Rock Berm Design for Pipeline Stability

2012 ◽  
Author(s):  
David J. Chamizo ◽  
Dean R. Campbell ◽  
Eric P. Jas ◽  
Jay R. Ryan
Keyword(s):  
Traditional Approach ◽  
Large Diameter ◽  
Mechanical Damage ◽  
Small Scale ◽  
Lateral Movement ◽  
Functional Requirements ◽  
Natural Gas Pipelines ◽  
Hydrodynamic Loading ◽  
Wave Heights ◽  
Subsea Pipelines

Stabilizing large diameter natural gas pipelines on the seabed against extreme hydrodynamic loading conditions has proven to be challenging in the northwest of Australia. Tropical storms, which affect the area annually between November and April, can generate wave heights exceeding 30 m and storm steady state currents of 2 m/s or more. Consequently, in shallow water depths, typically less than 40–60 m, subsea pipelines can be subjected to very high hydrodynamic loads, potentially causing significant lateral movement. To mitigate the risk of the pipeline suffering mechanical damage due to excessive lateral movement, quarried and graded rock is often dumped over the pipeline as a secondary stabilization solution. In order to satisfy functional requirements, the rock berm must comprise of a sufficiently large rock grading size and berm volume to withstand the design hydrodynamic loading such that the pipeline cannot break out of the berm. The design of rock berms for pipeline secondary stabilization has traditionally followed a deterministic approach that uses empirical equations for preliminary rock sizing, followed by small-scale physical modeling for design verification and optimization. Whilst the traditional approach can be effective in producing a robust rock berm design, opportunities for further optimization are inhibited by a lack of available data and an imperfect understanding of the failure mechanisms. This paper presents an overview of an improved approach for rock berm design optimization. A general overview of rock berms, the design principles, benefits and risks are also presented.

Pipeline Stabilisation Using Pre-Trenching and Sand Backfill

2012 ◽  
Author(s):  
David J. Chamizo ◽  
Dean R. Campbell ◽  
Carl T. Erbirch ◽  
Eric P. Jas ◽  
Liang Cheng
Keyword(s):  
Natural Gas ◽  
Large Diameter ◽  
Mechanical Damage ◽  
Clay Content ◽  
Carbonate Sand ◽  
Natural Gas Pipelines ◽  
Limited Success ◽  
Wave Heights ◽  
Subsea Pipelines ◽  
Very High

Stabilizing large diameter natural gas pipelines on the seabed against extreme hydrodynamic loading conditions has proven to be challenging in the northwest of Australia. Tropical storms, which affect the area annually between November and April, can generate wave heights exceeding 30 m and on-bottom steady-state currents of 2 m/s or more. Consequently, in shallow water depths, typically less than 40–60 m, subsea pipelines can experience very high hydrodynamic loads, potentially causing significant lateral movement. If the seabed is rugged, or at locations where the pipeline approaches a point of fixity, this can lead to the pipeline suffering mechanical damage, which is undesirable. In many places on the Northwest Shelf of Australia, there is a layer of minimum 3 m deep marine sediments. The sediments predominantly comprise of relatively stable, fine to medium sized carbonate silts and sands, sometimes with some clay content. Traditionally, in Australia and other parts of the world, post-trenching techniques such as ploughing and jetting have been applied in such areas. These techniques can successfully lower the pipeline into the seabed. However, in many situations on the Northwest Shelf of Australia, post-trenching has had limited success. This has in part been due to the unpredictable levels of cementation of the carbonate sand, which has often resulted in an insufficient trench depth, with the need to implement costly and time consuming remedial works to ensure pipeline stability. The uncertainties in the success of post-trenching tools lead to the development of the pre-trenching and sand backfill method, which was first applied in Australia in 2003 on a 42-inch diameter natural gas trunkline. This technique has several advantages compared to post-trenching and other conventional pipeline stabilization methods such as rubble mound pipeline covers or gravity anchors. This paper presents an overview of the pre-trenching and sand backfill method, its design principles, benefits, and risks and opportunities.

