8 Rockwell Automation Publication 843ES-UM001A-EN-P - February 2020
Preface
Terminology
This table defines common safety terms that are used throughout this
publication.
Abbreviation Full Term Definition
— Control application Program that is designed using Studio 5000 Logix Designer and downloaded to the controller.
— Safety control application
Safety program that is designed using Studio 5000 Logix Designer and downloaded to the
GuardLogix controller for functional safety.
— Safe motion monitoring drive
A drive that supports safety feedback and communicates safety function status or control over the
EtherNet/IP network.
—Standard
Automation devices, logic, or functions that do not participate in safety-related functions. Other
commonly used terms are “not safety-related,” “non-safe,” “unsafe,” and “normal integrity.”
1oo2 One out of two Refers to the behavioral design of a dual-channel safety system.
CAT.x Category
ISO 13849-1 safety category. Categories define the structure, either single or dual.
(CAT.1 and CAT.2 = single, CAT.3 and CAT.4 = dual).
CIP™ Common Industrial Protocol Protocol for industrial automation applications and trademarked by ODVA, Inc.
DC Diagnostic Coverage The ratio of the detected failure rate to the total failure rate.
EN European Norm
European Standards (EN specifications) developed by the European Committee for Standardization
for the European Union.
FMEA Failure Mode and Effects Analysis
Analysis of potential failure modes to determine the effect upon the system and identify ways to
mitigate those effects.
HFT Hardware Fault Tolerance
The HFT equals n, where n+1 faults could cause the loss of the safety function. An HFT of 1 means
that 2 faults are required before safety is lost.
IEC International Electrotechnical Commission
Non-profit, non-governmental international standards organization that prepares and publishes
international standards for all electrical, electronic, and related technologies, collectively known as
electrotechnology.
ISO International Organization for Standardization
Voluntary organization whose members are recognized authorities on standards, each one represents
a different country.
PES Programmable Electronic Systems
System for control, protection, or monitoring based on one or more programmable electronic devices,
including all elements of the system such as power supplies, sensors and other input devices, data
highways and other communication paths, and actuators and other output devices.
PFD Probability of a dangerous failure on demand The average probability of a system to fail to perform its design function on demand.
PFH Average Frequency of a Dangerous Failure The average frequency of a system to have a dangerous undetected failure occur per hour.
PLx Performance Level
ISO 13849-1 safety category. Replace the x with an a, b, c, d, or e (e is the highest level of safety
performance).
RPI Requested Packet Interval The update rate specified for a particular piece of data on the network.
SFF Safe Failure Fraction The sum of safe failures plus the sum of dangerous detected failures divided by the sum of all failures.
SILx Safety Integrity Level
A measure of a products ability to lower the risk that a dangerous failure could occur. Replace the x
with a 1, 2, or 3 (4 is not applicable to automation).
SNN Safety Network Number
Safety network number, which uniquely identifies a network across all networks in the safety system.
You are responsible for assigning a unique number for each safety network or safety subnet within a
system.
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