From: An information entropy-based risk assessment method for multiple-media gathering pipelines
First level | Second level | Weight | Third level | Weight | Description |
---|---|---|---|---|---|
Corrosion | External corrosion | Heavy oil (13/20)a; Thin oil (2/5); Gas (21/20); Water, Steam (13/20) | Soil corrosion | Resistivity (7) | >50Ω•m (2); 20~50Ω·m (4); <20Ω·m or none (7) |
pH (8) | 6.5~8.5 (2); 4.5~6.5 (4); <4.5 (8) | ||||
External coating | Type (6) | 3-Layer Polyethylene (1); Coal tar enamel/coal tar epoxy/epoxy powder (2); Yellow jacket polyurethane foam/polythene (3); Asphalt glass fabric/phenolic resins (4); Anti-rust oil (5), None (6) | |||
Quality (9) | Complete (2); Partial loss (5), Mass shedding (9) | ||||
Cathodic protection (10) | Normal use (3); Not used (6); None (10) | ||||
Internal corrosion | Heavy oil (24/29) Thin oil (1) Gas (4/8) Water/Steam (1) | Oil (58) | Water (6) | <50% (2); 50%~75% (3); 75%~95% (5); >95% (6) | |
Pressure (5) | <0.6 MPa (1); 0.6~0.8 MPa (3); 0.8~1.5 MPa (4); >1.5MPa (5) | ||||
CI- (10) | <1000mg/L (2); 1000~3000mg/L (3); 3000~5000mg/L (5); 5000~7000mg/L (7); 7000~9000 (8); >9000 mg/L (10) | ||||
H2S (10) | <0.005mg/L (2); 0.005~0.01mg/L (4); 0.01~0.015mg/L (7); >0.015mg/L (10) | ||||
Temperature (4) | <50°C (2); 50~70°C (3); >70°C (4) | ||||
pH (8) | 7~10 (2); 4~7 (4); <4 (6); >10 (8) | ||||
Hardness (5) | <100 mg/L (2); 100~300 mg/L (4); >300 mg/L (5) | ||||
Gas (40) | Water (10) | <5% (4); 5%~10% (6); 10%~15% (8); >15% (10) | |||
Pressure (8) | <1MPa (1); 1~4 MPa (2); 4~10 MPa (4); 10~20 MPa (6); >20 MPa (8) | ||||
Sulfide (12) | <42.68mg/L (3); 42.68~142.26mg/L (6); >142.26 mg/L (12) | ||||
CO2 (10) | <0.207%mol/mol (3), 0.207%~2.073%mol/mol (7), >2.073% mol/mol (10). | ||||
Water (38) | Oil content (6) | <2 mg/L (2); 100~500 mg/L (4); 2~100 mg/L (6) | |||
CI- (6) | <5 mg/L (2), 5~10 mg/L (4), >10 mg/L (6). | ||||
Salinity (9) | <1000mg/L (1), 1000~3000 mg/L (3), 3000~10000 mg/L (5), 10000~50000 mg/L (7), >50000 mg/L (9). | ||||
pH (5) | 7~10 (1); 4~7 (3); <4 (4); >10 (5) | ||||
Temperature (6) | <50°C (2), >60°C (3), 50~60°C 6. | ||||
Pressure (6) | <1 MPa (1); 1~2.5 MPa (2); 2.5~16 MPa (3); 16~20 MPa (4); 20~25 MPa (5); >25 MPa (6) | ||||
Steam (38) | Pressure (9) | <2.5MPa (2); 2.5~10 MPa (4); 10~12 MPa (5) 12~14 MPa (6); >14 MPa (9) | |||
CI- (12) | <5mg/L (4); 5~10mg/L (7); >10mg/L (12) | ||||
pH (9) | 7~8 (3); 6~7 (5); 5~6 (6); <5 (8); >8 (9) | ||||
Temperature (8) | <200°C (3); 200~300°C (5); >300°C (8) | ||||
Other corrosion factors (17) | Pipe grade (3) | X70 (1); X52 (1.5); X42 (2); Lower grade (3) | |||
Service years (8) | <5 years (2); 5~10 years (4); 10~20 years (6); >20 years (8) | ||||
Corrosion-induced failure history (6) |  | ≤1 (2); 1~3 (4); >3 (6) | |||
Corrosion inspection (9) | External inspection (4) | <1 per 1 year (1); 1 per 1~2 years (2); 1 per > 2 years (4) | |||
In-line inspection (5) | <1 per 1 year (2); 1 per 1~2 years (4); 1 per >2 years (5) | ||||
Total | 100 |