Reliability-Based Limit States Design for Onshore Pipelines

2002 ◽  
Author(s):  
Maher Nessim ◽  
Tom Zimmerman ◽  
Alan Glover ◽  
Martin McLamb ◽  
Brian Rothwell ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Traditional Approach ◽  
Large Diameter ◽  
Small Diameter ◽  
Mechanical Damage ◽  
Design Approach ◽  
Design Parameters ◽  
Pipe Failure ◽  
Limit States ◽  
Current Design

The traditional approach to pipelines design is to select a wall thickness that maintains the hoop stress below the yield strength multiplied by a safety factor. The main design condition implied by this approach is yielding (and by extension burst) of the defect-free pipe. Failure statistics show that this failure mode is virtually impossible as the majority of failures occur due to equipment impact and various types of defects such as corrosion and cracks. Recent investigations show that these failure causes are much more sensitive to wall thickness than to steel grade. As a consequence, current design methods produce variable levels of safety for different pipelines — small-diameter, low-pressure pipelines for example have been shown to have higher failure risks due to mechanical damage than large-diameter, high-pressure pipelines. In addition, the current design approach has been shown to have limited ability to deal with new design parameters, such high steel grades, and unique loading conditions such as frost heave and thaw settlement. The paper shows how these limitations can be addressed by adopting a reliability-based limit states design approach. In this approach, a pipeline is designed to maintain a specified reliability level with respect to its actual expected failure mechanisms (known as limit states). Implementation involves identifying all relevant limit states, selecting target reliability levels that take into account the severity of the failure consequences, and developing a set of design conditions that meet the target reliability levels. The advantages of this approach include lower overall cost for the same safety level, more consistent safety across the range of design parameters, and a built-in ability to address new design situations. Obstacles to its application for onshore pipelines include lack of familiarity with reliability-based approaches and their benefits and lack of consensus on how to define reliability targets. The paper gives an overview of the reliability-based design approach and demonstrates its application using an example involving design for mechanical damage.

scholarly journals Magnetosheath-cusp interface

2004 ◽  
Vol 22 (1) ◽  
pp. 183-212 ◽  
Author(s):  
S. Savin ◽  
L. Zelenyi ◽  
S. Romanov ◽  
I. Sandahl ◽  
J. Pickett ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Large Scale ◽  
Traditional Approach ◽  
Qualitative Difference ◽  
Small Scale ◽  
Nonlinear Phenomena ◽  
Solar Wind Interaction ◽  
Linear Superposition

Abstract. We advance the achievements of Interball-1 and other contemporary missions in exploration of the magnetosheath-cusp interface. Extensive discussion of published results is accompanied by presentation of new data from a case study and a comparison of those data within the broader context of three-year magnetopause (MP) crossings by Interball-1. Multi-spacecraft boundary layer studies reveal that in ∼80% of the cases the interaction of the magnetosheath (MSH) flow with the high latitude MP produces a layer containing strong nonlinear turbulence, called the turbulent boundary layer (TBL). The TBL contains wave trains with flows at approximately the Alfvén speed along field lines and "diamagnetic bubbles" with small magnetic fields inside. A comparison of the multi-point measurements obtained on 29 May 1996 with a global MHD model indicates that three types of populating processes should be operative: large-scale (∼few RE) anti-parallel merging at sites remote from the cusp; medium-scale (few thousandkm) local TBL-merging of fields that are anti-parallel on average; small-scale (few hundredkm) bursty reconnection of fluctuating magnetic fields, representing a continuous mechanism for MSH plasma inflow into the magnetosphere, which could dominate in quasi-steady cases. The lowest frequency (∼1–2mHz) TBL fluctuations are traced throughout the magnetosheath from the post-bow shock region up to the inner magnetopause border. The resonance of these fluctuations with dayside flux tubes might provide an effective correlative link for the entire dayside region of the solar wind interaction with the magnetopause and cusp ionosphere. The TBL disturbances are characterized by kinked, double-sloped wave power spectra and, most probably, three-wave cascading. Both elliptical polarization and nearly Alfvénic phase velocities with characteristic dispersion indicate the kinetic Alfvénic nature of the TBL waves. The three-wave phase coupling could effectively support the self-organization of the TBL plasma by means of coherent resonant-like structures. The estimated characteristic scale of the "resonator" is of the order of the TBL dimension over the cusps. Inverse cascades of kinetic Alfvén waves are proposed for forming the larger scale "organizing" structures, which in turn synchronize all nonlinear cascades within the TBL in a self-consistent manner. This infers a qualitative difference from the traditional approach, wherein the MSH/cusp interaction is regarded as a linear superposition of magnetospheric responses on the solar wind or MSH disturbances. Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers) – Space plasma physics (turbulence; nonlinear phenomena)

