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The average length of service of commercial light rail vehicles is 30 years. Maintenance is therefore an ever-present topic for operators. This involves diverse challenges with regard to fire protection, as verification must generally satisfy state-of-the-art standards. The fire protection requirements set for extensive modernisation projects are the same as those for the licensing of new vehicles. This article describes the procedure for implementing the fire protection requirements in maintenance or modernisation projects and gives practical examples.
During the approximately 30-year life cycle of a light rail vehicle (tram / urban rail), there occur signs of wear outs or defects, caused by operational stresses, or vandalism in a vehicle. Among other things, these can involve damage to seats, floorings and also the reaching of live cycle limit as in wheelset axles. In technical areas, defects can occur during the course of the life cycle, for example, in the heating systems or in the bogie. The combination of subsequent technical or administrative measures to correct these defects or rather to restore functional performance (reliability) are called “maintenance” precisely defined in the EN 13306. A differentiation is made between service/maintenance, inspection, repair and improvement.
In general, the terminology is adapted by specific companies or is extended with reference to the required measures, which ensure operational safety and reliability.
Maintenance therefore includes all measures for further operation until the time of final taking out of service (decommissioning). On the one hand, components in the vehicles are serviced/maintained, inspected or repaired (e.g. sanding system, pantograph, heating system) and on the other hand, the vehicle is refurbished or modernised. According to EN 13306 , this means “modification or improvement of the vehicle, taking into account technological advances ...” (for example, thermal resistance of the materials, installation of a fire detection system or an enhanced passenger information system).
The legal basis (in Germany) of maintenance measures to meet the fire protection documents are explained in the BOStrab  or rather in the fire safety/protection-relevant standards and regulations.
Paragraphs §2, §33, §62 of BOStrab  are listing the operator’s obligations and fire protection requirements. §2 and §62 define the procedure for compliance with operational safety/reliability and approval through the technical regulatory authority in general terms. Implementation of the fire protection requirements is based on demonstrating the state-of-the-art and/or focussing an equal proof of safety.
According to §33 BOStrab , among other things, state-of-the-art is met by meeting the requirements of specific standards. Here the European series of standards on fire protection on rail vehicles, EN 45545-1 to -7 is named. Other requirements are related to this, listed in EN 16334 Passenger alarm system , EN 13272 Lighting , EN 14752 Doors  and TRStrab Fire protection .
The procedure for implementing the fire protection requirements in maintenance or modernisation projects is specified using an “evidence plan”.
The evidence plan defines the strategy for the provision of evidence and is submitted to the technical regulatory authority (“technische Aufsichtsbehörde” - TAB) as the basis of an approval. The acceptance of the evidence plan by the TAB is a basis for successful putting into service. Meeting the protection objectives in case of fire is generally demonstrated by the introduction of new materials or design according to the EN 45545 series. Vehicles that have already been approved, for example, to DIN 5510-2 , do not require new test evidence for reused components. This applies as long as servicing work or maintenance measures are carried out and no new components or bonds are introduced.
A possible procedure for the provision of evidence is explained using the following examples.
A vehicle is thoroughly modernised towards the middle of its product life cycle. Among other things, the interior panelling is refurbished. To this end, the interior side wall panelling is to be repainted, whereby the substrate material, the underlying interior GRP panelling, is to be kept.
Removal and replacement of the old panelling is not proportionate with regard to the expected financial cost. A new paint finish on the side wall panelling leads to a new bond, which according to EN 45545-2: 2013 und A1 2015 , requires new provision of evidence according to the current standard. This means a bonding test according to the requirement set R1 in EN 45545-2: 2013 und A1 2015. This involves testing the fire spread and energy release rate as well as smoke gas release and the optical density of smoke. Depending on the result of a bonding test for a new paint finish on the side wall panelling, tests can be performed on the basis of proving the same safety, as allowed by §2 BOStrab. If the side wall panelling is refurbished without a new paint finish and is merely repaired as defined in EN 45545-2 clause 4.6, no further evidence is necessary. According to EN 45545-2, these are maintenance measures.
