QRA Rule Set

Steps performed in Quantitative Risk Assessment (QRA) : 1. Hazard Identification Hazard identification is done on the basis of experience, detail process knowledge etc. 1.1. HAZOP/ HazId Workshop Scenario are considered for QRA which having risk ranking equal to or more than 2 from HAZOP study. All Top Events from HazId which having ultimate consequences are considered for QRA study. If it is piping or process release, refer section 1.2 and isolate that portion completely and consider separate isolatable section for QRA. 1.2. Plant sectionalisation Method By considering all possible remotely operating valves and in special cases Non-Return valve, Pump suction, vessel/ tank are as isolation in the PFDs/ P&IDs. Mark each section such as it should be isolate completely. This is isolatable section. Find out and mark all possible isolatable section in the process plant using PFDs/ P&IDs. Each isolatable section is considered as separate scenarios. List out all isolatable sections, corresponding/ representative stream nos., phase of the stream, composition for the same, process temperature and pressure for the isolatable section/ representative stream, major equipment covered in the isolatable section and pipeline size. If isolatable section having both phases i.e. vapour and liquid, model both phase as different sub scenario. 2. Volume Calculation Calculate the volume of the isolatable section for major equipment covered in the isolatable section and pipeline given as below. 2

2.1. Pipeline volume : calculate Piping volume using formula V = (D /4)L for all possible diameter in the isolatable section. Where

V : Volume of the pipeline D : Diameter of pipeline L : Length of the piping section (Length is considered as 1.5 times the straight distance between two equipment from Unit plot plan provided.

2.2. Column Volume : 30% column volume is considered as vapour volume and 70% as liquid. 2.3. Vessel Volume : consider HHLL level to calculate liquid volume using equipment layout diagram provided. If not consider entire vessel volume as liquid or vapour depending on the phase of the isolatable section.

Quantitative Risk Assessment : Rule Set

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2.4. Heat Exchanger/ Filter Volume : exchanger and filter volumes are considered in the piping section. No need to separate calculation for heat exchangers and filter. Finally add all volumes and use for consequences analysis. 3. Assumption Register 3.1. Leak size selection Following leak sizes are considered for QRA study… A. Pipeline leakage As per the OGP Risk assessment data directory, March 2010 5 mm (representative leak size of 1 to 10mm) 25 mm (representative leak size of 10 to 50mm) 100 mm (representative leak size of 50 to 150mm) 150 mm (representative leak size of 150mm and more or rupture of the pipe) As per the Reference manual Bevi risk assessments version 3.2, module C, 2009 Leak of effective diameter of 10% of nominal diameter upto maximum 50mm Rupture in the pipe B. Tank leakage Atmospheric Fixed Roof tank: As per the OGP Risk assessment data directory, March 2010 As per the Reference manual Bevi risk assessments version 3.2, module C, 2009 Floating Roof tank: As per the OGP Risk assessment data directory, March 2010 As per the Reference manual Bevi risk assessments version 3.2, module C, 2009 Pressurized tank/ Cylinder: As per the OGP Risk assessment data directory, March 2010 As per the Reference manual Bevi risk assessments version 3.2, module C, 2009 3.2. Time of release Quantitative Risk Assessment : Rule Set

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3.3. Meteorological Data 3.4. Event Tree 3.5. Risk Criteria 4. Consequences Analysis Modeling 4.1. Release Rate Calculation 4.1.1.Leak/ Rupture in Pipe 4.1.2.Leak/ Rupture Tank 4.2. Jet Fire 4.3. Pool Fire 4.4. Explosion 4.4.1.Pressurized Vessel Burst 4.4.2.Vapour Cloud Explosion 4.5. Boiling Liquid Expanding Vapour Cloud Explosion (BLEVE) 4.6. Toxic Gas Dispersion 4.7. Runaway Reaction 4.8. Fire Ball 5. Frequency Estimation 5.1. Parts Count 5.2. Probability consideration 5.3. Event Tree 6. Risk Calculation 6.1. Process Plant Risk 6.2. Long Pipeline Risk 7. Findings 7.1. Individual Risk per Annum (IRPA) 7.2. Location Specific Individual Risk (LSIR) 7.3. Frequency-No. of fatality (F-N) curve

Quantitative Risk Assessment : Rule Set

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