Skip to main content

Table 3 Failure factors of gathering pipelines regarding corrosion

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

  1. aFor different media, the weight should be multiplied after the evaluation, e.g., it is necessary to multiply the weight 26/40 after evaluating the external corrosion of the heavy oil pipeline