VAG Verkehrs-Aktiengesellschaft Nuremberg replace seat upholstery, including seat covers approved to DIN 5510-2 of the DT3 underground rail vehicles with new upholstery assemblies qualified to EN 45545-2:2016. The original substrate continues to be used. Clause 4.6.2 of EN 45545-2:2016  summarises the necessary tests for the replacement of individual seat parts. A complete seat test is not necessary, as long as only a seat part (for example, a cover or interlayer) is replaced. However, if the seat cover and foam of the passenger seats are replaced at the same time, new testing of the whole seat is necessary (Requirement set R18 to EN 45545-2:2016 ). Apart from performing a test on the whole seat, it is also possible to demonstrate the same or equal safety according to §2 BOStrab. A positive fire test report to DIN 5510-2  exists for the original seat structure. This means that a UIC paper cushion was ignited on the seat, which at its peak released around 25kW heat on the seat materials . The new upholstery assembly was qualified according to the approval of G1 vehicles with a different substrate to EN 45545-2:2016 . A gas burner with 7kW output was used as the ignition source. By comparison, the thermal stress of the heat components when ignited with a UIC paper cushion is higher. As a consequence, the seat combination with the new seat upholstery assembly can be transferred to the original substrate. It was shown that there is no protection objective deficit for personal safety in the vehicle.
With regard to the requirements of the TRStrab Fire protection, it must not be forgotten that changing the seats also plays a role in the vehicle design fire and mostly influences it significantly. Here it is necessary to analyse the local fire spread of the new seat upholstery and to check and, if necessary, adjust the design fire.
With the introduction of the revised EN 45545-2 in October 2020, among other things, the testing of passenger seats to EN 16989:2018  was defined. A transition period is not specified in EN 45545-2:2020. EN 45545-2:2020  must therefore be taken into consideration as state-of-the-art for providing evidence for materials used in each approval process for new vehicle or vehicle modernisation project.
Selected relevant differences between the EN 45545-2: 2013 und A1 2015 standard issued in 2016 and 2020 are outlined in the following.
In addition to many minor adjustments, the new issue of the EN 45545-2:2020 contains two extensive changes.
On the one hand, the new seat test standard EN 16989:2018 "Fire protection on railway vehicles. Fire behaviour test for a complete seat" is references. With it, Annexes A and B of EN 45545-2:2013 und A1 2015 are deleted. On the other hand, reference is made to the new standard on testing for smoke toxicity, EN 17084:2020-10 "Railway applications — Fire protection on railway vehicles — Toxicity test of materials and components" and Annex C is thus deleted.
Regarding the seat test standard EN 16989:2018, it is not possible to transfer the results or compare the requirements in EN 45545-2:2016 to / with EN 45545-2:2020. In EN 16989:2018, slit and unlit seats must be tested . This was already part of the seat tests according to the withdrawn German national fire protection standard DIN 5510-2 , however, this was no longer performed within the scope of the European standardisation and provision of evidence according to EN 45545-2: 2016. In addition, the heat output of the ignition source was increased from 7 kW to 15 kW. During the test, this results in significantly higher thermal loading of the seats, which means that in general terms, the provision of proof for passenger sheets was provided under more stringent conditions. In EN 45545-2-2:2020, the ignition energy was increased to 15 kW.
Regarding the test for smoke toxicity, the content of the test methods for providing evidence of toxicity has not changed. The verification method for the determination of toxic gases of components for rail vehicles, however, was adjusted to more frequent sampling during the test process. According to the new standard, a sample is not only taken for analysis after four and eight minutes, but at least every 20 seconds. The evaluation of the test results according to the current standard continues to be only on the basis of the gas samples taken in the fourth or eighth minute.
