Risk Minimization; Residual Risk - Siemens Sinumerik 840D sl Function Manual

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1.2.10

Risk minimization

Risk minimization measures for a machine can be implemented using safety--rela-
ted control functions in addition to structural measures. To implement these control
functions, special requirements must be taken into account, graded according to
the magnitude of the risk. These are described in EN ISO 13849--1 or, in the case
of electrical control systems (particularly programmable electronics), in EN 61508
or EN 62061.
The requirements relating to safety--related parts of control systems are graded
according to the magnitude of the risk and the level to which the risk needs to be
reduced.
EN ISO 13849- -1 defines a risk flow chart that instead of categories results in hie-
rarchically graduated Performance Levels (PL).
EN 62061 and the series of EN 61508 standards use the "Safety Integrity Level"
(SIL) to make this type of classification. This is a quantified measure of the safety--
related performance of a control system.
The necessary SIL is also determined using the principle of risk assessment accor-
ding to EN ISO 14121 (EN 1050). A technique to determine the required Safety
Integrity Level (SIL) is described in Annex A of EN 62061.
It is always important, independent of which standard is applied, that all parts of
the machine control system that are involved in executing safety--related functions
fulfill these requirements.
1.2.11

Residual risk

In today's technologically advanced world, the concept of safety is relative. In prac-
tice, safety cannot be implemented that guarantees a "zero risk" situation. The re-
sidual risk is the risk that remains once all the relevant protective measures have
been implemented in accordance with the latest state of the art technology.
Residual risks must be clearly referred to in the machine/plant documentation (user
information according to EN ISO 12100).
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SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) - - 10.2015 Edition
Regulations and standards
1.2 Safety of machinery in Europe
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