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. This is increasingly true in countries such as the United States, where water usage for industrial purposes is 46 percent of al water consumption, according to Dr. Peter Glieck, president of the Pacific Institute for studies in the environment.
Todays manufacturers and fabricators are realizing they are major stakeholders in the global water conservation effort – and that water conservation saves cost. From giant conglomerates like Ford and Parker Hannifin to global heat-treating specialists like Bodycote, industry is beginning to focus on process water reuse, not only to conserve water but also to improve process uptime and product quality, along with reducing exorbitant disposal and maintenance costs. To do this they are taking actions such as incorporating advanced separation technology, and addressing pollutants like oil, grease or dirt, to increase the life of precious production fluids like cleaner solutions and coolants.
These automotive manufacturers and metal fabricators are using a new and highly efficient technology – dynamic oil separation – to continuously remove process oils and even minute contaminants from an aqueous cleaning solution while being used, with no process interruptions.
Traditional Separation Choices
Traditional mechanical separation methods are based on one of two principles: (1) gravity separation, in combination with centrifuges, weir skimmers and tank overflow, or (2) adhesion, with hoses, wheel/disks or belt skimmers used to adhere oil and lift it from the surface of bath water. Both methods have drawbacks, 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; this leads to dirty parts and requires 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. In essence, this method has you continuously add fresh water to the system, pushing the top layer of fluid – presumably with al the oil – over a lip or tank edge and down the drain. Every drop of this needs to be treated by a wastewater treatment plant, at great expense. Its not hard to do the math: Overflow at a mere 2 gallons per minute, and thats 14,000-plus gallons a week. (In fact, 2 gpm is about a tenth of whats typically seen.)
Another method, which uses honeycomb-like traps or plates called coalescing media to separate and capture oil and contaminants, can be inefficient and maintenance intensive due to its sensitivity to dirt. The media develops a thick coating of oil – as it should – but the dirt and fine particles in the fluid fill the spaces in the media, restricting the flow and short-circuiting the settling needed for oil/water separation.
By contrast, dynamic separation technology operates on a different principle – Bernoullis 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 and incorporated in its patented Suparator systems, specifically for this type of application.
This unique technology removes oil so effectively that lots of dirt and other foreign matter are separated with the oil. Elimination of these contaminants results in a much cleaner process and cleaner parts, translating to better quality products and fewer 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. The technology is completely scalable, as well, with systems in production that range from 2 gpm to 100 gpm.
Fords Pressing Need
At Ford Motor Co.s Dearborn stamping plant, a giant, 2,600-ton Schuler press using up to 300 tons of dies turns 700,000 pounds of steel per day into doors for bestselling Ford F150 pickup trucks. At the press area, stacks of steel blanks arrive, each blank 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 Fords Dearborn stamping operation, so the blanks have to be washed thoroughly. We dont 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 is stamping the doors – 700 pieces an hour – if a dirt problem is not identified quickly, this can result in the scrapping of a lot of metal in a very short time.
We have very tight demand, Spencer explained. We have an assembly department downstairs that puts the inner and outer door panels together, and then we ship it 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 Ford quality standards, which was essential, Spencer recognized that a truly effective oil separation technology would help maximize the uptime of the critical Schuler press that had to meet extraordinarily high volume requirements.
Now, 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. But 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, Spencer continued. And it works – about 100 times 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.
The stamping operations policy is to change the cleaner every two weeks now, versus dumping it every few days, as in the past. (In fact, Spencer indicated, 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 Schuler press.
Were realizing our major savings on quality and availability, he said. Uptime is now averaging up to 95 percent, excellent for the stamping industry. We also have less wasted materials and get extended cleaner life. Obviously, that adds up to a lot.
Parker-Hannifin Cleans Up
At the Hydraulic Pump/Motor Division 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 plants 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, plant engineer McCracken said. So, a Suparator unit was tried on Aqueous Recovery Resources 30-day trial program. Approximately 10 gallons 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 gallons per month to only 3,480 per month. Chemical losses, previously recorded at 298 gallons per month, were reduced by 244 gallons – a savings of almost 82 percent. The monthly cost of water disposal was reduced by approximately 80 percent, and the monthly cost of chemicals reduced by over 80 percent. The total annual savings has been at least $101,184.
Blaine Timmerman of Bodycote, the worlds largest provider of metallurgical testing and thermal processing services, said that his Rochester, N.Y., heat-treating facility has experienced multiple payoffs from the use of dynamic separation.
Bodycote treats every part imaginable, from deck screws to brake-shoe carriers. These parts must have the quench oil effectively removed prior to final temper, to prevent the oil from staining the parts and burning off in the temper oven. In high-volume production operations such as Bodycotes, downtime or quality rejects resulting from inferior separation methods is costly and causes 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 just-in-time demands.
Timmerman explained that in the past 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 didnt 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, said Timmerman, Our operation and our customers are very demanding, and conventional oil separators just havent met our needs.
After using a variety of separation devices, including disks, belts, mops and plates, Timmerman tried dynamic separator technology. The fact that the Suparator 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 dynamic separator technology saves Timmermans Bodycote operation on oil disposal costs: We used to have to pay a penalty to dispose of oil with high water content, he said. In 2002, relatively dry oil disposal cost was approximately 15 cents a 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 percent water, which was often the case, we had to pay around $1.05 per gallon – a very significant difference. In current dollars that penalty price for wet oil would be much higher.
Today, in addition to eliminating the rag (emulsified) layer and the water drag-out, the dynamic separation technology has enabled Timmermans operation cut oil disposal costs, as well as increasing the reuse of our bath water several times over.