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Exasperation and hope drove the call from Pat Huser, Manufacturing Engineer at Rolls-Royce Indianapolis, to Midwest Engineered Products. With two re-manufactured grinders installed to machine the turbine blades used on the engines Rolls-Royce supplies for the C130, P3 Orion and other planes, Huser needed a way to keep the cutting oil (so important to the grinding operation) clean.

"The machining is critical," Mr. Huser said -- "blade parts ground to a tolerance of .0006 and used in a section of the engine that reaches nearly 2,000 degrees; so the oil is used under high pressure and must be clean and cool to avoid any burning of the parts as they are machined."

In the turbine blade manufacturing cell, to filter the high volume of metal fines created by the machines, Huser was using any combination of filter bags, paper filtration, gravity filtration, and two small mechanical centrifuges. Once the centrifuges reached their one-cubic-foot capacity, they had to be shut off, and the swarf had to be scraped out by hand. The filter bags often clogged, he said, then broke, ruining the coolant, and requiring the drain tanks to be cleaned, new bags to be installed – and new oil to be added to replace the old.

"These are liabilities," said Huser. "Your processes stop, the increased volume of ruined filter bags and paper have to go to the landfill and, with the inability to remove particles no smaller than 40 microns, the count of deviated parts and resulting scrap go up, reducing the quality and number of finished parts that you produce."

His search for a solution led to Jeffery Beattey, president of Midwest Engineered Products Corporation, an original equipment manufacturer based in Indianapolis, Indiana, that now produces a state-of-the-art centrifuge that Beattey invented.

"Market necessity is the mother of this invention," according to James Beattey, who founded Midwest in 1981. Through years of calling on all kinds of processing operations and selling them the company’s filters, proprietary ScaleBuster™ de-scaler and Water Ringer™ evaporator (for oily wastewater from compressor applications), "an opportunity became clear," he said. "We realized that most of the centrifuges sold to get metal fines out of grinding swarf, coolants, phosphate baths, wastewater, and other process fluids, were broken down or abandoned in the corners and bone yards of plants."

Like at Rolls-Royce, centrifuges usually are installed on a side stream or kidney loop treating a specific manufacturing process. Traditional centrifuge designs, unchanged in 15 years, are notoriously unreliable, resulting in tremendous downtime and operator attention for maintenance, and bearing replacement.

High-speed revolution of the centrifuge’s bowl, required to separate and "pack" solid particles against the bowl wall, is brutal on rotor bearings. When bearings fail, it typically takes four-to-six hours to pull the rotor, just so maintenance personnel can begin to access the bearings. "And that’s on automatic units," said Jeff Beattey. Mechanical centrifuges also require additional maintenance and service. Every time the bowl is full, the solids need to be removed manually, before the next processing cycle can begin.

Midwest’s idea was to design around and through these drawbacks. The centrifuge is completely automatic and, once set up, "can operate out of sight and out of mind, while providing literally unprecedented fluid filtration-performance and product production benefits, in addition to saving huge operating costs," Beattey said. That payback lies in understanding the machine.

Mechanically, Midwest’s centrifuge positively synchronizes, for the first time, the bowl and blade assembly (which consists of two scraper blades and two stilling vanes). A unique positive locking clutch (see diagram) couples the bowl’s main spindle and the blade together so that both rotate at precisely the same speed when processing fluids. The motor is linked to the main spindle via a single chevron-style "timing" belt and pulley design that prevents any slippage.

"The fluid is forced to move smoothly throughout the bowl as it strikes an accelerator on entry and descends," notes Beattey. "Physically, that even ‘quiet’ flow maximizes the law of centrifugal force: any particles heavier than the liquid are thrown outward and packed against the bowl wall." Such synchronized rotation also prevents any oscillation of the blade, maximizing separation efficiency and minimizing bearing wear. Oscillation, he said, " is what you want to prevent, as it creates a washout of solids from the bowl, particularly super-fines." Because the bowl is a thick centrifugally cast stainless-steel precision-machined part, vibration is dampened further enhancing bearing life.

