Vengrynik T. Development of insulating-composite coating for strength incearsing for long-operated oil and gas pipelines

3. The new isolative coating and the methods and facilities for its covering are proposed in the dissertation, with a goal of a combination of oil and gas pipelines anticorrosion protection and an increase of its resistance to mechanical fracture, in-cluding on the stage of short fatigue crack growth. The isolative-composition coating is developed on the base of epoxy resin, reinforced by glass-fabric, which is distinguished by high thermal resistance, strength, adhesion with steel pipes and anticorrosion properties. The peculiarities of short fatigue crack growth in gas pipeline 17G1S steel are established ant it is revealed that long-term service of the pipeline decreased slightly fatigue crack growth resistance of the steel at the pulsatile load asymmetry but the negative influence of service is predicted to be increase with a rise of asymmetry. The method of an increase of fatigue short crack growth resistance in pipe steels by a deposit of the fluid component of the isolative coating what creates artificial crack closure effect and it combines anticorrosion protection with an increase of fatigue crack growth resistance of metal. Stress state of steel pipeline, covered by three layers composite coating, is investigated and it is established that it decreases slightly stresses in defectless pipe but noticeably in pipe with crack. .