Pipeline Stability: State of the Art

2008 ◽  
Author(s):  
Hammam O. Zeitoun ◽  
Knut To̸rnes ◽  
Gary Cumming ◽  
Masˇa Brankovic´
Keyword(s):  
Current Knowledge ◽  
Large Diameter ◽  
Research Work ◽  
Careful Consideration ◽  
Cost Driver ◽  
Engineering Practice ◽  
Design Codes ◽  
Limit States ◽  
Acceptance Criteria ◽  
Hydrodynamic Loads

Ensuring subsea pipeline stability on the seabed is one of the fundamental aspects of pipeline design. A comprehensive on-bottom stability design will include a detailed assessment of the hydrodynamic loads acting on the pipeline, the pipe-soil interaction, the structural response and a careful consideration of the acceptance criteria. Pipeline stabilisation is a major cost driver in some locations around the world, where the designer is faced with extreme design challenges including severe metocean conditions, shallow waters, large diameter lines, and uncertain or difficult geotechnical conditions. These may all contribute to complex stabilisation solutions resulting in costly construction techniques. The current knowledge and engineering practice applied in pipeline stability design is mostly based on the work performed during the 80s by the Pipeline Stability Design Project (PIPESTAB) and on the research conducted by the American Gas Association (AGA) in another Joint Industry project (JIP). At the time, these studies were aimed at gaining an understanding of the physics governing pipeline stability, in particular hydrodynamic loads on pipelines and soil resistance. These two aspects were investigated independently from each other. Understanding pipeline stability has evolved over the last decade due to the application of this knowledge, findings from further research work, the introduction and requirements of new pipeline codes, and advances in the understanding of pipe-soil interaction. Recently gained understanding has raised the question whether alternatives to the present design approaches and acceptance criteria, as specified in the design codes, could be developed. The areas of debate include the approach used for addressing pipe soil interaction, the hydrodynamic coefficients to be applied, the design kinematics to be considered, the design methodologies, the acceptance criteria, and compliance with design codes limit states. This paper presents an overview of the current available knowledge for addressing pipeline stability. The aim is to briefly summarise the key aspects of the pipeline stability design process and to include some historical perspective. The paper discusses the advantage and shortfalls of the different approaches with a view to consolidate understanding, rather than to provide a ready-made solution to a complex design problem.

scholarly journals A Research for Deviation Estimation Analysis for Driven Piles Foundation: A Case of Penang Second Marine Bridge

2018 ◽  
Vol 206 ◽  
pp. 01004
Author(s):  
Kang Huang
Keyword(s):  
Large Diameter ◽  
Technical Specification ◽  
Detailed Comparison ◽  
Original Position ◽  
Practical Application ◽  
Driven Piles ◽  
Acceptance Criteria ◽  
Preliminary Research ◽  
Simplified Calculation ◽  
Steel Pipe Pile

The aim of this preliminary research is to study the accept tolerance of driven piles with position’s deviation. More than five thousand driven piles were installed in the approach bridge, which adopted two classes, i.e.Φ1.6m steel pipe pile and Φ1.0m spun pile. The original position acceptance criteria was deviation tolerance less than 75mm. This was not reasonable enough to take into account the marine construction conditions. According to a detailed comparison of the existed different standards and simplified calculation with representativeness, The recommended acceptance criteria could be adjusted to 150mm. This study makes up for the lack of Malaysia pile foundation technical specification especially for large diameter driven piles and it will effectively promote the practical application of ones in Southeast Asia infrastructure works.

Dynamic Stability Response of Piggyback Pipelines

2010 ◽  
Author(s):  
Hammam Zeitoun ◽  
Masˇa Brankovic´ ◽  
Knut To̸rnes ◽  
Simon Wong ◽  
Eve Hollingsworth ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Dynamic Response ◽  
Dynamic Stability ◽  
Large Diameter ◽  
Hydrodynamic Forces ◽  
Model Testing ◽  
Equivalent Diameter ◽  
Pipeline System ◽  
Hydrodynamic Coefficients ◽  
Hydrodynamic Loads

