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Money to Burn: What Heat Cleaning Offers Rebuilders
By Doug Kaufman
It’s a subject that hasn’t changed much in the past few decades, yet heat cleaning of engine parts continues to be a hotly discussed topic. With economic and environmental concerns growing increasingly important, what does heat cleaning have to offer today’s (and tomorrow’s) engine rebuilder?
Plenty, as it turns out. There have been some new advancements in heat cleaning technology, and it is a process that can offer significant cost and labor benefits to rebuilding operations.
"Heat cleaning" is actually a bit of a misnomer in that, depending on the design of the equipment, the heat is used in different ways to clean parts.
"Thermal cleaning is a broad category which includes all types of heat cleaning equipment," says Mike Wilks, director of marketing at Winona Van Norman. "It’s the most pollution-free method for cleaning, and though this has been known for many years, recent concern for environmental regulations has caused a resurgence in interest in heat cleaning."
First, a look back. Heat cleaning was introduced to the engine rebuilding industry in the 1970s. "The same basic concept – of getting the part temperature above the point of breaking down the grease, oil and carbon – is the same since Fred Jones (a former Ford authorized engine rebuilder) pioneered the concept," explains Lyle Haley, sales and marketing manager, Peterson Machine Tool.
The process was refined in the 1980s, becoming a standard part of rebuilding shop operations. Since that time, says Guspro’s Kent Whelen, the basic concept has not changed much.
"But, modern electronics have allowed microprocessors to be applied to the equipment for temperature control," Whelen says. "This has allowed for a finer degree of control over the process, improved cycle times and helped to reduce energy consumption."
It is control – whether over economic, efficiency or environmental concerns – that continues to make heat cleaning a viable and attractive option to rebuilding facilities, say these industry spokesmen.
Cleaning is a necessary evil and is required to maintain any true resemblance of quality control in the rebuilding facility. For many years, solvent cleaning was one of the most popular methods of removing contaminants from parts, but due to increasingly tight restrictions on volatile organic compounds (VOCs) content in many states, solvent use is being phased out.
"Solvent use requires costly removal of used solution as hazardous waste," explains Wilks. "Heat cleaning is an alternative cleaning method which legally eliminates both the release of VOC content and reduces the need to have hazardous waste removed."
Ric Havel, consultant to the automotive division of Sunnen Products Co., says that thermal cleaning is as close to perfect as you can get. "I like that thermal cleaning is the one cleaning method that has no memory. In other words, there is so little maintenance or operator involvement, or dilution or contamination of water, it will always produce a first-class, clean component.
Another benefit, as Guspro’s Whelen explains, can be immediately obvious to the bottom line: "The real benefit to the rebuilder has turned out to be both a cost savings by eliminating chemicals, but also a tremendous savings in labor as well as providing among the cleanest engine parts available.
"Heat cleaning eliminates the labor-intensive grinding and scraping of gaskets and carbon," Whelen continues. "With oven cleaning, you put the part into the oven and at the end of the cycle remove them. Carbon and gasket materials are reduced to dust. This dust is then removed during a post-oven media blasting process."
Baking ovens, typically viewed as "slow bake" ovens, operate much like an ordinary oven. They are very well insulated and can clean large batches of blocks, heads and components at high temperatures. The insulation makes them very fuel-efficient and they are among the most economical to purchase, but they have slower cycle times. Shop owners trade a lower cost for typical cycle times of one to four hours.
Another type of oven is referred to as a "rotisserie" oven. This type of oven operates more like a convection oven than a conventional baking oven. The parts are loaded into baskets, which are attached to mechanical systems that rotate parts through heated air, causing the parts to heat up faster.
Parts are loaded into the heating chamber where one or more main burners heat them to a predetermined temperature. State-of-the-art insulating materials and computer temperature controls keep the heat in the machines where it belongs and where it can be used most effectively. As the grease, oil and other contaminants burn off, the resulting smoke and fumes are sent into an afterburner chamber where they are further burned, decomposed and emitted through an exhaust stack.
Actual cleaning takes place between 400° F and 800° F. But with the various contaminants bursting into flame and burning off, temperatures can reach much higher. Different technologies are used to maintain steady temperatures, including water sprays to displace oxygen in the combustion chamber and automatic fans to remove heat as needed.
Despite the high temperatures these ovens achieve (up to 1,000° F in the oven, over 1,400° F in the afterburner), they are still remarkably efficient.
"It has been proven time and again that heat cleaning uses less energy than a hot tank or jet washer," explains Whelen. "These machines require hot chemicals to operate and must be kept hot all day long, heating and evaporating the cleaning solutions in usually poorly insulated if insulated at all tanks. Heat cleaning ovens are very well insulated and are designed to keep the heat in the oven chamber. They only consume energy when operating."
Energy consumption is certainly a hot button for shops paying attention to overhead costs. Electric supplies, depending on location, are frequently short and fuel costs have skyrocketed; how does this type of equipment fit with a cost-conscious shop?
Despite being vulnerable to the increased cost of propane or natural gas, heat cleaning is still practical and efficient. "But machine shops need to be aware of their costs and pass them along to the customer so they can maintain their profitability," Peterson’s Haley explains.
