Method for predicating crack arrest of natural gas pipeline

Abstract

The invention discloses a method for predicating crack arrest of a natural gas pipeline, and belongs to the technical field of pipeline design and manufacture. The method incudes acquiring a critical damage facture absorption energy value in unit area during sample fracture; creating a numerical value model under the service condition of the pipeline according to the finite element method, calculating damage facture absorption energy in unit area of a pipeline crack tip region, and taking whether or not the damage facture absorption energy reaches the critical damage facture absorption energy value as a criterion; calculating a crack speed and a gas decompression wave speed from the finite element model according to the criterion; if the crack speed is larger than the gas decompression wave speed, determining that crack arrest cannot be achieved after crack formation under the current service condition of the pipeline, or otherwise, determining that crack arrest can be achieved after crack formation under the current service condition of the pipeline. On the basis of the damage facture absorption energy, the method is used for predicating crack arrest performance of the pipeline by the aid of a tensile sample, thereby having a certain demonstration effect for pipeline safety guarantee.

Description

technical field [0001] The invention relates to the technical field of pipeline design and manufacture, in particular to a method for crack arrest prediction of natural gas pipelines. Background technique [0002] In order to meet the growing demand for natural gas in the development of the national economy, natural gas pipelines are developing in the direction of high steel grade, large diameter and high pressure. While high-grade, high-pressure natural gas pipelines benefit the national economy and the people's livelihood, once an accident occurs, the consequences will be unimaginable. Among them, the long-distance propagation of pipeline cracks is the most unacceptable catastrophic consequence. Therefore, the basic requirement for the design of steel pipe performance is that cracks can be quickly stopped after crack initiation . Among them, the crack arrest design of brittle cracking can be realized by controlling the ductile-brittle transition temperature of the pipe, w...

AI Technical Summary

Problems solved by technology

Therefore, it can be considered that the CVN sample increases the constraint of the crack tip and underestimates the toughness value of pipeline steel

[0006] Second, it is worth discussing whether the existing semi-empirical formula for crack arrest prediction is effective for high-grade steel pipelines

The model successfully predicts the CVN value required for crack arrest of X70 and below pipeline steel under different working conditions. However, when the steel grade exceeds X80 and the pressure exceeds 10MPa, the prediction accuracy of the BTC method drops sharply, which needs to be corrected or re-established formula, but there is currently a lack of a more recognized forecasting formula

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