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Structural Evaluation of Pipeline

The parameter for pipeline damage condition is the calculation result of defect score, S is arithmetic mean value of the scores of each defect of pipeline, and Smax is the highest score among the scores of each defect of pipeline.

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Calculation of parameter for pipeline damage condition

The parameter for pipeline damage condition is the calculation result of defect score, S is arithmetic mean value of the scores of each defect of pipeline, and S_max is the highest score among the scores of each defect of pipeline. The parameter for pipeline damage condition shall be calculated according to the following formula:

max｛P_i｝
n = n₁ + n₂
Wherein: n——The number of structural defects of pipeline;
n₁——The number of defects with the longitudinal clear distance greater than 1.5m;
n₂——The number of defects with the longitudinal clear distance greater than 1.0m and not greater than 1.5m;
P_i1——The score of defect with the longitudinal clear distance greater than 1.5m; determine the value according to Table 3.1.2-1;
P_i2——The score of defect with the longitudinal clear distance greater than 1.0m and not greater than 1.5m; determine the value according to Table 3.1.2-1;
α——Influence coefficient of structural defect, related to the defect spacing. When the longitudinal clear distance of defects is greater than 1.0 and not greater than 1.5mm, α=1.1.

Calculation of parameter for pipeline structure defect
The structural defect parameter F of pipeline is determined by comparing the parameters of pipeline damage condition and choosing the big value. The switch effect principle of drainage pipeline defect is followed, namely, as long as one place is blocked, the whole line will be blocked. Therefore, the damage level of the pipeline depends on the most serious defect in the pipeline. The structural defect parameter of the pipeline shall be calculated according to the following formula:
When S_max≥S, F = S_max When S_max＜S, F = S
Wherein: F——Structural defect parameter of pipeline;
S_max——Damage parameter of pipeline, the score of the most serious damage among the structural defects of the pipeline;
S——Pipeline damage parameter, the average score calculated according to the number of defect points.

Calculation of structural defect density
If there is structural defect with the pipeline, the structural defect density shall be calculated according to the following formula:

Wherein: S_M——Structural defect density of pipeline;
L——Pipeline length (m);
L_i1——Length of structural defect with the longitudinal clear distance greater than 1.5m (m);
L_i2——Length of structural defect with the longitudinal clear distance greater than 1.0m and not greater than 1.5m (m).
The structural defect density of pipeline is the ratio of the total length of defect corresponding to the average value S of pipeline defect to the total length of pipeline. The total length of the defect is a calculated value and is not the actual defect length of the pipeline. The larger the defect density is, the more the quantity of defects of this pipeline is.