Power Protection

November 1, 2006
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Stainless-steel construction for motors, gearboxes and other power-transmission elements is a growing trend, but other refinements in the technology are being developed and debated, as well.

Flour dust in bakeries can be as destructive to motors as high-pressure washdown in meat plants, forcing equipment manufacturers to upgrade protection with stainless steel and other fabrications. Source: Dodge/Reliance.


The harsh realities of the production environment and the ongoing revolution in electronics are driving major changes in the power transmission components that drive food and beverage plants.

High-pressure washdowns and caustic cleaners have become the norm in meat and poultry operations, making stainless steel the fabrication material of choice for motors, gearboxes and other elements of power transmission. At the same time, manufacturers are weighing the pluses and minuses of decentralized controls for their power systems. Placing controls closer to machinery reduces wiring costs, proponents argue, but it also requires protection against dirt, dust and high-pressure washdowns that can short out circuitry and bring machines to a screeching halt.

Stainless steel motors, reducers and gearboxes were a curiosity a decade ago. Today, they are emerging as the standard in some segments of the industry. Suppliers consistently cite poultry processors as the stainless-steel standard bearer. Virtually every motor manufacturer offers stainless-clad versions of their units now, with stainless gears entering the market to complement them.

"Nine years ago, there was one guy building stainless-steel motors for pharmaceutical applications," recalls Walter E. Mashburn, president of Sterling Electric Inc., Dallas. White epoxy paint was the solution of choice in food and beverage plants where sanitation standards were being raised. As high-pressure washdown and caustic cleaners became more prevalent, paint chipping and flaking emerged as a concern, along with rusting of exposed metal parts. Consequently, more food manufacturers began specifying stainless motors, driving down the higher price they commanded. "Today's stainless motors come at a 20%-25% premium, maybe 50% for the biggest sizes," says Mashburn, "but they used to be 4-6 times more costly." Some price differential will always exist, he adds, because of the slower cutting speeds required when machining stainless steel.

High-pressure washdowns are the rule in today's meat plants and poultry facilities, creating a growing demand for all-stainless construction in motors, gearboxes and other power transmission components. Source: SEW Eurodrive.
Grafton, WI-based Leeson Electric lays claim to the industry's first stainless DC motor, expanding a line that includes three grades of stainless construction. "We're heavy into the poultry segment, and a lot of those processors are insisting on stainless steel," explains Product Manager Chris Medinger. Leeson's top-end stainless DC motor premiered a year ago and features all-stainless exterior components, laser- etched nameplates and Viton polymer sealing components. Three levels of stainless steel motors are assembled by Leeson, with the premium end suitable for pharmaceutical production. In recent years, the company has invested in the tooling necessary to fabricate stainless steel gearboxes.

Gearboxes were the last holdout for painted surfaces in food plant's power transmission infrastructure, observes George Tedesco, product manager at Buffalo, NY's Peerless-Winsmith Inc. "Four years ago, only a handful of us even offered stainless steel gearboxes," he says. Today, virtually every supplier offers at least a limited selection.

Unfortunately, wider use of stainless gearboxes won't drive down costs to the degree volume has lowered prices for stainless motors, Tedesco says. "The gearbox is a cast product, and it's a whole different technology to fabricate than a motor. The housing can be 35 percent of the gearbox's cost, and that isn't going to change with higher volumes."

High costs have caused some food companies to consider alternative technology. "In extreme caustic environments, there can be failures with epoxy coatings, and for those environments, we have stainless steel solutions," according to John Chi, product manager-enclosed gearing at Boston Gear's Charlotte, NC, production facility. "For those who don't have a long time horizon for the equipment, our SBK treatment is a lower-cost alternative."

Particles of 316 stainless impregnate an epoxy coating and form a chemical matrix on a steel surface. Boston Gear's epoxy solution was introduced two years ago, and some users swear by it. Darrell Kahler, assistant plant manager at Henningsen Foods Inc.'s David City, NE, egg processing facility, reports the coating has withstood high-pressure washdowns "and the occasional assault from CIP solutions" since the facility began using it on gearboxes.

