Application of SIL assessment, Bow-tie and API 14C to ensure a thorough Safety Concept Prepared by: Fabienne Salimi & Tino Vande Capelle 26 January 2011

Technical Safety Design

Causes of incident identified by HSE (UK)

Safety Barrier Management Bow-Tie

Safety barrier hierarchy & effectiveness This figure shows that Systematic failures can be anywhere in the Life Cycle, therefore having the right systematic approach with the necessary verification, validation and assessment techniques in place under a proper Functional Safety management with competent people could be your only way forward.

API 14C: at least 2 Independent & diverse levels of protection

Bow-Tie Diagram, a Life Cycle approach

Hierarchy of Safety Barriers

None of the Safety Barriers is Perfect! New technologies Increase redundancy Shorten the period of test Risk based inspection and preventive maintenance Procedures (design, procurement, construction, commissioning, maintenance and operation) None of the safety barriers is perfect and 100% functional on demand.These flaws are eliminated, reduced or prevented by:

Semi-Quantitative Approach LOPA

Risk Reduction by Layers of Protection

LOPA & SIL assessment In this example fire from distillation column is considered as the “impact event” for both “loss of cooling” and “steam control failure” as independent scenarios without any interaction on each other.

Loops are in interaction! If in this LOPA the interaction between condenser cooling and reboiler heating systems are considered then severity for both cases will be ranked as “Catastrophic” with possible impact on the public safety and property damage. Therefore, the higher “SIF PFDs” for both loops are required.

Semi-Quantitative Approach Risk Graphs

Calibrated Risk Graphs & SIL Assessment

Is a SIL3 protection against gas ingress required? A 2oo3 Gas detection, logic and two dampers are required to achieve SIL3.

Exposure time and Probability to advert danger Probability of adverse wind direction Size of gas release Distance of source of fuel and release Fuel Inventory and duration of release Congestion of process area and natural ventilation between source of fuel and source of ignition F&G ESD for process area Blowdown facilities at process equipment Depending on the judgement of SIL assessment team for “exposure time” and “Possibility of avert danger” due to the following factors the SIL requirements for gas ingress protection cab be reduced to SIL1 or SIL2: A SIL2 gas ingress protection system is achievable with a 2oo3 gas detection, logic and one damper and is in line with the common practice in oil & gas industry.

Quantitative SIL assessment

Combination of Event & Fault Trees

HIPPS

F&G ESD

Common Cause & Systematic failures

Thank You for your Kind Attention!