This standard specifies RAMS in terms of reliability, availability, maintainability and safety and their interaction; specifies a process, based on the system life cycle and tasks within it, for managing RAMS; enables conflicts between RAMS elements to be controlled and managed effectively; specifies a systematic process for specifying requirements for RAMS and demonstrating that these requirements are achieved.
This standard does not specifies RAMS targets, quantities, requirements or solutions for specific railway applications; does not specifies requirements for ensuring system security; such requirements shall be specified in sub-standards of RAMS for specific railway applications.
This standard is applicable:
a) to the specification and demonstration of RAMS for all railway applications and at all levels of such an application, as appropriate, from complete railway routes to major systems within a railway route, and to individual and combined sub-systems and components within these major systems, including those containing software; in particular:
— to new systems,
— to new systems integrated into existing systems in operation prior to the creation of this standard, although it is not generally applicable to other aspects of the existing system,
— to modifications of existing systems in operation prior to the creation of this standard; although it is not generally applicable to other aspects of the existing system;
b) at all relevant phases of the life cycle of an application;
c) for use by Railway Authorities and railway support industry.
Note: Guidance on the applicability is given in the requirements of this standard.
2 Normative References
The following normative document contains provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. For undated references, the latest edition of the normative document referred to applies.
GB/T 19001-2000 Quality Management Systems — Requirements (idt ISO 9001:2000)
GB/T 20438 (all parts) Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems [IEC 61508 (all parts), IDT]
IEC 60050(191):1990 Railway Applications — Communications, Signalling and Processing Systems — Software for Railway Control and Protection Systems
IEC 62279:2003 Railway Applications — Safety Related Electronic Systems for Signalling
3 Terms and Definitions
For the purposes of this standard, the following terms and definitions apply.
3.1
apportionment
process whereby the RAMS elements for a system are sub-divided between the various items which comprise the system to provide individual targets
3.2
assessment
undertaking of an investigation in order to arrive at a judgement, based on evidence, of the suitability of a product
3.3
audit
systematic and independent examination to determine whether the procedures specific to the requirements of a product comply with the planned arrangements, are implemented effectively and are suitable to achieve the specified objectives
3.4
availability
ability of a product to be in a state to perform a required function under given conditions at a given instant of time or over a given time interval assuming that the required external resources are provided
3.5
commissioning
collective term for the activities undertaken to prepare a system or product prior to demonstrating that it meets its specified requirements
3.6
common cause failure
failure which is the result of an event(s) which causes a coincidence of failure states of two or more components leading to a system failing to perform its required function
3.7
compliance
demonstration that a characteristic or property of a product satisfies the stated requirements
3.8
configuration management
discipline applying technical and administrative direction and surveillance to identify and document the functional and physical characteristics of a configuration item, control change to those characteristics, record and report change processing and implementation status and verify compliance with specified requirements
3.9
corrective maintenance
maintenance carried out after fault recognition and intended to put a product into a state in
which it can perform a required function
3.10
dependent failure
failure of a set of events, the probability of which cannot be expressed as the simple product of the unconditional probabilities of the individual events
3.11
down time
time interval during which a product is in a down state
[IEC 60050(191), modified]
3.12
failure cause
circumstances during design, manufacture or use which have led to a failure
[IEC 60050(191)]
GB/T 21562-2008 The following standards are cited：
