Environmental Engineering Reference
In-Depth Information
to a decrease in the operating life by the criterion of fatigue resistance. At
the same time, HT can be helpful in some cases. Analysis of the strength of
the structure using methods of fracture mechanics and taking into account
the residual defectiveness of the structures allows accurate assessment
of the usefulness of HT. Figure 6.12 shows the calculated probability of
rupture of DN500 pipelines after ISI as well as after ISI combined with
HT. In the case of successful HT the pipeline in operation has a high level
of reliability (probability of fracture of the pipeline is zero).
In general, it can be argued that the hydraulic tests fail to detect defects
smaller than the critical dimensions for the HT regime. In some cases,
successful hydraulic tests provide a high level of the reliability of structures
and can serve as a substitute for ISI.
The effect of HT is discussed in more detail in sections 8.1 and 9.
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