Nrtl Listing; Nfpa 79 - Siemens SINUMERIK 840D sl Function Manual

03.06
1.3.2

NRTL listing

All electrical equipment and devices that are used in the US to protect workers
must be certified for the particular application by a "Nationally Recognized Testing
Laboratory" (NRTL) certified by OSHA. These "Nationally Recognized Testing Lab-
oratories" are authorized to certify equipment and material in the form of listing,
labeling or similar. Domestic standards such as the NFPA 79–2002 and also inter-
national Standards such as e.g. IEC 61508 for E/E/PES systems form the basis for
testing.
1.3.3

NFPA 79

NFPA 79 (Electrical Standard for Industrial Machinery) applies to electrical equip-
ment 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.)
The new of NFPA 79 – 2002 Edition includes some basic requirements for pro-
grammable electronics and communication buses if these are to be used to imple-
ment and execute safety-related functions. If these requirements are fulfilled, then
electronic controls and communication buses can also be used for Emergency
Stop functions, Stop Categories 0 and 1 (see NFPA 79 – 2002 9.2.5.4.1.4). Con-
trary to EN 60204–1, NFPA 79 specifies that for Emergency Stop functions, the
electrical energy must be disconnected using electro-mechanical elements.
The core requirements placed on programmable electronics and communication
buses include:
System requirements (see NFPA 79 – 2002 9.4.3)
S Control systems that include software-based controllers must,
(1) If an individual fault occurs,
– bring the system into a safe state to shut it down
– prevent restarting until the fault has been removed
– prevent unexpected starting
(2) Provide protection comparable to hard-wired controls
(3) Be implemented corresponding to a recognized Standard that defines the
requirements for such systems.
In a note, IEC 61508 is specified as a suitable Standard.
Requirements placed on programmable equipment (see NFPA 79 – 2002 11.3.4)
S Software and firmware-based controllers, that are used in safety-related func-
tions, must be listed for such an application (i.e. certified by an NRTL).
A note states that IEC 61508 provides the requirements to design such a con-
troller.
© Siemens AG, 2006. All rights reserved
SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 03.2006 Edition
Regulations and Standards
1.3 Machine safety in the US
1-29