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Predicting the remaining life of pipelines after repairing surface defects by grinding

UDK: 622.692.4-192
DOI: 10.24887/0028-2448-2020-5-93-96
Key words: surface defects, criteria for fracture mechanics, cyclic loading, removal of surface defects by grinding, modeling of the stress-strain state of pipeline wall, predicting the residual life of the pipeline with surface defects
Authors: D.A. Neganov (The Pipeline Transport Institute LLC, RF, Moscow), E.E. Zorin (The Pipeline Transport Institute LLC, RF, Moscow)

Predicting the residual life of pipelines with surface defects has always been associated with time-consuming and high-cost testing of full-size pipes and pipe strings, since it is not possible to implement a biaxial stress-strain state that occurs in the pipe wall under the influence of internal pressure on standard samples. A method and a special form of the sample segment for cyclic testing of pipe steels according to the criteria of fracture mechanics have been developed. A full-thickness sample is cut from the wall of the pipeline under investigation. The minimum geometric dimensions of its working part, associated with the thickness of the pipe wall, are determined and allow modeling the stress-strain state of the pipeline wall loaded with internal pressure in the center of the working part of the sample under uniaxial tension. Applying an artificial surface crack-like stress concentrator in the center of the working part of the sample with a fixed depth and length of no more than 30% of the width of the sample’s working part allows using the "marks" method to evaluate the parameters of the metal crack resistance of the pipeline under cyclic loading conditions. Plotting of kinetic diagrams of fatigue fracture metal, for the pipeline wall allows assessing numerically the effect of duration of pipeline operation in difficult climatic conditions, the changes in the physico-mechanical characteristics of pipeline metal.

The authors also investigated the cyclic crack resistance of metal pipes made of steel of K52 – K54 strength class in the state of delivery and after 45-55 years of operation. The parameters of cyclic loading were taken from the existing oil trunk pipeline and schematized using the "rain" method. The remaining life of the pipeline wall with a 20% depth of grinding and a surface stress concentrator at the bottom of the grinding with a depth of 1.5 mm, a length of 20 mm, and an opening of 0.2 mm is predicted. Dimensions of the surface concentrator are selected from the condition of stable registration by non-destructive testing methods even in the underwater position. Samples from pipes of K60 strength class of controlled rolling were used to evaluate cyclic durability of the wall restored after electric arc grinding by electric arc build-up.

References

1. 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.

2. Lisin Yu.V., Neganov D.A., Makhutov N.A., Zorin N.E., Application of size-scale effect for main pipeline strength foundation (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2017, no. 6, pp. 112–116.

3. Zorin E.E., Razrabotka osnov prognozirovaniya rabotosposobnosti svarnykh truboprovodov iz ferrito-perlitnykh staley s uchetom usloviy ekspluatatsii (Development of the basis for predicting the performance of welded pipelines made of ferritic-pearlitic steels, taking into account operating conditions): thesis of doctor of technical science, Moscow, 1993, 333 p.

4. Demina N.I., Zilova T.K., Fridman Ya.B., Methods of mechanical testing of sheet materials under biaxial tension (In Russ.), Zavodskaya laboratoriya, 1964, no. 5.

5. Lyapichev D.M., Modelirovanie dvukhosnogo napryazhennogo sostoyaniya na krupnomasshtabnykh trubnykh segmentakh v usloviyakh odnoosnogo rastyazheniya (Simulation of a biaxial stress state on large-scale pipe segments under uniaxial tension): graduate work, Moscow, 2009.

6. Basov K.A., ANSYS: spravochnik pol'zovatelya (ANSYS: user guide), Moscow: DMK Press Publ., 2005, 640 p.

7. Zorin N.E., Eksperimental'naya otsenka rabotosposobnosti trub magistral'nykh gazoprovodov pri tsiklicheskom nagruzhenii (Experimental evaluation of the performance of pipes of gas pipelines under cyclic loading): thesis of candidate of technical science, Moscow, 2010, 143 p.

8. Neganov D.A., Makhutov N.A., Zorin N.E., Formation of requirements to reliability and security of the exploited sections of the linear part of trunk pipelines transportation of oil and oil products (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2019, no. 6, pp. 106–112.

