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Research Papers: Piper and Riser Technology

Pipeline Slug Flow Dynamic Load Characterization

[+] Author and Article Information
Ahmed Reda

School of Civil and Mechanical Engineering,
Curtin University,
Perth 6102, WA, Australia
e-mail: reda.ahmed@postgrad.curtin.edu.au

Gareth L. Forbes

School of Civil and Mechanical Engineering,
Curtin University,
Perth 6102, WA, Australia
e-mail: gareth.forbes@curtin.edu.au

Ibrahim A. Sultan

School of Science, Engineering
and Information Technology,
Federation University Australia,
Ballarat 3350, VIC, Australia
e-mail: i.sultan@federation.edu.au

Ian M. Howard

School of Civil and Mechanical Engineering,
Curtin University,
Perth 6102, WA, Australia
e-mail: i.howard@curtin.edu.au

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received August 20, 2017; final manuscript received May 22, 2018; published online August 13, 2018. Assoc. Editor: Hagbart S. Alsos.

J. Offshore Mech. Arct. Eng 141(1), 011701 (Aug 13, 2018) (8 pages) Paper No: OMAE-17-1152; doi: 10.1115/1.4040414 History: Received August 20, 2017; Revised May 22, 2018

Flow of gas in pipelines is subject to thermodynamic conditions which produces two-phase bulks (i.e., slugs) within the axial pipeline flow. These moving slugs apply a moving load on the free spanning pipe sections, which consequently undergo variable bending stresses, and flexural deflections. Both the maximum pipeline stress and deflection due to the slug flow loads need to be understood in the design of pipeline spans. However, calculation of a moving mass on a free spanning pipeline is not trivial and the required mathematical model is burdensome for general pipeline design engineering. The work in this paper is intended to investigate the conditions under which simplified analysis would produce a safe pipeline design which can be used by practicing pipeline design engineers. The simulated finite element models presented here prove that replacing the moving mass of the slug by a moving force will produce adequately accurate results at low speeds where the mass of the slug is much smaller than the mass of the pipe section. This result is significant, as the assumption of point load simplifies the analysis to a considerable extent. Since most applications fall within the speed and mass ratio which justify employing this simplified analysis, the work presented here offers a powerful design tool to estimate fatigue stresses and lateral deflections without the need of expensive time-consuming inputs from specialized practitioners.

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References

Sultan, I. A. , Reda, A. M. , and Forbes, G. L. , 2013, “Evaluation of Slug Flow-Induced Flexural Loading in Pipelines Using a Surrogate Model,” ASME. J. Offshore Mech. Arct. Eng., 135(3), p. 031703. [CrossRef]
Sultan, I. A. , Reda, A. M. , and Forbes, G. L. , 2012, “A Surrogate Model for Evaluation of Maximum Normalized Dynamic Load Factor in Moving Load Model for Pipeline Spanning Due to Slug Flow,” ASME Paper No. OMAE2012-83746.
Reda, A. M. , Forbes, G. L. , and Sultan, I. A. , 2012, “Characterization of Dynamic Slug Flow Induced Loads in Pipelines,” ASME Paper No. OMAE2012-83218.
Reda, A. , Forbes, G. , McKee, K. , and Howard, I. , 2014, “Vibration of a Curved Subsea Pipeline Due to Internal Slug Flow,” 43rd International Congress on Noise Control Engineering, Australian Acoustical Society, Melbourne, Australia, Nov. 16–19.
Reda, A. M. , Forbes, G. L. , and Sultan, I. A. , 2011, “Characterisation of Slug Flow Conditions on Pipelines for Fatigue Analysis,” ASME Paper No. OMAE2011-49583.
Reda, A. M. , and Forbes, G. L. , 2011, “The Effect of Distribution for a Moving Force,” Australian Acoustical Society, Gold Coast, Australia, ACOUSTICS 2011, Nov. 2–4, Paper No. 66.
Rieker, J. R. , and Trethewey, M. W. , 1999, “Finite Element Analysis of an Elastic Beam Structure Subjected to a Moving Distributed Mass Train,” Mech. Syst. Signal Process., 13(1), pp. 31–51. [CrossRef]
Casanova, E. , Pelliccioni, O. , and Blanco, A. , 2009, “Fatigue Life Prediction Due to Slug Flow in Extra Long Submarine Gas Pipelines Using Fourier Expansion Series,” ASME Paper No. OMAE2009-79642.
Casanova, E. , and Blanco, A. , 2010, “Effects of Soil Non-Linearity on the Dynamic Behavior and Fatigue Life of Pipeline Spans Subjected to Slug Flow,” ASME Paper No. OMAE2010-20126.
Kansao, R. , Casanova, E. , Blanco, A. , Kenyery, F. , and Rivero, M. , 2008, “Fatigue Life Prediction Due to Slug Flow in Extra Long Submarine Gas Pipelines,” ASME Paper No. OMAE2008-58005.
Cooper, P. , Burnett, C. , and Nash, I. , 2009, “Fatigue Design of Flowline Systems With Slug Flow,” ASME Paper No. OMAE2009-79308.
Rieker, J. R. , Lin, Y.-H. , and Trethewey, M. W. , 1996, “Discretization Considerations in Moving Load Finite Element Beam Models,” Finite Elem. Anal. Des., 21(3), pp. 129–144. [CrossRef]
Recommended Practice, 2006, “Free Spanning Pipelines,” Det Norske Veritas, Oslo, Norway, Standard No. DNV-RP-105.
Forbes, G. L. , and Reda, A. M. , 2013, “Influence of Axial Boundary Conditions on Free Spanning Pipeline Natural Frequencies,” ASME Paper No. OMAE2013-10147.

Figures

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Fig. 1

Slug schematic model

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Fig. 2

Validation of bending moment normalization at (slug/beam mass) = 5%

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Fig. 3

Validation of bending moment normalization at (slug/beam mass) = 50%

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Fig. 4

Impact of higher modes of vibration on maximum normalized DLF of bending moment for moving force model

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Fig. 5

Impact of higher modes of vibration on maximum normalized DLF of displacement for moving force model

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Fig. 6

Deviations of maximum normalized DLF of displacement at a damping ratio of 0.04

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Fig. 7

Deviations of maximum normalized DLF of bending moment at a damping ratio of 0.04

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Fig. 8

Zone A loading category graph for API Spec 5 L

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Fig. 12

Deviation of maximum normalized DLF of bending moment at a damping ratio of 0.04

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Fig. 9

Deviation of maximum normalized DLF of displacement at a damping ratio of 0.04

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Fig. 10

Moving mass versus moving force displacement DLF at a slug/beam mass ratio = 0.5

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Fig. 11

Zoomed moving mass versus moving force displacement DLF at a slug/beam mass ratio = 0.5

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