When the automatic process cycle is complete, the feed pump turns off, the locking clutch uncouples the blade assembly from the main rotor spindle and locks the blades into a fixed position. The bowl is then rotated and the dry, dense particulate that is scraped loose by the blades falls into a collection drum, ready for recycling.

With patents pending on the unique clutch and scraper design, Midwest credits new electrical control "for making the CentraSep a reality," said Jeff Beattey. "In this design, the electrical and mechanical components are fused and inseparable."

Midwest realized early on that getting optimum benefits from the clutch design "meant, by definition, using a single motor and single motor controller -- but we didn’t know if that was possible," said Beattey. The quick acceleration, high, breakaway torque and extremely precise motor control is provided via an ACS 600, 15 HP drive from ABB; the encoder-less technology built into the unit made MEP’s design a reality.

An ability to anticipate what the motor is capable of based on its load provides a significant benefit to centrifuge users, said John Emmert, the electrical designer who helped Midwest with the panel, motor and drive design. "If the load in the bowl, for example, would be too heavy, the AC motor would enter a stall mode, rather than turning the bowl and breaking the shaft or blade assembly. Unlike competitors’ products that use gear motors which often break shafts and scraper blade assemblies under those loads, the electrics anticipate and prevent such an occurrence," Emmert noted.

To adjust the speed – and centrifugal force -- of the bowl for different types of process fluids, Midwest uses a call-out on a PLC built into the panel. The drive, in tandem with the PLC, gives Midwest the flexibility to customize the centrifuge for any kind of application.

At Rolls-Royce, the installation of the first CentraSep last April immediately began to remove up to 99 percent of the sub-micron fines generated from the first machine the centrifuge was hooked to, according to Pat Huser. "It’s run 24/7 ever since, requires zero maintenance – and the quality of the grinds have improved immensely, along with reducing as much as is possible what we send to the landfill." Both nickel and aluminum oxide particles are removed from the coolant and recycled.

This ability to create solid swarf and increase reclaim ability has helped Rolls-Royce meet its ISO 14001 goals for qualification and certification.

Such effective removal of particulate also extends fluid life dramatically. Rolls-Royce maintenance personnel were changing the 350 gallons of cutting oil every three months; however, 15 months since the centrifuge installation, the oil is still in use. "In oil, alone, we are saving $3,600 a year on just one grinder," said Huser. "Add in cost of the downtime and maintenance and paper filtration, and it was easy to project yearly savings of $59K through just the first centrifuge installation."

As an additional point of illustrating costs, Huser noted that the CentraSep is attached to one of the CNC grinders, while a second grinder has remained attached to the older, existing mechanical centrifuge (with a one-cubic-foot capacity). In the last year, the low-capacity centrifuge has had replacements of six motors, eight belts, and numerous bearings, he said. And the grinder with the CentraSep stays clean, while the other grinder needs to be de-swarfed about every three months.

Most importantly, the ability to maintain virtual particulate-free process fluids year-in-year-out reduces friction between tools and work surfaces so that the quality of parts produced is higher. "This centrifuge is at 8,000 hours and counting in a zinc-removal application, one of the toughest possible," said Jeff Beattey. "And its removing aluminum fines in a wire-drawing application where the oil is as viscous as 4,000 SSU. The filtering prevents problems, such as die impaction or streaking on the wire."

Midwest notes such filtration capabilities also will play a more critical role in helping processors meet their zero-discharge commitments. "Strategically, you capture the maximum quantity of any contamination at the point of origin," said Pat Skidmore, technical support manager for the company. "It’s smart business; you improve and extend the life of the process fluids; you pack the particulate as tightly as possible – and you minimize any discharge of this captured particulate into the waste treatment stream."

The in-line performance of the first CentraSep units in a host of very difficult applications have only reinforced Midwest’s decision to offer a lifetime guarantee with the centrifuge. Through the warranty, Midwest exchanges, on an annual basis, the entire rotor assembly – all mechanical parts except the motor.

"It’s a win-win," according to James Beattey. "Our commitment to customers is long term. We know they want clean fluids, and we know this product can provide that. It’s why we were so deliberate in choosing the word ‘revolutionary’ to describe this original design."

