In the first weeks of June, the Anes Tunnel in Siero (Asturias) hosted the Gas Dispersion and Dielectric Stiffness tests of the pioneering worldwide project, RailNG, a study on the potential of LNG and hydrogen as a clean energy source for railways. The first results show a positive balance.
The facilities of the Barredo Foundation (Government of the Principality of Asturias) in Anes were the test bench chosen for these tests. This is a full-fledged laboratory, where real-time tests were carried out, as close as possible to the immediate future of hydrogen as an energy source for railroads.
In the framework of the CEF 2016 RaiLNG project, the necessary activities to have an implementation plan that allows the progressive introduction of liquefied natural gas (LNG) in the railway sector are being developed. In this context, in the “Demonstration study of the infrastructure associated with an innovative LNG traction solution in railway operations”, the engineering and design activities required for the transformation of a single-cab S-1600 diesel locomotive into a diesel/LNG hybrid engine are being developed.
Among other aspects, the priority of this project is focused on ensuring the technical viability and safety of liquefied natural gas, with less environmental impact, as an alternative fuel for commercial exploitation in rail transport. To this end, within the framework of the RaiLNG project, the hazards in the overall system has been evaluated and determined. Based on these studies and on previous experiences, two fundamental risks associated with the gas system have been identified, that must be addressed to avoid subsequent restrictions on circulation:
- Continuous gas leak from a moving vehicle that stops inside a tunnel. The immediate consequence is the accumulation of gas inside the tunnel that before any source of ignition can cause a deflagration or fire.
- Natural gas leaks due to uncontrolled vents of the installation in the presence of electrical potential. The consequence is the modification of the dielectric strength of air with the risk of electric arc formation and subsequent fire or deflagration between the electrified lines of the infrastructure (overhead catenary and electrical power lines at railway track level) and any gas outlet from the vehicle.
In order to mitigate these risks, the security measures to be implemented have been evaluated.
However, the operational restrictions proposed in previous pilot tests imply great limitations, with great impact on costs and delays. These conditions make a future commercial exploitation unfeasible so it is necessary to address these aspects from the initial phase of the project and design the system, so that the associated risk is low enough to be accepted according to the criteria established by the EU Regulation 402/2013.
However, given the innovative nature of the rail system modifications in the CEF project, the risk acceptance criteria established in EU Regulation 402/2013 are difficult to apply to the hazards identified above. This is one of the first LNG railway applications in Europe and this type of risk has not been considered before.
For this reason, given the complexity of analyzing the risk of the identified threats in a reliable way, a mixed approach of risk acceptance methodologies is proposed. On the one hand, carry out a theoretical simulation and on the other, carry out an empirical test in a similar environment or system, where the behavior can be analyzed in real conditions.
However, both the application of the methodology followed in the tests, as well as the conclusions and recommendations included in this report, have a much broader application than that of the RaiLNG project. Thus, these can be applied to any engine or locomotive which uses LNG as an energy carrier for its operation and which operates in the railway sector.