# A Dynamic Assessment Methodology for Accident Occurrence Probabilities of Gas Distribution Station
## 3 Application of the Methodology
### Calculating Prior Probabilities of REs, CE, and OEs
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**RE** & **Description** & **Prior** & **RE** & **Description** & **Prior** \\  & & **Probability** & **RE** & **Description** & **Probability** \\ \hline \(X_{1}\) & Improper inspection and maintenance & 2.47 \(\times\)\(10^{-3}\) & X\({}_{41}\) & Vent valve of pig trap failure & 4.67 \(\times\)\(10^{-2}\) \\ \(X_{2}\) & Solid impurities in natural gas & 1.90 \(\times\)\(10^{-4}\) & X\({}_{42}\) & Pig indicator failed & 8.00 \(\times\)\(10^{-4}\) \\ \(X_{3}\) & Separator outlet valve fails to shutdown & 2.70 \(\times\)\(10^{-2}\) & X\({}_{43}\) & Safety valve fails to active & 1.70 \(\times\)\(10^{-2}\) \\ \(X_{4}\) & Non-compliance with operating procedure & 4.50 \(\times\)\(10^{-2}\) & X\({}_{44}\) & Gas erosion abrasion & 2.37 \(\times\)\(10^{-3}\) \\ \(X_{5}\) & Non-professional operation & 4.30 \(\times\)\(10^{-4}\) & X\({}_{58}\) & Seal failure of blind plate & 1.70 \(\times\)\(10^{-4}\) \\ \(X_{6}\) & Separator drain valve fails to open & 9.57 \(\times\)\(10^{-2}\) & X\({}_{46}\) & Flange gasket breakage & 4.32 \(\times\)\(10^{-3}\) \\ \(X_{7}\) & Separator inlet valve fails to close & 3.12 \(\times\)\(10^{-2}\) & X\({}_{47}\) & Improper selection of flange gasket & 2.30 \(\times\)\(10^{-4}\) \\ \(X_{8}\) & Separator inlet pressure gauge failure & 8.64 \(\times\)\(10^{-2}\) & X\({}_{48}\) & Flange gasket aging & 2.69 \(\times\)\(10^{-3}\) \\ \(X_{9}\) & Separator pressure gauge failure & 8.64 \(\times\)\(10^{-2}\) & X\({}_{49}\) & Flange connection bolt failure & 1.70 \(\times\)\(10^{-4}\) \\ \(X_{10}\) & Separator manual vent valve failure & 4.67 \(\times\)\(10^{-2}\) & X\({}_{50}\) & Poor installation quality & 1.90 \(\times\)\(10^{-4}\) \\ \(X_{11}\) & Separator high pressure alarm failure & 4.22 \(\times\)\(10^{-2}\) & X\({}_{51}\) & Valve body defect & 1.30 \(\times\)\(10^{-3}\) \\ \(X_{42}\) & No human response to high voltage alarm & 8.00 \(\times\)\(10^{-4}\) & X\({}_{52}\) & Seal packing failure & 1.04 \(\times\)\(10^{-3}\) \\ \(X_{13}\) & Seal ring of manhole cover failure & 4.32 \(\times\)\(10^{-3}\) & X\({}_{53}\) & Poor seal between valve body and cover & 9.50 \(\times\)\(10^{-4}\) \\ \(X_{14}\) & Fastening bolt of manhole cover failure & 1.70 \(\times\)\(10^{-4}\) & X\({}_{54}\) & Artificial blockage leakage point failure & 2.50 \(\times\)\(10^{-2}\) \\ \(X_{15}\) & Equipment material defect & 9.80 \(\times\)\(10^{-4}\) & X\({}_{55}\) & Automatic ball valve fails to close & 1.18 \(\times\)\(10^{-2}\) \\ \(X_{16}\) & Equipment manufacturing defect & 1.00 \(\times\)\(10^{-2}\) & X\({}_{56}\) & Manual shutdown valve failure & 1.31 \(\times\)\(10^{-3}\) \\ \(X_{17}\) & Insufficient strength design & 2.30 \(\times\)\(10^{-4}\) & X\({}_{57}\) & No response to manual valve & 4.00 \(\times\)\(10^{-2}\) \\ \(X_{18}\) & Calculation method error & 