Rail connectors are required for inter-car and trackside applications, signalling, CCTV and braking systems, door control mechanisms, climate control equipment and passenger information and communication systems. However, no matter how diverse the application, many factors are common to all connectors used in the rail industry. Wherever the connectors are used they are subjected to severe stress, vibration, shock and fretting corrosion so it is vital that they have a secure locking system, high mechanical endurance and are environmentally sealed to at least IP67. 

Secure coupling and protection

Bayonet locking mechanisms are widely used because this method provides secure and quick mating with a simple quarter turn providing the high level of security required. In addition, the quick, sure connection simplifies maintenance and service, a key priority in the pursuit of reliability and safety within the industry.  

Typical connectors used are the Mil-C 5015 reverse bayonet, positive-lock connectors such as the ABCIRH range manufactured by AB Connectors that have become almost a universal connector in the industry together with its ‘sister’ range the ABCIRP. The latter has a removable insulator that allows for additional capacity to be incorporated at a later date and clip-retained crimp contacts as preferred and approved for rail equipment by SNCF, the French Mass Transit Authority and Alstom. Both ranges provide high shock and vibration performance without the need for time-consuming wire-locking and, in addition, a comprehensive range of backshells provides full environmental sealing.   

High strength conduit systems, such as those provided by Glenair, are also necessary for use on inter-car assemblies to protect sensitive cables against flying ballast and pervasive weather conditions. Connectors used in this environment are often fitted with rubberised coupling nuts and shells such as are produced by AB Connectors for its ABCIRH range.

New technology

Despite the use of highly secure coupling methods, individual contacts still come under severe pressure and this has led to new developments in the connector industry as manufacturers strive for improved methods. For instance, Hypertac's hyperboloid contact technology produces contact resistance figures as low as 0.05mW and this dramatically reduces resistive losses. This simplifies the task of thermal management, allows better power handling in a much smaller shell size and provides up to 1A per contact at 110V DC. It allows far higher connection density than is attained by other systems and the method also allows connectors to sustain their electrical integrity, even after more than 1,000 mating cycles.

Safety first and flexibility

Safety concerns are paramount and this leads to the use of low fire hazard and halogen-free rubber insulators, grommets and bushes that comply with the French specification NFF16-101 and BS6853. Connectors using non-cadmium plated components are also often specified.

Because of the variation of types of equipment installed in the rail industry, there is a strong demand for connectors to carry a wide range of power and signal contacts and this has led to the design of mixed format connectors that incorporate larger power contacts, small signalling contacts and coaxial and tri-axial contacts in the same body shell. 

AE 414X AB CIRP connectors

Another requirement in the rail industry is that because of the massive investments involved in rolling stock, it is essential that systems can be used to upgrade existing rail cars and this leads to a demand for modular connectors. Hypertac's L and H series are ideally suited to this, with the latter having a frame built to accommodate up to 1,000 contacts. The Hypertac hyperboloid contact described above provides another crucial advantage here in that the lower insertion force becomes a critical consideration when mating such a highly populated connector.

High speed data

Increasingly, there is a demand for high speed data transfer on board trains with growing requirements for Ethernet and fibre optic connections for passenger information systems, CCTV and monitoring equipment. The well-proven RSC range from Deutsch now includes an expanded beam version that enhances the performance of the optical interface with spring-loaded optical contacts and an anti-vibration coupling mechanism that maintains physical contact even under extreme vibration.

Conform or die

The IRIS certificate (International Railway Industry Standard) was introduced to ensure the quality and uniformity of systems and processes for suppliers to the European rail manufacturers. This is an extension of ISO9001 and is supported by UNIFE, the association of the European rail industry, and key manufacturers such as Bombardier, Siemens, Alstom and AnsaldoBreda. Holding the certification qualifies component manufacturers to work with railway equipment manufacturers, system integrators and assemblers. At Aerco we ensure that we work with major connector and accessory manufacturers who hold IRIS qualification such as AB Connectors, Hypertac, Glenair and ITT Cannon.

Aerco is also a member of RIA (Railway Industry Association), an organisation that represents the greater part of the UK rail supply industry and ensures that its members are provided with the latest technical, commercial and political information. RIA ensures that the industry’s interests are fully represented to the government and Network Rail. In addition, Aerco now subscribes to Link-up, an organisation that manages a list of approved suppliers to the rail industry.

Rewards for investment

The rail industry is very demanding for connector manufacturers and suppliers and it is essential that products comply with the standards and technical recommendations set by various industrial bodies and organisations before any success can be achieved in this area.  On the other hand it is a growing and vibrant market and to companies prepared to make the considerable investment it can be rewarding.

Alec Sluce is connector product manager at Aerco

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