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อัปเดต 2026-09-07
Risk matrix & LOPA
CCPS layer of protection analysis
Ranks a deviation's unmitigated risk on a click-to-select likelihood×severity matrix, then credits each independent protection layer (IPL) against the initiating-event frequency per CCPS LOPA methodology to check whether the mitigated risk is tolerable.
เมื่อไรจึงใช้
- A HAZOP/What-If deviation needs a quantified risk ranking, not just a qualitative severity call.
- Deciding whether existing safeguards are sufficient, or a new IPL (often a SIF) is needed to close a gap.
- Justifying a SIL target for a safety instrumented function from a documented initiating frequency and IPL credits.
ค่าที่ต้องกรอก
| ค่า | คำอธิบาย |
|---|---|
| Initiating event frequency | Base frequency of the hazardous event before any protection layer, e.g. events/year. |
| Independent protection layers (IPLs) | Each credited safeguard's PFD — must be genuinely independent; this becomes evidence in the sign-off record. |
คำนวณอย่างไร
Per CCPS LOPA, the mitigated event frequency is the initiating frequency times the product of every credited IPL's probability of failure on demand; the result is compared against a tolerable-risk criterion on the same matrix used for the unmitigated ranking.
สมการ
LOPA mitigated frequency
f_initiating = initiating-event frequency (per year); PFD_i = probability of failure on demand of each credited independent protection layer, per CCPS "Layer of Protection Analysis" methodology.
ข้อควรระวัง
noteAn IPL only counts if it is genuinely independent of the initiating cause and of every other credited layer — the tool doesn't (and can't) verify independence for you; that judgment stays with the study team.
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