All-stainless gear reducers to complement stainless steel motors are becoming more prevalent to meet food processors' demands for washdown-resistant power components. O-rings for a positive seal against moisture and a Viton double-lip seal on the output shaft are among the features on Leeson's 316-grade cast housing. Source: Leeson Electric.

Upgrading premium grade

Stainless steel construction isn't an option with the latest advancement in premium-rated motors to bear the NEMA (National Electrical Manufacturers Association) seal of approval. Premium grade kicks in at 1 HP, leaving out the millions of fractional horsepower motors powering conveyors in food and beverage plants. Nonetheless, plenty of big jobs are done by low-voltage motors: 70 1 HP motors roll the 93,600-sq.-ft. playing surface weighing 6,000 tons inside and out of the Phoenix Cardinals new stadium in Glendale, AZ, for example.

Premium grade was created in response to the federal Energy Policy Act of 1992, which mandated the creation of a high-efficiency alternative to three-phase induction motors by 1997. Motor manufacturers have found power efficiency to be a tough sell, though educational programs such as Motor Decisions Matter (www.motorsmatter.org), which helps manufacturers calculate the financial savings, are starting to pay off. The installed base of NEMA premium motors represents 10%-15% of the total US market now, calculates John Caroff, marketing manager with Siemens Energy & Automation Inc.'s low-voltage AC motor group in Norwood, OH.

Penetration should increase as the premium units get better. In February, Siemens introduced an upgrade on premium motors in the 1-20 HP range, with plans to extend the line to 400 HP units. A die-cast copper rotor replaces the typical aluminum rotor. Copper greatly enhances electrical conductivity while also making the motors much easier to balance and eliminating the air pockets or voids that are common in aluminum conduction bars and end rings. Longer windings in a comparably sized frame and better heat dissipation are other technical improvements.

"These motors run cooler, have better balance and are built better, with more mechanical features," says Caroff. "They should survive longer and require less maintenance, but it's difficult to quantify those advantages at this point."

Cumulative design improvements in multiple areas add up to efficiency gains that feed off each other, observes Chris Spees, food industry manager and a mechanical engineer at Rockwell Automation's Dodge and Reliance Electric divisions in Greenville, SC. "A more efficient motor runs cooler, which means you can use a smaller fan, which translates into even more efficiencies," he notes. Rockwell also is part of the Motor Decisions Matter initiative, though it is focusing on large industrial motors of 750 HP and better for super-conducting technology. For small motors, variable frequency drives offer a faster payback than state-of-the-art fabrication, Spees believes. Investments in sealed bearings with automated lubrication systems also are dollars well spent, he suggests.

Heat management is an issue with both mechanical and electronic power transmission. A differential drive on a new servo motor/control combination from Bosch Group's Rexroth Corp. in Hoffman Estates, IL, uses the motor casing as the heat sink to reduce the overall unit's size. "We suck the heat from the drive to cool the controls," according to Rami Al-Ashqar, product manager-Indra drives. Other manufacturers have put the drives on the back of the servo and added a fan, but that extends the length of the unit, "and you never want to add length to the motor," Al-Ashqar cautions.

Piggybacking the controls on the motor adds about 2 inches to the unit's profile, he estimates, but vertical space is less an issue than length in power systems. The payoff is a 50 percent reduction in cabling. If the drives are in a central cabinet, two cables must run to each motor on the machine. By putting the servo and drive together, "you're cutting half of the cable out of the picture, reducing assembly time and installation cost," he points out. When servos are daisy-chained together, control-cabinet space requirements are sharply reduced.

The negative relationship between electricity and water largely limits the role of electronic motors and drives to food plants' packaging areas, though manufacturers like Rexroth are trying to make their power systems more washdown friendly. Al-Ashgar says Steelite point, which is similar to Boston Gear's epoxy-and-stainless solution, is applied on request. "The need is there," he says.

