Function Manual
194 01/2017
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.
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). Like 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 are:
system requirements (see NFPA 79 9.4.3)
1. Control systems that contain software-based controllers must:
● In the event of a single fault
– cause the system to switch to a safe shutdown mode
– prevent the system from restarting until the fault has been rectified
– prevent an unexpected restart
● Offer the same level of protection as hard-wired controllers
● Be implemented in accordance with a recognized standard that defines the requirements for such systems.
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:
http://www.ul.com → certifications directory → UL Category code/ Guide information → search for category "NRGF"
TUV Rheinland of North America, Inc.
is also an NRTL for these applications.
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 findings of a risk analysis can be used to select a suitable safety system based on the safety class of the
application in question.
The situation in Japan is different from that in Europe and the US. Legislation such as that prescribed in Europe does not
exist. Similarly, product liability does not play such an important role as it does in the US.
Instead of legal requirements to apply standards have been defined, an administrative recommendation to apply JIS
(Japanese Industrial Standard) is in place: Japan bases its approach on the European concept and uses basic standards as
national standards (see the table below).
Earlier designation TR B 0008
Earlier designation TR B 0009
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