In the latest BtoBrail magazine, we discuss the solutions developed by CLEARSY for the realisation of railway interlocking using COTS SIL4 certified PLCs, which replace traditional hardwired logic solutions based on NS1 gravity relays or dedicated computers. This innovation allows for easy design, certification, deployment, and maintenance throughout the life of the system, as well as easy renewal.
The architecture proposed by CLEARSY is based on a HIMA safety PLC coupled with CLEARSY RS4 SIL4 relays, which interface with the trackside-controlled equipment. The documents are submitted to an independent certification body to obtain a positive SIL4 evaluation report. The resulting system is easy to integrate, is scalable during the project – there is no need to fix the number and the type of relays at the start of the project as is the case with relay cabinet-based solutions – and the space required is considerably reduced. The CLEARSY solution has been used in several tramway projects in Europe.