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eng.LOPA-risk-reduction Calculator
Calculates risk reduction from multiple independent protection layers in a LOPA study and determines the required SIL for an SIF. IEC 61511 LOPA methodology: target risk / initiating event frequency / IPL credit = required SIF PFD — this determines whether SIL 1, 2, or 3 is needed.
Inputs
Frequency Per Yr
Cycles per second (Hz). Audible sound: 20 Hz – 20 kHz. Make sure units match what the formula expects.
Pfd1
Reference formula or conversion factor shown for context.
Pfd2
Reference formula or conversion factor shown for context.
Severity Factor
Reference formula or conversion factor shown for context.
Results
mitigated event frequency (yr⁻¹)
The value at the specified point or condition.
risk score (freq × severity)
Numerical risk rating — higher typically indicates greater probability of an adverse outcome. The score is only as reliable as the inputs and model assumptions.
SIL requirement estimate
The value at the specified point or condition.
total risk reduction factor RRF
A dimensionless multiplier applied in the calculation.
LOPA: f_mit = f_IE × Π PFD_IPL
Reference formula or conversion factor shown for context.