SIL Starter
The following data help define the level of performance for SIL* starters.
|
B10: 1,000,000 |
|
% of dangerous failures*: 73% |
|
B10d: 1,369,863 |
Assuming number of operations = 131,400 cycles/year (average of 15 cycles/hour)
The calculated values of the SIL starter are provided in the following tables:
SIL Starter in Single Channel
|
Wiring Category* |
SFF |
HFT |
MTTFd (years) |
DC |
|---|---|---|---|---|
|
Category 1 |
27% |
0 |
100 years |
Not relevant |
|
Category 2 – Direct monitoring |
90% |
0 |
100 years |
≥ 90% |
SIL Starter in Dual Channel
| Wiring Category | SFF | HFT | MTTFd (years) | DC |
|
Category 3 |
27% |
0 |
100 years |
≥ 90% |
|
Category 4 |
90% |
0 |
100 years |
≥ 99% |
The relation between PFHd and PFD of the SIL starters, depending on the architecture and the test interval, is given in the following table:
SIL Starters — PFHd and PFD
|
Wiring Category |
PFH (IEC 61508) |
PFD (IEC
61508) |
PFD (IEC
61508) |
|---|---|---|---|
|
Category 1 |
1.10E-06 |
4.80E-02 |
4.82E-03 |
|
Category 2 – Direct monitoring |
1.10E-06 |
4.82E-03 |
5.06E-04 |
|
Category 3 |
4.5E-09 |
— |
1.30E-04 |
|
Category 4 |
2.5E-10 |
— |
2.5E-06 |
Architectural requirements defined in IEC 61508-2 Table 3 and EN 62061 Table 5 are met for levels up to SIL 2.
A Category 2 architecture is needed to meet SIL 2 architectural constraints (accomplished using direct monitoring Mirror In/Mirror Out).