Equipment Focus: Truck Scales

Pit or aboveground installation? Concrete or steel deck? Electric or hydraulic load cells? These and other weighty decisions face buyers of truck scales for scrapyards.

By Jim Fowler

The purchase of a full-length truck scale is not a decision to take lightly. After all, as one vendor puts it, “The scale is a scrap dealer’s cash register. It needs to be the best.” Scrap processors must consider many different factors, among them the maximum length and weight of customers’ trucks, the current and expected volume of truck traffic, and the space available for a scale and scale house. The answers to such questions, along with a site visit, will help scale manufacturers or scale dealers analyze and understand a yard’s needs and make a recommendation.

Government Mandates
Scale professionals can lead scrap processors through the ins and outs of the federal, state, and local government regulations that dictate many aspects of commercial scale use. For most, the starting point is the National Institute of Standards and Technology’s Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, the bible of the scale industry. Updated annually, the handbook—also known as H-44—is available online at ts.nist.gov/ts/htdocs/230/235/pubs.htm. 
   “H-44 dictates all federal specifications for the installation and operation of truck scales used for trade purposes and also covers user requirements—the standards a user must follow,” one scale manufacturer explains. For example, a legal-for-trade scale most likely needs to be certified by the National Type Evaluation Program, which ensures it meets H-44 requirements. 
   H-44 isn’t necessarily the final word, though. Some states and local jurisdictions have their own standards and certification processes for scales, which might be tougher or more lenient than the federal standards. Potential scale purchasers should check with their local weights and measures department for the relevant requirements. (The National Conference on Weights and Measures lists most state departments on its Web site, www.ncwm.net/state.) “When you are considering a new scale for your yard, get the state weights and measures inspector involved from the start,” one scale manufacturer recommends. “The inspector can be your best friend, or he has the authority to ‘red tag,’ or shut your weighing operation down.”
   Local authorities also might have zoning requirements pertaining to scales, and local regulations vary as to whether scale construction and installation requires a building permit.

