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In the face of rapidly depleted freshwater supplies, the industrial sector is learning that reducing water usage and increasing reuse is an essential ingredient of productivity and profitability today. This is increasingly true in countries such as the U.S., where water usage for industrial purposes is 46% of all water consumption, according to Dr. Peter Glieck, president of the Pacific Institute for studies in environment.
Today’s manufacturers and fabricators are now realizing that they are major stakeholders in this global water conservation effort and that water conservation saves cost. As such, giant conglomerates like Ford Motor Co., Parker Hannifin and global heat-treating specialists like Bodycote are beginning to focus on process water reuse to not only conserve water, but also to improve process uptime and product quality and reduce exorbitant disposal and maintenance costs. They are taking actions such as incorporating advanced separation technology and addressing pollution such as oil, grease and dirt, to increase the life of precious production fluids like cleaner solutions and coolants.
New Realities in Aqueous Separation
Automotive manufacturers and metal fabricators, for example, are using a new and highly efficient technology—dynamic oil separation—to continuously remove process oils and minute contaminants from an aqueous cleaning solution while it is being used, with no process interruptions.
Traditional mechanical separation methods are based on one of two principles: gravity separation, in combination with weir skimmers and tank overflow, or adhesion, with hoses, wheel/disks or belt skimmers used to adhere oil to lift it from the surface of bath water. Both methods are problematic, particularly in high-volume production settings where delays to change or maintain aqueous baths involve downtime.
For instance, adhesion separation often allows dirt to settle through surface oil and cycle back into the bath water, leading to dirty parts and requiring frequent solution change. The adhesion method also draws up and removes cleaning agents along with water and oils, creating “wet” oil and adding to oil disposal costs.
The overflow (decanting) method wastes vast amounts of coolant or cleaner from the bath, which is a waste of costly resources. Another method, which uses honeycomb-like traps or plates called coalescing media to separate and capture oil and contaminants, has proved to be inefficient and maintenance-intensive due to its sensitivity to dirt.
Instead, dynamic separation technology operates on a different principle—Bernoulli’s Effect, the phenomenon whereby increased stream velocity in a fluid results in internal pressure reduction. The Bernoulli Effect is probably best known as the principle that creates the “lift” of aircraft wings. Dynamic separation uses fluid pressure differential to enable the separation of liquids of differing specific gravities. This technology was developed by Aqueous Recovery Resources (ARR) and incorporated in its Suparator systems specifically for this type of application.
This unique technology removes oil so effectively that dirt and other foreign matter are separated with the oil. Elimination of these contaminants warrants a much cleaner process and cleaner parts, translating to better quality products and less rejects.
Dynamic separation also extends bath life, providing significant savings in detergents. Bath changes are greatly reduced, vast quantities of water are conserved, oils are more efficiently recycled and far smaller volumes of cleaners and coolants have to be disposed of.
Case No. 1: Pressing for Perfection
At Ford’s Dearborn plant, a 2,600-ton Schuler press using up to 300 tons of dies turns 700,000 lb of steel per day into doors for Ford F150 pickup trucks. At the press area, stacks of steel blanks arrive, each coated with a thin film of mill oil to preserve the metal against corrosion. The steel blanks have to be washed to get rid of the oil and any dirt or other foreign matter prior to being stamped.
“These oiled blanks attract dirt like a magnet,” said Ed Spencer, controls engineer at Ford’s Dearborn stamping operation. “The blanks have to be washed thoroughly [because] we don’t want that oil, which may have dirt in it, to get into the die. So, we spray-wash it with a detergent solution pumped up from a huge tank downstairs.”
If even one piece of dirt “birdshot” remains on a blank when the giant press hits it, the finished piece will have a dimple on it that ruins the door. At the rate the Dearborn plant stamps the doors—700 pieces an hour—if a dirt problem is not identified quickly, the result could be the scrapping of a lot of metal in a short time.
“We have very tight demand,” Spencer said. “We have an assembly department downstairs that puts the inner and outer door panels together, and then it is shipped off to assembly. If we remain shut down because of dirt issues with the cleaning solution, we have problems: productivity loss, manpower standing around and wasted parts.”
Recognizing the need for an efficient and reliable separation technology to maintain a clean process, the Ford stamping operation installed a Suparator unit in 2006. In addition to meeting high-quality standards, which was essential, Spencer recognized that a truly effective oil separation technology would help maximize the uptime of the critical Schuler press.
