The Solar dynamic rail weighing system meets the growing demands in the UK for accurate rail weighing that can be installed with the minimum of fuss. The Solar offers the high accuracy of traditional rail weighbridges without the track disruption and need for comprehensive foundations.

This rail weighbridge system offers exceptional performance of Class 0.5 (calibration error 0,25 %) as laid down by the internationally recognised OIML R106 requirements for approved (legal for trade) in motion, rail weighing systems. Although optimum accuracy is achieved at speeds of around 5-15 km per hour, the Solar has been used for weighing at speeds of up to 60 km per hour when it still returns accuracies of around 2% (non approved). The performance of the Solar is such that it can also act in static mode as the reference scale for weighing the railcars used for dynamic calibration of weighing systems. This removes the necessity for a separate, external static scale. This new technology is based on an innovative blend of sound mechanical principles, modern electronics and versatile software. Special weighing sleepers, whose size and weight exactly match standard concrete sleepers, are at the heart of this new concept. These are used to replace the existing sleepers over a designated length of track, thus converting the section into aa accurate weighing scale. There is no need to cut the track and a typical system can be installed and calibrated in less than two days, compared with conventional fixed installations which can take several weeks to fit.

The sleepers are made from steel plate and house two special fully sealed load cells mounted directly underneath the rail supports. The load cells have a pre-tensioning assembly to ensure consistent loading and are interconnected by means of an I beam which maintains track gauge stability. By using load cells specifically designed for the application, Pfister ensure optimum load introduction and high accuracy. By comparison, retrofit systems rely on fitting sensors directly to the rail itself and therefore are subject not only to errors arising from the anomalies of the track dimension and material but also low signal levels.

The Solar system does not rely solely on the weighing sleepers to provide accurate weight information. Lateral forces in the rail have a small yet significant affect on weighing performance and the errors introduced are dependent on factors such as speed and track settlement. To compensate for these errors, the Solar system uses lateral force sensors fitted directly in the track before and after the designated weighing section. These sensors measure the shearing strain between the measuring sleepers and the adjacent, non-sensored rail section. The results from these sensors are combined with the weight readings from the sleepers to compensate for lateral forces.