The ability to change-out the rotor assembly in record time also keeps filtration lines moving in customer’s plants without a hitch. "It’s eight bolts, the timing belt and air-line quick connects; the rotor exchange has been done in as little as three minutes and six seconds," said Skidmore.

Given the early receptivity to the OEM’s re-invention of this product, what’s next? "There are other new product ideas on our list waiting for our attention," said Jeff Beattey, "but we already know that increasing the capacity of this centrifuge line is a priority." Adding units that are able to process fluids from 150 - 225 gpm "is in our future," he noted. Sales prospects of the existing units are bright, too, he said, with Midwest predicting an increase of "several hundred percentage points per year over the next five years," for the CentraSep.

Success with the first unit at Rolls-Royce proved so dramatic that Pat Huser is expecting shipment of a second unit from Midwest soon. The second centrifuge will be dedicated to filtering fluid from a third grinding machine, he noted. Additionally, relocation of the cell is allowing Huser to consolidate a second grinder onto the original centrifuge. He said other Rolls-Royce plants are studying the way the Indianapolis facility has made these changes, reducing both the physical capacity the grinding cell requires, while simultaneously making it far more efficient and productive.

John Brown, 317-230-2000
john.W.Brown@rolls-royce.com

Jim Beattey
Midwest Engineered Products Corporation
5060 E. 62^nd St., Ste. 130
Indianapolis, IN 46220-5228
Ph: 800-258-0099; 317-257-2714
Jbeattey3@midwest1.com
www.separator.com

Becky Nethery, Manager, Marketing Communications
ABB Inc., Automation Technology Products Division
Drives & Power Electronics
16250 West Glendale Dr
New Berlin, WI 53151-2840
Tel: (262) 785-8363
becky.nethery@us.abb.com
http://www.abb-drives.com

Midwest Engineered Products was pleased to hear that Guardian Industries Corp. expects a lot from its equipment throughout its plants.

"Yes, we want everything! - to filter the water stream reaching the grinders, minimize new-water usage, and we want to remove more fines out of that stream," said the Senior Project Engineer at Guardian’s De Witt, Iowa, Float Glass facility, one of many Guardian plants worldwide. "And, operationally, we need to make this all simple – 24/7 automatic processing, with minimal maintenance requirements."

Installation of the new generation of centrifuges is a natural evolution for Guardian, as the company replaces units that wear out. The centrifuges being replaced are mostly two-motor units, with gears and clutches, and they are powered mechanically with chains/sprockets. These moving parts have meant that, historically, the units require three-to-four hours of maintenance per month to keep each unit operational, engineers said.

Uptime and machining/grinding within the glass tempering operation at the De Witt facility are critical. "It pays to focus on the obvious," said the engineering experts. "Water and the diamond wheels used to grind and edge the sheet glass are inseparable. Clean water equals faster grinding speed and eases your ability to maintain a high level of grinding quality."

To date, 10 of MEP’s centrifuges have been installed at various Guardian plants – both as retrofits and as new installations, and most on a turnkey basis. "The turnkey installation in De Witt took under three days and it has more than doubled our water-processing capacity. "Our uptime and throughput have increased, and the efficiency has improved dramatically, as well, meaning the centrifuge has increased the solidity of the swarf," engineers noted.

Most importantly, the ability to maintain particulate-free water year-in-year-out reduces friction between tools and work surfaces. "We’ve reduced our new-water consumption significantly, and we know there’s an increase in the life of the expensive diamond wheels we use," Guardian engineers noted.

Such filtration capabilities now play a critical role in helping processors meet their zero-discharge commitments, according to Midwest experts. "Strategically, you capture the maximum quantity of any contamination at the point of origin," they said. "It’s smart business; you improve and extend the life of the process fluids; you pack the particulate as tightly as possible – and you minimize any discharge of this captured particulate into the waste treatment stream."

For more information at Guardian Industries, contact:
Gayle Joseph
248-340-2109
gjoseph@guardian.com