Copper replaces aluminum in rotor construction of Siemen's new advanced NEMA premium motors, which deliver higher horsepower than conventional premium motors thanks to greater conductivity. Source: Siemens Energy & Automation Inc.
Daisy-chained drives also are an option with new flexible motion controllers from Omron Electronics. The FQMi series can be daisy chained to the drive or plugged into a communications network. Either way, the motors are beginning to make inroads in food-plant conveying, according to Carlos Melo, motion control manager at the Schaumburg, IL-based firm.

Grupo Bimbo recently deployed Omron's system in conveyors running in a Mexico City bakery. "The big problem in central drives with interconnected sprockets and shafts is that, if the chain or sprocket breaks, the whole line goes down," says Melo. "By decentralizing the system with a lot of small, compact servos, a failure is isolated and can be quickly fixed by debolting the broken component and replacing it." If continuous operation is critical, two compact motors served by one control box can be deployed for redundancy.

Decentralized control is a core concept at SEW Eurodrive, which plays in both the electronic and mechanical power ponds. The concept is particularly relevant to food and beverage plants with extensive conveying systems, points out Chris Wood, industry account manager-food & beverage for Lyman, SC-based SEW Eurodrive. "When drives are in a centralized panel, installation cost in a large facility is just phenomenal," he says. Electrical cabling and testing is labor intensive and time consuming. SEW's system requires three wires running from the cabinet to the first drive, with additional motors and drives daisy chained to it.

To cope with high-pressure washdowns, SEW offers an IP-69-rated enclosure as part of its new modular MOVIFIT series. A European standard, IP 69 exceeds NEMA 4X testing protocols, according to Wood. AC induction motors with variable speed control are housed in a single unit, which is coated with a surface treatment that repels liquid and stands up to aggressive detergents. A servo version of the drives will debut next year, Wood says.

The jury is still out on decentralized vs. central controls, Dodge/Reliance's Spees says. "Decentralized technology migrated to food & beverage manufacturing from industries such as automotive," he says, "but even they have gone back and forth on which is the best approach. We can do both."

Frank Custis professes indifference to the debate. "Do you really need centralized controls? We don't think it's necessary, but if that's what you want, it doesn't matter to us; we make drives, that's it," shrugs Custis, sales & marketing manager-electronics for Chambersburg, PA-based TB Wood's Inc. The company recently overhauled its electronic drives, including the incorporation of an IP 66-rated enclosure, which also exceeds NEMA 4X standards. "Our IP 66 can be submerged; we just don't tell anyone to submerge it," he jokes.

TB Wood's replaced its WFC and XFC series AC inverters with the E-trAC X4 AC drive in May. "The XFC had been around since 1991, and that's pretty old for an inverter line," allows Custis. Heat management from an enclosed drive was a central engineering consideration in the overhaul, which also takes advantage of advances in chip technology and switching devices. "We design and manufacture in the United States, so we have to do a smarter job of manufacturing our products and keep labor content out of the circuitry," he says. Minimizing end-user training was a consideration, as well, and that is making X4 "a back-door champion in a lot of maintenance engineering departments," he adds.

Twenty years ago, electronic drives represented 2% of TB Wood's business; today, it's 40%, according to Custis. Regardless of whether a manufacturer relies on mechanical or electronic power transmission, the expectation is that the system will perform while subjected to flour dust or water spray, without compromising the safety of the product. Whatever the specific requirements of a particular food or beverage plant, power transmission specialists have a range of solutions.

For more information:

John Chi, Boston Gear, 704-588-5610, john.chi@bostongear.com

Chris Spees, Dodge, 864-281-2486

Chris Medinger, Leeson Electric, 262-387-5410, chris.medinger@leeson.com

Carlos Melo, Omron Electronics, 847-884-7057, carlos.melo@omron.com

George Tedesco, Peerless-Winsmith Inc., 716-592-9310, tedesco@winsmith.com

Chris Wood, SEW Eurodrive, 804-740-2269, cwood@seweurodrive.com

John Caroff, Siemens Energy & Automation Inc., 513-841-3100, john.caroff@siemens.com

Walter E. Mashburn, Sterling Electric Inc., 800-866-7973, wern@sterlingelectric.com

Frank Custis, TB Wood's Inc., 717-267-2900, fcustis@tbwoods.com

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