a) be independent from the basic control system for
braking or an internal watch dog shall be provided in
the control system for braking;
b) be independent from the intention of the operator;
c) be performed at each spindle stop.
Where the test result is negative more than three times in
succession, it shall not be possible to operate the
machine. A negative test result shall be indicated.
The diagnostic coverage (DCavg) shall be ≥ 60%.
See Annex E of EN ISO 13849-1:2008 for DC estimation.
As an exception, a simple electronic brake (using simple
electronic parts like rectifiers, transistors, triacs, diodes,
resistors, thyristors) may be PL=b and designed in
category 1 in accordance with the requirements of EN
ISO 13849-1:2008 if the “mean time to a dangerous
failure” (MTTFd) according to Table 5 of EN ISO 13849-
1:2008 reaches a value of “high” (at least 30 years).
NOTE Complex electronic components like e.g.
microprocessors or PLCs cannot be considered as well tried
under the scope of EN ISO 13849-1:2008 and do therefore not
fulfill the requirements of category 1.
For calculating the probability of a dangerous failure for a
simple electronic brake component with no fault detection
(no DC) and no testing capability (category 1) the
procedure described in Annex D of EN ISO 13849-1:2008
can be used.
Verification: By checking the relevant drawings and/or
circuit diagrams, inspection of the machine and relevant
functional testing of the machine. For the determination of
un-braked run-down time and braked run-down time, if
relevant, the appropriate tests given in Annex I apply.
Where a control is provided to release the spindle brake
in order to enable rotation by hand and adjustment of the
tool (saw blade, grooving tool), release of the brake shall
only be possible when the spindle has stopped turning
(e.g. by a time delay in accordance with 5.2.1.2 b)
between control actuation and brake release).
It shall not be possible to start the machine before the
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