Basis of the New Criteria in ASME B31.8 for Prioritization and Repair of Mechanical Damage

2002 ◽  
Author(s):  
M. J. Rosenfeld ◽  
John W. Pepper ◽  
Keith Leewis
Keyword(s):  
Natural Gas ◽  
Safety Concern ◽  
Mechanical Damage ◽  
Operating Experience ◽  
Third Party ◽  
Detailed Review ◽  
Natural Gas Pipelines ◽  
Industry Research ◽  
Pipe Section ◽  
New Criteria

Mechanical damage in the form of dents has emerged as a key safety concern for pipelines. In response, ASME B31.8, with assistance from GTI, undertook a detailed review of industry research and operating experience with respect to various forms of mechanical damage. Revised criteria for prioritizing and effectively repairing damage in natural gas pipelines were developed based on the findings. The criteria address plain dents, third-party type damage, dents that affect weldments, dents affected by corrosion, and strain levels associated with deformation of the pipe section. This paper discusses the generalities of the scientific findings and basis for the changes to the Code.

Leading Practices for the Prevention of Mechanical Damage

2006 ◽  
Author(s):  
Mark Hereth ◽  
Bernd Selig ◽  
John Zurcher ◽  
Keith Leewis ◽  
Rick Gailing
Keyword(s):  
Common Ground ◽  
Mechanical Damage ◽  
Recent Change ◽  
American Petroleum Institute ◽  
Performance Excellence ◽  
Time Data ◽  
Natural Gas Pipelines ◽  
Time Period ◽  
Additional Detail ◽  
The Common

Practices that are used by pipeline operators to prevent mechanical damage are examined in this paper. A set of practices specific to pipeline operations is presented. The practices were initially developed by a group of subject matter experts working under the auspices of the American Petroleum Institute and the Association of Oil Pipelines (API/AOPL) Performance Excellence Team. The practices drew upon the work started within the Common Ground Initiative in the late 1990s and continued by the Common Ground Alliance. The practices presented were reviewed again in preparation of this report. The practices build upon practices defined by Common Ground Alliance (CGA), largely by providing greater specificity and ensuring completeness and follow through in communication and documentation. A subset of these practices became the foundation of the standard, API 1166 Excavation Monitoring and Observation. The paper also provides an overview of historical safety performance for the period 1995 through 2003; with a specific focus on mechanical damage related incidents including the additional detail available in the recent change in Pipeline and Hazardous Materials Safety Administration (PHMSA, US-DOT) Incident Reporting. This period was selected because it represented the time period where there was a heightened interest in preventing damage to pipelines as described above. The large majority of mechanical damage related incidents result in an immediate impact; a small portion occur at some later point in time. Data for the nine-year period indicate that approximately 90 percent of the incidents result in an immediate impact. This is significant in that it underscores the importance of prevention of damage. The experience of hazardous liquid pipelines has shown a continuing decrease in numbers of annual incidents. The experience of natural gas pipelines has not shown a decreasing trend; in fact, it is relatively flat for the period of study. While the heightened awareness and strong commitment to dedication are known to have had an impact on damage prevention through numerous stories and vast experience shared by a variety of stakeholders, it is prudent to be concerned that the performance may be reaching a “plateau”.

