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Nine Tips for Selecting an Application-Based Weighing System
May 24, 2016
4 Min Read
Xander Skoulis is the North American product marketing manager for weighing components, Mettler Toledo.
Weight measurements are often a critical factor for product consistency. Weight can also be used to improve process efficiency and ensure regulatory compliance. Consider the factors below to select a scale or integrated weighing system to reliably meet the needs of your operation.
1. Know the operational environment. The environment in which a scale operates will impact the performance and usable life of the equipment. Environment type (dry, dusty, wet, harsh) should be a primary consideration in scale construction and load cell protection against ingress. In sanitary environments, hygienic scales need to be cleaned quickly and efficiently, likely using high-pressure hose-downs. Other factors to consider are temperature fluctuations, production equipment vibrations, and the presence of magnetic fields (EMI, EMP).
2. Determine the weighing range. Specify the largest total gross weight you intend to weigh on the scale, including any tare container. This becomes the maximum scale capacity (with margin if there is any uncertainty). Then, specify the smallest net weight you intend to measure. This figure should be the material weight without any tare container. It is critical to accurately define minimum net weight, particularly with smaller weights, where relative weighing uncertainty is increased.
3. Define accuracy requirements and process tolerances. Tolerances are determined by process requirements, as well as any application quality management system or regulatory concerns. Tighter tolerances require higher accuracy. Allow for a safety margin if the workplace includes environmental factors that may impact the weighing performance (Tip 1). Good Weighing Practice (GWP) is a standardized scientific methodology that helps select a scale that meets specific process requirements.
4. Match the scale to the intended application. Today, many scales provide application-specific functions that can support your process by improving quality and productivity. For example, an automatic filling application requires a different function than counting or checkweighing. Sometimes this solution may come via a weigh module (integrated weighing sensor) or high-precision weighing application. Be sure to consider requirements for interface, functionality, process speed, and other user factors.
5. Select the right size and weighing-platform build-out. Consider the size of the material to be weighed and the space available at your production facility. Benchtop scales and floor scales are available in various sizes, and some manufacturers can even offer customized platform dimensions. When weighing pallets, drums, and other large containers, ensure that there is adequate space around the scale to maneuver. For large filling applications, it may be smarter to put weigh modules under a tank. Also, consider how the weighing indicator can be positioned to ergonomically facilitate efficient processes and reduce repetitive stress disorder injuries.
6. Consider how weighing data will be utilized. A key requirement for many companies is data traceability. Modern scales can capture weighing data and process information and store them securely. Connection with barcode readers, RFID readers, or printers can turn a weighing station into a robust hub to ensure correct order processing, material selection, and process documentation.
7. Integrate weighing into the process. Industry 4.0 does not slow down for weighing. More and more, scales are being integrated into production and enterprise resource planning systems for seamless process control and traceability. Ensuring a scale provides the correct data interfaces and protocols allows easy integration into existing or new company infrastructure. If PLC data integration is not required, PC-based serial or Ethernet TCP/IP data communication are viable options.
8. Ensure explosion safety when required. Scales used in potentially explosive areas must comply with local hazardous-area regulations, which requires selection based on regional hazardous-area classification. Equipment designed according to an intrinsic safety protection method can automatically provide considerable safety, functionality, and maintenance benefits.
9. Maintain weighing accuracy. As with any precision measurement instrument, scales must be maintained and calibrated to ensure consistent accuracy over time. Professional installation can help ensure accuracy from the moment the scale is commissioned. Integrated features such as automatic scale adjustment and routine testing guidance help to keep scales accurate. Regular professional calibration and maintenance also ensures reliable operation over the life of the system.
Xander Skoulis is the North American product marketing manager for weighing components, specializing in weigh modules, load cells, and automated precision weighing at Mettler Toledo.
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