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6 - Peripherals and Traffic Control
• Scale-mounted guard rails are attached to the weighbridge, by either bolting them to a bracket or welding them to the side of the weighbridge modules. They often can be supplied and installed by the scale supplier. • Standalone guard rails are built alongside the scale, but are not attached to the weighbridge. In most cas- es, guardrails will offer superior protection from driving off the side of the scale. They are not always avail- able directly from the scale supplier. Instead, they may need to be sourced and installed by the contractor preparing the foundation. 7 - Hazardous Areas and Materials If you will operate the scale in hazardous areas (flammable or explosive atmospheric concentrations of gases, vapors, mists, dust, or fibers), you will need a scale that has approval (generally from FM, UL, or ATEX) for use in your environment based on its classification. Hazardous area approvals typically are noted on the specifications data for load cells and terminals. For example, some hazardous area classifications place a limit on the amount of voltage that can be used in equipment. Some regulations require the use of energy-limiting barrier boxes to isolate signals. A good scale supplier should be familiar with these requirements and the types of peripherals that may be used in various areas.
Terminals Your scale will have a control unit, often called a terminal or indicator. It can range from simple to elaborate. Below are some of the advanced features you may consider when choosing a terminal: • Control more than one scale with a single terminal • Connect with USB/Ethernet to computers and networks to interact with scale software, transfer data across company networks, and take advantage of remote diagnostics
• Benefit from wireless connectivity with the scale and other accessories • Automate other scale accessories, such as gates and lights for traffic control • View data on graphic displays with varying levels of detail • Store tare/net weights with various memory capacities for transaction logging • Connect to various compatible ticket printers
The terminal also may serve as the power supply to some or all the load cells. Some will specify how many load cells they are able to support. If the power supply to the terminal is subject to fluctuation in your area, consider using an aftermarket power conditioner.
Please note: Hazardous area classification is not the responsibility of the scale supplier. A qualified safety officer at a customer site or local industry regulator must make that determination.
Gates Some sites place gates at one or both ends of the scale. Whether controlled manually or automated, these gates can indicate when a vehicle should drive on or off the scale. This can also be accomplished with traffic lights. Lights Often a green and red traffic light is placed alongside the scale to control the flow of traffic. These lights can be controlled manually or automated. Remote Displays A remote display is a numerical display unit that indicates the weight on the scale. They are often placed at the front of the scale so the drivers and/or filling operators can see the weight of their truck when it is on the scale. Guide Rails Also called guard rails or rub rails, guide rails are an option for most truck scales, although some industries and safety regulations require them. They can be used with pit-style scales to provide guidance to the truck driver approaching the scale. They are more frequently used with above-ground (pitless) scales as a safety device to prevent trucks from driving off the edge of the scale. There are two styles of guide rails.
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