Baker Hughes Masoneilan 12400 Series, Instruction Manual & Safety Manual, Page: 47 / 81

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8. Safety manual for SIL applications
8.1. RELEVANT STANDARDS
a.
IEC 61508 (also available as DIN EN )
Functional safety of electrical/electronic/programmable electronic safety-related systems
b. IEC 61511 (also available as DIN EN )
Functional safety - safety-instrumented systems for the process industry sector
8.2. TERMS AND DEFINITIONS
FIT
Failure In Time (1x10
-9
failures per hour)
FMEDA Failure Mode Effect and Diagnostic Analysis
HFT Hardware Fault Tolerance
Low Demand mode Mode, where the frequency of demands for operation made on a non-safety related system is no
greater than twice the proof test frequency
MTTR Mean Time To Repair
PFD
avg
Average Probability of Failure on Demand
Safety Accuracy The measurement error that occurs due to component degradation and failure during the useful life
of an instrument.
SFF Safe Failure Fraction, summarizes the fraction of failures, which leads to a safe state and the fraction
of failures which will be detected by diagnostic measures and lead to a defined safety action
SIF Safety Instrumented Function
SIL Safety Integrity Level
SIS Safety Instrumented System – Implementation of one or more Safety Instrumented Function. A SIS is
composed of any combination of sensor(s), logic solver(s), and final element(s).
Type A component "Non-Complex" component (using discrete elements); for details see IEC 61508-2
Type B component "Complex" component (using micro controllers or programmable logic); for details see IEC 61508-2

sd
Rate for Safe Detected failure

su
Rate for Safe Undetected failure

dd
Rate for Dangerous Detected failure

du
Rate for Dangerous Undetected failures