SAWL 485 for 48” Offshore Application in Thickness up to 41 mm

2008 ◽  
Author(s):  
Volker Schwinn ◽  
Alexander Parunov ◽  
Ju¨rgen Bauer ◽  
Pavel Stepanov
Keyword(s):  
Large Diameter ◽  
Development Program ◽  
Thick Wall ◽  
Diameter Pipe ◽  
Manufacturing Procedure ◽  
Pipeline Project ◽  
Qualification Testing ◽  
Nord Stream ◽  
Large Diameter Pipes ◽  
Subsea Pipelines

Vyksa Steel Works (VSW), part of United Metallurgical Company (OMK), has manufactured a trial batch of large diameter pipes for subsea pipelines in accordance with the DNV-OS-F101 standard and the specification of the Nord Stream project. The plates were produced by Dillinger Hu¨tte (DH). The batch included 1,220 mm (48″) diameter pipes of steel grade SAWL 485 (X70) with a wall thickness of 33 mm and 36 mm. All the requirements were met and OMK/VSW became Russia’s and the CIS’s first qualified producer of subsea pipes in accordance with DNV-OS-F101. In order to meet these high-class property requirements for thick wall pipes a successful development program was performed. The development program is outlined and the test results are explained. As a further consequence of the successful qualification work VSW became one of the two suppliers for the world’s largest and first 48″ diameter pipe subsea pipeline project (Nord Stream). Pipes will be supplied for the most sophisticated segment with wall thicknesses of 30.9 mm, 34.6 mm and even 41.0 mm. Results of manufacturing procedure qualification testing (MPQT) and start of production are presented.

Machine Learning for Subsea Pipeline Reeling Mechanics

2020 ◽  
Author(s):  
Eric Giry ◽  
Vincent Cocault-Duverger ◽  
Martin Pauthenet ◽  
Laurent Chec
Keyword(s):  
Design Of Experiments ◽  
Wall Thickness ◽  
Large Diameter ◽  
Local Buckling ◽  
Statistical Regression ◽  
Element Analysis ◽  
Excessive Strain ◽  
Weld Area ◽  
Subsea Pipelines ◽  
Pipeline Design

Abstract Installation of subsea pipelines using reeling process is an attractive method. The pipeline is welded in long segments, typically several kilometers in length, and reeled onto a large diameter drum. The pipeline is then transported onto such reel to the offshore site where it is unreeled and lowered on the seabed. The deformation imposed on the pipeline while spooled onto the drum needs to be controlled so that local buckling is avoided. Mitigation of such failure is generally provided by proper pipeline design & reeling operation parameters. Buckling stems from excessive strain concentration near the circumferential weld area resulting from strength discontinuity at pipeline joints, mainly depending on steel wall thickness and yield strength. This requires the characterization of critical mismatches obtained by trial and error. Such method is a long process since each “trial” requires a complete Finite Element Analysis run. Such simulations are complex and lengthy. Occasionally, this can drive the selection of the pipeline minimum wall thickness, which is a key parameter for progressing the project. The timeframe of such method is therefore not compatible with such a key decision. The paper discusses the use of approximation models to capitalize on the data and alleviate the design cost. To do so, design of experiments and automation of the computational tool chain are implemented. It is demonstrated that initial complex chain of FEA computational process can be replaced using design space description and exploration techniques such as design of experiments combined with advanced statistical regression techniques in order to provide an approximation model. This paper presents the implementation of such methodology and the results are discussed.

Application of High-Grade Steels to Onshore Natural Gas Pipelines Using Reliability-Based Design Method

2006 ◽  
Author(s):  
Joe Zhou ◽  
Brian Rothwell ◽  
Wenxing Zhou ◽  
Maher Nessim
Keyword(s):  
High Pressure ◽  
Wall Thickness ◽  
Design Method ◽  
Large Diameter ◽  
Economic Assessment ◽  
High Grade ◽  
Gas Pipelines ◽  
Natural Gas Pipelines ◽  
Reliability Based Design ◽  
Design Factors