2.50 \(\times\)\(10^{-4}\) & X\({}_{58}\) & Automatic emergency shut–off valve failure & 4.67 \(\times\)\(10^{-2}\) \\ \(X_{19}\) & Outluted design specifications & 1.80 \(\times\)\(10^{-4}\) & X\({}_{59}\) & Automatic emergency cut–off sensor failure & 2.89 \(\times\)\(10^{-2}\) \\ \(X_{20}\) & Poor coating repair & 1.84 \(\times\)\(10^{-3}\) & X\({}_{60}\) & Automatic emergency cut–off & 2.50 \(\times\)\(10^{-1}\) \\ \(X_{21}\) & Material damaged in handling & 4.90 \(\times\)\(10^{-4}\) & X\({}_{61}\) & Manual emergency cut–off valve failure & 3.12 \(\times\)\(10^{-2}\) \\ \(X_{22}\) & Material damage during installation & 1.80 \(\times\)\(10^{-4}\) & X\({}_{62}\) & No response to manual emergency valve & 4.00 \(\times\)\(10^{-2}\) \\ \(X_{23}\) & Weld defect & 9.30 \(\times\)\(10^{-4}\) & X\({}_{63}\) & Lightning spark & 1.80 \(\times\)\(10^{-4}\) \\ \(X_{24}\) & Earthquake & 1.30 \(\times\)\(10^{-4}\) & X\({}_{64}\) & Accidental external impact & 1.81 \(\times\)\(10^{-4}\) \\ \(X_{25}\) & Flood & 1.20 \(\times\)\(10^{-4}\) & X\({}_{65}\) & Sparks caused by short circuit & 1.80 \(\times\)\(10^{-4}\) \\ \(X_{26}\) & Subsidence & 1.20 \(\times\)\(10^{-4}\) & X\({}_{66}\) & Non–explosion–proof & 1.80 \(\times\)\(10^{-4}\) \\ \(X_{27}\) & Corrosion inhibitor failure & 5.10 \(\times\)\(10^{-4}\) & X\({}_{67}\) & Other non–explosion–proof & 2.20 \(\times\)\(10^{-4}\) \\ \(X_{28}\) & Inner coating thinning & 9.60 \(\times\)\(10^{-4}\) & X\({}_{68}\) & Clothing friction electrification & 1.95 \(\times\)\(10^{-3}\) \\ \(X_{29}\) & Internal coating peeling & 9.80 \(\times\)\(10^{-4}\) & X\({}_{69}\) & Other electrostatic & 9.80 \(\times\)\(10^{-4}\) \\ \(X_{30}\) & With water & 1.22 \(\times\)\(10^{-3}\) & X\({}_{70}\) & Station domestic fire & 1.90 \(\times\)\(10^{-4}\) \\ \(X_{31}\) & Acid medium & 2.30 \(\times\)\(10^{-4}\) & X\({}_{71}\) & Smoking & 1.10 \(\times\)\(10^{-4}\) \\ \(X_{32}\) & Harish environment & 1.90 \(\times\)\(10^{-4}\) & X\({}_{72}\) & Vehicles not fitted with spark arrestor & 4.20 \(\times\)\(10^{-4}\) \\ \(X_{33}\) & Outer coating thinning & 1.32 \(\times\)\(10^{-3}\) & X\({}_{73}\) & Friction at the leak & 4.80 \(\times\)\(10^{-4}\) \\ \(X_{34}\) & Outer coating peeling & 1.66 \(\times\)\(10^{-3}\) & X\({}_{74}\) & High speed collisions of solid impurities & 4.60 \(\times\)\(10^{-4}\) \\ \(X_{35}\) & Residual stress & 1.80 \(\times\)\(10^{-4}\) & X\({}_{75}\) & Tool impact sparks & 1.30 \(\times\)\(10^{-4}\) \\ \(X_{36}\) & Stress concentration & 1.90 \(\times\)\(10^{-4}\) & X\({}_{76}\) & Hot work without permission & 3.30 \(\times\)\(10^{-2}\) \\ \(X_{37}\) & Lack of periodic corrosion detection & 5.00 \(\times\)\(10^{-2}\) & X\({}_{77}\) & Not following hot work permit & 4.50 \(\times\)\(10^{-2}\) \\ \(X_{38}\) & Corrosion detection instrument failure & 2.40 \(\times\)\(10^{-4}\) & X\({}_{78}\) & Insufficient supervision & 3.40 \(\times\)\(10^{-2}\) \\ \(X_{39}\) & Electric ball valve of pig trap outlet fails & 1.18 \(\times\)\(10^{-2}\) & SCE & Spatial confinement event & 1.21 \(\