GM International PSD1206, Instruction Manual

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PSD1206 - PSD1210 - SIL 3 - SIL 2 Switching Power Supply 24 Vdc G.M. International ISM0076-7
PSD1206, PSD1210 Isolated Power Supply, 2 units in parallel
One way to calculate the PFDavg of a system with 2 power supply units in parallel architecture is by using the fault tree as presented in following figure:
System of two PSD12xx connected in
parallel architecture fails undetected
OR
Both PSD12xx fail because of
common cause (ß = 5 %)
First PSD12xx
fails undetected
&
Second PSD12xx
fails undetected
PSD1206, PSD1210 Isolated Power Supply, single unit, ND loads
Failure rates:
Failure rates according to IEC 61508:
Λ sd
0.00 FIT
λ su
327.20 FIT
λ dd
0.00 FIT
λ du
349.80 FIT
SFF
48.33%
PFDavg vs T[Proof], with determination of SIL supposing module contributes 10% of entire safety function:
Failure category Failure rates (FIT)
Total Fail Dangerous Undetected = λ du
Fail Dangerous Undetected
Fail High (1% of Total Fail High)
Fail “Annunciation Undetected” (1% of Total Fail “Ann. Undet.”)
Total Fail Safe Undetected = λ su
Fail High (99% of Total Fail High)
Fail Low
Fail “Annunciation Undetected” (99% of Total Fail “Ann. Undet.”)
Fail “Not Part” = λ notpart
MTBF = MTTF + MTTR = 1 / ( λ sd + λ su + λ dd + λ du + λ notpart) + MTTR
MTTF
S
= 1 / ( λ sd + λ su)
349.80
134.00
0.21
0.59
327.20
20.79
215.00
58.41
174.00
134 years
349 years
Fail “No Effect” 214.00
Total Fail Dangerous Detected = λ dd
0.00
Total Fail Safe Detected = λ sd
0.00
Fail Safe Undetected
34.00
Total Failure Rate (Safety Function) = λ sd + λ su + λ dd + λ du
677.00
Total Failure Rate (Device) = λ sd + λ su + λ dd + λ du + λ notpart
851.00
MTTF
D
= 1 / λ du
326 years
PFDavg vs T[Proof], with determination of SIL supposing module contributes 20% of entire safety function:
T[Proof] = 1 year
PFDavg = 1.53 E-03
Valid for SIL 1
See Note 9 in the section Notes
T[Proof] = 10 years
PFDavg = 1.53 E-02
Valid for SIL1
See Note 9 in the section Notes
T[Proof] = 1 year
PFDavg = 1.53 E-03
Valid for SIL 1
See Note 4 in the section Notes
T[Proof] = 5 years
PFDavg = 7.66 E-03
Valid for SIL 1
See Note 4 in the section Notes
T[Proof] = 9 years
PFDavg = 1.38 E-02
See Note 5 in the section Notes
T[Proof] = 10 years
PFDavg = 1.53 E-02
See Note 5 in the section Notes