After the dirt and oil are washed off the blanks, the cleaner returns to the holding tank, where the Suparator removes fluid from the surface. Any oil in this concentrated stream, with any entrained dirt, is separated from the fluid continuously and without water or detergent.
“In the past, we used a centrifuge system that spun and tried to get the heavy particulate out of the solution that way; however, that was a maintenance nightmare,” Spencer said. “We tried to remove the oil with a hose-type skimmer, a plastic tube that went around in a circle, and the oil would cling to it, supposedly, but it never really worked.”
“When we saw the Suparator technology, I thought we should test it,” he continued. “And it works better than the other system. We get only a small amount of water with the oil, but it is about 100 times more efficient than the other system. And the key is it takes out the fine dirt particles better than the centrifuge ever did.”
Spencer added that although the policy of his operation is to change the cleaner every two weeks, it stays clean enough to extend its use to at least two months. That pays off in added productivity, especially considering that there is no backup equipment for the giant press.
“We’re realizing major savings on quality and availability,” he said. “Uptime is now averaging up to 95%, which is excellent for the stamping industry. We also have less wasted materials and get extended cleaner life. Obviously, that adds up to a lot.”
Case No. 2: Extending Resources
At the Hydraulic Pump/Motor Div. of Parker Hannifin Corp., a Lindberg washer incorporated intentional overflow of the cleaning bath to remove quench oil from heat-treated parts. This method resulted in the loss of cleaner and “excessive volumes” of water being added to the plant’s effluent, according to Larry McCracken, plant engineer.
To reduce the costs resulting from those cleaning and disposal problems, the washer was modified to eliminate the need to continuously overflow the bath; however, some system was needed to control the oil concentrations in the bath.
“Initially, a belt-type skimmer was tried, but was unsuccessful,” McCracken said. “So, a Suparator unit was tried on ARR’s 30-day trial program. Approximately 10 gal of quench oil is removed from the bath daily. This result has greatly reduced operating costs as well as our getting cleaner parts from the washer.”
Cost savings included a reduction in water consumption from 19,080 to 3,480 gal per month (gpm). Chemical losses, previously recorded at 298 gpm, were reduced by 244 gal—a savings of almost 82%. The monthly cost of water disposal was reduced by approximately 80%, and the monthly cost of chemicals reduced by more than 80%. The total annual savings has been at least $101,184.
Case No. 3: Multiple Cost Savings
Blaine Timmerman of Bodycote, the world’s largest provider of metallurgical testing and thermal processing services, has said that his Rochester, N.Y., heat-treating facility has experienced multiple payoffs from the use of dynamic separation.
In high-volume production operations such as Bodycote’s, downtime or quality rejects resulting from inferior separation methods are costly and cause weekly or even daily maintenance problems such as dirty bath water and frequent bath changes. Such problems can lead to scrapped products as well as falling behind on demands.
Timmerman explained that his heat-treating process tended to create a rag layer between the oil and water in the dunk/spray washer. “We would get this nasty in-between layer that was an emulsification of water in oil,” he said. “It didn’t completely separate into either the oil or water. It tended to stay right there in the middle, sandwiched between the water and oil. And that hindered oil separation because the emulsified layer would roll down the skimmer rope or plate back into the water and stay there.” The result was more frequent bath changes and downtime.
“I had tried just about every oil separation technology,” Timmerman said. “Our operation and our customers are very demanding, and conventional oil separators just haven’t met our needs.”
After using a variety of separation devices, including disks, belts, mops and plates, Timmerman heard of the Suparator. The fact that the system removes oil-entrained solids and particulates means that they do not have time to settle through the oil into the water. This, too, significantly improves product quality, maintenance intervals and associated downtime.
In addition, the technology saves Bodycote’s operation on oil disposal costs. “We used to have to pay a penalty to dispose of oil with high water content,” Timmerman said. “In 2002, relatively ‘dry’ oil disposal cost was approximately 15 cents per gallon. But because of the water drag-out of our old oil separators, we were getting wet oil. If the oil had more than 10% water, which was often the case, we had to pay around $1.05 per gallon—a very significant difference.”
Today, in addition to eliminating the rag (emulsified) layer and the water drag-out, the separation solution has enabled Timmerman’s operation to cut oil disposal costs as well as increase the reuse of bath water several times over.