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A method of technical diagnostics for offshore structures

This paper discribes the results of measurements and analysis of the parameters, characterising technical state of offshore platforms in Vietnam Sea. Based on decreasing in time material characteristics because of corrosion and local destruction assessment on residua life time of platforms is given and variants for its repair are recommended. | Jour,;al of Mechanics, NCNST of Vietnam T. XVI, 1994, No 2 (43 - 48) A METHOD OF TECHNICAL DIAGNOSTICS FOR OFFSHORE STRUCTURES DO SON Institute of Mechanics, NCNST of Vietnam SUMMARY. This paper discribes the results of measurements and analysis of the parameters, characterising technical state of offshore platforms in Vietnam Sea. Based on decreasing in time material characteristics because of corrosion and local destruc;tion assessment on residua} life time of platforms is given and variants for its repair are recommended. The results allowed to confirm advantage of proposed technical diagnostic method in comparison with others and have been used for oil and gas platfonn of Joint Venture "Vietsovpetro" in South Vietnam. Key words technical diagnostics, offshore structures, corrosion, local destruction INTRODUCTION There are many fixed offshore platforms built for last 10 years in Vietnam Sea for exploiting oil and gas. Under action of sea environments in this regions the platforms have been rapidly declined. In order to estimate the durability and life time of this platforms, it is necessary to investigate sea-structures interactions, and to measure characteristics of structures and analyse the measured results as well as the Teal construction scheme. Vietnam sea is a region, in which the weather and climate are complicated and changing. The wind velocities reach 60 mfs. In the Eastern Sea usually waves move in the directions of the two monsoons:· the North - East direction is observed from October to March of next year and the West one is normally from April to September of every year. The wave height reaches 10-15 m, especially 20 m during seastorms. The surface currents are over 3m/s. Therefore the loads due to above factors are considerable. Beside the mechanical actions, in tropical sea condittions the constructions have been also strongly corroded. Corrosion velocity reaches 0.8 mmfyear in case the coatings are full destroyed. More than one method has