Pressure Behavior of a Steel Pipeline Experiencing Creep at Normal Temperatures
Publication: Journal of Aerospace Engineering
Volume 31, Issue 3
Abstract
This work was motivated by the need for knowledge about the natural decrease in water pressure from room temperature creep, separate from the decrease in pressure caused by leakage in tightness tests of new and/or repaired pipelines. In this context, a case study was conducted regarding the decrease in water pressure in a test pipe with dimensions of 530 mm in outside diameter and 7.8 mm in wall thickness. The system was pressurized to a pressure of 8.985 MPa, after which the water supply was stopped. The test pipe, 4 m in length, was made from linepipe steel L360NB and was closed by torispherical heads at both ends. Special attention was given to the thermal insulation of the test pipe, ensuring an average temperature of 14.5°C, with variation within 0.1°C over a period of 24 h. A nonlinear ordinary differential equation was derived to describe the time gradient of the water pressure in the test pipe in relation to time, pressure, coefficient of compressibility of water, and cross-sectional dimensions of the test pipe. The necessary creep parameters and static tensile properties were obtained from specimens manufactured from a ring 30 cm in width taken from the same pipe. The orientation of the specimens was circumferential. The creep tests were performed over a period of 24 h at ambient temperature. The creep strains were measured by the strain gauge technique, and the effect of temperature variation during the test period (24 h) was compensated by the use of a compensating strain gauge. The calculated decrease in pressure with time compared quite well with experimental results when the beginning of the pressure decrease was considered 2 h after reaching the initial pressure of water () and the supply of water was ended. The time period of 2–24 h follows the recommendations of a pipeline operating pressure standard. A family of “pressure-time” curves were constructed for a pipe from steel pressurized by water to specific initial pressure levels taken as multiples of the pressure at the yield. These curves cover a time interval of 2–24 h, and they can be used to check the total decrease in water pressure after the tightness test has been completed.
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Acknowledgments
This paper was supported by the Technological Agency of the Czech Republic (Project No. TE02000162) and by NET4GAS, s.r.o. The authors are also grateful to CEPS Plc. for providing test materials.
References
CGA (Czech Gas Association). (2013). “Gas mains and service pipelines for maximum operating pressure up to 100 bar included.” Czech Standard G70204, Prague, Czechia (in Czech).
Chen, W., and Wang, S.-H. (2002). “Room temperature creep behaviour of pipeline steels and its influence on stress corrosion cracking.” 4th Int. Pipeline Conf., ASME, New York.
Chen, W., Zhu, H., and Wang, S.-H. (2013). “Low temperature creep behaviour of pipeline steels.” Can. Metall. Q.: J. Metall. Mater. Sci., 48(3), 271–283.
Finnie, L., and Heller, W. R. (1959). Creep of engineering materials, McGraw-Hill, London.
Gajdoš, Ľ., et al. (2004). Structural integrity of pressure pipelines, Transgas, Prague, Czech Republic.
Gajdoš, Ľ., and Šperl, M. (2015). “Creep of pipeline steels at normal temperatures.”, Prague, Czech Republic (in Czech).
Gajdoš, Ľ., Šperl, M., and Pařízek, P. (2013). “Development of plastic deformations in steel under constant load and their importance for practice in the gas industry.” Plyn (Gas), 93(3), 198–203 (in Czech).
Gajdoš, Ľ., Šperl, M., and Pařízek, P. (2014). “Room temperature creep of L360NB+N steel.” Proc., 31st Danubia-Adria Symp. on Advances in Experimental Mechanics, VDI Verein Deutscher Ingenieure e.V., Düsseldorf, Germany.
Gittus, J. H. (1975). Creep, viscoelasticity and creep fracture in solids, Applied Science Publishers, London.
Guo, J. Q., Li, F., Zheng, X. T., Shi, H. C., and Meng, W. Z. (2016). “An accelerated method for creep prediction from short term stress relaxation tests.” J. Pressure Vessel Technol., 138(3), 031401.
Kassner, M. E., and Smith, K. (2014). “Low temperature creep plasticity.” J. Mater. Res. Technol., 3(3), 280–288.
Liu, C., Liu, P., Zhao, Z., and Northwood, D. O. (2001). “Room temperature creep of a high strength steel.” Mater. Des., 22(4), 325–328.
Nie, D., Zhao, J., Mo, T., and Chen, W. (2008). “Room temperature creep and its effect on flow stress in a X70 pipeline steel.” Mater. Lett., 62(1), 51–53.
Nogata, F., and Takahashi, H. (1995). “A creep damage estimation method for in-service fossil fuel boiler superheater tubes.” J. Pressure Vessel Technol., 117(1), 14–18.
Wang, S.-H., Zhang, Y., and Chen, W. (2001). “Room temperature creep and strain-rate dependent stress-strain behaviour of pipeline steels.” J. Mater. Sci., 36(8), 1931–1938.
Zhao, Z., Northwood, D. O., Liu, C., and Liu, Y. (1999). “A new method for improving the resistance of high strength steel wires to room temperature creep and low cycle fatigue.” J. Mater. Process. Technol., 89–90, 569–573.
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©2018 American Society of Civil Engineers.
History
Received: Aug 1, 2017
Accepted: Nov 14, 2017
Published online: Mar 9, 2018
Published in print: May 1, 2018
Discussion open until: Aug 9, 2018
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