Page 328 - 360.revista de Alta Velocidad - Nº 5

Mayoral, Juan. Jiménez, Pablo Lorenzo. Fernández-Sánchez, Gonzalo. Jardí, Ignacio.

voids exist under the sleepers, which could compromise the transmission of the load to the
ballast.
• Fastenings: during maintenance operations, it must be checked that they are correctly
tightened, that they are correctly positioned and that they have not been removed.
• Bridges and tunnels: check the structural condition, verifying that there are no cracks in
walls, boards, etc.
• Drainage systems: cleanliness of pipes, taps, culverts, siphons and gutters and the presence
of herbs will be monitored.
• Surroundings: there mustn’t be any obstacles that could obstruct access to the road by
maintenance personnel, and that the perimeter protections have not undergone any
alteration.
The operations to determine the status of this subsystem are as follows:
• Auscultation: measurement of parameters of the track and its elements. We distinguish
several types:
- Geometric auscultation: it measures the parameters of geometric quality previously
mentioned. For this purpose, a geometric control car is used, of which there are several
examples depending on the network. In addition to the control performed by this type of
trains, the geometrical control of the track can be performed by manual or topographic
methods or even using the records of the batting machines during their operation. o
Dynamic auscultation: it measures and records accelerations in bogies, journal box
and vehicle box. Each of the accelerations measured by the auscultation train reflects
different path defects. They also determine the comfort of the traveller.
- Ultrasonic auscultation of lanes: Ultrasonic auscultation allows the detection of internal
rail defects. This operation is not the object of this work, since this type of defects is
not observable by means of satellites.

• Walking routes/ train rides: routes and rides have a fundamental role in preventive
maintenance activities, since they are intended to verify the elements whose parameters are
not controllable through the different types of auscultation previously described. They can
be on foot (routes) or inside the train (rides): the former are more exhaustive, but much
slower; the second are faster, and allow to evaluate the dynamic behaviour of the trains. The
periodicity for the realization of both types is marked by the infrastructure manager.
In the energy subsystem, the determination of the state of the mechanical elements (posts,
contact wires, supports, etc.) is done by the use of special vehicles. The parameters that are
measured are the geometric quality of the catenary, and the wear of the wire. The status of the
catenary posts can be determined by means of train rides.
In the control, command and signalling subsystem, most of the elements are remotely controllable
(such as signal status). For this reason, most of the maintenance operations are either periodic,
or are based on the warnings that the different systems give about their operation. Train rides
may be used to determine the condition of cable conducts (open caps or misalignment), or the
condition of signal posts.
3.2 Artificial Satellites

There are different classifications of artificial satellites. Depending on their use, these include
meteorological satellites, military satellites, telecommunications satellites and so-called earth
observation satellites. Within the terrestrial observation satellites, we can distinguish between
optical satellites and satellites of image capture with synthetic aperture radar technology.

326 360.revista de alta velocidad