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The Aqueous Alternative: Cleaning Is The Cornerstone Of Every Rebuilding Operation
By Larry Carley
Cleaning is the cornerstone of every rebuilding operation, be it a small one or two man shop or a large scale production facility. Dirt, oil, grease, carbon and other contaminants must all be removed from components that are being processed so they can be inspected, machined and restored to like-new condition. Additional cleaning may also be necessary following machining and other repair operations to remove oils, residual debris and scale from the surface, and to prepare the surface for painting if required.
The cosmetic appearance of finished components has become so crucial in today’s competitive retail-oriented market that the cleaning process used can sometimes make the difference between a product that sells and one that doesn’t. This is especially important with unpainted aluminum components. Buyers want a bright, factory-like finish, not a dull or discolored appearance in their components. So how clean is "clean enough?" It’s clean enough when it satisfies the needs of your customers.
Cleaning is also an expensive process for most rebuilders. Cleaning can account for up to one-third of all overhead expenses when the cost of the cleaning equipment, chemicals, labor, maintenance and disposal costs are all included. Depending on the method used and the type of parts being cleaned, it can be a very labor and energy intensive endeavor. So there’s just as much incentive to reduce the costs associated with cleaning as there is to get better results for most rebuilders.
Additional factors that rebuilders must now take into account are the environmental and safety issues associated with their cleaning processes. In recent years, the focus has been on finding cleaning alternatives that are not only effective and cost-efficient but are also environmentally and worker friendly. Smelly solvents, concerns over toxicity and long-term exposure to certain chemicals, legal restrictions on waste disposal, cradle to grave responsibility for hazardous wastes, and increasingly stringent regulations on what cannot be dumped down sewers or vented into the atmosphere are all having a major impact on cleaning technology.
Aqueous (water-based) cleaning processes have been around since the 1970s, and have been gaining momentum in recent years, not only as an alternative to solvent-based cleaning but also as a means of reducing handling, labor and waste disposal costs and concerns. California’s recent decision to ban solvent cleaning in the Los Angeles area will likely spawn similar legislation in other parts of the country, creating added incentive to switch to aqueous cleaning as a means of maintaining environmental compliance. San Francisco will begin enforcing a similar ban on solvents in the Bay Area starting September 1st. Florida, New Jersey and a number of other states are also considering similar bans. Solvent-based cleaning has already been banned in most western European countries.
One of the main reasons why solvents are being banned is because of the vapors they give off. Volatile organic compounds (VOCs) are a major cause of smog, so reducing the use of compounds with high VOCs reduces smog and improves overall air quality. Most solvents are also toxic and have health risks associated with long term exposure. Even short term exposure can give some people headaches and cause eye, lung and skin irritation. Solvents are also flammable. Even so, they’re excellent cleaners, require little maintenance and can be recycled.
By comparison, water-based cleaning solutions have very low VOC ratings, making them a much better choice for areas with air quality concerns. Most water-based detergents and chemicals are also non-toxic, non-hazardous and non-flammable. Water is also recyclable, relatively cheap and much easier to dispose of. Contaminants in the water can be removed chemically, mechanically or biologically, or concentrated by evaporating away most of the water.
But does it clean?
According to the aqueous-cleaning equipment manufacturers, water-based detergents and washer systems clean just as effectively as solvents - provided the equipment and cleaning solutions are maintained properly. The combination of water pressure impinging against the surface, and the secondary action of the water and detergent dispersing and rinsing away the contaminants does an effective job on most automotive parts.
Aqueous cleaning is faster, too. A typical wash and rinse cycle may only take 10 to 15 minutes compared to hours of soaking in caustic or a solvent tank. Automated spray washers and flow-through systems mean you can load the parts, push a button and walk away, eliminating the need for a lot of manual scrubbing and brushing. This frees up time for other tasks such as billable labor for machine work or assembly work and helps boost overall shop productivity and profitability.
There are many different ways to clean with water-based cleaning solutions. Spray washers or jet washers generally use V-jet nozzles and some type of stationary manifold system to direct water at parts sitting on a turntable inside a cabinet. On some washers, the parts are stationary and the nozzles rotate to vary the spray pattern.
