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Research Papers: Materials and Fabrication

Effect of Reeling on Sour Service Fatigue Crack Growth Behavior of Welded API5LX65 Line Pipe

[+] Author and Article Information
Ramgopal Thodla, Feng Gui

DNV GL USA,
Dublin, OH 43017

J. R. Gordon

Microalloying International,
Houston, TX 77064

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received February 14, 2015; final manuscript received July 22, 2015; published online November 18, 2015. Assoc. Editor: Kunio Hasegawa.

J. Pressure Vessel Technol 138(2), 021405 (Nov 18, 2015) (11 pages) Paper No: PVT-15-1028; doi: 10.1115/1.4031165 History: Received February 14, 2015; Revised July 22, 2015

The effect of reeling on the fatigue crack growth rate (FCGR) behavior of welded pipe was investigated both in-air as well as in sour environment. The FCGR behavior of the reeled pipe in various notch locations, such as parent pipe (PP), weld center line (WCL), and heat affected zone (HAZ), did not exhibit any effect of reeling (i.e., the properties in the strained and aged conditions were similar to the as-fabricated welds). Frequency scan FCGR tests in sour environment (pH = 5/0.0031 MPa H2S) exhibited maximum FCGR in the range of 10× to 35× higher than the in-air values at frequencies in the range of 3–1 mHz and 3× to 5× at frequencies in the range of 0.3 Hz (risers). In sour service, WCL exhibited better fatigue performance than the PP and HAZ in all conditions. Fatigue performance of PP and WCL was independent of reeling. The poorest fatigue performance was observed in unstrained HAZ. Fatigue performance of HAZ extrados (side last strained in compression) and intrados (side last strained in tension) was similar and better than unstrained HAZ. It was also found that the FCGR in sour environments was controlled by the internal hydrogen due to bulk charging from the sour environment. The overall conclusion is that reeling has no detrimental effect on sour service fatigue crack growth behavior, i.e., sour service fatigue performance of reeled pipe is the same as unreeled pipe.

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References

Figures

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Fig. 3

Paris curves for PP, HAZ, and WCL in the unstrained, extrados, and intrados condition: (a) PP, (b) HAZ, and (c) WCL

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Fig. 2

Notch location of WCL, and HAZ in unstrained, extrados, and intrados pipes: (a) unstrained weld, (b) extrados weld, and (c) intrados weld

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Fig. 6

Crack length as a function of time for PP intrados in environment: (a) sample 1 and (b) sample 2

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Fig. 7

Effect of reeling on the FCGR frequency scans of HAZ in environment

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Fig. 1

Schematic illustration of notch orientations in a hollow bar or cylinder (ASTME399)

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Fig. 4

FCGR as a function of frequency in environment for PP, unstrained HAZ, and weld: (a) as-fabricated, (b) extrados, and (c) intrados

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Fig. 5

Effect of reeling on the FCGR frequency scans of PP in environment

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Fig. 8

Effect of reeling on the FCGR in environment on WCL

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Fig. 9

Effect of reeling and microstructure on the plateau FCGR in sour environments

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Fig. 18

Effect of changing gas chemistry from sour environment to pure N2 on the FCGR at a low frequency of 1 mHz

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Fig. 10

Effect of reeling on the Paris curves of the PP in sour environment

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Fig. 11

Effect of reeling on the Paris curves of the HAZ in sour environment

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Fig. 12

Effect of reeling on the Paris curves of the WCL in sour environment

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Fig. 15

Effect of YS on the plateau FCGR

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Fig. 16

Effect of changing gas chemistry from sour environment to pure CO2 on the FCGR at a low frequency of 1 mHz

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Fig. 17

Effect of changing chemistry on the FCGR as a function of frequency

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Fig. 13

Relationship between FCGR and plateau frequency

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Fig. 14

Relationship between YS and hardness

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