Relevant Standards; Abbreviations And Terms - WIKA T32. S Serie Manual De Seguridad

1. General information

1.3 Relevant standards

Standard Model T32.xS
Functional safety of electrical/electronic/programmable/ electronic safety-
IEC 61508:2010
related systems

1.4 Abbreviations and terms

Abbreviation Description
λ + λ λ
SD SU
A safe failure is present when the measuring system switches to the defined
safe state or the fault signalling mode without the process demanding it.
λ + λ λ
DD DU
Generally a failure to danger occurs if the measuring system, through this, can
switch into a dangerous or functionally inoperable condition. With detected
failures to danger, the failure is detected by diagnostic tests or proof testing,
for example, where the system switches to the safe state. With undetected
failures to danger, the failure is not detected through diagnostic tests.
Operating mode In this operating mode, the safety function of the safety system is only carried
with low demand out on request. The frequency of the request is no more than once a year.
rate
DC Diagnostic coverage, percentage of failures to danger that are detected by
automatic diagnostic online tests.
FMEDA Failure modes, effects and diagnostic analysis, methods to detect failure
causes, and also their impact on the system, and to define diagnostic
measures.
HFT Hardware fault tolerance, capability of a functional unit to continue the
execution of the demanded function when faults or deviations exist.
MooN (M out of The architecture describes the specific configuration of hardware and software
N) architecture in a system. N is the number of parallel channels and M defines how many
channels must be working correctly.
MRT Mean Repair Time
Mean Time To Repair
MTTR
PFD Average probability of a dangerous failure on demand of the safety function
avg
SC Systematic capability
The systematic capability of an element (SC 1 to SC 4) states that the
systematic safety integrity for the corresponding SIL is achieved.
Safe Failure Fraction
SFF
SIL Safety Integrity Level, the international standard IEC 61508 defines four
discrete safety integrity levels (SIL 1 to SIL 4). Each level corresponds to a
range of probability with which a safety-related system performs the specified
safety functions in accordance with the requirements. The higher the safety
integrity level of the safety-related system, the greater the probability that the
safety function is executed.
WIKA safety manual temperature transmitter T32.xS
safe detected + λ
SD SU
dangerous detected + λ
DD
safe undetected
dangerous undetected
DU
EN
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