"Although fuel prices have skyrocketed this year, most would agree that this hasn’t been a normal year," says Wilks. "There is cost involved in every cleaning method, all of which is on the increase."
Sunnen’s Havel continues: "Keep in mind that other technologies and methods typically share, as does thermal cleaning, the use of energy for the purpose of heating, circulating, pumping, agitation, pressurization, rotation, and air compressing. Other methods involve the purchase of consumables and require more maintenance and operator involvement. This is a poor use of time and erodes profits before the job begins"
The "baking" part of heat cleaning is just part of the process, these equipment representatives stress. "Thermal cleaning, when viewed as a process and not a machine, is very efficient and economical to own and operate," says Havel. "Results are very predictable from one load to the next. But baking ovens are just part of the puzzle for complete cleaning."
Wilks agrees. "When looking at thermal cleaning, shop owners need to understand that it is only one part of a full cleaning system. When parts come out of an oven, they are usually blackened. To complete the cycle, parts need to be put into an airless shot blaster where the metal is blasted back to its original state of a white or near white appearance. This process will turn out a final product that looks new or better than new."
Although heat cleaning requires no solvent recycling or other liquid waste considerations, the process doesn’t entirely absolve rebuilding facilities of the need for attention to the environment. Thermal cleaning can result in hazardous waste even if it is correctly installed, used and maintained.
"When shopping for any cleaning oven," states Wilks, "it is important to find one with an afterburner. In some states like California and New Jersey, the amount of discharge through the vent pipe is regulated. Normal oven operating temperatures are enough to burn the grease and grime, but the exhaust contains some hazardous wastes that would be discharged into the air if vented directly. An afterburner cleans the exhaust of remaining contaminants to pass stringent state regulations."
Whelen further explains a shop’s duties: "As with all environmental control equipment – and make no mistake, this is that kind of equipment – you will need a permit to install and operate a heat cleaning oven. You can get the permit from your local air quality agency, and all oven manufacturers have test data to support their equipment."
Once the equipment is installed, tested and operating properly, Whelen reminds rebuilders to pay attention to another concern of environmental agencies. "The rebuilder should, at least once a year, test his ash and dust residue to be sure he is under the threshold for heavy metals allowed by his state to dispose of the ash in his trash. In most states, the ash from cleaning engine parts is non-hazardous, but it is prudent to have a test report in your files in case an inspector asks about your disposal methods."
Cast iron blocks, heads and components can easily be cleaned in baking ovens, but manufacturers urge caution when it comes to heat cleaning aluminum engine components.
"There are some potential downsides, as overheating can destroy the induction hardening of valve seats in cast iron heads, and overheating can drastically change the hardness of aluminum parts," says Peterson’s Haley. "I would suggest that rebuilders pay attention to AERA’s technical bulletin 1843. General Motors has mandated that its 5.7L VIN code G aluminum cylinder heads should never be heated over 400° F during cleaning or straightening, and GM forbids uneven, nearly direct flame contact with this head."
According to Randy Neal, president of Cast Welding Technologies (CWT), the concerns over lightweight aluminum or cast iron castings was never an issue until recently.
"The major concern with the aluminum products is that uncontrolled heat could soften the casting," Neal says. "It should be noted that virtually all aluminum cylinder heads have a "T-6" rating, which signifies that the casting has been heat treated for the purpose of hardening, allowing the casting to maintain its shape during normal assembly and operating environments."
However, Neal points out that castings can lose this T-6 temper rating if a shop does one of two things:
1) Heats the casting to 600° F for one minute or more. Direct flame ovens can be susceptible to this concern, because even if the unit’s thermometer shows the oven air temperature to be at a relatively lower temperature, if the component is rotating through the flame, temperature spikes can anneal the part.
2)Heat the casting in a convection-style oven to between 450°F and 600° F for two hours or more.
"With today’s engine products, it is critical that tighter time and temperature parameters are controlled by the end user," says Neal. "Although the end user can become more attentive to these parameters, he may also be limited by the design of the oven."
How important is your decision regarding how to clean engine components? According to Havel, as much as 50 to 75 percent of each day is spent in cleaning. "Our industry is made up of creatures of habit," he says, "and habits are hard to break. Even with the widening of new technologies, many shop owners are reluctant to change. However, just ask someone who has stepped up to the thermal cleaning process and you’ll hear comments like, ‘I wish I had bought this a long time ago…’ or ‘It’s like having more employees without the expense.’ "
Concludes Wilks, the future looks bright for sales and use of heat cleaning equipment in particular – and for the rebuilding industry in general. "The number of shops closing continues to exceed the number of shops opening due to economic conditions, favorable interest rates and factory incentives offered on new automobiles.
The primary market for heat cleaning systems, in many cases, is the new shop. As the economy slows, the opening of new shops should begin to catch up with shop closings. New shops will be cleaner, more sophisticated and in-tune with environmental regulations, as will those existing shops that transition through the coming years. Heat cleaning will be the perfect fit for many of these shops.
You may e-mail Doug at: firstname.lastname@example.org.