid management firms Capsule Environmental Engineering, St Paul, MN, and Cincinnati Milacron, Cincinnati, OH, to take that first step toward optimizing its metalworking fluid management and initiate a facility-wide metalworking fluid management program.

Their study began, as all such evaluations should, with a complete review of manufacturing operations. More than eight different machining and stamping metalworking fluids used in manufacturing brass, bronze, cold-rolled steel, and stainless steel parts were identified. Production equipment included more than 30 pieces of machining, including screw machines, rotary transfer machines, broaches, milling machines, and grinders, and used straight oils and one water-based fluid.

In the stamping area, 28 high-speed presses, ranging from 45 to 200 tons, processed brass, bronze, cold-rolled steel, and stainless coil stock. Brass and bronze press operations used both straight oils and water-based fluid, while cold-rolled and stainless steel used straight oils only.

Rather than designing an aqueous cleaning process to remove all these fluids, it was decided to consolidate the fluids into a single water-based fluid, if possible, to simplify the cleaning process. The thinking was that a water-based fluid is much easier to remove from a part than straight oil. Consolidation to a single, water-based fluid would hasten the implementation of the fluid recycling and management program.

Criteria for selecting the water-based metalworking fluid to replace five or six straight oils included:

Lubricity--sufficient to work in the most severe application, the stamping operations.

Cleaning--easily removed from parts by aqueous cleaning.

Corrosion protection--sufficient in-process protection for brass, bronze, cold-rolled steel, and stainless steel.

Recyclability--resistant to bacterial contamination and stable enough to be recycled in recycling equipment added to remove tramp oils and particulates.

Compatibility--with Schlage's ultrafiltration wastewater treatment system.

Chemical restrictions--chlorine or chlorinated components were not to be used if at all possible.

Foam resistance--because the fluid would be used in individual machine sumps with various levels of aeration and types of filtration, foam was a potential problem. A non-silicone antifoam that would not interfere with recycling or wastewater treatment was recommended.

Based on these considerations, a soluble oil stamping fluid was chosen to be adapted to its various manufacturing processes. A soluble oil, it was reasoned, would provide a high percentage of oil as well as the benefits of a water-based fluid, such as better cooling properties, recyclability, and ease of parts cleaning in an aqueous cleaning system. Typically, the fact that soluble oil contains mineral oil is considered advantageous for the metalforming and heavier machining operations.

Project expenses related to new equipment, modification of existing equipment, or other costs were justified by savings found in reduced use of indirect materials such as oil and in reductions in hazardous waste management and disposal, since waste oil is regulated as a hazardous waste in California.

The total amount of oil used for metalworking was reduced through substitution to varying degrees ranging from 50% to 100%. Full substitution was not possible due to some equipment and process limitations having to do with the screw machines. Overall use of process coolant/lubricants was reduced because soluble oils are used in mix ratios on the order of 1:5 to 1:20, offering an immediate reduction over 100% oil, and because more efficient application equipment and recycling efforts reduced consumption greatly.

Estimated indirect material cost savings are $88,700. Savings from reduction in annual cost of hazardous waste handling added another $78,900, for a total cost savings after consolidation of $167,600 per year.

Questions about your parts and processes

Heinz-Dieter Erbel of PERO KG, Konigsbrunn, suggests that answers to these questions lead to sound decisions about selecting cleaning processes:

Which contaminants have to be removed?

What materials are involved?

How large is the throughput?

Is the cleaning medium acting in a neutral way vis-a-vis the metal?

What is the surface geometry of the workpiece? Sheet metal or housings? With pockets, undercuts, or other hard-to-reach areas?

Is it an intermediate or a final cleaning step?

If it is intermediate cleaning, what is the next step in the manufacturing process, and what surface quality or condition is required for that process?

If it is a final cleaning step, must the surface be absolutely free of residues?

If a preservative coating is used, how long must the protection against corrosion last?

Evaluating alternatives for metal part cleaning

With the phaseout of 1,1,1-trichloroethane (also known as 1,1,1-tri or methyl chloroform) accelerated to Dec 31, 1995, manufacturers are more concerned than ever about finding alternative surface cleaning systems that are environmentally acceptable, safe to use, and effective.

Adding to this concern, provisions of the 1990 Clean Air Act and other federal and state regulations are making vapor degreasing with 1,1,1-tri and the disposal of spent cleaners increasingly costly. For instance, a labeling law for products manufactured with Class I ozone depleting substances (ODS) goes into effect May 15. A new law under The Energy Policy Act of 1992 increased the tax rate applied to ODS sold or used on or after Jan 1, 1993.

Although no single cleaner or process can serve as a drop-in replacement for 1,1,1-tri, alternative cleaning systems have come on the market. In fact, the number of chemistry and equipment options is abundant, requiring manufacturers to dedicate significant resources to analyze technology, economics, and environmental considerations, and possibly modify their operations to implement an alternative solution.

With so many variables at work, wrong choices can lead to wasted time, money, and effort, as well as work flow interruptions and further environmental concerns. Clearly, the decision to convert to an alternative cleaning system must integrate the proper chemistry, equipment, and cleaning method.

