Nfpa 79; Ansi B11 - Siemens SINAMICS S120 Function Manual

10.3.3

NFPA 79

Standard NFPA 79 (Electrical Standard for Industrial Machinery) applies to electrical
equipment on industrial machines with rated voltages of less than 600 V. A group of
machines that operate together in a coordinated fashion is also considered to be one
machine.
For programmable electronics and communication buses, NFPA 79 states as a basic
requirement that these must be listed if they are to be used to implement and execute safety-
related functions. If this requirement is fulfilled, then electronic controls and communication
buses can also be used for Emergency Stop functions, Stop Categories 0 and 1 (refer to
NFPA 79 9.2.5.4.1.4). Just the same as EN 60204-1, NFPA 79 no longer specifies that the
electrical energy must be disconnected by electromechanical means for emergency stop
functions.
The core requirements regarding programmable electronics and communication buses in
accordance with NFPA 79 9.4.3:
1. Control systems that contain software-based controllers must:
– In the event of a single fault
– Offer the same level of protection as hard-wired controllers
– Be implemented in accordance with a recognized standard that defines the
2. IEC 61508, IEC 62061, ISO 13849-1, ISO 13849-2 and IEC 61800-5-2 are specified as
suitable standards in a note.
Underwriter Laboratories Inc. (UL) has defined a special category for "Programmable Safety
Controllers" for implementing this requirement (code NRGF). This category covers control
devices that contain software and are designed for use in safety-related functions.
A precise description of the category and a list of devices that fulfill this requirement can be
found on the Internet at the following address:
NRGF (http://www.ul.com) → Online Certifications Directory → UL Category code/Guide
information → search for category "NRGF"
TUV Rheinland of North America, Inc. is also an NRTL for these applications.
10.3.4

ANSI B11

ANSI B11 standards are joint standards developed by associations such as the Association
for Manufacturing Technology (AMT) and the Robotic Industries Association (RIA).
The hazards of a machine are evaluated by means of a risk analysis/assessment. The risk
analysis is an important requirement in accordance with NFPA 79, ANSI/RIA 15.06, ANSI
B11.TR-3 and SEMI S10 (semiconductors). The documented results of a risk analysis can
be used to select a suitable safety system based on the safety class of the application in
question.
Safety Integrated
Function Manual, 12/2018, 6SL3097-5AR00-0BP1
(a) Initiate that the system switches to a safe shutdown mode
(b) Prevent the system from restarting until the fault has been rectified
(c) Prevent an unexpected restart
requirements for such systems.
Standards and regulations
10.3 Machine safety in the USA
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