Two example onshore gas pipelines were designed using a reliability-based approach. The first example (1219 mm, 17.2 MPa) represents a high-pressure large-diameter pipeline; the second example has a smaller diameter (762 mm) and lower pressure (9.9 MPa). Three steel grades (X70, X80 and X100) were used to develop three design solutions for each example. The wall thickness-related life cycle costs of the designs were evaluated. The design outcomes show that the reliability targets for both examples can be met using X100 steels and high equivalent design factors (0.93 for the first example and 0.9 for the second example). Moreover, ruptures and excessive plastic deformation of a defect free pipe were found to be insignificant integrity threats even when the design uses X100 and relatively high equivalent design factors such as 0.85 and 0.9. The economic assessment results show that the X100 design is the most economical option for the high-pressure large-diameter example. However, using X100 does not show a clear economic advantage over using X80 for the second example mainly because the wall thickness for the design using X100 is governed by the maximum D/t ratio constraint. The study also demonstrates the advantages of the reliability-based approach as a valuable tool in assessing the feasibility and potential benefits of using high-grade steels on a pipeline project.

scholarly journals LARGE SCALE MODEL TESTS OF PLACED STONE BREAKWATERS

1976 ◽  
Vol 1 (15) ◽  
pp. 147 ◽  
Author(s):  
Charles K. Sollitt ◽  
Donald H. Debok
Keyword(s):  
Large Scale ◽  
Scale Model ◽  
Small Scale ◽  
Stable Model ◽  
Model Studies ◽  
Drag Forces ◽  
Port Facilities ◽  
Large Scale Model ◽  
Wave Heights ◽  
Water Depths

Large scale model studies reveal that Reynolds scaling can affect the apparent stability and wave modifying properties of layered breakwater structures. Results of a study for a breakwater configuration designed to protect offshore power and port facilities in water depths to 60 feet are presented and discussed. The armor layer of this structure is formed from quarried rock of irregular rectangular parallelepiped shape, individually placed perpendicular to 1:2 seaward slope and crest. The resulting armor layer is relatively smooth, densely packed and very stable. Model studies of similar configurations were studied at 1:10, 1:20 and 1:100 scale ratios. Stability, runup, rundown and reflection were measured for a variety of water depths, wave heights and periods. Analysis of the large scale test results establish that the placed stone armor is approximately as stable as dolos armor units. Runup, rundown and reflection respond similar to rough, impermeable slopes. Comparison of large and small scale results demonstrate that relative increases in drag forces at lower Reynolds numbers decrease stability and runup in small scale models.

scholarly journals TRANSPORT PATTERNS IN THE CHAP PHYA ESTUARY

1966 ◽  
Vol 1 (10) ◽  
pp. 36 ◽  
Author(s):  
E. Allersma ◽  
A.J. Hoekstra ◽  
E.W. Bijker
Keyword(s):  
Field Survey ◽  
Small Scale ◽  
Natural Phenomena ◽  
Municipal Water Supply ◽  
Approach Channel ◽  
Wave Heights ◽  
Water Salt ◽  
Transport Patterns ◽  
Hydraulics Laboratory ◽  
Insight Into

Present day's society asks for ever larger engineering works to be carried out in estuaries. The developing techniques of dredging and construction allow for great interventions in the natural phenomena with often far reaching consequences. The whole intricate system of transports of water, salt and sediments may be drastically changed,affecting the existing quasi-static equilibria between sedimentation and erosion. For the planning of such works a thorough knowledge of the estuarme hydrology is indispensable. The port of Bangkok, the mam gateway for traffic into Thailand, is situated in the estuary of the Chao Phya river (figure 1). Increasing navigation demands improvement of the harbour and its 55 km long approach channel but the interests of agriculture and municipal water supply must also be taken into account. The Netherlands Engineering Consultants (NEDECO) m combination with the Delft Hydraulics Laboratory have made a four-years study of the estuary covering a field survey and a hydraulic model test. The observations in nature served to obtain insight into the estuarme transport pattern m relation with the boundary conditions given by the regimen of the river and the state of the sea. The small scale tests gave indications of the changes in these phenomena to be expected from alterations of the situation m the estuary and of the discharge characteristics of the river. The field survey was carried out from 1961 to 1965 with four fully equipped survey vessels to measure current velocities (60,000 times) to take samples of water and sediments, to measure wave heights and for echo-soundings. In a laboratory the samples of water (70,000) and sediments were tested as to silt concentration, salinity and soil-mechanical properties. Together with meteorological, oceanographical and hydrological data from cooperating local authorities a picture was obtained of the phenomena in the estuary and the causes of the siltation m the dredged channel.

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