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Electromagnetic Feeder Provides Controlled, Consistent Feeding of Fine Powdered Metals to Batch Screeners

February 12, 2010

Equipment with components that often operate in harsh conditions gives rise to shortened working life, high maintenance cost, and increased downtime. A multitude of factors contribute to premature component malfunction, including heat, abrasion, corrosion, erosion, and galling.

Restoring the component back to peak working condition often requires the application of wear- and corrosion-resistant alloys, which significantly increase the resistance to extreme industrial environments. Deloro Stellite produces its own proprietary metal alloys from cobalt and nickel. These alloys have optimum metallurgical and physical properties ideally suited to solving wear problems of many components commonly found in the oil and gas, power generation, aerospace, mining, automotive, and agriculture industries, among others.

Screening for Fine Powdered Metals

Based in Goshen, IN, the Deloro Stellite Div. purchases raw materials like cobalt and atomizes the material into a fine powder between 80 and 325 mesh, or 180 to 45 µm, according to Nate Tallman, Deloro Stellite screening process engineer. The fine powdered metal is either used by Stellite’s hard-surfacing operation or packaged and sold to the company’s extensive customer base. However, before the cobalt-based powder gets to the packaging point, the material first flows through a series of screeners used in gradation.

“Our customers want certain sizes of powder, depending upon the application,” says Tallman. “Some want the powder to be very fine, while others want powder that is a little coarser. The powder is passed through screeners with various opening sizes to get the gradation the customer is requesting. Properly screened powder will neither puff nor surge during the coating process, nor will the powder coagulate, causing feed lines to clog. When you spray that powder, you want a near blemish-free surface; that is important to our customers.”

Stellite was using an older feeder system to convey the powdered metal from small hoppers to the screeners. Because the flow rate could not be precisely controlled, the powder was flooding the screeners, causing inconsistent gradation and wasting valuable product. “When you have a ton of powder resting on top of the screeners, you will get an inconsistent product. This affects your efficiency,” Tallman explains. “We needed to make a major improvement in the consistency of flow rate with our feeders.”

Flow Control Solved

Searching for a solution, Deloro Stellite turned to Eriez, an Erie, PA-based company that provides advanced technology for magnetic, vibratory, and  inspection applications. Deloro Stellite ordered several Eriez Model HD “High Deflection” feeders that are designed to handle powders that normally could not be fed with a standard electromagnetic feeder. Feed rates of up to 80 ft/min are achievable with some materials. The lower operating frequency combined with higher deflection of up to 3/16 in. makes the HD feeder ideal for handling fine powders.

Each HD 36C feeder was installed with a 5-in. wide × 24-in. long stainless-steel tray complete with quick-release cover. Another important component was the Model G30 solid-state control that can vary the feed rate from zero to 100 percent. A deflection monitor was mounted to the feeder tray that provides continuous feedback of tray deflection back to the control. The G30 control monitors the tray deflection to ensure precise control of bulk materials is maintained. The control is housed in an NEMA 12 type enclosure to ensure trouble-free service.

The constant feed rate system allows a Deloro Stellite operator to set the feed rate at the beginning and the control system automatically compensates for the changes in head load and any voltage fluctuations during the production run.

“The head load on the feeder drastically changes as the hopper empties,” Tallman says. “When the hopper gets close to empty, our older feeders would not adjust, so the powder would feed faster as the hopper emptied. The HD feeders adjust for that head pressure at the bottom of the hopper, so there is a more constant feed rate.”

“Our guys can easily change the amplitude and feed rate based on what type of material we are running. The adjustment is pretty easy. The Eriez control unit is the one component that allows us to have a constant, efficient flow rate.”

The quick-release cover and ease of cleaning means Deloro Stellite can run more than one powdered metal through the production process depending upon the customer order. The cover can be removed without tools for quicker access to the tray.

“We run two to three different powders per day and can’t have any contamination between the powders, so we need a system that is easy to clean out,” Tallman says. “The Eriez feeders have a cover that’s easy to change and clean with a standard vacuum hose and brush.”

Eriez’ magnetic separation, metal detection,  x-ray, materials feeding, screening, conveying, and controlling equipment has application in  the process, plastics, metalworking, packaging,  recycling, mining, aggregate, and textile industries. For more information, visit www.eriez.com.

80595.tifHD Series feeders are designed to handle fine powders and leafy products that normally could not be fed
 
80596.tifHD 36C feeders are completely enclosed so the drive element is protected against damage or decreased efficiency due to contamination by moisture and foreign materials.