Introduction of RAMS Assurance Strategy for a Metro 28/10/2016
Recently I have received an enquiry for a consultancy for a new Metro to develop a RAMS strategy
The RAMS Assurance strategy entails developing an approach to specify RAMS requirements and develop an assurance framework to manage the delivery against the RAMS requirements.
Any new metro envisages bringing convenience to people. How good a metro is assessed by the following key aspects such as:-
• how safe the Metro is,
• how reliable the Metro is,
• how quickly the Metro can transport passengers with adequate passenger comfort.
These aspects of the Metro are driven by safety, RAM and performance requirements.
A common issue with the specifications of the metros is that they generally specify a lot of technical requirements which often cross to the design territory thus transferring unnecessary risk to the client side. But these specifications often fail to specify these key safety/performance/RAM aspects in the form of tangible requirements. Even in the cases they are specified many a time there will not be a robust assurance process put in place for the realisation of these requirements
How safe is safe enough? The objective of safety requirements is to ensure adequate safety for passengers, staff and other members of public. Development of strategy encompasses developing technical safety criteria for various safety functions, stipulating engineering processes for design development, testing and commissioning, minimising safety risk adequately to comply with any legislations as well as adhering to good practices.
A preliminary functional safety analysis will be undertaken to identify the safety-related functions of the solution. This exercise will also help to determine the necessary fail-safe features and Safety Integrity Level (SIL) criteria for the functions. Further it can also facilitate in developing requirements for the various safety features required in the design.
System safety for the modern metro systems is ensured by the robustness of the engineering processes employed in the design development. Safety and RAM process requirements will be driven by the processes from CENELEC standards EN50126/128/129, Common Safety Methods. Bear in mind these are generic processes for product/subsystem/system level applications, a customised value-engineered application of these processes for the project under consideration is important to accomplish the required quality at a minimum cost.
A popular impression of RAM is that RAM is all about numerical RAM requirements. Though numerical requirements are key aspects to RAM, RAM performance of a system will be driven by value-engineered design development. How much reliable the Metro you want it to be, is a business decision. For e.g. A metro with all equipment in redundant and diverse configuration are likely to be highly available but will also have a high lifecycle cost.
A robust RAM specification is the basis to realise a reliable metro. Considering value engineering aspects, the specification can be developed based on proven solutions in the market plus any required level of function/performance improvement. Another aspect to keep in mind is that a solution becomes ‘proven’ after working through many years and after implementation of a lot of customised improvements to the solution. Consequence of this aspect is that a proven solution could very well be outdated.
Notwithstanding the typical failure impact of normal metro solutions, a preliminary functional failure analysis is useful to determine what type of failures which could have a significant impact in the Metro under consideration. This gives an opportunity that these issues can be designed out by specifying accordingly in the specifications. Another output of this exercise is a set of technical design/architecture features required to enhance the RAM performance.
The quantitative requirements which are derived from the established solutions in the market are then functionally modelled to evaluate the business benefits which can be realised. The output of this functional model can be used as a part justification of the business case for the Metro.
Assurance framework requirements
A popular misconception of Assurance is that it is a bureaucratic, expensive process with little value addition and cause delays to the delivery of the project.
The objective of assurance shall be to identify risk of non-compliance at the earliest opportunity so that mitigations can be taken well in time. A well-established assurance regime will improve the efficiency of delivery as well as ensure high quality. The assurance regime shall include progressive stage gate reviews, independent safety and RAM assessments, inter-discipline design reviews
Having said that, a collaborative working with the suppliers, client and assurance bodies is important for the timely delivery of the project whilst maintaining the independence of assurance regime. The primary objective of the Assurance is to engage with all stake holders in order to ensure implementation of adequate risk mitigation in a timely manner in order to meet the delivery deadlines.
The RAMS strategy for the Metro would detail the following key elements.
Develop a set of value-engineered technical RAM and safety requirements for the Metro systems namely Rolling stock, signalling, power, station systems and other trackside infrastructure systems. Development of RAMS requirements will use scientific RAMS techniques, in-service data from other Metros and any specific customer requirements.
These RAMS requirements will be validated by system modelling in order to justify business case and value engineering.
Develop engineering process requirements to efficiently realise the technical requirements by the design development.