One of the main aspects of subsea pipeline design is ensuring pipeline stability on the seabed under the action of hydrodynamic loads. Hydrodynamic loads acting on Piggyback Pipeline Systems have traditionally been determined by pipeline engineers using an ‘equivalent pipeline diameter’ approach. The approach is simple and assumes that hydrodynamic loads on the Piggyback Pipeline System are equal to the loads on a single pipeline with diameter equal to the projected height of the piggyback bundle (the sum of the large diameter pipeline, small diameter pipeline and gap between the pipelines) [1]. Hydrodynamic coefficients for single pipelines are used in combination with the ‘equivalent diameter pipe’ to determine the hydrodynamic loads on the Piggyback Pipeline System. In order to assess more accurately the dynamic response of a Piggyback Pipeline System, an extensive set of physical model tests has been performed to measure hydrodynamic forces on a Piggyback Pipeline System in combined waves and currents conditions, and to determine in-line and lift force coefficients which can be used in a dynamic stability analysis to generate the hydrodynamic forces on the pipeline [2]. This paper describes the implementation of the model testing results in finite elements dynamic stability analysis and presents a case study where the dynamic response of a Piggyback Pipeline System was assessed using both the conventional ‘equivalent diameter approach’ and the hydrodynamic coefficients determined using model testing. The responses predicted using both approaches were compared and key findings presented in the paper, in terms of adequacy of the equivalent diameter approach, and effect of piggyback gap (separation between the main line and the secondary line) on the response.

Influence of Porosity on the Integrity Properties of Butt Welded Super Duplex Stainless Steel Umbilical Tube

2015 ◽  
Author(s):  
Xiaoxue An ◽  
Alan Dobson ◽  
Chun Yip Chan
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Bending Moment ◽  
Steel Tube ◽  
Design Codes ◽  
Super Duplex Stainless Steel ◽  
Acceptance Criteria ◽  
Hydraulic Fluids ◽  
Weld Root ◽  
Main Component

Super Duplex Stainless Steel (SDSS) tube is the main component in steel tube umbilicals for the transportation of hydraulic fluids and chemicals, or gas injection into the subsea well. The umbilical tube is made from seamless tube joined together by girth weld. Therefore, porosity is one of the main weld defects that could be discovered within the welds, and these defects can have significant impact on the execution of the whole project, in term of both schedule and cost. This paper reviews the design codes and standards relating to the porosity acceptance criteria, and discusses the recent investigation on the influences of porosity (number, size and location) to the stress distribution within the weld. The study was performed using both FEA and practical fatigue test. The results demonstrated that the distance of the pores to the weld surface is a critical parameter to the increase and localisation of stress as the pore starts to interact with the weld root or cap. In addition, significant pore stress interaction has been observed when a bending moment is introduced to the weld. The study has demonstrated that the current porosity acceptance criteria applied to umbilical manufacture in the subsea industry are typically conservative and can be modified.

Large Diameter Pipeline PLEM Design for Remote, Arctic Application

2013 ◽  
Author(s):  
Jeroen Timmermans ◽  
Ian Luff ◽  
Nicholas Long
Keyword(s):  
North Sea ◽  
Large Diameter ◽  
Lessons Learned ◽  
Cost Driver ◽  
Pile Foundations ◽  
The Arctic ◽  
Normal Operation ◽  
Operating Life ◽  
Wide Range

While subsea production template and manifold designs have come to be dominated by standardized solutions tailored for specific hardware, the design of Pipeline End Manifolds (PLEM) remains largely project-specific. Nevertheless, some trends in PLEM design for large-diameter pipelines in moderate water depths have emerged in the past years in the North Sea and elsewhere; namely, large stand-alone structures on suction pile foundations with diverless spoolpiece tie-ins. This arrangement has proven successful on numerous projects; however, the move to remote arctic fields of significant production capacity and long design life introduces new design drivers that warrant a “fresh approach” to PLEM design. The developments currently being considered for the arctic will have to deal with: - Remote location making mobilization of installation assets a significant cost driver such that separate installation of pipeline and PLEM is relatively unattractive - Harsh conditions and short weather windows for installation favoring designs that reduce the number of separate installation steps and vessels - Poorer access for maintenance and repair during the operating life favoring designs that are modular and that allow recovery of critical components using the smallest possible intervention vessels. When combined with envisioned field production lives of 40 to 50 years, this means a very different set of design drivers will apply to the PLEM design. This paper presents an alternative PLEM design developed to overcome these challenges by: - Integrating of the PLEM with the pipeline to work around current industry limitations for large diameter diverless tie-in connector systems and to minimize ROV rotated sealing surfaces subsea in normal operation, - Introducing plug technology to remove the critical dependence on long-term trouble-free performance of large bore valves, - Introducing driven pile foundations to reduce structure size, prevent long-term settlements and eliminate the need for separate pipeline support frames by maintaining the pipe centerline close to the mudline, - Modularizing the system such that key components (all remaining valves) can be retrieved without complete shutdown of flow and such that installation / intervention can be performed using a wide range of vessels, and - Incorporating lessons learned from the successful design of a North Sea vertical diverless pig launcher unit. This paper presents an overview of the alternative PLEM design and discusses the status of the technologies required.

