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

Regulations and standards
2.3 Machine safety in the USA
exists in the US taken into account. Due to the product liability legislation, it is in the interests
of manufacturing and operating companies that they carefully maintain the applicable
regulations and are "forced" to fulfill the requirement to use state-of-the-art technology.
Third-party insurance companies generally demand that their customers fulfill the applicable
standards of the standards organizations. Self-insured companies are not initially subject to
this requirement but, in the event of an accident, they must provide verification that they have
applied generally-recognized safety principles.
See also
OSHA (http://www.osha.gov)
2.3.2

NRTL listing

To protect employees, all electrical equipment used in the USA must be certified for the planned
application by a "Nationally Recognized Testing Laboratory" (NRTL) certified by the OSHA.
NRTLs are authorized to certify equipment and material by means of listing, labeling, or similar.
Domestic standards (e.g. NFPA 79) and international standards (e.g. IEC/EN 61508 for E/E/
PES systems) are the basis for testing.
2.3.3

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 requirements
2. IEC 61508, IEC 62061, ISO 13849-1, ISO 13849‑2 and IEC 61800-5-2 are specified as
suitable standards in a note.
28
(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
for such systems.
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety Integrated