Swedish Measuring Wheels – Making Trains Safer All Over the World

Pioneers in Measuring Wheels

In the 1950s, Interfleet was part of the engineering division of SJ (Swedish State Railways), and even back then it was already a pioneer in measuring technology in the railways. The Swedish test team were the first in the world to use a measuring wheel (IWT) for rail vehicles, and they have built upon this to become world leaders today.

Next-generation measuring wheels are now in use, able to handle frequencies of up to 3 kHz (IWT4). The measuring wheels are fitted with sensors based on the very latest technology – testing factors like speed and acceleration, power, displacement and strain, parameters such as track force and stability, or wear issues like strain in the bogie frame, grooves in the track or flexural stresses in the axles. Measuring wheels for the global market are manufactured in the Interfleet lab in Solna, near Stockholm.

Up to 170 Measuring Points

Survey assignments are commissioned by vehicle manufacturers and owners including Siemens, Alstom, Bombardier, LKAB, Vale and Indian Railways, and Interfleet's engineers respond to them with a global solution covering the entire measuring chain. Data acquisition equipment is installed on the train along with the custom-built measuring wheels.

The data acquisition system is the QuantumX or MGCplus from HBM, with acquisition nodes in each car. The system supports on-board data monitoring and classification in real time. A large-scale survey assignment can involve as many as 160-170 measuring points, with sensors distributed around the vehicle and several pairs of measuring wheels in the trainset. They communicate with the system via optical fiber, which is laid through the cars. In large assignments, the measuring equipment may occupy several pallets, whereas it can all fit in one case in a small assignment.

Full-scale type approval can be completed in two to three weeks of traveling around the rail network. "In order to obtain all the data combinations we need for a thorough analysis, several gigabytes of data are collected every day," explains Jan Wännman, surveying expert at Interfleet in Sweden.

"By classifying the data as soon as we collect it, we can be certain that we're getting everything we need. We work on the train, in constant touch with the driver, asking for different speeds or to increase or reduce the load, making sure we cover all the necessary conditions. When we finish, we then take the data from binary files in the HBM data acquisition program catman and analyze it using the advanced mathematical program Matlab on the basis of predefined criteria – this operation can take up to a week."