By evaluating the residual life of a pipeline against the risks of fatigue damage, EXPERT-Méca has justified to the administration the periodicity of the hydraulic tests of a transmission pipeline.
COMPAGNIE PETROCHIMIQUE DE BERRE, of the LYONDELLBASELL group, operates a liquefied gas pipeline, property of the company ARKEMA, from the petrochemical complex of Berre l’Etang. The 114.3 mm diameter steel pipeline was put into service in 1980.
For pipelines that were first commissioned more than 30 years ago, the Decree of 04/08/2006 on "the safety of pipelines for the transport of combustible gases, liquid or liquefied hydrocarbons and chemical products" has reduced the time between 2 hydraulic tests from 10 to 6 years.
The carrier may, however, request a waiver of the above-mentioned reduced period from the Prefect providing that it can prove that the number and intensity of the pressure cycles actually undergone by the pipeline are very low compared to what the pipeline can withstand.
The PETROCHEMICAL COMPANY DE BERRE applied to EXPERT-Méca for an appraisal mission to investigate a study that would justify the exemption from application of the reduced duration between two successive hydraulic tests.
In order to prove that the number and intensity of the pressure cycles actually undergone by the pipeline are very low in terms of what the pipeline can bear, EXPERT-Méca carried out an evaluation by calculating the residual life of the pipeline against the risks of damage by initiation and propagation of fatigue cracks.
The time interval between two hydraulic tests of this pipeline was thus maintained at 10 years.