Methodology of hydrogen embrittlement study of long-term operated natural gas distribution pipeline steels caused by hydrogen transport

Oleksandr Tsyrulnyk,Halyna Krechkovska,Myroslava Hredil,Oleksandra Student,Leonid Unigovskyi,Hryhoriy Nykyforchyn,Olha Zvirko

doi:10.3221/igf-esis.59.26

Abstract

A methodology of experimental research on hydrogen embrittlement of pipe carbon steels due to the transportation of hydrogen or its mixture with natural gas by a long-term operated gas distribution network is presented. The importance of comparative assessments of the steel in the as-received and operated states basing on the properties that characterize plasticity, resistance to brittle fracture and hydrogen assisted cracking is accentuated. Two main methodological peculiarities are pointed out, (i) testing specimens should be cut out in the transverse direction relative to the pipe axis; (ii) strength and plasticity characteristics should be determined using flat tensile specimens with the smallest possible thickness of the working part. The determination of hydrogen concentration in metal, metallographic and fractographic analyses have been supplemented the study. The effectiveness of the proposed methodology has been illustrated by the example of the steel research after its 52-year operation.

Highlights

E nvironmental challenges are a global problem, and attention to these has become especially acute in recent years
Investigations of influence of natural gas/hydrogen mixtures on mechanical properties of pipeline steels demonstrate their susceptibility to hydrogen-induced embrittlement, which increases with the hydrogen partial pressure increasing [3]
It should be noted that hydrogen embrittlement in pipes is considered mainly due to a possible hydrogenating effect of the soil environment in the case of insulation cover damages [7,8,9,10,11], whereas less attention is paid to corrosion processes on the pipe inner surface, these could serve as factors of pipe integrity violation [12,13,14,15]

Summary

INTRODUCTION

E nvironmental challenges are a global problem, and attention to these has become especially acute in recent years. One of the ways to minimize environmental challenges is considered to be a radical modernization of energy policy, in particular, by decarbonizing energy sources This implies the use of hydrogen as an environmentfriendly fuel; the problem has been arising to transport hydrogen from potential places of its production to consumption places. Hydrogen transportation by gas pipelines is a complex problem, in which a important aspect is the possible integrity violation of the pipes due to the well-known detrimental effect of hydrogen on the mechanical properties of steels. Investigations of influence of natural gas/hydrogen mixtures on mechanical properties of pipeline steels demonstrate their susceptibility to hydrogen-induced embrittlement, which increases with the hydrogen partial pressure increasing [3]. A carbon pipeline steel after 52-year operation was investigated using the proposed methodology

MATERIALS AND METHODS

CONCLUSIONS