Use of the Threaded Plugs when Repairing Main Pipelines


To ensure the reliability and industrial safety of the main pipelines, their timely diagnosis and repair of detected defects are necessary. The design features of the threaded sealing plugs are considered in the article, and the technology is proposed for conducting non-destructive quality control of their welded joints.
In practice, pipeline repair showed that the installation of sealing plugs is carried out in those cases when the use of other repair parts (steel and fiberglass couplings, split tees) is impossible or inefficient.
Among many other repair technologies that allow to restore bearing capacity of the pipelines that have local through defects to the design level, the repair utilizing sealing plugs is the simplest and most cost-effective appropriate technology. It is the least expensive and does not require cutting out the defective section of the pipe (pipe spool or pipe section) and cutting in the new pipe spool or pipe section.
Practical experience in pipeline repair with through defects shows that the defects with up to 40 mm in diameter can be eliminated with the help of sealing plugs with mandatory subsequent quality control after their installation. Despite the relatively small sizes of the welded joints that are formed during welding when installing plugs, their quality control causes significant difficulties. Thus, the X-ray control must be carried out according to through the double-wall scheme, which is not always possible because two-way access is required to the object of control or to the problem area with the need to remove the transported product. Ultrasonic testing using the classic echo method has significant limitations due to the complexity of determining the height of the defect on the amplitude basis.
The visual and measuring control and the dye penetration inspection are insufficient. The method using ultrasonic diffraction-time method is proposed, which allows to perform quality control of the welded joints when repairing through holes in the pipe with the help of plugs.

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DOI: 10.24000/0409-2961-2020-3-65-70
Year: 2020
Issue num: March
Keywords : trunk pipeline welding welded joint ultrasonic control defect flaw detector sealing plug pipe repair structures diffraction-time method