The choices

Aqueous, semi-aqueous, and cold cleaning systems--in combination with the proper chemistries, equipment design, operating methods, TABULAR DATA OMITTED and cleaning mechanism--offer an effective, long-term solution to the 1,1,1-tri phaseout, while helping industry improve its overall environmental performance. While conversion to these systems requires a significant capital investment, the expenses are partially off-set by lower material and waste disposal costs.

The following provides an overview of these alternative cleaning systems:

Aqueous cleaning systems typically have three steps, but can have as many as five, particularly if the part is to receive a coating. First, a surfactant disperses the soil. The part then goes through one or more rinses and is oven dried.

The choice of cleaner and the number of steps necessary depend on the part, the soil to be removed, and the degree of cleanliness required. Different cleaners are required for different substrates, soils, and applications, making it more difficult to establish a universal aqueous system.

Because aqueous cleaners consist mainly of water, flammability concerns are minimized, and toxicity is low. Waste from aqueous cleaning can be treated by separating oils from the cleaner, returning the reclaimed cleaner for reuse, and recycling or incinerating the oils. Wastewater is generated throughout the process, therefore aqueous systems may be particularly well-suited for operations with established water treatment facilities.

Semi-aqueous cleaning can be accomplished with two different systems: an emulsion system and a modified cold cleaning system.

The semi-aqueous emulsion system is a four-step continuous process. First, the cleaning agent loosens oil and grease on the part. Then, the part is immersed in an emulsion of cleaner and water. A small amount of the emulsion is continually sent to a static tank, or coalescer, where the water is separated and returned to the emulsion tank. Oil and cleaner are either recycled or disposed of in an environmentally acceptable manner. In the third and fourth steps, the part receives one or more water rinses and is then oven dried. The spent cleaner is incinerated, and the rinse water is treated and recycled.

Modified cold cleaning is a three-step process. In the first step, the part is sprayed with or dipped in cleaner. In the second step, the part is removed from the cleaning solution tank as air is blown on it. Any remaining solution or soil is removed by one or two water rinses. The third step consists of forced air drying, which can be accelerated with the addition of an oven.

Semi-aqueous systems clean many types of soils from many types and sizes of parts. Compared to aqueous systems, certain semi-aqueous solutions may present somewhat greater concerns for toxicity, flammability, and volatile organic compound (VOC) status.

Cold cleaning systems involve a two-step process best suited for pretreatment to remove large amounts of dirt. This method is not advisable for precision cleaning. In the first step, parts are sprayed, dipped, wiped, or scrubbed with cleaning solution at ambient temperature. When spraying, caution must be taken to avoid igniting atomized droplets of cleaner. Drying occurs in the second step through a forced air system of evaporation. Drying time will depend on the cleaner's evaporation rate, the amount of cleaner on the part, and the use of air knives.

Although the cold cleaning process can utilize a wide variety of cleaners, nonflammable compounds are preferred. Frequent replacement of the cleaner must occur when it reaches its oil-dissolving limit; otherwise, dirt may be redeposited on the part.

While aqueous, semi-aqueous, and cold cleaning systems serve as viable alternatives, certain metal cleaning processes still require vapor degreasing. For such applications, ultra-tight degreasing systems permit continued use of 1,1,1-tri--as long it is available-- and other chlorinated solvents (such as trichloroethylene and perchloroethylene) that are not scheduled for phaseout. Unlike existing degreasers, the fully enclosed equipment brings the solvent to the parts, rather than the parts to the solvent. There is virtually no vapor loss because the solvent is not released into the air. Emissions are reduced by 99% compared with open-top degreasers of equivalent size.

Picking options

The variety of alternative cleaning methods, equipment, and chemistries presents a host of options. Manufacturers must evaluate chemistry, including alkaline and neutral aqueous cleaners, semi-aqueous cleaners, and solvent products; equipment design, including spray, immersion, or ultrasonics; operating times and temperatures; and cleaning mechanisms. Other issues that come into play include cleaning effectiveness, equipment costs, operating costs, production through-put, environmental impact, recycling, and downtime.

There are three steps in evaluating a manufacturer's needs:

* Analyze through-put requirements, available floor space, material handling capabilities, pre- and post-cleaning procedures, and the effectiveness of cleaning processes. Based on analysis of soiled parts cleaning effectiveness, a cleanliness and cleaning process recommendation is made.

* System design involves specific recommendations about machines and components that will fulfill cleaning process and cleanliness parameters. Drawing from a list of pre-screened, qualified equipment companies, a competitive price quotation package and recommendation are made.

* System implementation involves equipment procurement, installation, start-up, and optimization of the new system. A quality control plan is developed, and on-site worker training is provided.

In dealing with suppliers, make sure every system that is developed and designed is guaranteed to meet the specification identified during the system development step. Also determine if ongoing technical support, analytical services, regulatory compliance assistance, and information on new chemistry and equipment upgrades are available.
COPYRIGHT 1993 Nelson Publishing
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Title Annotation:includes related articles
Author:Lorincz, James a.
Publication:Tooling & Production
Date:May 1, 1993
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