To ensure the safety of crossings under roads and railways, pipelines are equipped with protective tubes. In this case, the choice of casing parameters of the protective tube is made because of the requirements for ensuring mechanical strength, stability, safety, and tightness of the tubular annulus. To ensure a guaranteed gap between the pipeline and the protective tube, as well as the absence of electrical contact when laying the pipeline in the case, support-guide rings are used, which are mounted on a rubber gasket with bolted connections. The space between the protective tube and the oil pipeline is sealed with rubber cuffs. Cuffs are installed at both ends of the protective tube. However, ensuring the tightness of the medium during a long service life is not always possible to achieve, as a result of which the insulating coating of the pipeline and the metal of the casing can be subjected to corrosive effects of the external environment. Given that, the assessment of the actual state of the transitions and the identification of the above complications for pipelines that are not subject to technical diagnostics using in-line diagnostics is a significant problem. In practice, they resort to indirect methods for assessing the technical condition of pipelines based on various physical principles (electrical, acoustic, etc.), which do not provide sufficient accuracy. In foreign countries operational remote control is implemented in the form of portable small-sized inspection devices for assessing the state of the annular space and the inner surface of the protective casing. In this article, the technological difficulties of designing the main elements are considered, the structural scheme is described, and the calculations are made for the main element of a small-sized inspection device - magnetic running wheels. The results obtained allow us to proceed to the next stage – the creation of a prototype of the inspection device.
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