scholarly journals Rebound Hammer Test: An Investigation into Its Reliability in Applications on Concrete Structures

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Antonio Brencich ◽  
Rossella Bovolenta ◽  
Valeria Ghiggi ◽  
Davide Pera ◽  
Paolo Redaelli
Keyword(s):  
Building Materials ◽  
Concrete Strength ◽  
Research Work ◽  
Third Party ◽  
Test Reliability ◽  
Surface Finishing ◽  
Engineering Practice ◽  
Rebound Hammer ◽  
Existing Structures ◽  
Concrete Maturity

The issue of concrete strength often arises in civil engineering practice, either due to quality control of new constructions or due to the assessment of existing structures. To this aim, one of the most widely spread techniques is the rebound hammer (Schmidt hammer) test, for which calibration is still related to the original Schmidt curve dating back to the early 50’s. In spite of the large amount of research work performed in the last decades, the uncertainties of the rebound test are still not clearly quantified and open to further insight. This paper presents and discusses a wide research campaign on laboratory specimens and on third-party specimens delivered to the Laboratory for Building Materials of the University of Genoa, Italy, for standard quality controls. While it is well known that moisture content, surface finishing, and concrete maturity strongly affect the test result, the effect of the stress state has not yet been studied and is found in this research to be a further parameter affecting the test reliability. The final outcome of all the uncertainties is variability in estimated concrete strength as large as ±70%; additionally, some issues are discussed on the intrinsic uncertainty of this test. As already demonstrated by many authors, the results of this research also show that a universal calibration curve to be used for any concrete, in any condition, conceptually does not exist.

Reality Check on Girth Weld Defect Acceptance Criteria

2010 ◽  
Author(s):  
Gery Wilkowski ◽  
Do-Jun Shim ◽  
Bud Brust ◽  
Suresh Kalyanam
Keyword(s):  
Base Metal ◽  
Safety Factor ◽  
Test Data ◽  
Large Diameter ◽  
Limit Load ◽  
Failure Stress ◽  
Specimen Thickness ◽  
Tier 2 ◽  
Acceptance Criteria ◽  
Weld Defect

This paper examines the inherent conservatisms of alternative girth weld defect acceptance criteria from the 2007 API 1104 Appendix A, CSA Z662 Appendix K, and the proposed EPRG Tier 2 criteria. The API and CSA codes have the same empirical limit-load criteria, where it has previously been shown that the conservatism on the failure stress is ∼30 to 50 percent compared to pipe test data prior to applying any safety factors. In terms of flaw length, it was found that the API/CSA limit-load equation might allow a flaw of 5% of the pipe circumference, where the properly validated limit-load equation would allow a flaw of 75% of the circumference, i.e., a safety factor of 30 percent on load corresponded to a safety factor of 15 on flaw length for that example case. Similarly there are conservatisms in a proposed EPRG Tier 2 girth weld defect acceptance criterion. This proposed criterion was directly based on curved-wide-plate data to assure that toughness was sufficient to meet limit-load conditions for a curved-wide plate. However, the curved-wide plates are really an intermediate-scale test, and still require proper scaling to pipes of different diameters. The proposed Tier 2 EPRG allowable flaw length is 7T from a large database of curved-wide-plate tests with the a/t value of less than 0.5 (or a < 3mm), and the failure stress being equal to the yield strength of the base metal (also requires the weld metal overmatch the base metal strength, and the Charpy energy at the defect location have a minimum > 30 J and average > 40 J). However, the widths of those curved-wide-plate tests are typically a factor 5 to 12 times less than typical large-diameter pipes. The proper limit-load/fracture mechanics scaling solution would have the flaw length proportioned to the plate width, not the specimen thickness. Additionally, the proper limit-load solution for a pipe in bending gives a much larger tolerable flaw size at the yield stress loading than a plate or pipe under pure tension. Example calculations showed that the EPRG Tier 2 approach is conservative on the flaw lengths by approximately 9 for pure axial tension loading, and between 34 to 79 for a pipe under bending. Suggestions are presented for an improved procedure that accounts for proper limit-load solutions for pipe tests, effects of pipe diameter, effects of internal pressure, and also a much simpler approach to incorporate the material toughness than the 2007 API 1104 Appendix A Option 2 FAD-curve approach. The fracture analyses could evoke SENB, SENT testing, or have relatively simple Charpy test data to assess the transition temperatures to ensure ductile initiation will occur.

