scholarly journals A Vibration-Based Strategy for Health Monitoring of Offshore Pipelines’ Girth-Welds

Sensors ◽  
2014 ◽  
Vol 14 (9) ◽  
pp. 17174-17191 ◽  
Author(s):  
Pejman Razi ◽  
Farid Taheri
Keyword(s):  
Health Monitoring ◽  
Offshore Pipelines ◽  
Girth Welds

A Modified Engineering Critical Assessment Approach for Offshore Pipelines

2018 ◽  
Author(s):  
Colum Holtam ◽  
Rajil Saraswat ◽  
Ramgopal Thodla ◽  
Feng Gui
Keyword(s):  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Fatigue Loading ◽  
Critical Assessment ◽  
Offshore Pipelines ◽  
Static Crack ◽  
Production Environments ◽  
Assessment Approach ◽  
Girth Welds ◽  
Crack Growth Rates

Environmentally assisted sub-critical static crack growth can occur in offshore pipelines exposed to aggressive production environments. Recent advances in fracture mechanics testing methods have shown that slow static crack growth rates can be reliably measured in sweet and sour environments under constant stress intensity factor (K) conditions. This has potential implications for the engineering critical assessment (ECA) of pipe girth welds subject to low cycle fatigue loading with long periods of operation under constant static load between cycles, e.g. lateral buckling. This paper demonstrates the influence of including static (i.e. time dependent) crack growth as well as fatigue crack growth in a modified pipeline ECA approach.

Arctic Pipeline Design Considerations

2008 ◽  
Author(s):  
D. DeGeer ◽  
M. Nessim
Keyword(s):  
Limit State ◽  
Frost Heave ◽  
Offshore Pipelines ◽  
Essential Information ◽  
Improve Design ◽  
Design Philosophy ◽  
Soil Loading ◽  
Failure Event ◽  
Yield Behaviour ◽  
Girth Welds

Since the discovery of reserves in arctic regions, operators have been faced with a number of challenges, including assessing appropriate methods of transporting produced hydrocarbons to market. For pipeline systems, designers are required to deal with a number of unique environmental conditions not normally present in other regions of the world. These include ice scour, permafrost thaw and/or frost heave, leak detection and containment, and installation techniques. For offshore applications, novel design alternatives that have been considered to address these issues include pipe-in-pipe systems, non-bonded flexible pipes, composite wrapped pipes, and hybrid pipes. Each alternative offers strengths and weaknesses, depending on the specific hazards or failure event consequences that may exist at the location of interest. For buried onshore pipelines, the key design issue is the potential for high bending strains resulting from frost heave and thaw settlement. For both onshore and offshore pipelines, possible ways to address these issues includes the use of pressure and diameter combinations that lead to thick walls, integration of in-service inspection and maintenance within the design philosophy, stringent quality control for girth welds, and selection of materials with appropriate post yield behaviour. Because of the lack of traditional design solutions to these challenges, limit state, reliability-based and strain-based design methods are now preferred for arctic applications. The implementation of these methods requires a good understanding of linepipe material behaviour, soil loading conditions, ice loading mechanisms, and the consequences associated with product release. They allow the integration of analytical and experimental assessments into the overall design philosophy, which has been shown to improve design concept confidence and reduce overall uncertainty. This paper describes some of the key challenges facing the design of both onshore and offshore pipelines. It describes some of the current design options and how reliability-based and strain-based methods can be used to integrate essential information from a number of analytical and experimental sources into an overall framework that addresses the challenges and leads to optimal design decisions. It discusses the state of the art in this area and identifies knowledge gaps that need to be filled.

Validation of Crack Growth for an Finite Element Based ECA Procedure for Reel-Laid Pipelines With Under-Matching Girth Welds

2015 ◽  
Author(s):  
T. Sriskandarajah ◽  
Daowu Zhou ◽  
Lingjun Cao
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Large Scale ◽  
Limit Load ◽  
Bending Test ◽  
Offshore Pipelines ◽  
Reference Stress ◽  
Trial Test ◽  
3D Fea ◽  
Girth Welds

There is a concern on the fracture integrity of the partially over-matching or under-matching weld during reel-lay installation where there is large plastic strain in the pipe. Conventional ECA procedures such as BS7910 and DNV-OS-F101 are applicable for fully over-matching welds only, due to limitations in the reference stress solution (or limit load solutions). The ECA procedure based on 3D finite element (FE) analysis was developed for partially over-matching welds or under-matching. The methodology has been successfully applied to several projects of industry-wide significance, with partially over-matching welds in offshore pipelines. This paper provides a case study validating the crack growth from FE based ECA methodology against the large scale bending trial test where the pipe containing the notched defect was pre-strained under a series of straining cycles. A comparison of the crack growth between 3D FEA and the large scale bending test was presented.

