Basic and verification methods for substantiation of main oil pipeline strength taking into account life cycle stages

UDK: 622.692.4.01:539.4
DOI: 10.24887/0028-2448-2019-5-100-103
Key words: strength, calculation method, limit state, safety factor, pressure, stress, wall thickness, pipeline diameter
Authors: D.A. Neganov (The Pipeline Transport Institute LLC, RF, Moscow)

The paper deals with the scientific and applied problems of determining and standardizing the strength of main oil pipelines. These problems can be solved using basic and verification strength calculations for all major stages of pipeline life cycle. At the design stage, the basic strength calculation is carried out using a deterministic method based on comparing operating stresses with permissible ones determined by safety factors (foreign standards) or limit states and limit resistances (Russian standards). The purpose of the basic calculation is to determine the minimum required pipe wall thickness for specified pipe pressures and diameters and selected pipe steels. During the construction, testing, and operation phases, a system of strength verification calculation is used, taking into account time factors with changes in mechanical properties (due to aging and degradation) and wall thickness (due to corrosion and defect growth). During the prolonged operation of a pipeline, changes accumulate, which are related to the conditions of its operation: transportation process parameters, rheological properties of pumped products, and composition of equipment of pump stations change. From time to time, there is a need to change the transportation pattern, while replacing pipeline sections during major repairs and overhaul makes pipeline length change. These changes (taking into account the effect accumulated over a long period of operation) may result in a change in the operating pressures on the pipeline route, established in the original project. These processes affect the values of safety factor, which also become a function of time. Based on the calculations, taking into account the actual safety factors, the decision is made on further operation, decommissioning or repair and renewal of a pipeline section.

The factors that need to be taken into account when substantiating the strength of a main pipeline that has been operated for a long time are provided; the main ones include: use of actual mechanical characteristics of pipes, accounting of accumulated damage, susceptibility of a pipe steel to aging and degradation, as well as data on actual loading of a pipeline due to internal pressure. The paper underlines the main methods of obtaining the information necessary for strength calculation, including intra-pipe diagnostics and mechanical tests of pipe and metal samples. The areas of change of safety factors when deterministic, statistical, and probabilistic design characteristics are introduced are analyzed. The problems for which statistical and probabilistic verification calculations are used are identified. Basic calculation expressions for basic and verification calculations for corresponding stages of pipeline life cycle are proposed.

References

1. SNiP 2.05.06-85. Magistral'nye truboprovody (Trunk pipeline).

2. API 579/ASMEFFS-1. Fitness for servise.

3. DIN 17457. Truba nerzhaveyushchaya svarnaya (Welded stainless pipe).

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

5. Radionova S.G., Zhulina S.A., Makhutov N.A. et al., Research prospects in the field of risk analysis for improvement of government regulation and safety increase of the oil and gas chemical complex objects (In Russ.), Bezopasnost' truda v promyshlennosti, 2017, no. 9, pp. 5–13.

6. 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.

7. Makhutov N.A., Prochnost' i bezopasnost': fundamental'nye i prikladnye issledovaniya (Strength and safety: fundamental and applied research), Novosibirsk: Nauka Publ., 2008, 528 p.

8. Lisin Yu.V., Makhutov N.A., Nadein V.A., Neganov D.A., Probabilistic analysis of transportation systems for oil and natural gas, In: Probabilistic modeling in system engineering, London: IntechOpen Publ., 2018, pp. 81–103.

9. Bezopasnost' Rossii. Pravovye, sotsial'no-ekonomicheskie i nauchno-tekhnicheskie aspekty. Bezopasnost' sredstv khraneniya i transporta energoresursov (Security of Russia. Legal, socio-economic and scientific-technical aspects. Security of energy storage and transportation facilities): edited by Makhutov N.A., Moscow: Znanie Publ., 2019, 928 p.

10. Lisin Yu.V., Makhutov N.A., Neganov D.A. et al., Integral mechanical tests in the strength calculations of the main pipeline for transportation of oil and oil products (In Russ.), Zavodskaya laboratoriya. Diagnostika materialov, 2018, V. 84, no. 4, pp. 47–59.

