July/August 1992
Here are some guidelines for balancing the pros and cons of different types of scales for the scrap recycling industry.
Weight. In the scrap recycling industry, there's probably nothing quite as important. In fact, whether you're talking about cans, cars, or corrugated, buying and selling scrap commodities comes down to that one common denominator.
An accurate scale might even be called the cornerstone of a recycling business, so these instruments must be chosen carefully. One of the first basics scrap recyclers should consider in the shopping process, notes Bob Reese, a marketing manager at Fairbanks Scales (Meridian, Miss.), is that whenever a scale is used as the basis for a purchase or sale, the scales must be legal for trade.
According to the National Institute of Standards and Technology (NIST) (Gaithersburg, Md.), which publishes reference guidelines on which state laws governing commercial scales are patterned, to be considered legal for trade, a scale must be divided into 10,000 graduations and must be accurate within 0.1 percent of the displayed weight. For example, a legal-for-trade scale with a capacity to weigh loads of up to 100 tons would measure in 20-pound increments, and, if weighing a 50-ton load, would have to accurate within 100 pounds. (Although it doesn't take many 100-pound differences to add up to substantial quantities of scrap, Ron Cantwell, technical service manager for CMI Weighing Equipment [Oklahoma City], notes that losses and gains tend to average each other out.)
Many states supplement the NIST standards with additional specifications, and most require an official inspection and certification. Thus, if purchasing a scale for trade use, contact your state weights and measures (or comparable) department for specific legal criteria.
Electronics vs. Mechanicals
Perhaps the most controversial factor in scale selection is whether to purchase a mechanical or electronic instrument. Scales in the former category typically measure using a lever system that breaks down the "pull" of a load into a smaller, geometrically similar pull. This pull is connected to a dial or balance beam with a graduated poise that multiplies the smaller pull to display the weight of the actual load. Electronic scales, meanwhile, employ load cells—sensing devices operated by carbon-strain gauges that measure the resistance of attached metal as it bends under a load.
Each type of measurement control has its advantages and its advocates. Reese, for example, prefers mechanical scales and reports that about 60 percent of Fairbanks 's business is in mechanicals. "Electronic scales are a function of time," he says. "It's like, if you buy a television receiver today, 10 years from now, whether you've turned it on five times or 1,000 times, it's going to be out of date. New technology is going to have taken over." Mechanical scales, he says, "are a function of use. If you use them normally and take care of them, they will last you 40 or 50 years, and are as accurate or more accurate as an electronic scale." Electronic scales are more prone to electrical interference, Reese explains, and are more likely to have their weight thrown off by debris. Furthermore, electronic scales can be put out of commission during a power outage.
Reese also believes that mechanical scales are "beefier" than their mechanical counterparts. As proof of this assertion he tells the story of a quarry operation that handles 10 million tons of material a year and had to throw away its electronic steel deck scale after two years of use. "If it had been a mechanical scale, all they would have had to do would be to refurbish the levers." For this reason, companies like Weigh-Tronix (Fairmont, Minn.) are paying new attention to mechanicals after ignoring them for many years, notes Carol Carroll, who works in the scale company's advertising department.
Mechanical scales are often the only option when a scale must be installed in an area with no electrical hookup. (Battery-operated electronic scales are said to be just coming on the market.) In addition, some industries prefer mechanical scales, Cantwell says, because they can be used in remote applications and often can be moved from site to site.
What do users think? Bill Becker, vice president of Garland Steel (Garland, Texas), has traditionally purchased mechanical scales, but now has a decided preference for electronics. Although he says he's never had a problem with a mechanical scale, "Electronics are clearly the wave of the future and have been for the past 10 years," he notes. "They're quick and easy."
Garland recently bought a 70-foot, 135-ton electronic truck scale, a decision Becker says was based on the fact that the scale doesn't have moving parts, which means it should be less likely to wear out. "We wanted something maintenance- and hassle-free," he adds. "We have enough problems in our business without having to worry about the scale."
Cantwell backs Garland 's decision to go the electronic route. "For accuracy and long-term durability, electronic is the way to go," he says, claiming that less moving parts means less to wear. The downside, he admits, is that electronic scales tend to be more sensitive to moisture and slightly more expensive (though prices appear to be coming down). Still, he says, "Electronic scales can do a lot of things that mechanicals can't." For example, electronic scales can calculate weights quicker than mechanical scales and allow users to switch back and forth between pounds and kilograms at the touch of a button, he notes.
In addition, Cantwell points out, electronic scales can be accessorized with software, enabling them to release information to computers, printers, and LED- or LCD-display scoreboards. In fact, many scale manufacturers (as well as software companies) have developed special scale software just for the scrap recycling industry. In addition to generating scale tickets that reflect tare, gross, and net weights, such programs can calculate and print prices immediately, identify trucks and drivers, and tie into other accounting and operation management software.
For some of the best ingredients of both worlds, a handful of manufacturers are now making electromechanical scales, which use mechanical levers attached to a single electronic load cell instead of the traditional beam and poise or dial.