Recent Developments on Welding, NDT and ECA of Clad and Lined Offshore Pipelines

2019 ◽  
Author(s):  
Petrônio Zumpano ◽  
Alexandre G. Garmbis ◽  
Diogo O. Moraes ◽  
Fausto Hirata ◽  
Bruno R. M. Cunha ◽  
...  
Keyword(s):  
Non Destructive Testing ◽  
Destructive Testing ◽  
Offshore Pipelines ◽  
Alloy 625 ◽  
Recent Developments ◽  
Bimetallic Materials ◽  
Corrosion Resistant Alloy ◽  
Purge Gas ◽  
Girth Welds ◽  
Non Destructive

Abstract Due to the level of contaminants of Brazilian pre-salt fields, alloy 625, e.g. UNS N06625, clad or lined steel linepipes have been chosen in order to resist such environmental conditions. Recent advances on welding, non-destructive testing (NDT) and Engineering Critical Assessment (ECA) approaches for bimetallic materials have significantly changed since discussed in OMAE-2012. Regarding welding of alloy 625 clad and lined pipes, maximum welding interpass temperature, back purge gas control, root discoloration, visual inspection, root profile for fatigue performance and other issues are discussed herein. The Fatigue Crack Growth Rate (FCGR) to be adopted for alloy 625 is still one of the issues, since curves for alloy 625 in specific environment are normally not available. New appendix C of DNVGL-RP-F108 gives orientations regarding how to conduct tests in sour environment. DNVGL JIP on clad and lined material has made an extensive approaching of the undermatching condition of alloy 625 weld metal under different design strain levels. Regarding NDT, developments and improvements in Automated Ultrasonic Testing (AUT) methods have been obtained for inspection of Corrosion Resistant Alloy (CRA) girth welds and weld overlay. Film and digital radiography are still used for the inspection of the pipe end of the mechanically lined pipe, but ultrasonic solutions are under development. Welding and NDT challenges of alloy 625 reported in 2012 have been overcame by state-of-art technologies used in offshore rigid risers construction and installation. Alternative CRA materials are under research and development, but alloy 625 still is the most reliable option.

Ductile Damage Study of Defective Girth Welds for Oil and Gas Pipeline: A Tailored Numerical and Finite Element Method Calibration From SENT Fracture Mechanics Test

2017 ◽  
Author(s):  
Roberto Bruschi ◽  
Marco Rossi ◽  
Alex Di Michele ◽  
Daniele Scarsciafratte ◽  
Enrico Torselletti
Keyword(s):  
Finite Element ◽  
Oil And Gas ◽  
Calibration Procedure ◽  
Ductile Damage ◽  
Element Analysis ◽  
Gurson Model ◽  
Offshore Pipelines ◽  
Crack Driving Force ◽  
Girth Welds ◽  
Model Preparation

In this paper, the evolution of ductile damage in pipe girth welds for offshore pipelines application is studied with the use of Finite Element Analysis. To this purpose, the Gurson-Tvergaard-Needlmen (GTN) model is calibrated and applied to different finite element simulations. Saipem internally developed software, written in Matlab® environment, is used to automatically calibrate the Gurson model from experimental data and run several Finite Element Models of the pipe with different flaws in the girth weld. The objective of this paper is to present and discuss this numerical tool, developed by Saipem coupling a Matlab® GUI and the ABAQUS FE solver. The tool allows speeding up and automatizing the calibration procedure of the Gurson model and making a rapid evaluation in terms of the Crack Driving Force (CDF) for defective girth weld. The tool allows also a quick and efficient model preparation, full FE analysis and post-processing, with saving of engineering hours.

Reliability of Inspection for Root Flaws in Riser Girth Welds

2004 ◽  
Author(s):  
J. R. Rudlin ◽  
C. R. A. Schneider ◽  
G. R. Razmjoo
Keyword(s):  
Fatigue Loading ◽  
Theoretical Models ◽  
Public Domain ◽  
Background Information ◽  
Offshore Pipelines ◽  
Inspection Method ◽  
The Public ◽  
Extreme Loads ◽  
Small Root ◽  
Girth Welds

The fatigue loading on deep water risers leads to a requirement for the detection of small root flaws during manufacturing inspection. Mechanised welds for offshore pipelines are also subject to extreme loads during laying, leading to a similar requirement. Automated Ultrasonic Testing using zonal methods have been adopted as the inspection method of choice for these inspections, but there is little information in the public domain regarding the expected reliability of the various systems available. Extensive individual inspection qualifications are carried out for each installation. The extent of these could be reduced by the availability of such background information. This paper reviews data from joint industry projects in the area carried out by TWI, and compares results from these with such data as is available in the public domain. An analysis of future requirements and capability of currently available theoretical models for extending the range of qualifications is also given.

