SIL Allocation Calculation

The allocation of Safety Integrity Levels (SIL) to safety functions is a crucial process in ensuring the systems safety. MODsafe, aligned with EN 50129, and Layer of Protection Analysis (LOPA) per IEC 61511, have informed the current practice; both employ semi-quantitative risk assessment techniques. These methodologies share a common goal: to systematically evaluate and implement safety measures that mitigate risks effectively, quantifiably and reliably, thereby assuring safety of systems. Here is the tool ...

Hazard Description:

Provide a brief description of the hazard being analysed (e.g., 'Train collision due to overspeed').

Sample text Severity Level:

Select the potential consequence severity of the hazard if it occurs.

-- Select -- Insignificant - Minor injuries or negligible damage Marginal - Major injuries or moderate damage Critical - Severe injuries, permanent disability, or significant system damage Catastrophic - One or more fatalities or catastrophic system failure Exposure Probability (E):

Choose how often the risk group (e.g., passengers) is exposed to the hazard.

-- Select -- 1 - Frequent or permanent exposure 0.1 - Rare exposure 0.01 - Very rare exposure Accident Probability Reduction (P):

Select the effectiveness of additional barriers or controls in preventing the hazard from leading to an accident.

-- Select -- 1 - No additional barriers 0.1 - One independent barrier 0.01 - Two independent barriers

Description of Accident Probability Reduction:

Describe the barriers or controls contributing to the accident probability reduction (e.g., 'Driver intervention and interlocking system').

Sample text

Consequence Reduction Probability (C):

Choose the ability of measures to reduce the severity of the hazard's consequences.

-- Select -- 1 - No consequence reduction 0.1 - Significant consequence reduction 0.01 - Major consequence reduction

Description of Consequence Reduction Probability:

Describe the measures reducing the severity of consequences (e.g., 'Emergency evacuation procedures').

Sample text

Safety Function Description:

Describe the safety function that is intended to mitigate the hazard (e.g., 'Overspeed detection and emergency braking').

Test Safety Function