Another unique variation according to Perry Crabb, marketing manager for Axe Equipment, Council Grove, KS, is a family of spraywashers that uses a planetary system to drive two to four turntables simultaneously during the wash cycle.
"This new system produces zero deflection from other parts in the machine throughout the wash cycle," Crabb explained. "Rebuilders can, at a minimum, double their present output by cleaning the heads and the block at the same time. In fact, the entire assembly including heads, block, sheet metal and crankshaft can be cleaned in one cycle when necessary."
Power or pressure washers, by comparison, operate at higher pressures to dislodge dirt and grime. Other washers use a water wheel rather than a pump and nozzles to wash the parts. Spray washers and power washers come in a variety of sizes and configurations, with prices ranging from $6,000 up to $50,000 or more.
Flow-through spray wash and power wash systems for continuous cleaning in large scale rebuilding operations are also available. This type of setup is ideal for high volume applications and continuous workflow. Prices range from $20,000 up to $130,000 or more.
Other options include aqueous wash tanks and sinks (typically used for hand cleaning small parts), vibratory washers that use an aqueous solution rather than solvent, and ultrasonic equipment that uses sound waves to dislodge dirt and grime.
"The trend over the past eight to 10 years has been to move away from solvents for degreasing," said Deron Lock, general manager for Viking Corp., Wichita, KS. "Our vibratory equipment for cleaning CV shafts, alternators, starters and A/C compressors used to use solvent, but we’ve since changed to aqueous."
Making the change
Switching from a solvent-based cleaning process to one using water-based detergents or chemicals is not a simple one-for-one substitution in most instances. For one thing, most aqueous cleaning processes require a certain amount of care to maintain the concentration of detergent and other chemicals in the solution. To clean effectively, the additives in the water must be maintained within a certain range or concentration.
Maintenance includes adding make-up water as needed to compensate for water which is lost during cleaning operations and to evaporation, adding detergent and other chemicals such as rust inhibitors to maintain the proper balance in the solution, replacing or cleaning filters and oil skimmers as needed to slow the buildup of contaminants, and periodically removing sludge and other solid matter that accumulates in the bottom of the cleaning equipment.
"The key to successfully cleaning parts with most aqueous-based processes," said Steve Winters, president of A.R.E. Industries, Wichita, KS, "is keeping the water clean. This requires a change in the mind set of those who have been using solvent to clean their parts because water-based cleaning equipment usually requires some maintenance. So it’s important to make sure they’re trained how to maintain the water-based cleaning solution."
Clean water is especially important in spray washers because dirty water can clog spray nozzles, reducing the overall cleaning effectiveness of the process. Spray washers and power washers depend mostly on the force of the water striking the surface to loosen and wash away dirt and grease, but many also rely on the detergent or other chemicals to complete the job.
Oil skimmers are commonly used with aqueous-cleaning equipment to separate oil from the water, which is relatively easy because oil and water don’t mix. The oil floats to the surface where it can be skimmed off and collected in a separate container. For this reason, the type of detergent used in a spray washer should be a poor emulsifier so the oil will separate from the water. Emulsified oil will remain in solution and shorten the life of the cleaning solution.
Filters are also used on many washers to prolong the working life of the cleaning solution. By trapping solids, a filter helps prevent nozzle clogging and reduces the need for equipment maintenance and replacement chemicals. But eventually all filters have to be cleaned or replaced. Screen mesh filters are usually washable but fiber filters must usually be replaced. Replaceable filters may cost from $10 to $30 or more depending on the application. How often a filter needs attention will depend on the design of the filter itself, the quantity of parts being cleaned, how dirty the parts are and the number of wash cycles per day. Generally speaking, the finer the filter, the cleaner it keeps the solution but the faster it clogs up.