ECA for Girth Welds of Offshore Pipelines: A Modified BS7910 Analytical Approach vs 3D FE Analyses

2015 ◽  
Author(s):  
Roberto Bruschi ◽  
Valerio Leonzio ◽  
Angelo Ferrulli ◽  
Daniele Scarsciafratte ◽  
Enrico Torselletti
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Analytical Approach ◽  
Bending Moment ◽  
Longitudinal Stress ◽  
Gas Industry ◽  
Offshore Pipelines ◽  
Primary Stress ◽  
Definition Of ◽  
Girth Welds

In the last decade new standards or revisions of existing guidelines have been launched on the subject. Among those, BS 7910 (now in edition 2013) [1] and DNV-OS-F101 (now in edition 2013) [2] are considered as reference in many world offshore districts of the Oil & Gas Industry. What is peculiar in offshore pipelines with respect to pressure vessel or nuclear plants, for which an engineering criticality assessment (ECA) was first established, it is the fact that in many circumstances offshore pipelines exceed the elastic limit (global pipe bending is a primary stress that causes mainly membrane stress through the pipe wall). This implies the extension of a stress based ECA into a strain based ECA, further including the bi-axial state of stress, caused by the presence of internal pressure and hoop stresses. An important step of ECA is the definition of loads and load effects at pipe girth weld, from global applied loads on the pipeline to the local effects at the crack. Finite elements (FE) are currently used to develop the relevant bending moment stress vs. strain relationship for the given pipe diameter, wall thickness and materials, both parent pipe and weld. Related longitudinal stress distribution on the pipe cross section without flaws in the weld is calculated for different pipe life stages (installation, pressure test and operation). The calculated global (or far from the flaw) longitudinal stress distribution is an input for the ECA analysis. For this aspect the new DNV OS-F101 (2013) has reviewed the appendix A requiring the use of 3D FE analyses to account for the effect of the internal pressure on the Crack Driving Force (CDF). In this paper it is discussed an analytical approach both to assess the pipeline strength in presence of flaws in the girth welds of offshore pipelines and to define defect acceptance criteria for specific new projects. The approach follows the framework of BS7910 and of DNV OS-F101 and includes load conditions under both installation and operation. In particular specific 3D FE analyses are presented to enforce the applicability of the proposed analytical approach.

Techniques for Fracture Toughness Testing of Offshore Pipelines

2009 ◽  
Author(s):  
Andrea Fonzo ◽  
Giorgio Melis ◽  
Luigi Di Vito ◽  
Gianluca Mannucci ◽  
Philippe Darcis ◽  
...  
Keyword(s):  
Crack Growth ◽  
Structural Integrity ◽  
Element Analysis ◽  
Offshore Pipelines ◽  
Three Point Bending ◽  
Mechanics Model ◽  
Need To Evaluate ◽  
Edge Notch ◽  
Notch Orientation ◽  
Girth Welds

The need to evaluate the significance of flaws in welded pipelines for gas transportation requires the knowledge of the material resistance to ductile tearing. In particular, the fracture resistance of pipe girth welds should be evaluated since they may potentially be critical for structural integrity. Standard toughness Three Point Bending tests (SENB) are too conservative since they are more constrained than actual pipeline. In this case, the adoption of a reduced notch depth, which is considered to reproduce well actual stress-strain conditions at the crack tip of a weld flaw, increases critical toughness values when compared to standard specimen configuration. Alternative solutions may be applied, even if not yet included in toughness standards. In particular, the Single Edge Notch Tensile (SENT) test is a possible solution reducing conservatism. A matter of concern for toughness characterization of weld joint is also represented by the notch orientation, since the weld microstructure is inhomogeneous in nature. The L–R oriented specimen (notch at the pipe inner surface) typically shows CTOD values strongly lower than the ones of L–T oriented specimens (through thickness notch) for both weld metal and heat affected zone. All these issues are discussed within this paper, while an advanced approach is presented to determine the resistance curve by using a single SENT specimen with the compliance method for crack growth evaluation. A relationship between the specimen elastic compliance and actual crack growth was determined through Finite Element Analysis and a Fracture Mechanics model. Such a relationship is presented and compared to other solutions available in scientific literature.

An Overview of Strain-Based Fracture Assessment of Pipelines

2018 ◽  
Author(s):  
Guiyi Wu ◽  
Longjie Wang
Keyword(s):  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Test Data ◽  
Oil And Gas ◽  
Full Scale ◽  
Plastic Strains ◽  
Offshore Pipelines ◽  
Pipeline Networks ◽  
Fracture Assessment ◽  
Girth Welds

Development of remote energy requires large pipeline networks to be placed in more challenging environments such as offshore in deeper waters or on land in Arctic or near-Arctic locations. Pipeline installed and operated in such regions may be subjected to large plastic strains. Engineering critical assessments (ECA) are commonly carried out during design, installation and operation of offshore pipelines to determine acceptable flaw sizes in pipeline girth welds. A number of fracture mechanics-based procedures are available for ECA of pipeline girth welds. Most of these methods are primarily stress-based assessments and are therefore not directly applicable to cases where the displacement-/strain-controlled loading generates large amounts of plastic deformation. For such cases, strain-based fracture assessment for pipeline/girth welds should be carried out instead. However, limited guidance on strain-based assessment is available in the current codes and standards used primarily by the oil and gas industries. This paper reviews the existing strain-based fracture assessment methods, and reports the results of preliminary studies performed to compare the methods reviewed with the available full-scale pipe test data.

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