Catalog relay modules - DOLD - #25

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Safety technique CCF Common Cause Failure Failures of différent units due to a single event, with the failures being not due to each other. DC Diagnostic coverage Ratio between the failure rate of detected dangerous failures and the fail­ure rate of all dangerous failures Discrepancy monitoring Tolerates the lack of synchronization of related signals over a defined time window. REMARK 1: Also the term "Simultaneity monitoring" is used. REMARK 2: The monitoring of signal transmitters is used to increase the functional safety. It is done by checking the signal transmitters's signal change within a specified time. If this time is exceeded, no enable signal will be output. Such a monitoring is required for some safety systems (— two-hand operation). Diversity Diverse redundancy System design with different measures for the same objective to avoid systematic errors. Speed monitoring, safety-related Safety-related monitoring of a defined rotational speed. NOTE 1: The drive is turned off or an alarm is issued when this speed is overun or underrun. Dynamic testing - Testing Earth-fault detection When an earth fault is detected the device goes to the agreed safe state either immediately or in the course of a cyclic self-monitoring. Expansion unit An expansion unit is a - safety-related evaluation unite that can only be used in connection with a - basic unit for purpose of contact or input multiplication. - Output expansion units are incorporated in the - cyclic self-monitoring. Distinction: - Output expansion unit for multiplication of safety outputs —Input expansion unit for multiplication of safety inputs Fault response time First fault occurrence time: This is the time interval in which the probability that a safety-critical first fault occurs for the requirement class involved is sufficiently low. The time interval starts with the last instant in time at which the system involved was in a state that can be assumed as being fault-free for the requirement class being considered. NOTE: Fault-controlling measures are not taken into account. Occurrence time for multiple faults: This is the time interval in which the probability that combined safety-critical multiple faults occur is sufficiently low for the requirement class involved. The time interval starts with the last instant in time at which the system involved was in a state that can be assumed as being fault-free for the requirement class being considered. Fault tolerance time Time interval in which the process can receive incorrect control signals without a hazardous state occurring. FIT F ailure i n T ime Describes the failure rate of technical components, in particular electronic components. The unit FIT indicates the number of components that fail within 109 hours. Statistically, components having a high FIT value fail more frequently than those having a lower FIT value. Failure rate at a FIT value l = 1/109 h, that means once in approx. 114 000 years. l Failure rate of a component in — FIT total Failure rate Failure rate of the device in — FIT. FMEDA Failure Modes, Effects and Diagnostic Analysis Enable circuit Generates a safety-related output signal. NOTE: To the outside, enable circuits act as NO contact (— OSSD). Function test Testing of the expected function of a device. NOTE: The function test can either be realized automatically using the control system or manually by monitoring or testing - when operational and at defined time intervals or as a combination depending on the requirement [DIN EN 60204-1, paragraph 9.4.2.4]. Controlled stopping — Stop function Simultaneity monitoring The simultaneity monitoring of signal transmitters by the safety-related evaluation unit is used to increase the functional safety of the protective safety device. The monitoring function is realized by checking the signal change of the signal transmitters within the specified time - the synchro-nous monitoring time. If this time is exceeded, no enable signal will be output. A simultaneity monitoring is required for several safety devices (— two-hand circuit). Basic device — Basic unit Category Classification of safety-related parts of a control system with respect to their resilience against and behaviour during faults (B, 1, 2, 3, and 4) that is reached by the structural arrangement of the parts and/or their reliabili-ty. [DIN EN 954-1, see also DIN EN ISO 13849-1]. Magnetically-operated switch — Signal transmitter, PDF Occurrence time for multiple faults — Fault response time — Occurrence time for multiple faults Signaling output — Signaling circuit Signaling circuit A signaling circuit is used to generate a non safety-related output signal. MTTFd Mean Time To Failure dangerous Muting The safety-related function is correctly and deliberately disabled using ad-ditional sensors for a limited time (a type of bypass function). [IEC / DIN EN 61496-1]. 27