For a 100-gallon spray washer cabinet that handles 10 to 11 loads a day, the filter may have to be cleaned or replaced once a week or every couple of weeks. For a small parts washer sink, a filter may last for many months. Some manufacturers, though, do not recommend using filters with their washing equipment because a filter can reduce the water pressure produced by the pump. The filter may also create an obstruction if it becomes clogged. Gary Minkin, president of MART Corporation, St. Louis, MO, is one manufacturer who does not use filters with his cleaning equipment. "Our power washers direct solid streams of water under very high pressure at the surface of parts to remove dirt and grime. The nozzles we use are a quarter inch in diameter so they don’t clog up, and the recirculated dirt acts like grit to further help blast the surface clean."
Detergents and chemicals
With many aqueous-based cleaning processes, choosing the "right" detergent and/or chemical for the application is very important. The same spray washing equipment may clean very differently when different detergents are used. The best advice here is to follow the equipment suppliers' recommendations for chemical usage.
Most spray washers require some type of foam suppressant in the detergent to prevent foaming. Some cleaning products are formulated for specific types of applications like aluminum or cast iron, while others are "general-purpose" cleaners. Several manufacturers recommend using a milder or less aggressive cleaner on aluminum because some products designed for cleaning ferrous metals can etch or discolor aluminum making it difficult to achieve a bright like-new finish.
Scott Mansur, senior product marketing manager for Landa Water Cleaning Systems, Portland, OR, said "the pH scale is what dictates the aggressiveness of the cleaner. Time and temperature are also critical. That’s why many people use two different brews, one for aluminum and another for cast iron."
Ian Bagnall, sales manager of RMC Rogers Machine, Bay City, MI, and Patrick Garbutt, of Georg Fischer Disa Goff, Inc., Seminole, OK, are others who also recommend using one type of cleaner for aluminum and a different one for cast iron.
Using different cleaning solutions for aluminum and cast iron can complicate the cleaning process, so some rebuilders set up separate cleaning lines for each type of metal. Many rebuilders also use different cleaning techniques for different metals, using a spray washer for aluminum and an oven for cleaning cast iron blocks and heads. Others may use an oven to bake off grease and oil, and a spray washer, rather than a shot blaster to clean off the scale and ash left by the oven. Spray washers also seem to be a popular choice for final cleaning to removing oils and residue after parts have been machined.
Some aqueous-cleaning equipment manufacturers sell their own brand of detergent and/or chemicals while others do not. Most equipment suppliers do provide a list of recommended products for their washers. Spray washers that operate at lower pressures and rely more on the surfacant action of the detergent to clean parts will be more sensitive to the type of cleaner used and the concentration of cleaner in the solution than equipment which operates at higher pressures and relies more on the force of the water to loosen and remove dirt.
Water disposal and treatment
As the cleaning solution becomes dirty, it must eventually be treated or disposed of and replaced. That’s one of the drawbacks of any type of liquid cleaning process, be it water or solvent-based. Filters and skimmers can prolong the life of the solution, but cannot do so indefinitely unless other means are employed to treat and restore the solution.
Dirty water poses fewer environmental dangers than solvents, but it depends on the contaminants that are in the water. Heavy metals such as lead, cadmium and chromium are the main concerns. Heavy metal contamination can be minimized by removing bearings and plated parts prior to washing. But if the water contains significant amounts of these contaminants, it may have to be disposed of as hazardous waste. For this reason, waste water should always be tested to determine what’s in it and whether or not special handling is required.
Hauling away large quantities of dirty water can be very expensive. One way to minimize disposal costs is to reduce the volume of liquid through evaporation or distillation. An evaporator can reduce a 55-gallon drum full of dirty water down to a few pounds of sludge. The rate of evaporation will depend on the temperature of the water and relative humidity. Using heat increases the rate of evaporation, but also the cost of getting rid of the water. But speed usually isn’t that important unless you’re dealing with very large quantities of waste water.
Filtration is another way to remove contaminants and recycle the wash water. Several companies including Landa Water Cleaning Systems and MART Corp. have portable water filtration units that their distributors use to clean their customer’s wash water.