11. 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 tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2016, no. 6, pp. 30–37.

The paper deals with the scientific and applied problems of determining and standardizing the strength of main oil pipelines. These problems can be solved using basic and verification strength calculations for all major stages of pipeline life cycle. At the design stage, the basic strength calculation is carried out using a deterministic method based on comparing operating stresses with permissible ones determined by safety factors (foreign standards) or limit states and limit resistances (Russian standards). The purpose of the basic calculation is to determine the minimum required pipe wall thickness for specified pipe pressures and diameters and selected pipe steels. During the construction, testing, and operation phases, a system of strength verification calculation is used, taking into account time factors with changes in mechanical properties (due to aging and degradation) and wall thickness (due to corrosion and defect growth). During the prolonged operation of a pipeline, changes accumulate, which are related to the conditions of its operation: transportation process parameters, rheological properties of pumped products, and composition of equipment of pump stations change. From time to time, there is a need to change the transportation pattern, while replacing pipeline sections during major repairs and overhaul makes pipeline length change. These changes (taking into account the effect accumulated over a long period of operation) may result in a change in the operating pressures on the pipeline route, established in the original project. These processes affect the values of safety factor, which also become a function of time. Based on the calculations, taking into account the actual safety factors, the decision is made on further operation, decommissioning or repair and renewal of a pipeline section.

The factors that need to be taken into account when substantiating the strength of a main pipeline that has been operated for a long time are provided; the main ones include: use of actual mechanical characteristics of pipes, accounting of accumulated damage, susceptibility of a pipe steel to aging and degradation, as well as data on actual loading of a pipeline due to internal pressure. The paper underlines the main methods of obtaining the information necessary for strength calculation, including intra-pipe diagnostics and mechanical tests of pipe and metal samples. The areas of change of safety factors when deterministic, statistical, and probabilistic design characteristics are introduced are analyzed. The problems for which statistical and probabilistic verification calculations are used are identified. Basic calculation expressions for basic and verification calculations for corresponding stages of pipeline life cycle are proposed.

References

1. SNiP 2.05.06-85. Magistral'nye truboprovody (Trunk pipeline).

2. API 579/ASMEFFS-1. Fitness for servise.

3. DIN 17457. Truba nerzhaveyushchaya svarnaya (Welded stainless pipe).

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

5. Radionova S.G., Zhulina S.A., Makhutov N.A. et al., Research prospects in the field of risk analysis for improvement of government regulation and safety increase of the oil and gas chemical complex objects (In Russ.), Bezopasnost' truda v promyshlennosti, 2017, no. 9, pp. 5–13.

6. 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.

7. Makhutov N.A., Prochnost' i bezopasnost': fundamental'nye i prikladnye issledovaniya (Strength and safety: fundamental and applied research), Novosibirsk: Nauka Publ., 2008, 528 p.

8. Lisin Yu.V., Makhutov N.A., Nadein V.A., Neganov D.A., Probabilistic analysis of transportation systems for oil and natural gas, In: Probabilistic modeling in system engineering, London: IntechOpen Publ., 2018, pp. 81–103.

9. Bezopasnost' Rossii. Pravovye, sotsial'no-ekonomicheskie i nauchno-tekhnicheskie aspekty. Bezopasnost' sredstv khraneniya i transporta energoresursov (Security of Russia. Legal, socio-economic and scientific-technical aspects. Security of energy storage and transportation facilities): edited by Makhutov N.A., Moscow: Znanie Publ., 2019, 928 p.

10. Lisin Yu.V., Makhutov N.A., Neganov D.A. et al., Integral mechanical tests in the strength calculations of the main pipeline for transportation of oil and oil products (In Russ.), Zavodskaya laboratoriya. Diagnostika materialov, 2018, V. 84, no. 4, pp. 47–59.

11. 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 tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2016, no. 6, pp. 30–37.


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