9. Geyt A.V., Zorin E.E., Mikhaylov I.I., Application of automated ultrasonic inspection systems in assessing the quality of girth welds of main pipelines (In Russ.), Nauka i tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2018, V. 8, no. 3, pp. 92–101.

Predicting the residual life of pipelines with surface defects has always been associated with time-consuming and high-cost testing of full-size pipes and pipe strings, since it is not possible to implement a biaxial stress-strain state that occurs in the pipe wall under the influence of internal pressure on standard samples. A method and a special form of the sample segment for cyclic testing of pipe steels according to the criteria of fracture mechanics have been developed. A full-thickness sample is cut from the wall of the pipeline under investigation. The minimum geometric dimensions of its working part, associated with the thickness of the pipe wall, are determined and allow modeling the stress-strain state of the pipeline wall loaded with internal pressure in the center of the working part of the sample under uniaxial tension. Applying an artificial surface crack-like stress concentrator in the center of the working part of the sample with a fixed depth and length of no more than 30% of the width of the sample’s working part allows using the "marks" method to evaluate the parameters of the metal crack resistance of the pipeline under cyclic loading conditions. Plotting of kinetic diagrams of fatigue fracture metal, for the pipeline wall allows assessing numerically the effect of duration of pipeline operation in difficult climatic conditions, the changes in the physico-mechanical characteristics of pipeline metal.

The authors also investigated the cyclic crack resistance of metal pipes made of steel of K52 – K54 strength class in the state of delivery and after 45-55 years of operation. The parameters of cyclic loading were taken from the existing oil trunk pipeline and schematized using the "rain" method. The remaining life of the pipeline wall with a 20% depth of grinding and a surface stress concentrator at the bottom of the grinding with a depth of 1.5 mm, a length of 20 mm, and an opening of 0.2 mm is predicted. Dimensions of the surface concentrator are selected from the condition of stable registration by non-destructive testing methods even in the underwater position. Samples from pipes of K60 strength class of controlled rolling were used to evaluate cyclic durability of the wall restored after electric arc grinding by electric arc build-up.

References

1. 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.

2. Lisin Yu.V., Neganov D.A., Makhutov N.A., Zorin N.E., Application of size-scale effect for main pipeline strength foundation (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2017, no. 6, pp. 112–116.

3. Zorin E.E., Razrabotka osnov prognozirovaniya rabotosposobnosti svarnykh truboprovodov iz ferrito-perlitnykh staley s uchetom usloviy ekspluatatsii (Development of the basis for predicting the performance of welded pipelines made of ferritic-pearlitic steels, taking into account operating conditions): thesis of doctor of technical science, Moscow, 1993, 333 p.

4. Demina N.I., Zilova T.K., Fridman Ya.B., Methods of mechanical testing of sheet materials under biaxial tension (In Russ.), Zavodskaya laboratoriya, 1964, no. 5.

5. Lyapichev D.M., Modelirovanie dvukhosnogo napryazhennogo sostoyaniya na krupnomasshtabnykh trubnykh segmentakh v usloviyakh odnoosnogo rastyazheniya (Simulation of a biaxial stress state on large-scale pipe segments under uniaxial tension): graduate work, Moscow, 2009.

6. Basov K.A., ANSYS: spravochnik pol'zovatelya (ANSYS: user guide), Moscow: DMK Press Publ., 2005, 640 p.

7. Zorin N.E., Eksperimental'naya otsenka rabotosposobnosti trub magistral'nykh gazoprovodov pri tsiklicheskom nagruzhenii (Experimental evaluation of the performance of pipes of gas pipelines under cyclic loading): thesis of candidate of technical science, Moscow, 2010, 143 p.

8. Neganov D.A., Makhutov N.A., Zorin N.E., Formation of requirements to reliability and security of the exploited sections of the linear part of trunk pipelines transportation of oil and oil products (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2019, no. 6, pp. 106–112.

9. Geyt A.V., Zorin E.E., Mikhaylov I.I., Application of automated ultrasonic inspection systems in assessing the quality of girth welds of main pipelines (In Russ.), Nauka i tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2018, V. 8, no. 3, pp. 92–101.


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