Proper Cable Protection Supports Secure Connections in Rail Industry Applications

By Frank Ball | August 06, 2019

Rail industry electronics must perform under extremely harsh conditions. A rigorous set of tests and standards helps protect connectors and cables and the power and data they deliver to modern rail transport applications ranging from engines and alternators to passenger Wi-Fi.

In rail industry electronics, the loss of power or data can have serious safety consequences, the least of which is severe disruption of services. Carriage interiors, areas above and under carriages, and inter-car jumpers and couplings must withstand a number of cabling hazards, which might include immersion due to flooding, dust penetration in tunnels, the risk of cable theft, and the ongoing possibility of vibration working connections loose. These scenarios necessitate the need for a high-performance fitting that, when paired with the correct conduit, protects against all of these risks and more for the lifetime of an installation. Proper rail industry application fittings can manage and control risks and mitigate costly downtime.

Cable protection and its secure interface with equipment is vital. When specifiers consider the lifetime costs of a cable protection system, including maintenance and the potential loss of revenue due to service outages on track, in rolling stock, or in stations, lasting performance is essential.

Cable protections for the rail industry

Key considerations for cable protection include ingress protection (IP) ratings, fire performance, vibration and shock resistance, and chemical and abrasion resistance. Luckily, technological and engineering advancements, namely in the areas of connectors and fittings, are helping railroads better deal with harsh conditions.

Rail Industry Electronics Safety and Standards

To ensure passenger safety and operational integrity, fittings must be subjected to detailed quality auditing in the manufacturing process, including the International Railway Industry Standard (IRIS). IRIS certification is an efficient, transparent system used to audit rail industry suppliers, replacing the need for individual management system evaluations by the four founders of the initiative, Alstom Transport, AnsaldoBreda, Siemens Transportation Systems, and Bombardier Transportation.

The globally recognized rail industry quality standard, IRIS rev.03, is based on the ISO 9001:2015 structure, the world’s leading quality management system standard, and adds railway-specific requirements. By holding IRIS certification, companies demonstrate competence in supplying the railway industry with a broad range of systems that meet rigorous application demands. 

Cable Protection Characteristics for Rugged Rail Industry Electronics 

Ingress Protection (IP) Ratings — Cable protection is critical for demanding applications where continuity of supply, performance, and safety is essential. Flooding is one of the most extreme hazards for electrical systems. If products are submerged in water, ingress protection of the fitting/system is of utmost importance. The higher the IP rating, the more protection there is against contaminants entering the system. Ingress protection is normally tested using EN IEC 60529 with the levels of protection designated by a two-digit code. The first digit signifies protection against solid objects and dust. The second digit designates protection against water. IP tests to EN IEC 60529 give an indication of system performance, but are short tests conducted in ideal laboratory conditions, at room temperatures and in straight lengths. This isn’t always a realistic application. Therefore, many applications require “over and above” standard IP tests.

To validate product performance, look for a manufacturer that has met these environmental demands by undergoing more than 1,000 individual ingress protection tests and meets IP66, IP67, IP68, and IP69 performance.

Cable protections for the rail industry

Fire — The challenge of reducing fire casualties is to employ the proper protections and equipment so that a fire does not pose additional hazards such as toxic fumes or smoke. Rail industry electronics including connectors, cables, and conduits should exhibit low-fire-hazard properties, such as flame retardancy, low smoke emissions and toxicity, and halogen-free materials. Just as there are various procedures and codes to reduce the risk of fire, numerous tests and measures are used to ensure a low-fire-hazard product.

Flame Retardance — To assess how flame-retardant a material is, the defined test method is to measure the Limiting Oxygen Index (LOI) according to BS EN ISO 4589-2, which determines the percentage of oxygen that needs to be present to support combustion. The higher the LOI percentage, the greater the flame retardancy of the material. A normal oxygen level is approximately 21%.

Smoke A specified sample of material is burned under controlled conditions in a smoke chamber, and the smoke observation of a defined beam of light is measured. The lower the smoke density, the more efficient evacuation and safety becomes.

Toxicity A specified sample of material is burned under controlled conditions in a smoke chamber, and the fumes are analyzed for various gases. The concentration of each gas is then multiplied by its toxic potency to give a toxicity index. Although toxicity and smoke tests are similar, the results and the requirements are different. If halogen, sulphur, or phosphorus is present, the material is unlikely to pass the low toxicity test. 

Halogen Halogen-based materials give off highly toxic fumes and often thick smoke. A material cannot be considered a low fire hazard if it contains halogen. However, all halogen-free materials do not necessarily qualify as low fire hazards; they must also be low-toxicity, low-smoke, and highly flame-retardant. Halogen content is assessed by various chemical tests and analytical techniques.

Connectors, cables, conduits, and fittings should also comply with the strictest rail industry electronics standards, including NFPA 130, which specifies fire protection and life safety requirements for underground, surface, and elevated fixed guideway transit and passenger rail systems to ensure safety.

Cable protections for the rail industry

Vibration and Shock Resistance — Moving rail cars are constantly exposed to vibration hazards during regular operation. The proper connectors, cables, conduits, and fittings can help offset this risk by providing anti-vibration performance that has been tested to and complies with EN 61373 Railway Applications for Rolling Stock Equipment. EN 61373 tests conduits against vibration and shock, ensuring that system integrity is maintained. Additional tests can be run for fatigue life on systems that have constant motion such as inter-car jumpers. This fatigue life test subjects the system to one million cycles, representing 35 years of service life. Assuming that there are no signs of failure during the tests, it shows that the products can exceed one million cycles.

Tensile Strength — Specifiers, installers, and contractors rely on tensile strength to ensure the integrity of the system when there is a lot of motion, vibration, and pulling on connectors, cables, and conduits. Tensile strength is the maximum stress that a material can withstand while being stretched or pulled before breaking. Connector systems should offer a superior tensile and impact compression strength. Look for a fitting with all-round teeth to provide anti-vibration protection together with a high pull-off strength (up to 154 pounds).

Strong Supplier Partnerships Support Success in Rail Industry Applications

The rail industry is a technically demanding sector that presents numerous challenges when it comes to product performance and compliance to global standards. To position your operations for success, find a trusted supplier that will partner with you on material technologies and industrial design to manage and control risk, make procurement more efficient, and continuously strive for improved operations.

To learn more, visit Flexicon online.

Like this article? Check out our other Connector and Cable Basics articles, our 2019 Article Archive, and our Transportation Market Page.

Frank Ball
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