When it comes to track condition monitoring, how many sensors would need to be used for accurate measurement?
The question of how many sensors are actually needed to ensure accurate monitoring information is often raised by operators.
Position Partners Market Development Manager – Deformation Monitoring, Andrew Jones, tells Rail Express that it’s “a fair question”.
“It’s a subject which can be looked at in a few different ways depending on the scenario,” he said.
“In the case of a large structure or an infrastructure project, the quantity may be mandated by a monitoring scope which, depending on the technology in the mind of the engineer, could result in a reduced number of monitoring points.
“In other instances, an engineering specification such as a trackbed monitoring standard often drives the quantity and spacing of sensors.”
Beyond these scenarios, he said Position Partners clients have requested solutions for structures such as walls, embankments, highwalls, dams, benches, plinths, chimneys, wind turbines, tunnels, bridges, high rises, conveyors, crushers, rail tracks and transmission towers … “just to name a few”.
“We work with a range of expertise levels a nd enjoy showing how new technology can provide not just a better monitoring outcome, but also a more productive way of working,” Jones said.
“Inevitably at some stage, we’re often asked how many sensors we think are required for the project.
“The short answer, apart from having to satisfy some basic criteria for some structure, is that it is not up to us.
“However, there are some questions that can help come to some decision around the spacing of the sensor which typically then defines the quantity.”
One line of thinking is to distinguish between brittle and ductile deformation.
Is the structure likely to bend or crack?
“A series of non-contiguous tilt sensors is great at picking up trends over time and across points but sometimes less effective in monitoring a structure that might be expected to fail in a discrete location,” Jones said.
“This may require the sensor layout to be adjusted to cater for this kind of deformation. “In either a brittle or ductile deformation scenario, another consideration is the size of the failure to monitor for.
“This may be applied to earth embankments and other geotechnical scenarios where a probabilistic or engineered approach has been taken towards the size of a failure.
“In this instance an approach may be to space sensors at half the size of the potential slump in the case of an tailings dam wall or a wedge failure in an open cut to ensure the sensor array covers the area of concern.”
The decision could be budgetary and may be influenced by the duration of the monitoring requirement.
In any instance, there is often more than one way a monitoring system can be configured.
Importantly, the system can easily be scaled and adding sensors after an initial installation is very straightforward.
“We can talk through the difference between systems that provide an isolated indication of movement versus a measurement of deformation of the underlying structure,” Jones said.
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