The use of stainless steel for motor and drive equipment in the food industry is on the upswing. Some years ago, coated iron and steel were the norm. A tough, white epoxy coating would keep corrosion at bay reasonably well, and could stand washdowns, at least for a while. Stainless was expensive and used only when necessary. When the price of stainless started to come down, according to Mark McElhinny, business manager of food and beverage industries for Rockwell Automation, regulations and company standards started to require it. For that reason McElhinny expects to see users moving to “stainless motors, stainless reducers, stainless bearings much quicker than they have in the past.” However, there are still plenty of epoxy-coated drives on the market, many with stainless-steel shafts.
Years ago, line or process speed variation required the use of a traction drive, a variable-pitch belt drive, or some other variable speed transmission between the motor and the drive. Then variable frequency drives (VFDs) came along, but they were big, expensive, and unreliable. In time they became smaller, more reliable, easier to use, and best of all, cheaper.
A VFD for a 20 hp motor used to be almost the size of a refrigerator, says John Thornton, marketing manager, Emerson Power Transmission; now it’s the size of a loaf of bread. As a result, VFDs have been replacing mechanical variable-speed drives for some time.
With persistent corporate downsizing, it’s no longer possible to assign a process engineer or electrician to set up and adjust drives. That means training plant maintenance and operations people to use the drive, and perhaps perform on-line changes of parameters like acceleration and deceleration times. For this reason VFDs must be simple to work with.
According to Dave Ballard, manager of engineering and marketing, SEW-Eurodrive, a VFD with the right features can improve the efficiency of a whole process. “OEMs,” he says, “are trying to get more productivity, more throughput with their machines without having to redesign them. They’re finding that there are many ways to increase the productivity of the machines and processes by just sitting back and evaluating the current dynamics of the machine.” Once the dynamics are really understood, he continues, it’s possible to tune it up with electronics, or maybe a new drive system.
But VFDs are not always the best way to go. The overall cost of the mechanical is still lower, according to Peter Feil, VP of sales and marketing, Stober Drives. On top of that, he says, mechanical drives are simpler to use than VFDs, and require fewer workers training to use them effectively. “The mechanical is very simple to use; you can use it where people have very little knowledge of electronics. They plug it in, hit a switch. It’s on/off, and then they can adjust the speed manually.”
The third alternative is to skip the enclosure altogether, and use a motor with an integral drive. These started showing up for general industrial applications a few years ago, and now NEMA 4X-rated units are becoming available. Much of the impetus behind them, says Stan Ho, product line manager at Rockwell Automation, comes from machine builders, who see integral drives as a way to minimize both costs and long cable runs. And this can mean real savings in installation, because all the control-to-motor wiring is done by the OEM, instead of on-site by electrical contractors.
Not everyone finds integral drives the best solution. While an integral drive may be a good deal for the OEM, says Walter Mashburn, executive vice president of sales, Sterling Electric, it may not be so good for the end user. “If the drive fails,” he points out, “you’ve got an entire motor and drive problem, as opposed to just a motor and then a control mounted on the wall. If one goes bad, then all goes bad.” That means more downtime, which is why he expects integral drives to be accepted more slowly by the food and beverage industry.
Motivation to save energy usage may depend on a plant’s location, says Mashburn. In California, for example, or New England, where peak electric rates can be $.25 per kWh, there’s more incentive to look for ways to save, he says. But in places like the South or the Pacific Northwest, with rates at six or eight cents per kWh, energy costs, he says, maybe less of a concern.In addition, food plants have a great number of small motors, many of which don’t run all the time. Here it’s more difficult to make the case for high-efficiency motors. And there can be another consideration, says Ballard. Many applications require motors to start and stop every few seconds as part of the normal machine cycle, and premium efficiency motors don’t always handle that kind of duty very well.
It’s a good idea, he says, to look beyond the motor. “If you’re trying to increase your overall efficiency, you can gain more by looking at the whole system,” Ballard says. He contrasts American and European practices in this area. “Their engineering practices have been more size for the load, don’t oversize motors, look at the overall system, cut out inefficient components to raise the efficiency of the overall system.”
Jan Lindholm, industry account manager for SEW-Eurodrive, says that a good place to start is with the mechanical transmission. “With a worm gear you have efficiencies of 50 to 85%,” he explains, “whereas the helical gearboxes are typically 94% to 97%.” Avoid any external transmissions, like timing belt or chains, Lindholm says, because with every external transmission “you lose about 10% of the efficiency.”
Feil concurs. “Many worm reducers are used in the food and beverage industry,” he says, “and they’re very inefficient.” A good gearbox, he maintains, can save energy because it can match the motor to the load properly.
But doing that depends on the sophistication of the company. “So much of our business is read and replace,” says Thornton. “The worm came down, by golly, guess what goes back up there?”
Awareness of the savings to be had in motor efficiency varies, says McElhinny, with some large bottlers being fully up to speed. Other areas, he says, are further behind, but there’s hope.
“Customers are becoming more educated about energy and how they can take advantage of energy conservation,” he says. Today food and beverage manufacturers can team with their suppliers to perform energy audits. According to McElhinny, suppliers can identify energy concerns, specify premium efficient motors, or specify control drive motor packages that really fit the application parameters.
Equipment designers have a big role to play in this area, as well, adds Stan Ho. The equipment must be more or less self-sufficient, he says, “and the accompanying literature and documentation must be very succinct: If you have this type of a problem, this is what you do. Then that swap-out or change-out or whatever you have to do has to be so simple that the non-degreed electrical engineer type person can do it.”
The food industry is moving with the times, adapting to changing regulations, paying some attention to energy conservation, and beginning to realize the benefits of tying motors and drives into plant-wide information systems.
Anheuser-Busch, like any beverage company, needs dependable equipment. The brewer required a bearing that would last 20,000 hours, maintenance-free, in washdown conditions on a packaging line. The company found its solution with the Rockwell Automation Dodge E-Z Kleen, polymer-housed, corrosion-resistant ball bearing with a premium lubricant, 65¿ setscrew locking system (SCEZ), and snap-on end closure
Known in the brewing world as the DODGE beverage bearing, the E-Z Kleen helps with sanitation. Its injection-molded design eliminates bacteria traps and uses an anti-microbial polymer that helps prevent bacterial and fungal growth.
For some of its washdown applications, Anheuser-Busch chose the DODGE beverage bearing with the concentric D-LOK design (DLEZ), which makes it easier to get the bearing on and off the shaft. Like the SCEZ insert, the DLEZ insert has corrosion-resistant plating on the inner and outer raceways. This is used in wet area conveyors feeding and taking away from the filler, pasteurizer, and rinser.
Emerson Power Transmission