As the limit values in EN 45545-2:2020 have not changed, it is possible to transfer the results from the test method to EN 45545-2:2016 to EN 45545-2:2020.
This should be assessed by an independent inspection body or the competent TAB. This change involves a re-orientation of the test processes, but effectively there is no tightening of the standard.
Furthermore, a table regarding the multiple qualification of components was added in Annex B of the standard. The requirement sets of an HL classification are compared with the currently effective requirement sets.
The adjustments in Clause 4.2 "General” of the new EN 45545-2:2020 show partial weakening of the requirement with reduced assessment/testing effort or at least increased specification of the requirements with regard to extending the application.
In Clause 4.3 , grouping rules have been specified based on practical experiences. For example, in the provision of evidence for printed circuit boards, UL 94 V0 is explicitly named as evidence, as the printed circuit boards mostly already include this proof.
Each refurbishment or maintenance project must be considered individually, to ensure protection objective-orientated provision of evidence. At the same time, it must be taken into consideration that acceptance of the evidence plan, including measures, must be obtained from the technical regulatory authority. This forms the requirement for positive putting into service/commissioning or maintaining service on the basis of the documents made available.
 EN 13306:2018-02 "Maintenance - Maintenance terminology"
 German BOStrab “Verordnung über den Bau und Betrieb der Straßenbahnen” dated 01/01/1988, last amended 10/10/2019
 EN 16334:2014-12 Railway applications - Passenger Alarm System - System requirements
 EN 13272:2019-12 Electrical lighting for rolling stock in public transport systems
 EN 14752:2020-03 Railway applications. Body side entrance systems for rolling stock
 Germany TRStrab Brandschutz:2014 Technische Regeln für Straßenbahnen Brandschutz in unterirdischen Betriebsanlagen
 DIN 5510-2 2009-05 Preventive fire protection in railway vehicles - Part 2: Fire behaviour and fire side effects of materials and parts - Classification, requirements and test methods
 EN 45545-2: 2016-02 Railway applications. Fire protection on railway vehicles Part 2: Requirements for fire behaviour of materials and components
 EN 45545-2:2020 Railway applications. Fire protection on railway vehicles Part 2: Requirements for fire behaviour of materials and components
 EN 45545-1:2013-08 Railway applications. Fire protection on railway vehicles Part 1: General
 EN 45545-3:2013-08 Railway applications. Fire protection on railway vehicles Part 3: Fire resistance requirements for fire barriers
 EN 45545-4:2015-11 Railway applications. Fire protection on railway vehicles Part 4: Fire safety requirements for rolling stock design
 EN 45545-5: 2016-01 Railway applications. Fire protection on railway vehicles Part 5: Fire safety requirements for electrical equipment including that of trolley buses, track guided buses and magnetic levitation vehicles
 EN 45545-6: 2015-11 Railway applications. Fire protection on railway vehicles Part 6: Fire control and management systems
 EN 45545-7:2013-08 Railway applications. Fire protection on railway vehicles Part 7: Fire safety requirements for flammable liquid and flammable gas installations
 EN 16989: 2018 Railway applications. Fire protection on railway vehicles. Fire behaviour test for a complete seat
M.Sc. Corinna Trettin has been a team leader and EBA-recognised fire safety assessor in the Fire Protection Department of TÜV SÜD Rail GmbH since 2017. Prior to that she was a scientific assistant in fire and explosion protection (2010-2017) at the Bergische University Wuppertal, at which she had studied safety engineering and fire protection.
Dipl.-Wirtsch.-Ing. Miriam Jost has worked as an expert for fire protection in rail vehicles at TÜV SÜD Rail GmbH since 2012. From 2008 to 2012, she worked for FOGTEC Brandschutz GmbH in Cologne as a sales engineer for fire alarm and fire-fighting technology for rail vehicles. She studied industrial engineering at the HTW University of Applied Sciences in Berlin.
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