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Table 4 Failure factors of gathering pipelines regarding design

From: An information entropy-based risk assessment method for multiple-media gathering pipelines

First level

Second level

Weight

Description

Design

Pipeline strength

Safety design factor (34)

\(\frac{\textrm{Actual}\ \textrm{wall}\ \textrm{thickness}}{\textrm{Design}\ \textrm{wall}\ \textrm{thickness}}\): >1.8 (0); 1.61~1.8 (3.5); 1.41~1.6 (7); 1.20~1.4 (14); 1.1~1.20 (21); 1.0~1.1 (28); <1 (34)

Water hammer

Elevation change (9)

Gently topography (0); Design pressure - MAOP > Maximum elevation pressure (4);

Design pressure - MAOP < Maximum elevation pressure (9)

Protective (6)

Slow closing device (2); Pressure relief valve (3); Buffer tank (5); Operating procedures for preventing water hammer (6)

Integrity assurance

Usage time (10)

0~5years (2), 5~15 years (4), 15~20 years (6), 20~25 years (8), >25 years (10).

Inspection time (7)

<1 year (1); 1~2 years (2); 2~3 years (3); 3~4 years (4); > 4 years (7)

Welding quality

Welding level (10)

Strictly follow the operation procedure, i.e., high quality (2); According to the operation procedure, i.e., average quality (6); Random welding, i.e., poor quality (10)

Inspection rate (10)

100% (2); 80%~100% (6); 60%~80% (8); <60% (10)

Backfill quality

Backfill depth (8)

>76.2 cm (2); 7.62~76.2cm (4); <7.62cm or uncovered (8).

Backfilling method (6)

Both process and method are correct (2); Process is correct but the method is incrorrect (4); Both backfill process and method are incorrect (5); None (6).

Total

 

100