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The Science Of Aqueous Cleaning
By Jenna Bates
The notion that aqueous cleaning consists only of a steel drum and hose is obviously a thing of the past. Aqueous cleaning entered the realm of advanced technology years ago and has been improving by leaps and bounds annually.
These technological advances have prompted many rebuilders to re-evaluate their cleaning processes and perhaps take a second look at aqueous cleaning as a primary source of cleaning, something that was out of vogue in the machine shop as recently as 10 to 15 years ago because of increasingly stringent Environmental Protection Agency (EPA) regulations. At that time, many rebuilders and remanufacturers turned to baking and shot blasting as their primary cleaning process because of the ability to clean baked-on carbon and other contaminants without the hassle of a lot of follow-up cleaning. But, improvements in waste water processing have also encouraged some rebuilders to take a second look at aqueous cleaning.
In addition, Ed Kiebler, national sales manager for the MART Corp., claims that heat cleaning and shot blasting can create a lot of extra work for rebuilders. The MART Corp. makes 34 different models of aqueous cleaning machines that feature 104 different options.
Another reason aqueous-based cleaning is gaining more favor these days with some rebuilders is because solvent cleaning is being legislated against.
"There is more of an acceptance for aqueous-based cleaning," says Frank Pedeflous, of Omegasonics. "With regulations changing against solvents and people looking for labor-saving devices, aqueous is gaining favor."
The MART’s Kiebler agrees.
"What I see happening, especially with the production engine remanufacturers (PERs), is that they are realizing that heat cleaning and shot blasting — both wonderful ways to clean parts — create an awful lot of extra work," Kiebler explains. "Your deck surfaces all have to be remachined. Your line bores tend to have to be rehoned or remachined. There’s a lot of retapping of threads, etc. A rebuilder can spend up to 45 minutes just chasing threads and making sure that everything’s OK once it has come out of the shot blaster. Now, we (think there is) a pretty strong movement back to aqueous cleaning as a primary cleaning method — especially for aluminum."
Why aluminum? Though the debate continues as to the maximum temperature to which aluminum should be heated, most rebuilders don’t heat aluminum past 450° F; most baking ovens get hotter than that in order to dry all the ash out.
Ray Meyer, president of RMC, Inc., has seen the same trend.
"About eight to 15 years ago, thermal cleaning was the hottest thing going," he says. "It was the newest and greatest thing in technology. But, with the onset of a lot of aluminum, rebuilders are coming back to aqueous cleaning as their primary cleaning process."
Also drawing rebuilders and remanufacturers back to aqueous cleaning are the new chemicals on the market today — chemicals that are formulated in a lab by an engineer — chemicals that perform more effectively than those of just a decade ago. In most cases, these chemicals are much safer than those used in solvent cleaning, a cleaning process that is being legislated against in many states.
According to Wally Dankmyer, product manager for water services for Safety-Kleen, aqueous cleaning is continuing to make up a larger segment of the cleaning market, but mostly because the market is regulating solvent cleaning.
"In my opinion, our customers would rather continue using the solvent cleaners, but that’s not an option for many shops anymore," Dankmyer says. Safety-Kleen offers a wide variety of aqueous cleaning options, including immersion, spray, manual degreasing and ultrasonic equipment. They can provide the equipment, the solution used in the equipment and the disposal of that solution based on the needs of the individual rebuilder. Safety-Kleen also sells the aqueous cleaning chemistry for machines other than their own.
Dankmyer explains that a rebuilder must take into consideration several factors before switching to an aqueous cleaning process. Among these considerations is the type of subsurface. Is it aluminum? Is it steel? Do you have to worry about corrosion afterward? What are the soils being taken off, because different cleaners remove different soils.
It’s a sentiment that George Cheves, product manager for DISA Goff, Inc., echoes.
"There are many aqueous cleaning factors," he explains. "These include parts, parts handling, chemistry, solution temperature and time cycles."
What are the parts that need to be cleaned? What type of metal are they made of? What is the critical area? What is considered "clean"? What is the type of contamination? Only after these questions are answered can a rebuilder begin to understand what cleaning process is right for him.
According to Cheves, testing or previous experience with the part is the best way to know how to handle parts to get the optimum cleaning from a parts washer.
"Things like size of batches and how many units the customer wants to clean per hour or day will direct you to the best parts handling system for your parts washer and their cleaning process," says Cheves.
Chemistry and Solution Temperature
Determining the proper chemical for your contamination is crucial in getting the results that you are looking for from your aqueous parts washer.
"Concentration is also an area that must be monitored," Cheves explains. ‘"If a little is good, a lot must be better’ is not the rule to follow in getting the correct concentration for your chemistry. In some cases, it can do more harm than good."