Above or Below Ground?
Truck scales come in two basic types: pit scales, which are mounted flush with grade level, and aboveground scales, which are 16 to 20 inches above grade level. Which type do you need? Consider the following:
   Available Space. A typical 18-wheel tractor-trailer is 60 feet long and 8 feet wide and would require a scale 70 feet long and 10 feet wide. (Per H-44, the scale must hold the entire truck at one time.) Add to that the legally mandated space required for trucks to enter and exit the scale. “It’s safe to say that with a 70-foot aboveground scale [the size most commonly installed in the scrap industry today], you would need 140 feet of real estate,” one manufacturer says. “That’s 35 feet for the ramp and entrance up to the scale, 35 feet for the exit and ramp to leave the scale, plus 70 feet for the scale.” In contrast, he says, “a 70-foot pit scale only requires an additional 20 feet—10 for entrance and 10 for exit.” Keep in mind that local requirements for the length, width, and slope of approaches to a scale might differ from those national requirements.
   Calculations should leave space near the scale for a scale house, too. From the scale house, “the scale operator should be able to identify trucks and drivers, communicate with drivers, ensure that the entire truck is on the scale, control the traffic flow, and examine the truck’s payload,” one manufacturer explains. The scale house also should “accommodate all peripheral equipment needed, such as a computer, printer, indicator, and AC power,” he adds.
   A scale professional can help plot the scale’s location to best accommodate a particular yard’s needs. Because traffic flow within the yard, to and from the scale, is a major consideration, one vendor suggests that this is a “good time to consult your fleet manager or truck drivers to ensure your plans are functional solutions for all parties involved.” 
   Despite the greater space requirements, manufacturers generally concur that aboveground scales are the most prevalent in scrapyards today. Still, “there will always be some instances where pit scales actually are a better 
solution,” one manufacturer points out—“conditions such as overhead obstructions, height restrictions, or not enough real estate to install an aboveground scale.”
   Durability. One manufacturer asserts that pit scales tend to last almost twice as long as aboveground scales. “An aboveground scale typically lasts seven to 20 years,” he says. “The big difference is that virtually all pit scales have concrete decks, which are a superior surface.” Further, he says, “a pit scale has a more massive understructure than
an aboveground scale [because above ground] you can only put so much steel in the 16- to 20-inch height you have to work with.”
   The two types of scales have other structural differences as well, the manufacturer says. “In a pit scale installation, you’re typically working with 24-inch I-beams, not 9- to 10-inch I-beams [that] are used in an aboveground scale,” he says. “On top of the 24-inch I-beams you’ve got 6 inches of structural channel that are part of the concrete deck. As a result, you have a more massive structure because you’ve got all of the depth of the pit to work with.
   “More steel or thicker steel in your deck means a stronger weighbridge,” which means less fatigue, and fatigue is what causes the scale to wear out, he says. “Aboveground scales have to be replaced because, ultimately, the entire scale will fatigue from the trucks running over it.”
   One way to judge the amount of steel is to compare the scales’ shipping weights, one vendor says. A lighter weight is less expensive, but it also might mean less steel. “Keep in mind that a heavier scale will have more longevity,” he says.
   Buyers should ask how manufacturers protect scale components in harsh applications to keep out moisture and keep cables from being cut by pieces of scrap that get shoved under an aboveground scale, one vendor suggests. 
   Water is a particular concern for pit scales, another notes. “You have to maintain them and not allow them to fill up with water,” he says. One Midwestern scale dealer says the water issue is what gives aboveground scales the edge in durability. “Aboveground scales last longer because pit scales always feel the moisture and never dry out, while wind flows underneath aboveground scales and dries them out. Although you can see the deterioration on an aboveground scale, it’s a lot slower than [deterioration on] a pit scale.”
   Maintenance. That dealer, who no longer installs pit scales in scrapyards, says he believes aboveground scales also have become more prevalent because of OSHA requirements such as confined-space rules. “You have to have two people to work on a pit scale,” he notes. “One is in the pit doing maintenance or repairs, and the other is controlling the lifeline. With aboveground scales, one person can handle it, and it’s a safer system to service.”
   Price. Pit scales tend to be more expensive because of the installation and construction expenses, but “if you amortize the cost of a pit scale over its expected life, its cost is half that of an aboveground scale,” one vendor says. 
   To get the best picture of price, “look for someone in the industry who is using the kind of scale you’re considering,” one vendor recommends. “Find out how it has worked for them. Ask what kind of response and support they’ve gotten from the manufacturer and/or dealer. These are crucial elements of the cost of ownership. Look at competing products and then run the numbers. You’ll often find the cost differential is fractions of a cent per truck over the life of the scale.”
   Ultimately, recyclers should ask a lot of questions, consider their environment, and review the pros and cons of each type of scale before deciding. 

