The LPM TPM measures the rails around the world

An OEM product for SPENO International SA
Railway industry
Measuring the rail to automate its maintenance
Qualimatest solution secures rail transport

The system presented is used on a "milling train", used on railroads around the world. This grinding system corrects the shape of the rails to meet the needs of rail traffic. As a reminder, the transverse profile of the rails is adapted according to the shape of the track, ie turning to the right, to the left, switching etc.


The name of the transverse profile corresponds to the part of the rail potentially in contact with the wheel on a section orthogonal to the direction of the rail. The longitudinal profile is defined as the height variation of the rail - wheel contact point relative to a reference along the rail axis. The wear of the rails appears a) on their transverse profile, in which case it is a friction wear of the edge of the wheels on the rail (mainly in bends), or by creep of the rail if excessive loads are put in circulation; b) on their longitudinal profile, forming corrugations the amplitude of which increases with each passage of railway convoys (mainly in the acceleration and deceleration zones).

The correction of the transverse and longitudinal profiles is essential for the safety of the rail traffic (holding, adhesion, guidance etc.), to reduce the maintenance costs of the tracks (the less the profiles are used and the less they wear out), and finally to reduce vibratory problems (loss of traction energy, reduction of noise emitted by the passage of a convoy, increased passenger comfort).

The developed measuring system is used to determine the transverse and longitudinal profiles on the train which carries out the correction of the rails by grinding. It tells the conductor the areas and the intensity of the grinding. This system consists of five subsystems: determination of transversal profiles by laser (KLD), comparison and management of transverse profile measurements (MPT), determination of longitudinal profiles by mechanical height sensors positioned on a rolling cart (MPL), a supervisor and a test and calibration bench.


As in any engineering project, the overarching goal is to get the most reliable features for a minimum investment. The industrial context also imposes ruthless reliability criteria and downtime, so troubleshooting, minimums. Thus, in a single development, several pseudo-independent and inter-communicating subsystems have been developed using the solutions proposed by National Instrument.

Longitudinal measuring module (MPL)

This subsystem integrates the acquisition of the height measured by the sensors in contact with the rails, processes the data to display the information useful to the conductor, records them, then regenerates them on a plotter in order to have a hard copy of the measurements. . This system must be able to be autonomous, to print data coming from another identical subsystem, or to work with the supervisor. This module has no output screen or keyboard.

Transverse Measurement Module (MPT)

This subsystem consists of the laser system and the MPT management system. The MPT receives the data from a profile measurement sensor and compares it to reference profiles stored in a library to indicate which wheels to use (and how deep) to correct the profile. He then prints the cross profiles on a printer. This system must also be able to be autonomous or work with the supervisor.

Supervision module

This subsystem makes it possible to configure the MPL and MPT modules, to display their measurements "on the fly", possibly to supervise other systems present on the train. It must be able to be stopped without disturbing the operation of the two subsystems.

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industrialized by QMT

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Measuring the geometry of the rail

An OEM product developed and produced by Qualimatest to guarantee the safety of rail transport