Blog post: The importance of RAMS in power supply of rail infrastructure

January 28, 2020

Across the globe, railway authorities need systems which are reliable, safe, high-quality and have low operating and maintenance costs.

The power supply system is a critical sub-system in any railway application. In order to ensure the performance of this sub-system, the establishment of the Reliability Availability and Maintainability (RAM) Programme in combination with a solid safety plan are essential components in the realization of this objective. The interaction between the four elements reliability, availability, maintainability and safety and weakness in any of them or mismanagement of the conflicts between their requirements can prevent achievement of a dependable system. Especially in case of power supply system the objectives, requirements, deliverables and verification and validation activities need to be assessed throughout the life cycle phase. Any power supply system supplier offering ready to operate turnkey solutions has various risks inherent to the system, but some risks are so huge and certain outcomes are intolerable and cannot be justified at any cost.

Understanding the boundary between the system and its environment and the interactions with its interrelated subsystems is a pre-requisite to understanding how failures of the power supply system might contribute to an incident and what its hazards are. Depending on the power supply system design additional requirements might also be needed to ensure proper functioning of the system.

At Linxon the detailed design stage involves, engineering of sub-system and equipment’s that implement the RAMS requirements of the system. Hence in order to ensuring compatibility between the different sub systems/equipment’s and thus implement the refined requirements ensuring the coherence the technical and contextual requirements.

RAM analysis and design trade-offs are generally made during the design implementation phase. The design consideration for RAM allows minimizing the system life cycle cost, especially maintenance costs, and the disturbances of the service operation. These guidelines during design phase are based on our experience from previous projects and system knowledge developed over the years. During the design phase reliability is built into the system through the use of fault tolerance and design margins. It assesses the failure characteristics of systems to identify areas of design weakness and propose corrective solutions.

We ensure that the RAM programme and safety plan should give an overview of the activities within the power supply system to demonstrate and to ensure that the requirements for RAM can be met for the system. RAMS document includes comprehensive details of the management process from development to operation of the power supply systems. Also during the procurement phase our selection of components/products within the power supply system is not only based on the parameters of Mean Time to Maintain corrective or preventive, availability of spare parts but also Mean Time between Failures (MTBF) or failure rate and Mean Time to Restore (MTTR) along with consideration of obsolescence management. Appropriate tools and methods are be used for conducting and managing RAM Programme and Safety Plan.

Further throughout the life cycle of the project we prepare and update interface management Plan which ensures overall system is successfully integrated and harmonizes correct operation of the equipment’s for the project. Failure to integrate these power supply systems properly will introduce the probability of an electrical or control system failure. This could then have a subsequent disturbance to the operation of the railway.

Thus Linxon takes into consideration the life cycle cost of the system which starts at the system definition phase carried through the design phase to construction to start of revenue operation until the end of the warranty period for power supply system. Railway authorities also need to recognize the criticality of RAM programme and safety plan for power supply system and proper integrations of power supply systems with overall system. Failure to do so will have a subsequent consequence on delivering a railway free from electrical disturbances during the operation and maintenance period of the project.

By Yasir Shah
LinkedIn post here.