Tech Update: Primo Power Transmission
The food industry puts heavy demands on motors and drives. The equipment has to survive in continual high humidity and washdown with chemicals, and it must not drop paint flakes or lubricant into the product. Today, food manufacturers also require the equipment to have a high performance rate but also to use less energy.
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.
Variable speed drivesVarying lines speeds maintains flexibility, accommodating variations in product consistency that require variations in processing time. It also helps to keep a line running despite minor breakdowns downstream, slowing things down until a stoppage can be cleared.
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.”
Motors with integral drivesIn food processing applications, VFDs require NEMA 4X enclosures or remote cabinets, sometimes in stainless. The plus with a NEMA 4X enclosure is that the controls are easily accessible—although sometimes accessible to people who shouldn’t touch them. VFDs in cabinets could be put some distance away. It’s safer from curious fingers, all the electronics are together, and you don’t need a NEMA 4X enclosure. But if the wires between the VFD and the motor are too long (beyond 1,000 feet) you can get some nasty electrical effects (the reflected wave effect); then you have to use a terminating device like an R-C Circuit (resistance-capacitance), which protects the motor, but increases costs.
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.
Energy efficiencyAs energy costs increase, there’s been a push to reduce energy usage in food manufacturing. According to NEMA, electric motors consume 10 to 25 times their purchase price in electricity each year. Much energy savings can come from high-horsepower motors that run continuously, especially under variable load.
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.
Drives and intelligenceMotor and drives can do more than just save money on energy. Many of today’s drives can be connected to a plant-wide information system, and, says McElhinny, a fair number of users are taking advantage of this, using the information from the drives to feed a network using batch process software, for example. “They will be tying in a closed-loop system to help measure the recipe consistency or the integrity of the recipe that they’re producing.” But, he says, the really big savings will come from using this information as an input to predictive and preventive maintenance programs. Proactive maintenance is much cheaper than unscheduled downtime. Companies are learning the value of level 3 vibration analysis, thermography, and oil analysis, bringing in consultants to train their people or perform their tasks. “If they can get extra capacity out of a line, that might mean the difference between having to build a completely new line or not having to spend millions of dollars on building a new line,” says McElhinny.
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.
This bearing’s for Bud
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