In Situ Test and Mechanical Analysis of Multi-Arch Tunnel with Large Section in Soft and Weak Rock Mass

2011 ◽  
Vol 250-253 ◽  
pp. 1262-1265
Author(s):  
Tong Liu ◽  
Zi Chao Dong ◽  
Hai Yong Yang
Keyword(s):  
Research Work ◽  
Safety Monitoring ◽  
Mechanical Analysis ◽  
Surrounding Rock ◽  
Monitoring Data ◽  
Engineering Practice ◽  
Construction Monitoring ◽  
Construction Methods ◽  
Information Construction ◽  
Weak Rock Mass

According to the characteristic of multi-arch highway tunnel,based on a practice engineering, the monitoring work was consisted of four sections:the displacement of surrounding rock; such as crown settlement, displacement of the ground, displacement of inner surrounding rock; that of stress and stain of support structure; that of force in middle-wall. In course of construction,monitoring data was analyzed in time.Structural timbering parameters were modified in response to abnormal monitoring data in order to guarantee safety.the testing results of the safety monitoring system are satisfactory, which serves as a symbol of our research work. Thus, our engineering practice has proved the applicability and feasibility of the safety monitoring and information construction methods.

Reliability Analysis of Piles in Multilayer Soil in Mooring Dolphin Structures

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Reda Farag ◽  
Achintya Haldar ◽  
Mahmoud El-Meligy
Keyword(s):  
Nile Delta ◽  
Limit State ◽  
Large Diameter ◽  
Hybrid Approach ◽  
Element Model ◽  
Limit States ◽  
Soil System ◽  
Sea Bed ◽  
Contact Nonlinearity ◽  
Reliability Method

Reliability of complicated mooring dolphin structures (MDS) is estimated using few deterministic evaluations and an improved response surface method denoted as IRSM-second-order reliability method (SORM). It is a hybrid approach consisting of an IRSM, SORM, and several advanced factorial schemes. For this type of sophisticated analysis, simulation-based algorithm is impractical to implement. The concept is applied to estimate the risk of an existing MDS at the shore of Nile Delta. It is a large diameter steel-pile embedded in the sea bed. The Pile–Soil-System is represented by a nonlinear finite element model (NLFEM). In NLFEM, the steel pile is assumed to behave linearly under the considered working loads, but the soil is considered to behave nonlinearly. Moreover, the contact nonlinearity between the pile and the soil is taken into account. It is demonstrated that the reliability information on MDS can be extracted using tens of deterministic evaluations. It has been found that incorporation of the contact nonlinearity into analysis has no effect on the pile behavior. In the probabilistic analysis, the uncertainties in loading, material properties, and geometric details are taken into account. Both operational and structural limit states are considered. For the MDS considered in this study, it has been observed that the strength limit state (flexural) is more critical than the operational limit state (drift). The most important variables are the mooring loads, the radius and thickness of the pile, and the modulus of elasticity of steel.

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.

Remaining Uncertainties in Predicting Long-Term Performance of Nuclear Waste Glass From Experiments

1993 ◽  
Vol 333 ◽  
Author(s):  
B. Grambow ◽  
Kernforschungszentrum Karlsruhe
Keyword(s):  
Current Knowledge ◽  
Research Work ◽  
Waste Glass ◽  
Dissolution Mechanism ◽  
Glass Dissolution ◽  
Radionuclide Release ◽  
Long Term Performance ◽  
Term Performance ◽  
Term Maintenance

ABSTRACTThe current knowledge on the glass dissolution mechanism and the representation of glass dissolution concepts within overall repository performance assessment models are briefly summarized and uncertainties related to mechanism, radionuclide chemistry and parameters are discussed. Understanding of the major glass dissolution processes has been significantly increased in recent years. Long-term glass stability is related to the long-term maintenance of silica saturated conditions. The behavior of individual radionuclides in the presence of a dissolving glass has not been sufficiently and results do not yet allow meaningful predictions. Conservative long-term predictions of glass matrix dissolution as upper limit for radionuclide release can be made with sufficient confidence, however these estimations generally result in a situation were the barrier function of the glass is masked by the efficiency of the geologic barrier. Realistic long-term predictions may show that the borosilicate waste glass contributes to overall repository safety to a much larger extent than indicated by overconservatism. Today realistic predictions remain highly uncertain and much more research work is necessary. In particular the long-term rate under silica saturated conditions needs to be understood and the behavior of individual radionuclides in the presence of a dissolving glass deserves more systematic investigations.

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