Assessment of permissible defects for steel pipes and weld seams during the operation of offshore subsea pipelines

Authors: A.S. Avdonkin, S.V. Balagura, S.P. Markov

 

Abstract

 

Based on the analysis of existing Russian and foreign methods for calculating the strength and durability of pipes with defects, the article presents a part of the R&D results for assessment of the degree of danger of operating offshore subsea pipelines with corrosion loss of metal and crack-like defects, taking into account their geometric parameters and external loading. The assessment of permissible metal loss due to surface corrosion of pipes has been carried out in accordance with the minimum failure pressure in the pipe in compliance with regulatory documents when the wall is thinned on a part of the length. The assessment of the permissible sizes of cracks and crack-like defects in pipes is based on the FAD (Failure Assessment Diagram) and the two-parameter criterion that combines the conditions of purely brittle and purely ductile fracture. On the basis of computational comparisons, approaches have been recommended enabling the most effective prediction of the criticality of the detected defects during the operation of the pipeline. The expediency of taking into account the probability of negative consequences of accidents of a subsea pipeline, the scale of which is determined by the pipeline hazard class, has been shown. The results of computer calculations have been graphically presented in the form of diagrams of the permissible loss of metal and diagrams for failure assessment in the presence of a crack-like defect, which for practical purposes are converted to functional dependence on the permissible depth of the defect on its length.

 

Keywords: pipe metal defects, corrosion wear rate, stress intensity factor, failure of offshore subsea pipelines, safety factor, two-parameter fracture criteria, failure assessment diagram (FAD).

 

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About authors:

 

A.S. Avdonkin - FAI "Russian Maritime Register of Shipping", St. Petersburg

S.V. Balagura - FAI "Russian Maritime Register of Shipping", St. Petersburg

S.P. Markov - PhD, St. Petersburg State Marine Technical University, St. Petersburg

Issue: 64/65 (2021)

For citation: A.S. Avdonkin, S.V. Balagura, S.P. Markov. Assessment of permissible defects for steel pipes and weld seams during the operation of offshore subsea pipelines. Research Bulletin by Russian Maritime Register of Shipping. 2021, No. 64/65, pp. 68-81.

UDC 621.643.053

Pp: 68-81