SEPTEMBER/OCTOBER 2007
Onboard weighing devices can increase a scrapyard’s productivity, vendors say, by keeping track of inventory movement within the yard and better estimating the loads filling a container, truck, or railcar.
BY LYNN R. NOVELLI
A scrapyard can’t operate without a scale. Accurate weight measurement is essential for buying or selling scrap. Truck scales and railcar scales are the legal standard for those transactions, but other scales—those designed for forklifts, front-end loaders, and cranes—can make a significant contribution to the bottom line. “In the scrap industry … the more progressive companies are concerned about production, and that’s where onboard weighing systems can make a difference,” says the president of company that manufactures a full line of scrap industry scales.
Scrapyards can use onboard weighing systems throughout the inventory and production cycle. For incoming inventory that arrives in bundles or on pallets, “a scale on the loader or forklift makes it easy to check the weight quickly to verify the stated value of the shipment,” says a product manager with a large industrial scale manufacturer. During scrap processing, an onboard scale can track production and help equipment operators avoid overloading or overlifting, thus avoiding a safety hazard and potential damage to the loading device. The more sophisticated scales also can expedite inventory management by relaying weight and other information directly into the accounting system to confirm the receipt of material or to cross-check the reading of a truck scale. For outgoing materials, a loader or crane scale can help prevent costly overloading or underloading of railcars or trucks.
Onboard scales have a high degree of accuracy, with virtually no differences among the various brands. For loader and forklift scales, “the industry standard is plus or minus 1-percent accuracy,” one sales manager says. “Within that range, it depends on the material being transported.” For crane scales, the standard accuracy is 1 percent for a stationary load and 2 percent for a swinging load. They are not legal for trade in the United States, so they cannot entirely replace the truck, floor, or rail scale, but by taking on certain weighing tasks they can cut down on the traffic facing those always-busy devices.
Forklift Scales
Fewer trips to the floor scale—that’s the primary advantage of forklift scales, which help maintain productivity by providing onboard tracking of inventory while it’s being transported. Instead of interrupting production to line up at a floor scale to verify the weight of inventory the forklift is carrying, the operator simply checks the onboard scale for immediate feedback.
The most common type of forklift scale is a self-contained unit with a sensing module that attaches to the lifting cylinder and detects the hydraulic pressure, which is directly proportional to the weight. A Canadian manufacturer has come up with a different design, which uses pressure sensors built into special forks that replace the lift truck’s standard forks. The product the truck is lifting puts pressure on the two sensors on each fork, which measure the degree of compression and send that information to the processor, which calculates the weight.
Most forklift scales can weigh accurately with the forks in motion, but the tilt of the mast can affect the reading. Some manufacturers have engineered around this problem to measure weights accurately whether the mast is tilted forward or backward.
Depending on the brand, a forklift scale is either installed by a company technician or purchased as a do-it-yourself kit. For do-it-yourselfers, vendors recommend looking for a system with integrated cables for easier installation and greater portability.
Loader and Crane Scales
Scrapyards use most front-end loader and crane scales to facilitate the efficient loading of trucks and railcars so they don’t exceed legal weight limits. These devices can quickly pay for themselves, manufacturers say, by verifying the load weight of a vehicle before it leaves the yard without repeated trips across the truck or rail scale.
One scale company executive calculates the value of these weighing devices this way: About 15 percent of trucks or railcars are overloaded when a loader scale isn’t used, he says, requiring a reweigh and offloading the material. Figure “$1.25 per minute to operate the loader, times 15 minutes to offload, and that’s [nearly] $20 per overload. Multiply that times the 15 percent, and you can see that a loader scale system pays for itself pretty quickly.” Another company’s sales manager points out that “demurrage and overage fines are outrageous and can easily equal the cost of the scale.”
These scales also can improve productivity by preventing underloading. Drivers prefer to carry the maximum legal limit, and reaching that weight the first time avoids time-consuming reloading and reweighing.
A loader scale has one or two transducers tied into the machine’s hydraulic lift circuit to measure hydraulic pressure and an angle sensor that detects the angle of lift. The sensors send an electronic signal to the microprocessor control module in the cab, where the operator views the weight on a digital LCD screen.
The traditional design allows the operator to measure weight while lifting the bucket, but just as with forklift scales, lift angle can be a problem. Weighing at too low an angle means the pressure is not smooth and the weight will not be accurate; too high an angle can be a safety problem. Engine rpm, which varies during lifting, also affects accuracy.
Manufacturers have taken several different approaches to counteract these issues. Some calibrate their loader scales at a range of rpm. Others take multiple weight readings at a single angle and electronically compile them to yield the result. And other loader scales sound an alarm to warn the operator if uneven surfaces or speeds are affecting the weight accuracy.
The two basic varieties of crane scales in the scrap industry differ in their load-cell technologies. Weighing systems based on shear force use a load-sensing pin installed between the yoke and the attachment. Those based on strain-gauge technology use a resistor bonded to a steel plate that measures the change in resistance under a load. Crane scales usually offer a control module in the cab that displays the weight or a transceiver for viewing weights remotely.
High-Tech Options
Several manufacturers offer a basic onboard scale that is designed strictly to weigh the load it’s carrying. These models have the lowest price tag, starting at about $1,000 for a basic front-end loader scale.
