Severn Tunnel Pull Wire System Risk Assessment

Vertex Systems Engineering (Vertex) has been awarded a contract from Network Rail for the provision of CSM support services for the Severn Tunnel Pull Wire Risk Assessment.

The South Wales Immunisation Mainline Project (SWIM) has been established to provide signalling support for the electrification of the Great Western Main Line between Patchway and Cardiff. There are two main elements of the SWIM project:

Provide gauge clearance of signal structures to the UK1 pantograph gauge which includes the relocation of signals to mitigate the impact of the new OLE on the sighting of the signals.

To immunise the signalling infrastructure on the lines where OLE is to be provided to ensure that the signalling system retains the same level of reliability, availability, maintainability and safety under electrification.

The SWIM project is remitted by GWRM to immunise all signalling assets within Route Section 8 & 9 this includes the Severn Tunnel Pull Wire. Early discussions with the manufacturer has revealed that replacing the current pull wire with a new AC immune system will be difficult and coupled with this there is a strong desire within the Wales Route to remove the pull wire with resulting gains in safety (by reduction to staff exposure to hazardous environments) and maintenance burden (by removal of the periodic tasks associated with the pull wire).

Vertex’s remit is to undertake a risk assessment be undertaken to propose a solution for immunisation of the Severn Tunnel pull wire system. The definition of immunisation to be considered includes removal of the current system by demonstrating that its function is replicated by existing systems or that it can be replicated by existing systems following amendments to the architecture, operational procedure and/or maintenance regime of the existing systems. The risk assessment to be used is the explicit risk estimation process in accordance with CSM-RA (Commission Implementing Regulation (EU) 402/2013) to demonstrate that the solution proposed is acceptable, unless a viable alternative method is proposed which is compliant with CSM-RA.

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