Protran Technology partnered with Maryland Transit Administration (MTA) on Wireless Sensor Monitoring Network
The US Transportation Research Board (TRB) awarded Protran Technology and QinetiQ North America a grant in November 2013 to further develop and test QinetiQ’s Intelligence Rail Integrity System (Iris) which monitors changes in rail neutral temperature (RNT) to determine track deterioration. Protran Technology partnered with Maryland Transit Administration (MTA) to provide the first real-time network of remote sensors installed on continuous welded rail (CWR).
Thermal loads develop in rail due to daily heat/cooling cycles. When a rail heats it expands and is in compression, but when it cools the rail contracts and is in tension. Somewhere in between these two points, the rail is neutral and there is no compression or tension. Rail temperature with no force due to thermal loading is the rail neutral temperature (RNT). Extreme fluctuations in rail temperature from RNT can cause buckling and breaks and lead to derailments if undetected.
Iris continuously monitors changes in rail temperature, longitudinal rail force and RNT. If rail buckling or breaks are detected, Iris alerts the location to designated personnel by text or e-mail. In these times of dwindling resources, Iris can be used to prioritise maintenance and establish the performance trends of different track structures.
ris provides a network of remote sensors installed on CWR and offers the following four primary functions:
• continuous monitoring for broken or buckled rail
• emergency notification to the railway
• web-accessible GIS user interface, and
• assists in rail de-stressing operations.
Iris has three main components: a sensor unit (SU), a collector unit (CU) and a configuration status unit (CSU). The SU continuously monitors rail temperature, RNT and rail forces for hazardous rail conditions. When detected, rail failures trigger an alert system that sends an emergency text and/or e-mail. The information collected populates a database that offers a simple web-accessible user interface which can be used for data analysis and presentation. Each CU can receive data from up to 13 individual SUs and transmit the data to the web-accessible database.
The CSU is a hand-held device that communicates with individual sensors and is used for various functions, including configuration during sensor installation and assistance in field-weld maintenance operations.
Once the equipment is properly installed it immediately starts recording data and looks for changes in temperature. Rail temperature is much greater than RNT prior to buckling and causes excessive compressive loads. Most of the compressive force in the rail is released after a buckling event.
By definition, the RNT is the rail temperature when the force in the rail is zero. After a rail break, the RNT approaches the ambient rail temperature as typical CWR condition no longer exists and the longitudinal force in the rail is reduced. Prior to breaks however, rail temperature is much lower than RNT which causes excessive tensile loads. Force at the rail is released after a break and, again, approaches zero. After the rail break, the RNT approaches the ambient rail temperature, as typical CWR condition no longer exists. By monitoring dramatic changes in RNT, a railway can predict potential rail breaks and lateral buckling to help prevent derailments.
Although Iris can be used for any track application, the optimum location for Iris is in curves and at abutments in non-direct fixation track. The sensors should be installed 183 to 244m apart and the sensor units can be linked to the control centres to cover a 40km area of “dark” track.
Installation of Iris is relatively straightforward. To install the strain gauges for the rail-mounted sensor units, the rail requires light grinding to remove the external layer of corroded steel, followed by fine sanding to remove any depressions in the rail caused by the grinding. After grinding and sanding, the rail needs to be wiped with a clean rag to clear the area of rust grindings.
The strain gauges are covered with petroleum-based M-Coat to make them weather proof. The SUs are magnetically mounted on top of the strain gauges. The battery-powered sensors communicate wirelessly for continuous data collection. An onboard processor calculates RNT and monitors for possible track failure.