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1 - Road-Going Weight Regulations Regardless of what your trucks are transporting, regional and/or federal transportation authorities define the maximum allowable weight allowed on public roadways. This is often defined as a maximum allowable weight for a specific configuration of axles. There may also be a maximum overall gross vehicle weight, but sometimes the axle-based regulations stand alone. Check with the transportation authority in your jurisdiction to find out the legal roadway limits for the type of trucks you will be using. Some sites use their truck scale to load their vehicles with the maximum weights allowable without going over. Overweight trucks can result in steep fines. Ensure the scale configuration you choose is capable of providing the information you need, especially if you plan to load your trucks close to legal limits. For example, a scale designed to weigh the complete truck may not provide the weights of each axle group unless it is a multi-axle scale. 2 - Legal-for-Trade Applications If your scale is to be used in business transactions, your application needs to be “legal for trade.” Most often, legal-for-trade applications most often are required to meet a set of federal, local and/or regional require- ments. This can include criteria for construction, scale specifications, operation principles and calibration intervals intended to protect business transactions from scale inaccuracy or fraud. Non-legal-for-trade appli- cations can include scales used exclusively to check for proper axle loading and/or compliance with maxi- mum roadway weight limits. While those are important uses, they are not trade-related applications, and therefore might not be required to meet the same guidelines.
3 - Metrology Authorities Metrology is defined as the “scientific study of measurement.” Most locations look to a recognized metrology authority for measurement standards to ensure equality in business transactions. When it comes to truck scales, those agencies will provide certifications to equipment and components that meet their performance requirements.
OIML In many European and Asian countries, the Inter- national Organization of Legal Metrology (OIML, www.oiml.org, headquartered in France) provides the standards that measuring devices must meet for commercial applications. That includes vehicle scales and their components, such as load cells. OIML regularly updates its series of recommenda- tions, guides and other reports and documents. Devices that comply with OIML specifications will carry an OIML classification. For vehicle scale com- ponents, such as the weighbridge and load cells, this will define tolerances for their accuracy and capacity, which are verified by standardized testing. For example, OIML document R 60 outlines perfor- mance characteristics for load cells.
NIST and NTEP In the United States, regulations are defined by the National Institute of Standards and Technology (NIST www.nist.gov) Handbook 44, “Specifica- tions, Tolerances, and Other Technical Require- ments for Weighing and Measuring Devices.” It is most often referred to as Handbook 44 or simply H-44 and is revised annually. H-44 provides the federal specifications for the performance of a truck scale. It also covers the user requirements or tasks that the scale user and owner are to do. Devices that are intended for commercial appli- cations will carry the National Type Evaluation Program (NTEP) certification issued by the National Conference on Weights and Measures (NCWM). This signifies that the product or com- ponent has been tested to conform to the NIST H-44 requirements.
Other Locations
Many other federal and provincial Weights and Measures authorities around the world acknowledge the standards of the aforementioned organizations. Many will accept devices carrying certification from one of those agencies. Your regional weights and measures authority can provide further details regarding the certifications it accepts for commercial vehicle weighing equipment.
Canada The Canadian agency, Measurement Canada, notes that load cells in trade devices must conform with NTEP
or OIML regulations. Source: Bulletin M-25
Australia The National Measurement Institute (NMI) in Australia performs supplemental testing and certifications for commercial weighbridge load cells based on OIML standards. Source: NMI R 60
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