Knowledge of the payload of freight cars is of utmost importance to shippers and carriers, used for billing and ensuring compliance with overload regulations. Typically, rail cars are weighed at dedicated sites, using strain-gage based pit-type scales, or weigh-in-motion scales. Shippers often weigh the shipped payload using mass flow meters, or force transducers integrated into infrastructure such as hoppers. Although accuracy on the order of 0.2% is achievable with these weighing methods, they carry high installation and maintenance costs, are sparsely distributed, and often require re-routing and decoupling of rail cars.
The need for a high-accuracy (less than 1% of full-scale) vehicle-mounted, standalone solution has been expressed by chemical, grain, and coal shippers. This paper presents the key benefits of a standalone system, including real-time monitoring of car filling, and periodic monitoring. Real-time monitoring during filling allows customers to monitor and control fill rates, optimize filling methods, and prevent over-loading assets. Weight penalties can thus be avoided and infrastructure damage can be reduced. Periodic monitoring, when combined with GPS tracking, allows the customer to monitor filling/emptying events and the subsequent location. Theft and tampering can be monitored using alerts to notify customers of events taking place outside of designated facilities.
Additionally, the development and implementation of a proprietary weighing system is presented. The performance of several prototype instrumented bogies is shown, including: 1) the results of repeated calibration cycles using full-scale bogie loads in a load frame, and 2) field performance computed by comparing instrumented bogie readings to reference instrumentation used by a chemical shipper.