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Statistical factors of strength of oil pipelines

UDK: 622.692.4.01:539.4
DOI: 10.24887/0028-2448-2018-11-131-134
Key words: main oil pipeline, strength, safety factor, loads and impacts, allowable stress
Authors: D.A. Neganov (The Pipeline Transport Institute LLC, RF, Moscow)

Conventional Russian and foreign strength calculations of pipelines transporting liquid and gaseous hydrocarbons are presented as a deterministic estimation of wall thickness based on the given design pressure, the selected pipe diameter and mechanical properties of the pipe steel. In deterministic estimates, basic strength calculations are performed using a force-determined strength condition expressed as nominal rated stress vs. permissible stress. A set of safety and reliability factors is introduced into these calculations to account for basic design, process and operational factors.

The article provides a quantitative assessment of the role of statistical factors of operational loading, the breaking point and the yield point, mechanical tolerance for wall thickness and pipe diameter, and pipe material degradation. It links the safety factors used in the international standards (API 579 and DIN 2470) and the Russian Construction Code SNiP 2.05.06-85*. The article suggests considering the statistical data on operational loading of oil pipelines by recording pressure at the inlet and outlet of the given oil pump station and measurement of local pipe stress in representative pipeline sections. The paper also contains proposals to consider that the strength properties of pipes may be affected by pipe steel degradation, especially in surface layers, in the course of long-term operation. Strength reserve values were obtained to account for other factors such as welds present, manufacturing defects in pipes and pipe steel, local corrosion, loading cyclicality and cyclic crack extension). These values should be further considered with advent of the new basic and check calculation methodology, to account for their stochastic nature.

References

1. Mazur I.I., Ivantsov O.M., Bezopasnost' truboprovodnykh sistem (Safety of pipeline systems), Moscow: Elima Publ., 2004, 1104 p.

2. Lisin YU.V., Makhutov N.A., Neganov D.A., Varshitskiy V.M., Comprehensive analysis of the pipelines safety and basic mechanical properties of the pipe steels (In Russ.), Nauka i tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2017, no. 1(28), pp. 30–38.

3. Rodionova S.G., Revel'-Muroz P.A., Lisin Yu.V. et al., Scientific-technical, socio-economic and legal aspects of oil and oil products transport reliability (In Russ.), Nauka i tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2016, no. 5 (25), pp. 20–31.

4. Makhutov N.A., Permyakov V.N., Resurs bezopasnoy ekspluatatsii sosudov i truboprovodov (Resource of safe operation of vessels and pipelines), Novosibirsk: Nauka Publ., 2005, 516 p.

5. PNAE G-7-002-89, Normy rascheta na prochnost’ oborudovaniya i truboprovodov atomnykh energeticheskikh ustanovok (Norms for calculating the strength of equipment and pipelines of nuclear power plants), Moscow: Energoatomizdat Publ., 1989, 525 p.

6. Makhutov N.A., Konstruktsionnaya prochnostʹ, resurs i tekhnogennaya bezopasnostʹ (Structural strength, life and man-made safety), Novosibirsk: Nauka Publ., 2005.

7. Lisin Yu.V., Makhutov N.A., Neganov D.A. et al., Identification of pipe steels of domestic and foreign manufacturing (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2018, no. 2, pp. 90–95.

8. Pluvinage G, Bouledroua O., Meliani M.H., Corrosion defect harmfulness by domain failure assessment diagram, Pipeline. Science and Technology, 2018, no. 3, pp. 163–177.

9. Neganov D.A., Maslikov S.N., Sergaev A.A., Ehrmish S.V., Application of in-line inspection data for calculating the bearing capacity of pipelines with the use of improved material reliability factor (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2017, no. 8, pp. 130–133.

Conventional Russian and foreign strength calculations of pipelines transporting liquid and gaseous hydrocarbons are presented as a deterministic estimation of wall thickness based on the given design pressure, the selected pipe diameter and mechanical properties of the pipe steel. In deterministic estimates, basic strength calculations are performed using a force-determined strength condition expressed as nominal rated stress vs. permissible stress. A set of safety and reliability factors is introduced into these calculations to account for basic design, process and operational factors.

The article provides a quantitative assessment of the role of statistical factors of operational loading, the breaking point and the yield point, mechanical tolerance for wall thickness and pipe diameter, and pipe material degradation. It links the safety factors used in the international standards (API 579 and DIN 2470) and the Russian Construction Code SNiP 2.05.06-85*. The article suggests considering the statistical data on operational loading of oil pipelines by recording pressure at the inlet and outlet of the given oil pump station and measurement of local pipe stress in representative pipeline sections. The paper also contains proposals to consider that the strength properties of pipes may be affected by pipe steel degradation, especially in surface layers, in the course of long-term operation. Strength reserve values were obtained to account for other factors such as welds present, manufacturing defects in pipes and pipe steel, local corrosion, loading cyclicality and cyclic crack extension). These values should be further considered with advent of the new basic and check calculation methodology, to account for their stochastic nature.

References

1. Mazur I.I., Ivantsov O.M., Bezopasnost' truboprovodnykh sistem (Safety of pipeline systems), Moscow: Elima Publ., 2004, 1104 p.

2. Lisin YU.V., Makhutov N.A., Neganov D.A., Varshitskiy V.M., Comprehensive analysis of the pipelines safety and basic mechanical properties of the pipe steels (In Russ.), Nauka i tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2017, no. 1(28), pp. 30–38.

3. Rodionova S.G., Revel'-Muroz P.A., Lisin Yu.V. et al., Scientific-technical, socio-economic and legal aspects of oil and oil products transport reliability (In Russ.), Nauka i tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2016, no. 5 (25), pp. 20–31.

4. Makhutov N.A., Permyakov V.N., Resurs bezopasnoy ekspluatatsii sosudov i truboprovodov (Resource of safe operation of vessels and pipelines), Novosibirsk: Nauka Publ., 2005, 516 p.

5. PNAE G-7-002-89, Normy rascheta na prochnost’ oborudovaniya i truboprovodov atomnykh energeticheskikh ustanovok (Norms for calculating the strength of equipment and pipelines of nuclear power plants), Moscow: Energoatomizdat Publ., 1989, 525 p.

6. Makhutov N.A., Konstruktsionnaya prochnostʹ, resurs i tekhnogennaya bezopasnostʹ (Structural strength, life and man-made safety), Novosibirsk: Nauka Publ., 2005.

7. Lisin Yu.V., Makhutov N.A., Neganov D.A. et al., Identification of pipe steels of domestic and foreign manufacturing (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2018, no. 2, pp. 90–95.

8. Pluvinage G, Bouledroua O., Meliani M.H., Corrosion defect harmfulness by domain failure assessment diagram, Pipeline. Science and Technology, 2018, no. 3, pp. 163–177.

9. Neganov D.A., Maslikov S.N., Sergaev A.A., Ehrmish S.V., Application of in-line inspection data for calculating the bearing capacity of pipelines with the use of improved material reliability factor (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2017, no. 8, pp. 130–133.



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