Another way to treat dirty water is to use a "splitter" chemical that encapsulates oils and other contaminants, turning them into a solid material that settles to the bottom of the tank. The solid material can then be removed for disposal, allowing the original water to be reused. This approach eliminates the need to haul away or replace dirty water. But it adds the cost of buying special chemicals to treat the water. One supplier said a pail of chemical that cost $20 can treat a 55-gallon drum of dirty water.
In many instances, the solidified waste material can be landfilled because the encapsulation process prevents the heavy metals and hydrocarbons from leaching out. If the material passes a laboratory "TCLP test" it can usually be landfilled. At least one supplier, MART Corp., will custom formulate their encapsulation product based on an analysis of a shop’s waste water. This ensures the water will be fully treated and the waste products won’t leach out.
A third approach to minimizing or eliminating waste water disposal is "bioremediation." When the Exxon Valdez struck a rock and spilled millions of gallons of crude oil in Alaska, oil-eating microbes were put to work to help clean up the mess. The same approach is used in bioremediation to break down and digest oils and other hydrocarbons. Oil-eating microbes transform the grease and other gunk into water and carbon dioxide. The process is relatively slow and it requires maintaining the water temperature within a certain range, usually no hotter than 110° to 120° F, and replenishing the microbes regularly.
Tom McNally, general manager of ChemFree, Norcross, GA, says his company’s truck grade "OzzyJuice SW-3" can digest motor oil, cutting oil, transmission fluid and even bearing grease with ease. ChemFree makes a wash sink that uses a water-based solution and a microbe-impregnated filter which must be replaced monthly at a cost of $10. The filter and microbes keep the solution in the tank clean, said McNally, and virtually eliminates the need to clean sludge out the tank or replace the water.
Greg Meyers of ATEC Steelabrator, San Antonio, TX, said his company also sells a bioremediating aqueous parts washer. "Maintenance costs are relatively low with this system, typically about $40 every four to six weeks depending on use for a filter and make-up solution."
Meyers said bioremediation eliminates the need to haul away or replace the cleaning solution. The microbes keep sludge from building up inside the tank. Bioremediation also eliminates the need for troublesome oil skimmers, and allows the use of a cleaning solution with strong surfactants and emulsifiers to break up grime and disperse oils.
Because microbes are killed if temperatures exceed 120° F, some companies are using enzymes rather than microbes to break down oils and grease. Frank Pedeslus of Omega Sonics, Simi Valley, CA, said enzymes allow much higher water temperatures to be used for better cleaning.
"We’re using an aqueous solution with detergent and enzymes in our ultrasonic parts washer. The combination delivers excellent results." Pedeslus said ultrasonic equipment is a good choice for cleaning intricate parts that have internal surfaces and blind holes such as carburetors, transmission components and alternators.
For water to clean effectively, it usually needs heat. The hotter the better. The recommended temperature range will vary according to the type of equipment and chemicals used, and may range from 105° up to 190° F. Many spray washers operate best in the 140° to 180° F range. If the water temperature is too hot, though, water loss due to evaporation may become a problem requiring more make-up water to maintain the cleaning solution. Some equipment suppliers recommend a slightly lower water temperature when cleaning aluminum while others do not.
Hot water means the equipment needs a heat source, which may be gas or electric. Electric heating coils inside washer cabinets require some maintenance to keep them clean because a buildup of scale and grime can reduce their efficiency.
Tim Vondemkamp, engineering manager for Kansas Instruments, Council Grove KS, said the design of a spray washer can also make a big difference in its operating costs. "A well insulated gas heated 100-gallon spray washer that does 10 loads a day can cut energy costs down to about $3 to $5 per day if you’re using gas heat, or $5 to $10 a day, depending on rates, if you’re using electric."
One of the more common drawbacks of using a water-based cleaning solution in a plain steel tank or washer cabinet is rust. Over time the equipment will rust if the metal is not adequately protected both with some type of corrosion-resistant finish and rust inhibitors in the cleaning solution or rinse water.
Rust is also a cosmetic concern on ferrous parts. Again, using some type of rust inhibitor in the rinse can minimize the problem, as can decreasing the drying time with fans or heaters after parts have been washed.