The Standards: Truck and Floor Scales
The final major consideration involved in any scale purchase is what type of scale to buy. For those rare customers who are unsure of the type of scale they need, Cantwell suggests that they think about the type and quantity of scrap they handle, how they handle it, and what their traffic patterns are like: Does the company do much nonferrous processing or is most of the scrap bulkier grades? Does the firm use forklifts to run material back and forth within the plant area or does it bring it all in on trucks?
Most scrap plants rely on two scales: a low-profile floor scale (also known as a pallet or deck scale) and a truck scale. Floor scales, which typically range in size from 3-by-3 feet to 8-by-7 feet, sell for about $2,000 and up and can vary in capacities between 5,000 and 20,000 pounds. These relatively low capacities mean the scales should be calibrated to measure more precise weight increments, and, thus, are used primarily to weigh more costly metals such as copper or aluminum, according to Cantwell. Garland Steel, in fact, uses a truck scale for 99 percent of its measurements, Becker says, but employs its floor scale "when we need more refined, definite weights."
On average, truck scales have capacities of about 100 tons, allowing them to weigh loads in pickup trucks, tractor-trailers, and every size vehicle in between. Scrap plants that move material via railroad often supplement their truck scales with a rail scale or use a combination rail/truck scale, the largest and most expensive scale made, manufacturers say. These big scales start at around $25,000 for a truck scale to more than $100,000 for a rail scale or rail/truck scale.
Truck Scale Specifics
Within the truck scale category are two basic installation types: pit or above ground. Pit installations are more popular than pitless designs, Reese says, because they do not need approach ramps and thus require less space for installation and truck maneuvering. Pit scales also are easier to keep clean of ice and snow, and may be the only choice in cold climates. Among the advantages of above-ground scales are their ability to be relocated with relatively lower foundation costs, Reese says.
Truck scale technology still in the works includes in-motion scales that will make it unnecessary for trucks to come to a complete stop to be weighed, Cantwell says.
In any case, truck scale buyers have a few other issues to factor in. Installation, for one thing, presents a whole other series of considerations. Although the scale vendor can often oversee the installation and site preparation, in some instances it may be necessary or cost-desirable to hire a separate contractor.
If an outside contractor is employed, it's important to ensure that the work is done in accordance with the manufacturer's specifications, Reese points out, noting that, with pit scales in particular, if the preparation does not meet scale design requirements, the scale will not operate properly, if at all. And regardless of who performs the site preparation and installation, a variety of jurisdiction-specific permits may be required.
Scale location is also a big factor, Cantwell says. "You want it to be easily accessible, with access plates or proper ground clearance so that cleaning it is not a problem." Dirt collects on scales from trucks, particularly in unpaved plants, he notes, so they need to be cleaned out periodically using a high-pressure hose.
Construction of a scale house is another important consideration in a truck scale purchase. All truck scales—whether mechanical or electronic, pit or pitless—need a scale house (often a small trailer) to protect the mechanisms of the indicators. Scale houses are usually built near the scale, but they can be remote, notes Reese, "provided that you have audio and visual communications at the scale." Fairbanks has worked with a gold refinery whose scale house was more than a mile from the scale, linked with closed circuit television and short haul modems.
Balancing Weighing Options
Other scales mentioned for use in the scrap recycling industry, although not as frequently as floor and truck scales, include belt, crane, and lift truck scales.
The first type, also known as conveyor scales, is designed for weighing things in motion. Used most often in the asphalt business (for blending applications when they need to mix and weigh things on the fly), belt scales have found a niche in recycling operations with shredders, Cantwell notes. At a price of about $8,000 to $10,000 each, these scales, he explains, allow a shredder operator to weigh material as it runs up the belt into a railcar, and can be especially helpful to those who do not have a rail scale.
Like belt scales, crane scales have seen limited use in the scrap industry, primarily because the lack of material uniformity can make precision weighing impossible, Becker says. Nevertheless, he notes, magnet cranes scales can be useful when loading a barge directly from a scrap pile.
Lift truck (or forklift) scales are being used more frequently in scrap recycling plants, but are rarely, if ever, legal for trade, and, thus, may simply be helpful as an approximate check on a reported weight. Still, notes Terry Dazey, director of advertising with Measurement Systems International (Seattle), which specializes in electronic crane and lift truck scales, lift truck scales can meet plenty of scrap plants' needs. Without a lift truck scale, he explains, "you have to lift a load with your lift truck, run it down the road to a platform scale in your warehouse, then run it over to another scale for shipping." With a lift truck scale, "you could go right over to the load, lift it up, and drive it directly to shipping, totally forgetting about that platform scale," he says. "Although it sounds like no big deal, take that extra five minutes, multiplied by how many times you do that a day, by how many times you do that a week, by how many times you do that a year, and you've got a lot of time, and time is money. So if you can eliminate a step in your process you're saving money right off the top."
—Beth Rogers, a Bethesda, Md.-based freelance writer
Here are some guidelines for balancing the pros and cons of different types of scales for the scrap recycling industry.