BECKHOFF TwinSAFE - Manual (Page 17)

Circuit examples
Application Guide TwinSAFE 15
ܯܶܶܨ
ௗ
ൌ
ܤ10
ௗ
0.1 כ ݊
௢௣
Insertion of the values results in:
S1:
݊
௢௣
ൌ
230 כ 16 כ 60
10080
ൌ 21.90
ܯܶܶܨ
ௗ
ൌ
100000
0.1 כ 21.90
ൌ 45662.1y ൌ 399999120h
K1/K2:
݊
௢௣
ൌ
230 כ 16 כ 60
10080
ൌ 21.90
ܯܶܶܨ
ௗ
ൌ
1300000
0.1 כ 21.90
ൌ 593607.3y ൌ 5199997320h
and the assumption that S1, K1 and K2 are in each case single-channel:
ܯܶܶܨ
ௗ
ൌ
1
ߣ
ௗ
results in a
ܲܨܪ ൌ
0.1 כ ݊
௢௣
כ ሺ1 െ ܦܥሻ
ܤ10
ௗ
ൌ
1 െ DC
MTTF
ୢ
S1:
ܲܨܪ ൌ
1 െ 0.90
45662.1 כ 8760
ൌ 2.50E െ 10
K1/K2: actuation 1x per week
ܲܨܪ ൌ
1 െ 0.60
593607.3 כ 8760
ൌ 7.69E െ 11
K1/K2: actuation 1x per shift
ܲܨܪ ൌ
1 െ 0.90
593607.3 כ 8760
ൌ 1.92E െ 11
The following assumptions have to be made now:
Safety switch S1: According to BIA report 2/2008, error exclusion to up to 100,000 cycles is possible,
provided the manufacturer has confirmed this. If no confirmation exists, S1 is included in the calculation
as follows.
Relays K1 and K2 are both connected to the safety function. The non-functioning of a relay does not lead
to a dangerous situation, but it is discovered by the feedback signal. Furthermore, the B10d values for K1