Safety Engineering

LOPA-Based SIL Target Verification: PFDavg Compliance Check for Safety Instrumented Systems Calculator

LOPA-Based SIL Target Verification: PFDavg Compliance Check for Safety Instrumented Systems engineering calculator.

Quick Answer

Calculate LOPA-Based SIL Target Verification: PFDavg Compliance Check for Safety Instrumented Systems

Calculator

Average probability of failure on demand (dimensionless)
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Result Interpretation

LOPA-Based SIL Target Verification: PFDavg Compliance Check for Safety Instrumented Systems Calculator computes Average probability of failure on demand in dimensionless using the defined engineering formula and the input values provided.

Worked Example

Verified calculation

Given:

  • Automatic diagnostic test interval = 8760
  • Proof test interval = 8760
  • Dangerous detected failure rate = 1.2E-5
  • Safe failure rate = 0.00021
  • Dangerous undetected failure rate = 8.5E-6

Expected Result:

  • Average probability of failure on demand = 1.8829805426769

Engineering Interpretation:

Under the given input conditions, the calculated result is: Average probability of failure on demand = 1.8829805426769 dimensionless.

The actual numerical result is computed by the Runtime engine using the persisted tool definition. The values shown here come from automatically validated test cases.

Formula / Method

average probability of failure on demand = (dangerous detected failure rate * automatic diagnostic test interval + dangerous undetected failure rate * automatic diagnostic test interval / 2 + safe failure rate * proof test interval) / (1 + dangerous detected failure rate * automatic diagnostic test interval / 2)

Formula family: formula_safety_sil_target_verification_calculator_lopa_based_pfdavg_compliance_check

Variables

SymbolLabelRoleDescription
lambda_d Dangerous detected failure rate INPUT Dangerous detected failure rate
lambda_dd Dangerous undetected failure rate INPUT Dangerous undetected failure rate
lambda_s Safe failure rate INPUT Safe failure rate
t_test Automatic diagnostic test interval INPUT Automatic diagnostic test interval
t_proof Proof test interval INPUT Proof test interval
result Average probability of failure on demand OUTPUT Average probability of failure on demand

Calculation Steps

  1. Enter the dangerous detected failure rate in 1/hour.
  2. Enter the dangerous undetected failure rate in 1/hour.
  3. Enter the safe failure rate in 1/hour.
  4. Enter the automatic diagnostic test interval in hour.
  5. Enter the proof test interval in hour.
  6. Step 1: Compute average probability of failure on demand.
  7. Read the average probability of failure on demand (dimensionless) from the results.

Engineering Summary

Calculate LOPA-Based SIL Target Verification: PFDavg Compliance Check for Safety Instrumented Systems

Frequently Asked Questions

What does this calculator calculate?

The LOPA-Based SIL Target Verification: PFDavg Compliance Check for Safety Instrumented Systems Calculator estimates Average probability of failure on demand based on the input parameters you provide

Why is dangerous detected failure rate important in this calculation?

dangerous detected failure rate is inversely proportional to average probability of failure on demand. When you enter dangerous detected failure rate in 1/hour, the calculator uses it in the engineering formula to compute the output

How should I interpret the result average probability of failure on demand?

The calculator outputs average probability of failure on demand in dimensionless. The result is computed directly from the input values using the defined engineering formula

What units should I use for the inputs?

Enter each value in the units shown next to the input field: Dangerous detected failure rate (1/hour), Dangerous undetected failure rate (1/hour), Safe failure rate (1/hour), Automatic diagnostic test interval (hour), Proof test interval (hour). Make sure all inputs use the specified units for consistent results

What assumptions does this calculator use?

This calculator uses automatically validated engineering formulas. Results are approximate and should be validated against site-specific conditions, applicable codes, and professional engineering judgment

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