ISO 19880-1-2020 pdf download.Gaseous hydrogen一Fuelling stations一 Part 1: General requirements.
3.71 safety function
function to be implemented by a safety-instrumented system (172). which is intended to achieve or maintain a safe state for the process, with respect to a specific hazardous situation
Note 1 to entry: Other technologies or risk reduction measures have a safety function not achieved through a safety-instrumented system, however validation of these measures Is equally important.
3.72 safety-instrumented system
S’S instrumented system used to implement one or more safety-instrumented functions
Note ito entry: A safety-instrumented system is composed of any combination of sensors, logic solvers, and final elements.
Note 2 to entry: A separate safety-instrumented system (SIS), typically with a greater reliability than the more basic process control system (BPCS) (j4), can be required, according to the manufacturer’s risk assessment (3.Ith). to respond solely to safety critical alarms. Further information is provided by IEC 61508 and IEC 61511.
3.73 safety Integrity level
SIL discrete level (one out of a possible four), corresponding to a range of safety integrity values, where safety integrity level 4 has the highest level of safety integrity and safety integrity level 1 has the lowest
Note Ito entry: The target failure measures (see IEC 61508-4) for the four safety integrity levels are specified in IEC 61508-1:2010, Tables 2 and 3.
Note 2 to entry: Safety integrity levels are used for specifying the safety integrity requirements of the safety functions (171) to be allocated to the E/E/PE safety-related systems (174).
Note 3 to entry: A safety integrity level (SIL) is not a property of a system, subsystem, element or component. The correct interpretation of the phrase SlL n safety-related system” (where n is 1, 2, 3 or 4) is that the system is potentially capable of supporting safety functions with a safety integrity level upton.
Note 4 to entry: See Z.
[SOURCE: IEC 61508-4:2010, 3.5.8, modified — Note 4 to entry has been added.J
3.74 safety-related system
designated system that both implements the required safety functions (121) necessary to achieve or maintain a safe state for the EUC and is intended to achieve, on its own or with other E/E/PE safety- related systems, other technology safety-related systems or external risk reduction facilities, the necessary safety integrity for the required safety functions
Note 1 to entry: The term refers to those systems, designated as safety-related systems, that are intended to achieve, together with the external risk reduction facilities (IEC 61508-5:2010, 3.4.3), the necessary risk reduction in order to meet the required tolerable risk (IEC 61508-5:2010, 3.1.6 and Annex A).
Note 2 to entry: The safety-related systems are designed to prevent the EUC from going into a dangerous state by taking appropriate action on receipt of commands. The failure of a safety-related system would be included in the events leading to the determined hazard (1.36) or hazards. Although there can be other systems having safety functions, it is the safety-related systems that have been designated to achieve, in their own right, the required tolerable risk. Safety-related systems can broadly be divided into safety-related control systems (111) and safety-related protection systems. and have two modes of operation (IEC 61508-5:2010, 3.5.12).
Note 3 to entry: Safety-related systems are potentially an integral part of the EUC control system or interface with the EUC by sensors and/or actuators. That is. the required safety integrity level (173) is achieved by implementing the safety functions in the EUC control system (and possibly by additional separate and independent systems as well) or the safety functions can be implemented by separate and independent systems dedicated to safety.ISO 19880-1 pdf download.