Development and research of a flexible induction heater of internal insulation of a welded joint of pipelines

To ensure the quality of applying anti-corrosion insulation of welded joints inside pipelines with the internal protective coating, it is necessary to keep temperature regimes of a welded joint specified heating zone with high accuracy, including the heating rate and keeping the heating temperature of anti-corrosion insulation for a certain time. Nowadays, the industry does not produce compact and easy-to-use devices for heating welded joints of small-diameter pipelines when applying internal insulation in the field environment, so it is necessary to study the development of such types of devices and identify the efficiency of their use in practice. During the study, the author applies the induction heating method using a flexible induction heater of a pipeline welded joint. The heater is easy-to-install and ensures the required technological modes of heating the insulation inside the pipelines. The paper presents the results of modeling thermal processes, and, using the COMSOL Multiphysics package, studies temperature distribution along the joined pipelines. The study identified that due to uneven heating of a pipeline joint, temperature deviations falling outside the specified range occur. The author proposes a solution for this problem, which is a structural solution for the developed flexible inductor. The author used a specific laying of inductor winding to ensure the required heating characteristics. The experimental dependences of temperature change on the heating time inside the joined pipelines at the specified heating zones, which indicate the compliance with the requirement for the technology of insulating coating application, when entering various heating modes are obtained. The induction heater power required for heating the pipeline with a diameter of 159 mm and wall thickness of 8 mm was no more than 3 kW. The developed heaters provide the possibility of quick and convenient installation on pipelines, safety, and automation of insulation application. The study solves an important aspect of the problem of practical use of the technology of anti-corrosion protection of a welded bell-and-bell joint of pipelines of small diameters in the oil-and-gas industry.