Offshore Qra Checklist

Offshore QRA Checklist

Offshore QRA Checklist Preface: Offshore QRA (Quantified or Quantitative Risk Assessment) is a critical assessment considering realistic hazard data from various sources to calculate risk levels (Individual Risks and Potential Loss Of Life) involving spreadsheets, drawings, matrices and modeling software. QRA also evaluates whether the risk levels are ALARP (As Low As Reasonably Practical) or not. The primary objectives of risk assessment in this context are to identify and rank the risks so that they can be adequately managed and to examine associated risk reduction measures to determine those most suitable for implementation. The following checkpoints are compiled considering the importance of this specialized and quantitative assessment so that the offshore operating company or the field owner can check if the assessment done is comprehensive and realistic.

Number

Checkpoint

1.

Were the latest revisions of drawings and documents shared for the study? Ensure that the consultant has used the latest references / guidance / standards / data sources / regulations for the assessment. Discuss and agree on the leak sizes, success probability of safety systems, ignition probabilities, detection & isolation times, before start of FEA. Were all the sensitive receivers (escape routes, control rooms, accommodation block, life boat stations) defined in advance so that their impairment is assessed from fires and explosions?

2.

3.

4.

Comments

Hint: Request the consultant to define them in advance and agree them internally before proceeding with the assessment. 5. Was the manning (POB) distribution reviewed by OIM or Operations manager? 6. Did the consultant notify the QRA assumptions and seek an agreement? 7. Were all the fire and explosion scenarios considered are realistic? Was any hydrocarbon section left out? Hint: Request a table from the consultant containing fires and explosion scenarios for all sections containing hydrocarbon. Let the design and HSE engineers review this to ensure that no process section is left out in the Fire and Explosion Assessment (FEA). 8. What are the assumptions considered in the blast / explosion modeling? Congestion, blockage ratio, etc. 9. Was the most prevailing wind direction and speed considered based on metocean data or the worst case

November 2008/ Sreejith

Offshore QRA Checklist

10. 11. 12. 13.

14.

conditions considered in FEA? Were all the safety systems considered while calculating event / impairment probabilities? Were the fuel used in the utility sections (boilers, diesel driven pumps, etc.) considered in the FEA assessment? Were the transportation details provided for assessment in line with the proposed logistics plan? If the shipping lane is far away (50 km plus) from the proposed offshore location, should the errant merchant vessel collision be considered for risk calculation? If water deluge provided on gas sections, the credit for it should be taken while calculating the explosion impairment probability calculation.

Note: As per some research (FABIG, OTH, etc.), activating deluge on confirmed gas detection has proved to reduce explosion over pressures by around 40%. But there are arguments against this (static discharge acting as an ignition source, etc.). A recent study commissioned by HSE (OTO 2000 042) concluded that 'activation of deluge on gas detection can make a significant improvement in the level of safety '...... providing the implementation is appropriate'. The consensus appears to be activation of deluge on gas detection is not the universal answer. However, there is a lack of guidance as to the circumstances under which adoption of this mitigation measure would be beneficial and, if so, the design considerations which apply (deluge activation time, protection of electrical equipment, nozzle type, application rate etc). 15.

The consequences of potential fire escalations are to be included in the FEA. BOE (Boil Over Explosion) from jet fires.

Note: BLEVE (Boiling Liquid Expanding Vapour Explosion) may not be possible with crude, but BOE may be possible if jet fire flames impinge the vessels containing liquid hydrocarbon. 16. Are the QRA risk improvements based on risk or consequence based recommendations? Hint: Ideally the recommendations should be risk based (considering impairment and its probability). If the risk levels are not tolerable, then the CBA (Cost Benefit Analysis) methodology may be followed through the ICAF (Implied Cost to Avert a Fatality) process to take a final decision. 17. Are there any practical Passive Fire Protection (PFP) recommendations based on Fire & Explosion Assessment? If not, let the consultant to justify. 18. ALARP workshop is to be conducted to demonstrate ALAP through the ICAF (implied Cost to Avert a Fatality) process for various agreed sensitivity cases.

Author: Pillai Sreejith ([email protected])

November 2008/ Sreejith