NR/L2/RSE/0005 ISSUE 2
Product Design for Reliability
|Publication Date:||2 December 2017|
This business process describes the process to design reliability into specific products seeking PA from Network Rail. It applies to existing and potential suppliers, and Network Rail staff in departments including Engineering, Procurement, Supplier Quality Assurance (SQA), Reliability and Product Acceptance.
In line with the Railways (Interoperability) Regulations 2011, any additional tests or requirements stated in this procedure for characteristics that are already defined in the TSI, do not apply and the assessor should request the certification instead, or ask the supplier to demonstrate they have met the essential requirements.
This business process does not outline the full set of PA requirements or entire design process. Other non-reliability specific steps are included for context. This process starts once the need for a product has been identified and ends once the product is being used in service with the confidence that it meets its required reliability performance, which either:
a) improves upon the reliability, availability or whole life cost of the item it replaces (or is no worse than an obsolete product it replaces that performed with the desired level of reliability);
b) has a net reliability benefit when implemented to address another issue; or
c) resolves an inherent safety issue even if the MTBF of any proven rapid interim fix would normally not be acceptable, followed by a redesign using this procedure that achieves both the safety and reliability requirements or a justification of why a redesign is not possible/desirable.
This business process applies to new and changed rail infrastructure products, systems, sub-systems, gauges, materials, On-Track Machines and rail specific parts of On-Track Plant entering the PA process. It also applies to products for use in new applications with changes in product requirements. NR's requirements should allow innovation by not being unnecessarily solution specific, but rigorous structured assessment and testing is still required. To use part of an approved product, made by the same manufacturer, as a spare for itself, no DFR assessment will be required, as part of the PA process.
This business process integrates proven tools and methodologies into a supplier's existing design processes to create documented, traceable, controlled evidence of reliability, availability and maintainability. It helps enable compliance with BS EN 50126 before product acceptance (PA) is granted by Network Rail and addresses train delay risk resulting from asset reliability.
Reliability tools and methods are now mandated and integrated into the design process in an effective sequence. This means that changes are identified earlier, add more value, are easier, more time efficient and more cost effective to implement. This process focuses upon products, rather than geographical areas consisting of a range of products, although similar techniques can be applied.
The requirement definition steps can help focus innovation in the correct direction. Many of the subsequent steps are most powerful when applied to novel designs in order to build confidence in the absence of historic data.