More sophisticated models have data management capabilities that allow companies to track loads by customer, product, job number, truck, and multiple other possibilities. Today’s top systems can track up to 1,000 different customers, 50 operators, and hundreds of products and projects. Prices on these high-tech systems start at around $5,000 and go as high as $20,000, depending on weight capacity and data management capabilities.
Systems with such data collection capabilities vary in the methods they use to get the data out of the system. Methods include printing a ticket directly from the scale, having an onboard slot for a memory chip or stick that users can transfer to a PC via a USB port, or real-time communication with a yard management system, in which a modem attached to one or more scales relays weight and inventory management information during operation. Such systems can centralize data management for companies with multiple locations.
Some scales can export their data as Excel files, which can feed directly into a corporate accounting or management program, a manufacturer explains. “There’s no more typing necessary. It takes the operator out of the process because it’s all done electronically, and it speeds the process control.”
Manufacturers whose products provide extensive data management capabilities say it enhances productivity, but others are skeptical. “Data collection can be too much for the operator to have to do,” one vendor maintains. “You can have information overload.” Because these scales are not legal for trade, he says, “it’s not possible to bill with the information, so why add all those complexities? When you keep the system simple, it’s more of a guarantee that the operator is going to use it.” His loader scale weighs individual and total forklift loads and stores up to 10 user-defined cumulative totals in memory. “It’s not the most technologically advanced scale available,” he says, “but in my experience it is sufficient for 99 percent of applications.”
A different technology innovation is gaining ground, however: Wireless technology is replacing conventional systems that use wires to connect the transducers with the readout module. “The advantage of a wireless system is that it eliminates the cabling that often causes failure,” one scale company owner explains. “During production, wiring often is snapped or cut by jagged pieces of metal.”
Wireless has its own drawbacks, though, a crane scale manufacturer notes. It “can be high-maintenance and expensive to maintain or repair. There aren’t any cables to break, but the transmitter can still get whacked.” Most manufacturers offer wireless technology as an upgrade or add-on for as much as $2,500 more than a wired system.
Durable Goods
Onboard weighing systems are built to last. Standard warranties are two to three years; at least one manufacturer offers a five-year warranty on its scales. “The components don’t wear out or give up. These [scales] will go for years,” one crane scale maker says.
Decreased accuracy is more of a problem than actual component failure, vendors say. Vibration is the most common cause of inaccuracy in forklift scales, a product manager explains. “Forklifts operate under tough conditions, on hard surfaces that can cause the mountings to loosen,” he says. To prevent problems, he recommends a 30-day maintenance inspection program that includes tightening all the fasteners. To speed that process, he advises buyers to look for a model that anchors the bracket in place with as few fasteners as possible.
For loaders, a scale company vice president advises recalibrating the scale when the seasons change to adjust for the effect of temperature on material weights. Crane scales usually require recalibration only if the machine goes through a major trauma, such as a tip-over or a hurricane. Other maintenance requirements on these devices are minimal, vendors say. The readout screen in the cab will most likely need periodic cleaning to keep it free of grime.
Despite these scales’ generally trouble-free lifespans, it’s still important to consider the availability of service and parts in the buying decision. Most scale manufacturers have a wide distribution and service network, but they don’t all cover every state or region.
A Weighty Decision
Scale manufacturers agree that their products basically are very similar in quality, with the major differences being the additional features each offers. The buyer must determine which of these are important and how much of a premium he or she is willing to pay to have them.
In some cases, the size and capacity of the base machine will need to factor into a purchasing decision. Certain manufacturers offer different models based on the base machine’s ITA class. The advantage of this approach, they say, is that scales designed for heavier-duty applications are more robust. Vendors typically sell crane scales based on the weight the cranes are lifting, and several will customize their scale to the buyer’s specifications. Other scales are one-size-fits-all, so size or capacity of the base machine does not matter in scale selection.
Scale Innovations
To gain a competitive edge, scale manufacturers are refining their products to be safer, more precise, easier to use, and capable of even more levels of data management. Loader scale makers are focusing a lot of attention on improving weighing accuracy during motion. One manufacturer has developed a system that closes the hydraulics before the sensors take the pressure measurement reading. “This eliminates concern about changes in rpm, oil viscosity, and movement of the machine so that the scale is more accurate in all conditions,” the company owner explains. Further, he says, “this design lessens the impact that the operator has on the accuracy because the scale now compensates for these changing factors instead of relying on the operator to recognize and compensate for them.” Other manufacturers say weighing while the boom is in motion causes less wear on the lift cylinders, however.
For greater safety, one manufacturer offers an alarm that sounds when the sensor detects an overload. “The higher a load goes, the less safe it is,” the company owner explains. “A sensor detects when the weight of the load exceeds the maximum for that lift height.”
As several companies increase their scales’ data management capabilities—even adding features that are specific to certain industries and applications—at least one manufacturer is doing the opposite: The company plans to introduce a no-frills version of its most popular loader scale. As the company’s vice president puts it, “The less-expensive control head will meet the needs of customers who want a high-quality scale that simply weighs.”
Lynn R. Novelli is a writer based in Russell, Ohio.
Onboard weighing devices can increase a scrapyard’s productivity, vendors say, by keeping track of inventory movement within the yard and better estimating the loads filling a container, truck, or railcar.