To ensure the safe operation of the pipeline, calculations must be made and the permissible working pressure must be set. Calculation of the permissible operating pressure is carried out by the criterion of ensuring the normative safety factor according to SNiP 2.05.06-85* using data on the actual wall thickness of the pipes measured during in-line diagnostics, category of sections, strength characteristics and results of hydraulic tests.
The characteristic determining the permissible operating pressure of the pipeline is its load-bearing capacity, while the calculations use the standard safety factors; their separate rationing for the operated pipes is absent. The application of the standard coefficients in the calculation of the bearing capacity provides, in fact, a double safety margin of the pipelines in operation. At the same time, with such an approach, excessive rejection of pipe sections, which does not provide the required design bearing capacity for the operating pressure, are possible. The system of standard reserve factors, applied at present in the Russian Federation, has not changed fundamentally since 1975. However, the last 30 years are characterized by a significant development of pipeline transport technologies: progress has been made in construction, technical diagnostics, automation, development of settlement and project software.
In this article, the authors present an algorithm for a detailed analysis of the results of in-line inspections, taking into account the results obtained in determining the improved material reliability factor, used in calculations of bearing capacity of operated pipelines. Calculation of the improved reliability factor for the material is suggested to be performed taking into account the margin for minus tolerance in the manufacture of pipes, analysis of the distribution of the wall thickness within the pipe sections, as well as measurement errors in in-line inspections.
References
1. Aynbinder A.B., Raschet magistral'nykh i promyslovykh truboprovodov na prochnost' i ustoychivost' (Calculation of main and field pipelines for strength and stability), Moscow: Nedra Publ., 1991, 287 p.
2. Varshitskiy V.M., Updating calculations to define bearing capacity of laid pipes (In Russ.), Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov, 2011, no. 2, pp. 48–49.
3. Lisin Yu.V., Neganov D.A., Sergaev A.A., Defining maximal working pressures for main pipelines in extended operation from the results of in-line diagnostics (In Russ.), Nauka i tekhnologii truboprovodnogo transporta nefti i nefteproduktov, 2016, no. 6, pp. 30–37.