Additional Factors
Beyond the aboveground-versus-pit decision, truck-scale purchasers must sort out numerous other variables. 
   Capacity. Two measures of capacity weigh into a scale purchase. First is scale capacity, the ultimate weight the scale can bear. Though a truck’s typical legal highway weight limit is 80,000 pounds, a yard that receives specially permitted trucks or off-road trucks that haul heavier loads will need a scale capable of meeting those needs.
   Manufacturers also must rate their scales based on concentrated load capacity, as defined in H-44. CLC is a rating of the strength of the weighbridge: The stronger the weighbridge, the less it will exhibit structural fatigue. Scale professionals can determine the correct CLC rating for a yard’s scale based on the number of trucks per day and their weight. For example, the recommended CLC for an operation that weighs up to 50 trucks a day is 60,000 to 80,000 pounds; 50 to 150 trucks is 80,000 to 90,000 pounds.
Scale professionals can help buyers figure out the correct scale capacity and CLC for their scrapyards, taking into consideration both present requirements and projected future growth.
   Deck Material. The deck, the surface the truck drives on, can be made of concrete or steel. Each has its pros and cons. Steel decks are more prevalent today because they are less expensive and faster to install, according to one manufacturer. Concrete takes 21 to 28 days to cure after being poured into the scale modules. Precast concrete modules can eliminate the curing time, but they greatly increase shipping costs. 
   Concrete deck advocates cite benefits such as long wear and good traction. “When drivers get out of their trucks on the scale, 90 percent of the fatalities are caused by slipping on the steel deck,” one scale dealer notes. (Some scale technology allows drivers to transmit information to the scale from within the truck, reducing the risk of a slip or fall on the scale deck.)
   Moreover, steel decks have “low inertia and low resistance to lateral forces, which increase wear on moving parts, while concrete decks have high inertia and high resistance to lateral forces, which reduce wear of moving parts,” one manufacturer says. On the other hand, steel decks are easily moved and can be repaired if the structure is damaged. 
   Load Cell Technology. Load cells are the heart of the scale’s ability to weigh. Electronic load cells, which have been in existence for about 25 years, are the most prevalent type in scrapyards today. An older, less extensively used technology employs hydraulic load cells.
   Manufacturers hold strong opinions about the advantages and disadvantages of each, and they are quick to suggest that potential purchasers study the subject closely and get references to talk about their experiences using their scales and their competitors’ scales. In particular, they recommend asking about calibration, reliability, durability, diagnostics, serviceability, and operation in harsh environments. If a manufacturer states that its load cells are “hermetically sealed,” find out what exactly that means. 
   Also, scale manufacturers use varying techniques to change the analog load-cell signal to digital before it goes to the scale indicator. Purchasers should ask about the technique each manufacturer uses to determine which approach will work best for their facility.
   Data Management. Scales can provide a lot more information than weight. How a scrapyard can use that information and incorporate it into its accounting system is something else to consider when comparing products. “Most scrap dealers are filling out scale tickets by hand and adding them up at the end of the day,” says a representative of one company that produces scale software. In contrast, buyers who approach data interfacing correctly at the outset can create a seamless system, one manufacturer says. “You export the weighing data in a format that you can pull right into your accounting package, so you don’t have to touch the data two or three times. You pull it in to do your invoicing—it can be that clean.”
   How worthwhile is that software investment? “Run the numbers on what it costs to have someone add up those tickets at the end of the day and key that data into your accounting systems,” the vendor suggests. “The return on 
investment on a piece of transaction software is incredible.”
   Construction. Some scale manufacturers and some dealers offer construction services, or purchasers can hire their own contractors. Consider the cost as well as the experience of the contractor in scale foundation construction.
When construction is complete and the scale is installed, it will have to be tested and calibrated. Then, depending on the locale, someone from the local weights and measures department or the department’s designee will certify that the scale meets the H-44 requirements, making the scale legal for trade. 
   Buying and installing a new scale is a heavy assignment. Keep in mind, though, that if you take shortcuts in determining what is just right for your yard, you won’t be able to make it up on the scale. 

Beyond Truck Scales
Truck scales are some of the most common equipment in scrapyards, but they aren’t the only devices recyclers use for weighing tasks. Here’s a short list of other types of equipment that handle weighty scrap matters.
  Axle Scales. These scales allow the weighing of vehicles where permanent truck scale installations aren’t feasible. They can provide various types of weights, including individual axle, axle group, or total. These scales, offered in portable and semiportable models, are available in a variety of widths and lengths.
  Rail Scales. A rail scale uses a weighbridge to turn a section of railroad track into a weighing system. Such scales can be used for static weighing or for weighing railcars that are coupled together and in motion. Some manufacturers also offer combination truck and rail scales that can weigh both types of vehicles.
  Floor Scales. Also referred to as dock and drum scales, these general-use devices can offer significant weighing capacity—up to 30,000 pounds, says one manufacturer—but they’re usually used for lighter tasks in scrap operations, such as weighing gaylords, drums, palleted material, and retail loads. The compact size of these scales makes them ideal for warehouses and smaller scrapyards. These units can be flush with the floor or sit on top of the floor, with access ramps available so loads can be rolled onto the scale.
  Mobile Loading Scales. This category encompasses weighing devices attached to mobile equipment such as forklifts, wheel loaders, and material handlers. Though these scales can be installed on the mobile equipment itself—such as in the boom of a material handler—they also often are part of related attachments such as grapples and lifting magnets. Recyclers use these devices for on-the-spot weighing to calculate the exact tonnage for a shipment, track the total amount of weight moved for production and/or maintenance reasons, and ensure that the base machine isn’t exceeding its lifting capacity. 

Jim Fowler is retired publisher and editorial director of Scrap.