Protecting rail electronics

4 mins read

Easy to install, durable edge protection is used in train carriages to protect cables from damage, as New Electronics discovers.

The modern train is full of communication technology in order to exchange information between on-board systems and the outside world.

Each carriage contains an extensive network of cables that are hidden in walls, floors and ceilings, and sometimes in very confined spaces. The cables pass sharp edges, which, if inadequately protected, can cause cracks and lead to a short circuit – which could, in turn, result in data loss, system failures or fires.

As a consequence, hard-wearing materials are required which are able to protect cables from abrasion, vibrations, or extreme temperature fluctuations.

DTi is a European subsidiary of Device Technologies, companies that are specialised in developing high-performance cable protection solutions for critical electronics systems. DTi has developed the SL-FST cable protection solution specifically for use in trains. It is particularly durable and can also be attached by simply plugging it on without the use of adhesives.

In this way, productivity can be increased as fewer work steps are required and additional costs, for example adhesives, are eliminated reducing installation costs by as much as 50%.

The steel reinforced SL-FST solution is also heat and flame resistant. As a result, variants are able to meet the high requirements of the European rail industry, including EN45545 or FST/UV exposure. The material was initially used in the aviation industry and has proven itself in environments with high vibration levels, making it suitable for use across a wide range of rail applications.

An extensive network of cables is hidden in walls, floors and ceilings, sometimes in very confined spaces

Protecting communications

The driver's cab, passenger monitors, train-land communication interfaces or automatic door controls are just a few examples of on-board systems in trains that need to communicate with each other to ensure smooth train operations.

As a result, modern trains are becoming more and more like high-performance computers on wheels, whose most important lifelines - the connecting cables between the individual electronic components and signalling devices - must pass through sharp edges and narrow transitions.

“If the cables are damaged, for example by continuous abrasion, short circuits can occur, which in the worst case can paralyze a critical system such as the brakes or cause a fire, " said Meike Kurzak, Managing Partner of DTi. "But data loss or faulty signal control can also occur because of abrasion damage. In addition, these cables are laid in very confined spaces with very little play and are also sometimes subject to high vibration or temperature fluctuations.

“For this reason, the edges to be passed are equipped with a special edge protection, which previously had to be applied with the use of adhesives in a time-consuming process. Especially, in case of fire, the nylon grommets themselves which when combined with the adhesives were found to cause an increased toxic load and smoke development. For this reason, DTi customised its leading grommet edging solution Spring-Fast by optimising it for use in the rail transport.

“The SL-FST edge protection consists of a particularly hard-wearing, non-flammable and steel-reinforced special thermoplastic, so that in the event of a fire it does not burn further or produce additional toxic smoke. Compared to conventional plastic edge protection, this material also cannot dry out or become porous, even if it is exposed to extreme changes and temperatures,” explained Kruzak.

Minimising potential hazards

"The SL-FST consists of a stainless-steel core that is completely encapsulated in a halogen-free and low-toxic thermoplastic compound," said Kurzak. "This special material is flame-retardant and particularly corrosion-resistant. Because of its properties, the plastic edge protection normally used in the rail industry is more likely to dry out and become brittle if exposed to heat or cold for long periods of time. It can break under sufficient pressure, stress or vibration."

The special composition of SL-FST makes it very resistant to these extreme temperature fluctuations. As a result, the edge protector can be attached to the train both inside and outside. Even the high vibrations occurring on high-speed lines can be absorbed by the special construction of a securely fitting steel core and resistant plastic.

SL-FST is designed with a steel core with castles, or gripping teeth, that angle into the edge creating edge retention without adhesives.

DTi's engineers have used their experience working in the aviation sector to develop the SL-FST, as the material has to perform under extreme speeds, G-forces and vibration environments in aircraft.

"As more and more high-speed lines are being laid for trains in Europe, this synergy was a logical step in the development process," Kurzak reported.

In particular, how the material behaves when it comes into contact with fire was a key factor in its adaptation to the European railway sector.

"As many sections of track run through tunnels, fire safety requirements are particularly high in," explained Kurzak. "We therefore optimised the plastic so that in terms of flammability and toxicity it does not add to the

smoke and fire development, as would be the case with a plastic that contains questionable additives or is attached with adhesives."

In practice this means that in a fire the SL-FST will not support combust and will burn insignificantly, and will only produce a very small and manageable amount of smoke. As a result, the material meets the strict requirements of DIN EN 45545-2 and is qualified for Hazard Levels 2 and 3, which are the highest material-technical requirements within the framework of this DIN.

The SL-FST edge protection consists of a particularly hard-wearing, non-flammable and steel-reinforced special thermoplastic, so that in the event of a fire it does not burn further or produce additional toxic smoke

Easy assembly

The SL-FST edge protection system can be completely installed without adhesives. This minimises the production or set-up time from several minutes to simply a matter of seconds.

As a result, productivity can be increased because the same amount of parts can be installed in a fraction of the time normally required. This even leads to an overall cost reduction when compared to adhesive-based plastic variants, as less working time and costs are required for the additional steps and materials that would otherwise be necessary. To achieve this, the edge protector simply has to be pushed on along the shape of the edge and pressed firmly into place.

The SL-FST castles lock automatically and provide strong edge retention. Nevertheless, the protection can be easily removed again. Since no adhesives are used, workers are no longer exposed to toxic chemicals (VOCs) and odours and do not have to wear gloves or masks when attaching the edge protection.

"Adhesives and other solvents must be specially stored and disposed of and must be identified there by warning notices. Since the SL-FST installs completely without this, it is much easier to work with and at the same time it’s a very green alternative to what is currently being used," concluded Kurzak.