Proper temperature is also one area that very few people take a look at. There are chemicals in use that are not effective at all over 140° F, and when you maintain a temperature in the 180° to 190° F range with your parts washer, it looks as though the parts washer is not working.
"Cast iron can handle a temperature of 190° to 200° F with very few side effects," explains Cheves. "On the other hand, Autocraft, a transmission rebuilder in Oklahoma City, OK, completed some testing and found that a temperature of 170° to 180° F was much better and produced a cleaner part."
If production is the driving force behind your cleaning process, this is an area that can be very critical. It is also the driving force behind what type of machine you are required to use in your operation.
Says Tom Schroder, product manager for parts cleaning service at Safety-Kleen, the advantages to aqueous cleaning include more user-friendly chemistries and time savings.
"The fastest growing segment of aqueous cleaning is the automated cleaning segment," explains Schroder. "About 95 percent of all solvent cleaners are manual. When you change to an aqueous process, it allows the user to automate the process, which saves time and money."
Switching to aqueous cleaning is a bigger initial investment than a traditional solvent cleaning process, Schroder says, but a rebuilder can then eliminate the need to pay a technician to stand there and clean the parts.
In addition, some companies provide cleaning machines that can deliver much higher pressure than spray washers of the past.
Add to that the non-hazardous nature of aqueous chemistries and the waste minimization as compared to solvents, and the benefits seem clear.
But, what about the EPA? After all, if anything, EPA regulations have become more stringent over the years.
Again, many companies in the aqueous cleaning field are now offering solutions to that very problem.
"Waste water processing has improved greatly. The industry does a much better job of managing solutions today," says the MART Corp.’s Kiebler who explains that his company’s new systems actually have conveyers that draw or pull the sludge out, so remanufacturers no longer have to shut the machine down to clean it out. There are also oil skimmers that combat the problem of solutions becoming ineffective very quickly.
In the case of the MART Corp., the EQ1 Waste Water Processing system pumps all solution out and treats it to remove oils, greases, solids and dirts and drops them out of suspension. What’s left is the clear, clean liquid that is pumped back into the system and reused.
The leftover treated sludge is rolled up into a filter paper and dried into a brick form. This then can pass the "T-clip test" (leachability) and is allowed by the EPA to be placed into a standard landfill.
Waste related to aqueous cleaning is probably the most misunderstood part of the process, says Lyle Haley, sales and marketing manager for Peterson Machine Tool, which offers approximately 20 different models of aqueous cleaning machines in various configurations.
"You can buy a chemical, and if you can dilute it with enough water, you can put it down the sewer," he explains. "The problem is that when you clean an engine part, you inherit all kinds of bad things from the customer. If it’s cast iron, you can inherit arsenic; you can inherit chrome; you can inherit the heavy metals that come out of bearings and rings. A lot of people went to heat cleaning because they thought they could avoid dealing with those waste products."
Haley says that the chemicals, processes and waste disposal have undergone such improvement in the last decade, that many of the considerations that drew rebuilders away from aqueous cleaning a decade or more ago aren’t problems anymore.
In addition, new chemicals are constantly being developed. One aqueous cleaning equipment manufacturer is currently working on a new chemical that will remove carbon from parts — one of the reasons people switched to heat cleaning and blasting in the first place.
There are other changes on the horizon as well.
"The one thing that has changed and will continue to change to enhance the parts washers on the market is the way the parts are handled," says DISA Goff’s Cheves. "This is one of the factors that you must look at when washing parts and especially if production is a key factor. A rotating table may have been enough five years ago to handle everything that you needed to do, but now it may not give the user the number of clean parts that they need to clean."
Also factoring into aqueous cleaning is the possible cost savings in terms of energy use.
"I think you’re going to continue to see baking used in high production areas. But, because of the energy cost, it’s going to be a labor dollar vs. energy cost tradeoff that isn’t going to be as advantageous as before," explains RMC’s Meyer, who says that the increasing energy costs could make baking even more costly than aqueous cleaning in some cases. "Even the high production shops will have to supplement with aqueous cleaning for those parts that can’t withstand the heat or the blasting."
And, Peterson’s Haley recommends that rebuilders really take a second look at aqueous cleaning and try to overcome some of the preconceived notions of decades past.
"The fear that people have of disposal is something they should get over," Haley says. "You do have to follow the rules, but it’s not as difficult as it’s been made out to be."
What Dave Maxwell of Omegasonics has been hearing most is that if you can find something that cleans and really works then cost and time are not factors.
As Kiebler of the MART Corp. says, "People don’t buy machines; they buy a way to get their parts clean."