High demand
mode
The safety function is only performed on demand, in order to
transfer the EUC (Equipment Under Control) into a specified safe
state, and where the frequency of demands is greater than one per
year (IEC 61508-4).
Low demand
mode
The safety function is only performed on demand, in order to
transfer the EUC into a specified safe state, and where the
frequency of demands is no greater than one per year (IEC
61508-4).
PFD
AVG
Average Probability of Failure on Demand
PFH
Probability of dangerous failure per hour.
PPT
Partial Proof Test
Random Integrity
The SIL limit imposed by the architectural constraints that must be
met for each element.
Safety Demand
Interval
The expected time between safety demands.
Systematic
Capability
A measure (expressed on a scale of SC 1 to SC 4) of the confidence
that the systematic safety integrity of an element meets the
requirements of the specified SIL, in respect of the specified
element safety function, when the element is applied in
accordance with the instructions specified in the compliant item
safety manual for the element as per 61508-4
SFF
Safe Failure Fraction
SIF
Safety Instrumented Function
SIL
Safety Integrity Level - a discrete level (one out of four) for
specifying the safety integrity requirements of the safety
instrumented functions to be allocated to the safety instrumented
systems. SIL 4 has the highest level of safety integrity, and SIL 1 has
the lowest level.
SIS
Safety Instrumented System (SIS) - an instrumented system used
to implement one or more safety instrumented functions. An SIS is
composed of any combination of sensors, logic solvers, and final
elements.
Type B device
Complex device using controllers or programmable logic, as
defined by the standard IEC 61508.
1.5 Skill level requirement
System design, installation and commissioning, and repair and maintenance shall be
carried out by suitably qualified personnel.
1.6
Documentation and standards
This section lists the documentation and standards referred to by this safety manual.
Before you begin
4 Rosemount
™
8800D Safety Manual
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