Corrosion of the Internal Wall of a Field Gas Pipeline
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SCIENCE FOR PRODUCTION CORROSION OF THE INTERNAL WALL OF A FIELD GAS PIPELINE S. Yu. Kovalenko,1 A. O. Rybakov,1 A. V. Klymenko,1,2 and L. H. Shytova1 We have determined the causes of depressurization of a pipeline of diameter 114.30 mm and wall thickness 6.02 mm (pipe steel of category X60), which transports natural gas from the gas field to the gathering point. We have performed spectral, electrochemical, and metallographic investigations of a metal fragment from the damaged pipe as well as chemical analysis of the corrosion products on the wall internal surface (X-ray microspectral analysis). Polarization measurements have been carried out in deaerated solutions and those aerated by air oxygen, having different salt content. It has been shown that, with increase in the salt content, the corrosion resistance of pipe steel decreases, and the corrosion rate increases from 0.06 to 0.89 A/cm 2 under aerated conditions and from 0.16 to 1.48 A/cm 2 under deaerated. Keywords: corrosion, gas pipeline, depressurization, corrosion rate, aerated and deaerated conditions.
Corrosion damages, causing the destruction and decrease in the serviceability of equipment of the oil and gas industry, lead to significant economic losses. To ensure the accident-free and failure-free operation of field pipelines under conditions of the transport of products and the action of technological media and working loads, it is necessary to have efficient methods of rust protection. At present, due to the increase in the humidity of transported gas, the corrosion problems become even more accentuated, and the general specific frequency of pipeline breaks within the limits of a single region can reach from 0.19 to 0.8 breaks/(km⋅yr) [1]. Internal corrosion damages represent one of the causes of pipeline breakage. Therefore, it is quite important to prevent their premature stress corrosion failure. For this purpose, it is necessary to clarify the preconditions of appearance of these damages and to establish the factors of influence on the course of corrosion processes. The aim of the present work is to establish the causes of depressurization of a gas pipeline of category X60 (the working pressure is 9.09 МPа, and the gas temperature in the well is 54°С) at its section from the field to the gathering point and to study the electrochemical and structural changes in pipe steel. Procedure of Investigations We tested specimens made of a fragment of a damaged pipe with a longitudinal weld, cut out of a gas pipeline of diameter 114.30 mm and wall thickness 6.02 mm, which transports natural gas from the gas field to the gathering point. 1 2
Paton Institute of Electric Welding, Ukrainian National Academy of Sciences, Kyiv, Ukraine. Corresponding author; e-mail: [email protected].
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 48, No. 2, pp. 97–102, March–April, 2012. Original article submitted March 17, 2012. 1068-820X/12/4802–0225
© 2012
Springer Science+Business Media New York
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S. YU. KOVALENKO, A. O. RYBAKOV, A. V. KLYMENKO,
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