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Research Papers: Piper and Riser Technology

A Simplified Approach to Estimate the Probability of Otter Board Hooking at Pipelines

[+] Author and Article Information
Xiaopeng Wu

Centre for Ships and Ocean Structures (CeSOS),
Norwegian University of Science and Technology,
Trondheim 7491, Norway
e-mail: xiaopeng.wu@ntnu.no

Vegard Longva

Fedem Technology AS,
Trondheim 7014, Norway

Svein Sævik

Department of Marine Technology,
Norwegian University of Science and Technology,
Trondheim 7491, Norway

Torgeir Moan

Centre for Ships and Ocean Structures (CeSOS);Department of Marine Technology;Centre for Autonomous Marine Operations
and Systems (AMOS),
Norwegian University of Science and Technology,
Trondheim 7491, Norway

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 June 17, 2015; final manuscript received September 19, 2015; published online October 15, 2015. Assoc. Editor: Hideyuki Suzuki.

J. Offshore Mech. Arct. Eng 137(6), 061702 (Oct 15, 2015) (21 pages) Paper No: OMAE-15-1048; doi: 10.1115/1.4031670 History: Received June 17, 2015; Revised September 19, 2015

Hooking events, defined as trawling gear becoming firmly “stuck” under a pipeline, rarely occur during bottom-trawling operations. However, hooking events can have detrimental consequences. There is no existing method for quantifying the hooking probability of bottom-trawling operations. In this study, an approach is proposed to quantify the trawl board hooking probability using simulation tools and statistical data. Numerical simulation use the SIMLA code to establish simplified hooking criteria. The criteria link the pipeline data to the fishing activities data, enabling the quantification of hooking probability. First, the numerical simulations of both pull-over and hooking events were compared with small-scale model test results. Reasonable agreement was reached. Based on the simulation results, simplified criteria for trawl board hooking were proposed. Finally, data from the EUROPIPE II pipeline section in the Norwegian sector were used as a case study. Data regarding free span as well as fishing activities in that region were used to obtain the statistical input. The Monte Carlo simulation technique was then used to estimate the hooking probability. Parametric studies were first performed to investigate the effects of important parameters. Then, based on the findings from the parametric studies, the hooking probability with the most reasonable parameters was estimated.

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References

Figures

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Fig. 3

Model of the MALO-type trawl board

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Fig. 2

Model test setup at the MCLab: plain view on the top and side view on the bottom

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Fig. 1

Typical otter trawl gear crossing a pipeline [4]

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Fig. 7

Final hooking positions of the trawl board in the model test for 5.0 m span height and 45 deg crossing angle: (a) Test 3211, (b) Test 3212, and (c) Test 3214

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Fig. 8

Final hooking positions of the trawl board in the model test for 5.0 m span height and 20 deg crossing angle: (a) Test 3312, (b) Test 3313, and (c) Test 3314

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Fig. 9

Body geometry element

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Fig. 10

Contact geometry of the MALO-type trawl board

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Fig. 11

Model configuration

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Fig. 12

Warp line tension, α = 90 deg: (a) HSP = 0.5 m, (b) HSP = 1.0 m, and (c) HSP = 5.0 m

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Fig. 13

Warp line tension, HSP = 0.5 m, α = 90 deg, flat

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Fig. 18

Different stages in a simulation of trawl board pull-over, HSP = 5 m, α = 45 deg, top view. The numbers indicate the different stages as follows: (1) warp line–pipeline contact begins; (2) trawl board leaves the seabed; (3) the tip of the trawl board passes the centerline of the pipeline; (4) trawl board–pipeline contact begins; (5) trawl board becomes horizontal; (6) warp line–pipeline contact ends; and (7) trawl board–pipeline contact ends.

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Fig. 19

Warp line tension in the simulation, α = 90 deg, flat, D = 1.20 m

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Fig. 20

Simulation snapshots, α = 90 deg, flat, D = 1.20 m: (a) HSP = 0.25 m, 31 s, (b) HSP = 0.25 m, 33 s, (c) HSP = 0.25 m, 35 s, (d) HSP = 0.36 m, 31 s, (e) HSP = 0.36 m, 33 s, and (f) HSP = 0.36 m, 35 s

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Fig. 14

Warp line tension, HSP = 5 m, α = 45 deg, with span shoulder

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Fig. 15

Simulation snapshots, HSP = 5 m, α = 45 deg, with span shoulder: (a) 29.5 s, (b) 30.5 s, (c) 31.5 s, (d) 32.5 s, (e)35.5 s, and (f) 37.5 s

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Fig. 16

Warp line tension, HSP = 5 m, α = 20 deg, with span shoulder

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Fig. 17

Simulation snapshots, HSP = 5 m, α = 20 deg, with span shoulder: (a) 29.5 s, (b) 30.5 s, (c) 31.5 s, (d) 32.5 s, (e) 33.5 s, and (f) 34.5 s

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Fig. 21

A cross-sectional sketch of the five-point data

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Fig. 22

Event chain of trawl board hooking events: the boxes with light and dark background colors represent events and conditions, respectively

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Fig. 23

Hooking events reported by fishermen in the North Sea from 2011 to 2013 (Source: The Norwegian Fishery Directorate)

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Fig. 24

Existing and planned pipelines (Source: The Norwegian Petroleum Directorate 2013)

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Fig. 25

Sliding distance as a function of the angle of attack at different span heights: (a) l1, D = 1.20 m, (b) l2, D = 1.20 m, (c) l1, D = 0.75 m, and (d) l2, D = 0.75 m

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Fig. 27

Fishing activities along the EUROPIPE II from KP 0 to KP 180, the KP values refer to Fig. 26(a): (a) crossings counting example (10 km interval), in 2012, the numbers represent the number of crossings within the corresponding pipeline section interval (b) distribution of crossings, from 2011 to 2013, and (c) distribution of relative trawling direction, from 2011 to 2013

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Fig. 28

Event chain of trawl board hooking events with simplified conditions: the boxes with light and dark background colors represent events and conditions, respectively

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Fig. 26

Information about the EUROPIPE II from KP 12 to KP 166: (a) KP location of the pipeline section of concern, (b) distribution of the maximum span height, and (c) distribution of the free span length

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Fig. 29

Cumulative average number of hooking incidents per 4000 events, with different crossing angles: (a) hitting location uniformly distributed and (b) hitting location based on trawling frequency

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Fig. 30

Cumulative average number of hooking incidents per 4000 events, with different rates of destabilization: (a) hitting location uniformly distributed and (b) hitting location based on trawling frequency

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Fig. 31

Cumulative average number of hooking incidents per 4000 events, at different trawl board heights: (a) hitting location uniformly distributed and (b) hitting location based on trawling frequency

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